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Item H0611,117-f;7 Z17TITI ► 1 t i AGENDA ITEM SUMMARY Meeting Date: September 16, 2015 Department: Building Bulb Item: Yes X No — Staff Contact Person/Phone #: Christine Hurley, 289-2517 Ed Koconis, 453-8727 AGENDA ITEM WORDING: Approval of a resolution of the Monroe County Board of County Commissioners adopting FEMA Technical Bulletin 5 "Free -of -Obstruction Requirements" dated August 2008 as required pursuant to Monroe County Code Section 122-2(c). ITEMBACKGROUND: Chapter 122 of the Monroe County Code "Floodplain Management" includes rules for interpreting flood hazard issues. The building official shall be guided by the current edition of FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical bulletins as adopted from time to time by the board of county commissioners. FEMA's Technical Bulletins ("bulletins") provide guidance concerning the building performance standards of the National Flood Insurance Program (NFIP), which are contained in Title 44 of the U.S. Code of Federal Regulations. The bulletins are intended for use primarily by State and local officials responsible for interpreting and enforcing NFIP regulations and by members of the development community, such as design professionals and builders. New bulletins, as well as updates to existing bulletins, are issued periodically as needed. The bulletins do not create regulations; rather they provide specific guidance for complying with the minimum requirements of existing NFIP regulations. Adopting these documents as well as internal County policies would serve to allow the County to not only remain in the NFIP as stated in Section [22-1(b), but also to move forward with the intent of becoming eligible to enter FEMA's Community Rating System (CRS). The proposed resolution would adopt FEMA Technical Bulletin 5 "Free -of -Obstruction Requirements" dated August 2008 as required pursuant to Monroe County Code Section 122-2(c). PREVIOUS RELEVANT BOCC ACTION: January 18, 1994 — BOCC approved Ordinance No. 002-1994 adding the language "as adopted by resolution from time to time by the Board of County Commissioners" to the rules for interpreting flood hazard issues. July 15, 2015 — BOCC rejected proposed ordinance amending Section 122-2(c) and directed staff to continue proposing resolutions for adoption of both new and amended documents to be used by the building official for guidance on floodplain management. CONTRACT/AGREEMENT STAFFRECOMMENDATION: Approval DIFFERENTIAL PREFERENCE: COST 1 1UNTY: N/A SOURCE OF FUNDS: REVENUE PRODUCING: 1 1 i APPROVED BY: County Atty XOMB- V,/Purchasing Risk Management DOCUMENTATION: Included X Not Required_ ISPOSITION: AGENDA ITEM # 1 2 3 4 5 6 7 8 9 10 1.1 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 MONROE COUNTY,FLORIDA MONROE COUNTY BOARD OF 1UNTY COMMISSIONERS RESOLUTION NO. 1 WHEREAS, Monroe County is currently a participating community in the National Flood Insurance Program (NFIP) and is working on internal County policies to improve upon its interpretation of NFIP regulations; and WHEREAS, Monroe County desires to became eligible to enter FEMA's Community Rating System (CRS); and WHEREAS, Monroe County Code Section 122-2(c), in part, requires that in interpreting other provisions of this chapter, the building official shall be guided by the current edition of FEMA's 44 CFR, and FEMA's interpretive letters, policy statements and technical bulletins as adopted by resolution from time to time by the board of county commissioners; W III]Oki I 1 Section 1. Pursuant to Monroe County Code Section 1.22-(c), the Board hereby adopts FEMA Teehnical Bulletin 5 "Free -of -Obstruction Requirements" dated August 2008, a copy of which is attached hereto. Section 2. The Clerk of the Board is hereby directed to forward one (1) certified copy of this Resolution to the Building Department. 1 2 `5 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 PASSED AND ADOPTED by the ward of County Commissioners of Monroe County, Florida, at a regular meeting held on the 16Ih of September, 2015. Mayor Danny L. Kolhage Mayor pro tem Heather Carruthers Commissioner Sylvia Murphy Commissioner George Neugent Commissioner David Dice IC • e = kyj Lei 09 1'• i • � (SEAL) ATTEST. AMY HEAVILIN, CLERK. Deputy Clerk Mayor Danny L. Kolhage �. r- ����. 0 Free- of- Obstruction Requirements, i for Buildings Located in Coastal H igh Hazard Areas in accordance with the Natioinal Flood Insurance Progra] Technical Bulletin S /August 2008 R T,; FEMA 7111�77D SVO Table of Contents I nooduCtimm.......... .................. ...................... ........... ---__---...................................... l NFlP RCO'u|lliona.................... --................ ...... ---_-------....................... --�3 Flood Insurance Ioro0cudooy-__--....... -------....—__—................ ....... ---- ...... [)baoucdouConsiderations .......... --.--_-...—................................................. ........ —5 Brmv+BFE Building- Elements ---_------................................................. ------_0 Acc«ssSuirsand Ramps ... ...... ---__—.............. ........................... .... .... ......... M Decknand Patios ............ .................. ...................... --- ......... ................... .... ......... --0 Ekevuun-S...... —.................... ........... ....... .......... ....... —................ —... ........................ 1U Enclosed Areas .... ............ ...... ----.._._-----......... ......... ...................... lD EguiPosCmr...... —.... .... —....... —................ —_—_—_-------__...... ----l0 Foundation 13racng—_—.............. -----....... ....... -----...................... --'l2 GradeDcaozs_—__........... _—_----......... ....... -.---......... .................. 'l3 Shear\4aUn—........................... _............ ...................... --_-------......... 14 BJabo.... ................... --........... ---_............................. ....... ......................... 15 Site 0erel`onoeot:Practices and IeauCS ................ .................................................... -----�l8 AcccsoryScnuture*----------------------- 18 DeCaclicd ........... —...... ............ ........ ....... ....... ................... --....... --l8 Erosoa(�`ocnl Structures —__-----........... _-------...—.^^—^^--_-19 Fences and Privacy \Val ..... -------.......... ---_--_------------21 Fill........ .............. ...... ------...... --...... ------...... ........... —.............. 2l (romund E[evaconxAlarAkcvctlie DFE............... —_--------_------_'24 Rcu|rowoz and CmnxfortStations ----_--.......................................... '25 ScpLICGvSuyom...... ---.---............. ................................. --_.................. ......... 25 Swiourinn'gP,xolsand Spas —...... ...... —...... —......... --_----............................ 26 TlchJFTP----_----_—_--------........................ ----_................................ 27 NFI[3cchnicalBoUecbnu....... ----.................................................................................... .27 Ordering Technical BulUedua .......... —...................................................... ....... .................. -28 Further Tnt6runuLImu................... --------............ ---...... ......... --....... .......... �28 Comments onthe Technical Bulletins should bedirected to: Department *fHomeland Security FE[NA Mitigation Directorate 500 C Streel, SW. Washington, D.C,20472 Technical Bulletin 5'00 replaces Technical BuQoUn 5-93, Free -of -Obstruction Requirements. Cover photo: Area heneathane|evated building that isfree ofobstructions. Protec,tincy buildings that are constructed in special flood hazard areas (SMAs) froun darn- acre caused by flood fOrces is an ln,iportaiii objective cif the National Flood Insurance Program (NFTP). Tn support of this objective, the NFIP regulations include 1111111111LU-11 building design criteria that apply to new construction, repair 01"SUbsLaritially darnalo-cd buildings, and substan- tial improvement ol"existing buildings in SFHAs. The base flood is used to delineate SFHAs on 0 Flood Insurance Rate Maps (FIRNls prepared by the NFlP. The base flood is the flood that has as 1-percent chance ol'being equ aled or exceeded in any op'veo n year (crrinionly called the In "1 00-vear" flood). Certain terITIS Used in this Technical TILLIlerin are defined in the Glossarv. Coasial waves and flooditl(), Ca11 exert strong hydrodynamic Forces can ally building elCHICIlt that is exposed to the waves or flow of, Water. Therefore, foundations that offer minimal resistance 10 �V-AVCS and floodwaters passing beneath elevated buildings (e.g., pile and column Foundations) are required in Coasral High Hazard Areas (Zones V, VE_ and VI -VM). Standard founidation,s such as solid inasonry or coricrete OF wood-fi,alyie Walls will gellerally Obstruct flow and be at. rise; of damage froni high -velocity flcpod forces. In addition, these sol- id f0tindatiozis and other obstructions may cause, wave runtip or n-Alection, or diver[ f , loodwaters, into the elevated porti011 of the buildinc, or into adjacent IRILICH[IgS. USC Of structural fill LO SUI)IDOYL bUilCtit1kYS in. V zones is prohibited because I wi I 7 be subject to erasion dttririo- a flood event. Tn either case., the.1� result is daina(YC to, Or catastrophic failure oC, the affected bl_Lildillc_S. For floodplain manage- ment purposes, an area beneath a structure elevat- ed on an open foundation is considered to be free of ob- structions it flood flow and waves can pass through the area relatively freely. Some flow diversion, wave reflection, and wave run- up will occur as flood flow and waves encounter the foundation, but the effects will be small and localized, and will not lead to flood damage to the elevated structure. Under the NNFTP general requirement. diatbuildings be constructed by triethods that, will ruin- irnize flood clanaage, the placement of any CMISLFUCtlori clurficut (as described later -in this This Technical Bulletin dis- cusses obstaictions below the BFE. Readers should check with the communi- ty to determine whether a higher elevation standard is enforced. For example, communities may add free- board or may regulate to the design flood elevation (DFE). In those cases, ref- erences in this Technical Bulletin should be con- strued as references to the community's regulatory requirement. bulletin) on as building site iii a V zone must. include consid- eration of the potential effects on the building g and adjacent ) building.s, In addition to potential wave and floodwater d1VC1__ sion effects, obsiructioris can beconic floodl-.)orne delay -is that inav strike OrhCr bUildirIgS, resulting in large inipact fcwces orl the buildings. The NFIP requires that all ricav and substantially improved struciurcs in V z(,)n(-,,,s bc to 01' al-)OVe the base flood elevation (BFE), on open f(Atfidations (pilings, colurrins, or 'S piers, mid, soirict.inies, shear kvalls) that, allow floodwaters and waves to pass beneath the elevated structures. The NFTP f"ur- fficF requires [haL the area beneath the.se c1cvaLed si.ructures renlain free of, any obstructions that would Prevent the free flow Of Coastal flooche'aters and waves during a base flood event. These requirements have been instituted to minitnize Technical Bul I eTin 5 — auGuST 2008 the transfer of flood forces to the btrilding foundarron and to preclLide the clefIcction or recli- rection of flocadforces ffiat coidd damage the elevated bilildinc_)- oi- neifyliboying bitildin-s. This Technical BtffleLin provides SPCCifiC 0,111clance concerning the NFIP's free-of-obsIFILC 11011 reqUiVCrrrcrrL in V /.ones, as Well as the general reqrtirement for conSLI-IIC[Ioll OILIt Will FrlinfiriiZe flood damage potential, as it applies to V .one, construction. Typical building elements and SiLe deg-eloprnc.m issues discussed in this Technical Bulletin incInde: Below-BFE Building Elements • Access stairs and ramps • Decks and patios • FlevaLors • Enclosed areas • Equipment • Foundation bracing ® Grade hearns a shear ivalls 0 Slabs Site Development: Practices and Issues • Acccssot-y structures ® Detached garages • Erosion control str-tictures • Fences and privacy walls • Fill • Gr-ound elevations at or above Clue ME • Restroom bUildin("S and comfort stations • Septic systerins • SIVIIIIFF6110'pools and spas I') Under the free -of -obstruction rerlitirenicrits in the NFTP regulations, any LvpC of lower area enclosure or other construction practice (as described belmNT) that prevents the fi-ee flow of Coastal floodwaters arid t�avcs J-.)eneath art elevared building during a Ixtse flood event. is not fall m\cd, Any coirsTritcrion c1carcm, Ul-IJI is StVLICttII_aIllY (lC'l)CndCIIC ()It, than is attached to, or upon which a V zone bUilding depends, is considered to be part of thatbuilding and must meet the rc- quirernerits of'Sectrons (4), (), and (6). 11'ariv of'rhese elements are attached to the buildiril- and located below the lowest.horizoriml structural member of the building, they ma.v COrESHLULC an obsti-tiction and may be prohibited. The attachrmnit ofany feature that is pro- hibited I)v INTIP regulations ic) an otherNvise compliant building Will result in a significandy 0 higher flood inSUFMICe premium because of the increased risk ofdarnap-e to the building Further, if a community is [,()Line[ 10 IMVC a pattern and praCLiCC of failirig to address such vio- Luions, the NFIP inay exerdse its authority to place the comnittriky on probation or under suspension, Which 'affects Elie cost and availability ofFederal flood 11-ISUFaIrCe. Construction elernt-_mLS outside the perimeter (footprint) of' and not attached to a coastal I-Mildin(Y' (SLICh as bt.ilkheads, swimming pools, MId ;ICCCS,1.301­V structures) and site. develop- ment practices (e.g., the addit.iori of fill) iriay alter the physical chaFaC(CFiS6CS of flooding or si(,Ytiif'tcatitli7iiict-ease tt,;ive or debris impact forces affecting nearby buildings. As part of[he cer- tification PrOCC-SS for V ZOIJC bUrIctiric's, the design professional MUSL Consider the effects that these elements and practices Will have on the building in cltiesuoil and on nearby bUildilICYS. Coristi-riction clemenis and practices [hat Will increase flood -related loadings on the brulding 2 Technical Bul I eTin 5 — auGuST 2008 (and that are not specifically prohibited by the NFTP re7tr1a[i(rr1s) unay° be constructed if' the i iiparcted buildings are designed to withstand the additional flood and wm'c forces. Increased f0trndarticrri eternen[ embech-nent depth, size, and ntrrrrher- might, he erriploved Lo coniperisate for increased flood forces. Stich compensatory design calculations nItrst be made by the reg- istered design pro[essional, who nrtist pro�icle a V zone ceruficatiorr C(A- tare structure prior- to construction. t ' i 'r i I x I's The NFTP regulations ford' zone construction are codified in -Title 44 of the Code o Federal Reo-ulanons. Specific to this Technical Bulletin, Section 60.3(a)(,I) of the NFIP reg-trlat.ion states: "Ifa proposed building site is in a oodprone area, all new construction and substantial improvements shall ... (iii) be constructed by methods and practices that min inrize cod damages ..." Section 60.3(c) (1) states that a cr:nmnitinity shall r-ccltrarc: "... that all new construction and substantial improvements in Zones Vl-V30. VE, and also Zone V if base ood elevation data is available, on the community's FIRM, are elevated on pilings or columns so that: (i) the bottom of the lowest horizontal struc- tural member ofthe lowest oor (excluding pilings or columns) is elevated to or above the base ood level', and (ii) the pile or column foundation and the structure attached thereto is anchored to resist ota.tion, collapse, and lateral movement due to the com- bined effectsofwind and water loads actingsirnultaneouslyoil all buildingcomponents. Water loading values used shall be those associated with the base cod. Wind loading values used shall be those required by applicable State or local building standards. A registered professional engineer or architect shall develop or review the structural design, speci cations, and plans for theconstruction, and shall certifythat tlaedesign and meth- ods of construction to be used are in accordance with accepted standards of practice for m ctingthe provisions of paragraphs (e)(4)(i) and (ii) ofthis section." Section 60-3 (e) (5) further states that a corrimtinity slratll rec{trire: "... that all new construction and substantial improvements within Zones V1-V30, V, and Von the community's FIRM have the space below the Lowest oor either fine of ob- struction or constructed with non -Supporting breakaway walls, open wood lattice -work, or insect screening intended to collapse under wind and water loads without causing col- lapse, displacement, or other structural darnage to the elevated portion ofthe building or supporting foundation system. For the purpose of this section, a breakaway wall shall havea design safe loading resistanceof not lessthan 10 and nomorethan 20 pounds per Square foot. Use of breakaway walls which exceed a desigt3 safe loading resistance of20 pounds per square foot (either by design or when so required by local or State codes) may be permitted on ly if registered professional enLrineer or architect certi es that the designs Technical BulIeTin 5—auGusT2008 proposed ined the following conditions: (i) Breakaway wall collapse shall result from a water load less than that which Would occur during the base ood, and (6) Theelevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other Structural damage due to the effects of wind and water loads act- ing sl mu Ita n cou sly on a I I building cornpon en ts (structural a n d non-structural). Water loading values used shall be those associated with the base ood. Wind loading values used sha I I be those rcqu 1 red by a pp I i ca bl e State or local bu i Id i n - stan da rds. Such enclosed space shall be useable solely for parking of vehicles, building access, or stora ge. Section 60.,3(e) (6) states that a corrinitinitv shall: "Prohibit the use of 11 for structural support of buildings within Zones VI_30, VE, and Von the community's FIRM." The NFIP Technical Bulletins provide guidance on the minimum requirements of the NFIP regulations. Community or State requirements that exceed those of the NFIP take precedence, Design profes- sionals should contact the community to determine whether more restrictive provisions apply to the building or site in question. All other applicable requirements of the State or local building codes must also be met for buildings in all flood hazard areas. Furthcr <ILH(LLlICC err Coastal C01IS11-11CLi011 C',AU bC` found in the Coastal Construction Manual (FFNI,-� 55) and in the Horne Builder's GUideto Coastal Construction (FENIA -199), Further grtid- ance on the breakaway wall requireinctiLs of Section 60.3(e) (,,-)) Can be fourid in 'I"echnical RU11CL411 91 Design and Construction Guidance for Breakaway Walls Below Elevated Buildings. It Is ire 1pOrUUIttO ]lot(- tllr.Ltl)Ltil(titigiiiatc°t-ials uscd below the BFE 111LISL Meet [he flood (lainage- resistant rllaU'rials requirelnenL of' Section 60.3(a) (3i). Ft.irlher guidance on this I-CCILlirellIellt can be found in T Clinical RuIletin 2, Flood Darnago-Resistant Materials ReqUirallents for Buildings Located in Special Flood Hazard Axeas. The floodplain nianagellielit and HISUralICC Programs of the NFtP may treat Some below-RFE bitilding elements differentIv. NFIP flood,plain management reutila uolls allow Certain Cori- struction eletnerits beloxv the lIFE, which rnav or rnav not break mvav during the base flood, and which may orrnay noc he consid.ered obstructions for Fecteral flood ilisill-Wice rating pur- poses ( . stairwells, elevator shafts, shear %valls). Desigri 1--)rofessionals and owners may t,vlsh Lo contact as qualifie(I irISUrance agent. or the NFIP - before at hullcling is designed arict constructed- regarding the flood 111SUrarice PI-CITIRL111 1111- plications of obstructions- For exaniple 4 Technical Bull eTin 5 —auGuST2008 n The NFIP floodplain. nianagernenl, re-tilations in 44 CFI Section 60.3 allow open wood lattice, insect screen nu, and non.-load-bcarin(y solid breakawav walls below all elevaLCd bifilding in the Coastal High flazard,krea. These feaLtires have beenjudged not to be ob- strucilons to flood flow or waves, but building designers and owners should be aware that solid breakawav walls and (Tarac-e doors — even thonah pet-illiLLCCI bv floodplain nianage- 1_Z� I-) I'D anent rec)_Ldations — call result in sio-nificarith, hig-her flood insurance prerniLLIIIS. Thus, -Ltse ot'breakaN,faw'c(.)nstrLicLioii below the BFE will not allow as sti-nmire to be classified as "free of' obsirticrions" Cor flood nISLLrance rating PUVPOSCS (a free -of -obstruction classificabon snakes the building clivible for the lowest V zone flood insurance prenijUln rate). n NFIP floodplain inanalacinctit Fcgillations restrict uses of space below the BFE to park- infy elf` Vehicles, hUildin- access, and storage. Stairs, rarrips, and elevators are permitted, However, dcperidinoi on how they are C011,StrLICIC(l, Stairs, ranips, and elevators may be con- sidered obstructions for Hood Insurance rating purposes, and could rICSUlt ill Sig1lificantly higher flood insurance prernitinis. For flood insurance rating purposes, an area beneath a structure elevated on an open foundation is considered to be free of obstructions only if the following criteria are satisfied: There are no solid walls of any kind — including breakaway walls — below the BFE (insect screen- ing, open lattice, and open slats are not considered obstructions). Any stairs below the BFE are open (any stairs enclosed by or containing solid walls are considered obstructions). There is no machinery or equipment below the BFE. Machinery and equipment include any items permanently affixed to the structure and that provide utility services to the building (e.g., furnaces, hot water heaters, heat pumps, air conditioners, elevators, etc.). Several of' lhtr NFIP's flood -resistant design and construction reqUireinents are performance rc,quiretnenLs, not prescriptlVC FCClLLfi_Cl_r1CY1tS. In other words, the expected building perf'()V_ I inance is stated, but the walvs by which that pci-Ci-n-mance rnay bc- achieved are not prescribed. It is lip to tile cornn-itinity ofticial to determine whether as spe- cific design submitted by as design professional satisfies the perforniance requirernents. In ffic case of the Free-of'obstrUCLion requirentent, it is not always cleai-whelher as particular bi.tilding eternenLerr sate devel- opinent Practice will be at significant (A)SLI-LICtion Lhfl. prevents the free passage of' floodwaters and waves. The terni "sionlfi- calit" is Lised here be.cause any constrk..tcdori or olevetopincrit pi-actice betow the flood level wwill calise a localized disruption of, Flow and waves dni-11-1,g the base flood. Deterniiiiing whether the disruption is significaiiL Is not always easy, In sonle cas- es, the analytical tools necessary to answer the question ivith Any construction or devel- opment practice below the BFE (even piles and col- umns permitted by the NFIP) will cause a local- ized disruption of flow and waves during the base flood. Whether the localized disruption is great enough to harm the elevated build- ing or surrounding buildings is the central question, Technical Bul I eTin 5 — auGuST 2008 5 certainty are not available and local cxperience., post-c-lisaster invesugations, and coastal process and building science prin- ciples must be relied upon in order to reach as Coll chision, Nlany local floodplain manag-erneiiL ordinances contain [an- gutagc that calls for evaluating Potential obstructions below or near a building for their effects on flow, deflection and wave runtip (or "rarnping'). Standard fluid mechanics texts and coastal engineering references such as the U.S. Arrity Corps of Frigitivers (USACE) Coastal Engineering Manual pro�jde sonic guidance, but the methods contained therein yeneral- ly are not capable of evalLMtiucl the potential effects of'small huildin,g elen-lents, small M11OLUILS OHill, etc., on flooding and waves during a base flood. NUnierical inodels for coastal storm surge and waves do not have the resolution required to rt,s0lVe bUilding clement. -sized disruptions to flow ano-1 wave fields, and constructing such models at this tirrw would be technical- ly challerigii](", tinic-consuri-iing and cost -prohibitive. Recently developed, sophisticated riurntl,rical inodels show some prorn- jSe oaf heir able to reSojNTe and analyze Flow around potential 1 obstructions, bait their use at present is not, econornically feasible f'OF C0141111 LIM Lies, oivners, or desio-rier's interested in CXanlillitl- PO(,CutiaAl Obstructions such as those (USCLUSSC(t in this Technical BulleLin. Potential flow diversion - and wave runup or wave reflection - toward pre - FIRM buildings at or near grade is problematic. Many of these buildings may be damaged or destroyed dur- ing a base flood, regardless of the presence of new NFIP-compliant structures. Communities must deter- mine whether and how to weigh the presence of low -elevation pre -FIRM buildings when construction and development decisions are made. This Technical Bulletin does not recommend a blanket prohibition of below-BFE building elements and site development practices when pre -FIRM buildings at or near grade are nearby. The sections that f0llmv discuss common bitilding elements that may significantly affect tile free passage oaf' flood flow and waves under elevated bullctjn,;S. 11v following the "t-lidance be- 1OW, PO[CrILMI ObStl LICLive of ecis are mininlizcd and the (.4einents acre judged to comply Avich (he NFJP fi-ce-of-o.)bstruction requirement. Access SILairs and ranips that are attached to or beneath an elevar.ed hUildin'o- nmy be criclosed with breakawav walls rat- may be tinenclosed, 'WiLhOuL walls. Howcvcr, Stairs and ramps, like f'OUndalion bracing, can impede the intended (ailure of breakaway walls. U'riericlosed stairs and camps are preferred. Stairs and, ramps are no( required tea break aW-aN [11CIIISelves, but this is a design option, Stairs and ramps 111LISL be dcsigned and construcLed LO either: n Break awav during base flood conditions -wi(hottt causing dainage LO the building or its foundabon, or 6 Technical Bul I eTin 5 - auGuST 2008 n Resist flood loads and reniain in place di-11-ing the 1)ase flood. It' this option is selected, the elevated bu[ildina I and its f'Otindanon rriu.st be designed tO R'SiSL any flood loads that are transferred ftorn the stairs or ramp tO the building. Figin-c I shows an exa.niple of stairs that did not break away cleanly - die stairs palled OUt the exterior wall of elevated bt,filding- as they failed. Conscr-oiction of access stairs i�,irh sides and risers open (if) the extent that building codes allow) will niinitnize flood, loads acting on the stairs the roiselves, therel)y 11-ii I I irnizing flood olan I - age, and also ininirnize transfer OHIOOCI loads to the elev"lled I)Lillding. Open stairs stioti.ld be considered whenever possil-le (see FigLire 21), Ranips MUSt f_)C (ICSio-11CCI and constrtictccl to minimize the ol)stract.ion of floodwaters and waves, and CoIlfi(,LII-CCI So that floodwaoers and waves canno( flow directly up the Yarnj_-) to- w,ard the elcvated 1)t.fildina. This means that rallips IntISL he positioned to avoid a straight alio-nnient that exLencts fi-0111 Lhe elevated htiildincy down toward a likely directloti of Nvave and st.trlge approach. Technical Bul I eTin 5 — auGuST 2003 A solid entry door capable of resisting all design loads must be installed at the top of any access stairs or ramps. Access stairs are some- times constructed inside a breakaway enclosure, with an entry door at the bot- tom of the enclosure, but without an entry door into the elevated building. This practice leads to building damage. The lack of an en- try door at the top results in a large opening in the building envelope when the enclosure breaks away. This exposes the building inte- rior to higher internal wind pressures and wind -driven rain, and provides floodwa- ters an easy path into the building. Figure 1, Stairs did not break away cleanly, elevated building. Decks and Patios Decks a if d patios tYpically lisp outside tire footpt It it of e I cvatedVzonc residential a ri (I conk I ne r- cial buildings, and can be constructed at elevations varying frorn at grade, to above grade but below the BFE, to at or above the BFE. n If a deck is structurally attached to a su-ticture, the bottorn of the lowest horizontal sup- portirio- member of the deck must, be at or above the BFE; clerk sUpI)OFtS that extend below the BFE (e.g_ pilinlys and bracing) rnust comply xvith V zone design and construc- tion requirernems; and the StrLLCLUre must. be designed to accortimodate any increased loads resulthig from the attached deck. I n Sorne attached decks are located above the BFE but rely cm support elements that ex- tend belmv the BFE. These supports inlLSt COMPIV with XT zone design and construction requirements. n If' a deck or patio (not: counting its supports) ties in Whole OF ill Pall below the BFE, it HIM'St be SVTLICflAral1V iTACI)CIRIC111 Ft-0111 the structure and its foundation system. Decks and patios must not advcrscly affect the a(Ij fill g base flood conditions by diverting floodwaters and ,�nves. Foi- floodplall'i arirrna ernent pur- Clecks and IAA UosCOnStRIC.ted at natural gyracle or on small amounts of fill for t11e section oil Fill) will nor. lead to harniftil diversion of flood - %VaLel'S OrWaVC FLIII Ild r'CflCCtiOI_l. A- "low -profile" deck or patio is defined as on(. , where the vertical thickness ofthe deck of- patio is 12 inches or less, some of'whicm h av be belmv the adjacent finished grade. This thickness (IOCS HOL HICILKIC railirilgs (iOilch should be open). Seats, benches, tables, planters, or other obstructions triust not be built illLo or attached to the deck or patio. Decks and patios musthe desig-ned arid COUSLFLICied so that, when subject to base flood con- ditions, they (Jo trot create debris that, will damn-e NHP-compliarit structures. For H mana2,emerit, mimoses, this means that decks and oatlos nium elther: a) remain ITILacL and in place during the base flood, or b) break apart into SMUH DieCeSso that the r-C'SUlting debris will not lead to structural darnage of NFIP-coiriLDliant structures. Decks that are structurally attached to V Zone StITI(AvIres Must be supported to resist the sl_ InUltalICOLLs aCLAOH ofdcsl,(_Yn wind loads and base flood loads. In sonic cases, attached decks c,an be cantilevered but, in most cases, attached decks mustbe supported on piles, posts, or coluruns cirlhed(Iccl inter the gFOLLHd and capable of sk,trviving anticipated erosion air(-[ scour. PoSt-SLOI-111 illVesLityaciOris frequentLy identih, decks that were elevated on small diameter posts of- �vere elevated Oil Sli'LICLUl'al eleH]CIlLS WlthOLIL SUfficierfl: crnbedr-rient into the ground. "Hie result of inadecltuite SUPPOrL, is loss of the decks and sometimes clanialge it) the elevated struc- tures as the decks Call. T-1-41less the building code or local conirriunity prescribes otherwise, a Rile oftliumb is the foundation for an elevated deck attached to a V zone structure Should be. s ' 'lar i mi - to the structure's foundation. Technical Bul I eTin 5—au uST2008 9 A • s r� Elevators attached to or beneath an elevated V zante str°aac:ture crust comply with bnilditrg, fire::, electrical, and, nrechanicaal code recittirernents. Like access stairs, elevators are exclufled front the NFII' breakaway recluirenrertt, but natast meet the NFIP flood darna e-resistant rrtarc.rial regLurernents. Elevator ecltt pinent below the BFE te-ill result in higher flood instrrance prerni- uri1S. Flood loads acting can the elevator conaponerats and any raon-breakaway shaft. walls rnt.rst; be ac- coin-tred for in the design of the elevated stratctnre and its foLaidation system; dicsrefore, it is adsantageol,Is to nlinitnize the sizes of residential elevators. Additional details can be fonnd in Technical Btillenn 4, Elevator Installation for Buildings Located in Special Flood Hazard Areas, Tech- nical Btalletin 2, Requiretnents for Flood Damage -Resistant Materials for Buildings Locates[ in Special Flood Hazard Areas, and M Flexed Resistant Design and Construction (ASC:E 24).ASCE 24 is refer- enced by iriodel building codes and has been deternained by FE tA to be consistent with the NFTP regttlaticans. L'se of enclosed areas is restricted to Larking of vehicles, building taccess, and steerage;. En- closed areas, including fO c•rs, ralu t, be constrtacted. of fleeced clararaa c-resistant rnaterrals and not he finished. Enclosed areas must not be Used (gar habitablct OF J."C r-CMiOnal'. Put-pOSCs. The NFIP regarlat:ions state that the area beneath they elevated portion rrf' as V zones ,strtacture naav bc• enclosed onli with open lattiC e, insect: screening ning or non-strppc;rting breakawav galls (see Technical 13nllcstin 9Design and Construction Guidance for Breakaway Walls Below Coastal Buildings). GLtiflance on lattice has been cle'veloped and incorporated into Fl NL\ doc•timent.s, irre:lut:Iing they Flood'' IGIStn-anceManatal. The guidance states the following- as being acceptable lattice: n Wooden or' plastic Iatrlce, With at least. 40 percent of it,s t'f°ca open, arid. rn ade of material no thicker than �1' inch. n Wcacatlera OF IalaSUC slats car shaft CPS, girl at least 0 percent oaf their area Open, and niade ofanaterial no thicker than I inch. Figtares 'l and a show exanalales of contlilirant slats, which ovpi- cally are installed flat against the fcrtanclaticatt pilings (I agtn e 4) OF angled like lcatavers bet,a-een the pilings (Figtare 5 The NRP does not limit the size of enclosures under elevated structures. How- ever, higher NRP flood insurance premiums will be assessed for V zone struc- tures with enclosed areas that are 300 square feet or more in size (including stairwells and elevator en- closures), even if enclosed by compliant breakaway walls. The NFIP does not require flood openings in V zone enclosures; however, some communities may have such a requirement. Ira general, rnechataical, electaical, and Plaarrrbitag ecluilantent, and fiXtures are recluired to be elevated at or above the BFF. Th r e are some c Xce pl_iOns fear elevator ecluiptaaent that cannot be c:lc vated, laut tlresac° exceptions are very specific and are otatlined in Teschnic:al Bulletin 4, Elevator In staIlation for Buildings Located. in Special Flood Hazard Areas and Ai` CE 24, 10 Technical Bul I eiin 5 - auGuST 2008 Figure 4. Wood slats installed flat against foundation pilings Figure 5. Wood slats installed between pilings at an angle (louvers) Utility risers, electric: Illeters, alld SH-1-111al- clemciits that ryiL,ist I)e located I)etow the BFE MLLSt he imsiallcd Lo minimize flood dMliage. The following techriiqtLCS 11CIP to achlcve this ob' 9CCLIVe: n The elernents IlItISL iiot I-)c attached LO or perieLrate throu(-n)-h breakaway walls. n The elements shouild he loC21ed oil the sides of I)iles wid coltinins that are opposite brill the anticipated dire.coon of flood flow and ivave approach, where possiNe. Additiollal guidance cats I-)e I-Ourid iri Protecting Building Utilities From Flood Damage (FENLk 348). Desl�ners and owiicrs should he awarc that the presence ofeqLtiprneriu. helow die ME, ever l if allowed I)y pero-fit, call result ill hil(Ther NFIP flood itistirarice prellIlLTITIS, Technical Bul I eTin 5 -- auGuST 2008 I Bracing is often used to stiffen pile foundations and,/Ol, to illiprove coinfort and reduce swati in elevated buildim.,.s. ks a acneral ride, building; designs that do) not include bracinwill ii-lini- g mizc obstructions to flow and waves and are preferred. 'However, if bracing is required for a Stable deli tr, ILS Use should be ri,-iininiized. 1� Diagonal finiber cross-bracinu is the, niost coannon tv, l- e of bracliUsed Ou Oil f0ndatiOnS till - der der COUSLal homes (see Figure 6). Uffl"Offtlnat,ely, timber braces frecittendy fail during; severe flood eve rns dae to wave and or debris impacts, If they survivc,�, they can trap debris and trans- fer lateral flood ](lads to Llie foundation. NICLal rod braces, while less susceptible to Failitre, can also trap floating debris (see Figure 7). Knee braces at the tops of pilings are sonietinies preferred since the ' v will likely c.XtCfld a shorter distance. below the flood sni-face and present less obstruction to flow and waves. Frec-of-obstruction considerations call for using, Only the nnninitini airlOunt, of'bracin"g- that is necessary to add rigidity io the clesign fOr the conif-Ort oCoccupants. Mariv coastal construction experts and references SL[ggCS( FC[Ving con shore -perpendicular bracing and Inininirzing the Use OfS.110fe-parallel bracing. However, since wind and scisinic a loads clan act in anv direction, '7i this alrernatl'VC fllaV not always provide the structural stability that is required in some loca- tions. Increasing; the titiniber of piles (I)v decreasing; horizontal spacing), detailing nionicia connections ar the top,,, of the piling (in the case oCconcreie piles and heams), using gi-acte beams, and extending pilings above the first elevated floor level are accepted ways of elfininaL- '7 incy or rechicing die need fear bracing ) Where foundation bracing IS Used below the BFE, it. must be placed so as not to interfere Nvith the Intended i'aflUre ofbreakaway wall panels. Avoiding Hirer-Fel-ence may recitlire eliminating; breakawav walls, shifiincy the locaL101-1 ofbi-cakaNvay -,valls, Or rCdeSiglIiI10' the tbUndaLlOn So the need fc)r certain braces is ellininated. Breakaway walls and fouriclation bracing should not he ]faced In (-lose prox.Hinty if either can affect the intended perfOrniance offfic other, Figure 6. Elevated coastal home with timber cross -bracing, principally in the shore -perpendicular direction 12 Technical Bu I I eTin 5 - au Gu ST 2008 C;rade beams typically are made of'reint'Orced cmicrete orwood� they are used to tie t1ourerher 0 the f'Oulidatioli piles or cofl.Limns to provide additional lateral support. (;racte bearris chat are placed with their iipper sti,rfices HUAI With or below the iiati.ii-al grade are not colisidered obsli-Lictiotis and are alh,)tN-ed utider the NFIR Flo wever, storm Crosioti and local scottr will ofteri expose and Linderi-rihic grade beams, Icaving cheiri suspet-ided above the frost-starlli groill-id Profile. Designers mkisi- this circiinistarice mid design 'g-rade beams to resls� flood, wave, am-1 debris loads alld to Femaiii iri place, and ftinctiorial wheii tirlderriiiiied (see Figiire 8), (wade bearris also rritist be desi(--med aiad coristi-LicLed so that OIC VertiCz11 thickness is minimized, thereby reducing dic lateral flood, wave, arict debris loads acting on the hearer aiid limiLitig- the trarlst"er c)fthese loads i.o the f-oi.tridat.ioii. Desio-riers are catitioi-ied that (yradc bearris should riot. be LISCA as a suhstitiite fo)r adequate iiomiher. size, atid et-Tibedmerit ol* piles Or COILIIIIIIS, Figure 8. Grade beams must resist flood, wave, F,nd debris loads when — undermined. Technical Bul I eTin 5 — auGuST 2000 A strict interpretation of the NFIP regulations indicates that Only pilC and COIL1.1.1111 [Ounda- Lions are permitted in V zones. In practice, this requirement has been relaxed to allo-.v solid walls thar are necessary to transfer lateral loads acting on the upper stories of tall buildings to the (.,round, particularly in extreme -wind zones. These walls, called shear walls, are often constructed parallel to the MItiCipated direction of' flood How and wave attack (i.e., perpen- dIcnlar to the shoreline) so as to allow floodwaters and waves to pass freely. In some cases, however, buildin- desio-ns require both shore -perpendicular and shore-patUllcl shear walls. tTse ofshorc-parallel shear wall seglylents should be Ilintited to that minimum leno-th required 1.7 1� to transfer upper ston- loads to the fOLmdation. Shore -parallel shear walls should be designed with openin,.Ts in and between shear wall se.(,;nwnLs, to nunirnize trapping offloodwaters, waves and debris, and to mHurnize the total flood load actin; on the building. In anv case:, flood forces on these NA'aIlS must be certified as part of the overall Vzone certification requir-ed b,,,- a communir.y. Low-rise,'V zone buildinUS CMI USUallv be designed ivith pile and COIL111111 Foundations only, al- though SOMC COMMUniLieS ailM,' below -ME shear ovalls withOLU, regard to buildina height oi- size. Thus, some ImNrise buildings have been constructed in V zones with shear walls below the BFE (ISCC FIgUI_C 9), Usually with the Nvalls perpendicLilar tea the shoreline. elevated on shore - perpendicular shear walls. This design approach is risky for low-rise buildings since lateral out -of -plane loads (wind and flood acting on the faces of the shear walls) can be large and special design considerations and! detailing are required, The practice of allowing shear walls beneath low-rise cotistructioti is controversial, This is due, to the, fact that anv solid Foundation wall below the BFE ca.n act as an obstruction, and these walls can he SLII)jC(:t to (AU-CITIC, IWICIS dUl-ing a base flood event. Indeed, post -flood investi(Ira- tions havc, found LI-ULL inany such walls do not sure a scvere storm event_. This is illustrated in Fib Yure 10, which shows an example Of bUildill- SUPPOFIed On COILLITIns and shore-perpendic- Ular walls, where a wall section failed, leading to failure Ot'Llie elegy aced floor beam and floor. In this instance, the building was a pre-FIRNI building With the solid Nvalls restingoil shallow footings (a i-neans of support neat permitted under post-FTRM V zone regulations), and the failure was likelv due to boLhlateral flood loads and f0undaLion undermining Ill Technical Bul I eTin 5 — auGuST 2008 Figure 10. Failure of shore -perpendicular (and shore - parallel) solid foundation walls, and of beam and floor system supported by the shore -perpendicular wall (pre -FIRM structure) Sheai-Nvtk I Is beneath low-rise V zone structures, re() 'a I'd- JeSS Of'01-iCtILM011, al-C ObStYUCtiOnS that are COritrary to the NFIP Uree-of-obSl_ruction reciuireineiiLs. Thew should riot he perinlited unless special Justification exists, such as the need for a public, inilitary, or ftinc- tionallAT dependent, low:v rise structure in a V zone, which cannot be si.tpported on piles and COILInins alone. Even in these cases, they Should be allowed only if deLailed engineering calculations denionstrate that the Couridanon and buildino- are desio-ned to resist all base flood conditions (including erosion, which will increase the height or` waves and wave forces striking the foundation), all desi-n loads, and all appropi-laW load coinhinaLiOns. For floodt3iairi rnanaL-enient iDurr:)oses, below,v-BFE Sheal'Watk ShOUld. OuIV be iDernutted below fully-en�inecred raid- and 1-1101-risestructures, Where the walls are nccessary to transf-cr lateral loads frorn upper stories to the ground, and. where engineering Cal('Uhttl(WIS (ICAT1011SIrate the viability of such an al)p1'Oe1Ch Linder dcsi(,,-n wind and flood Conditions. Below -LIFE shear walls should be oriented perpendicular to the shoreline -whenever possible. Shofe-parallel shear wails below the BFE should be limited to the abSOILIte. nritinnuin nece.'ssary bv desio-riino- lhe'rn to be as narrow as Possible VViL.11 opts nulk-s' and separated or offset, to present thentizxictltuii possible obst'rucLion to water and waves. M, W C'oncretc slabs benca(h (,,Jcva(:cd[ V xone buildincrs are coninion1v used for vehicle parkin,, atict as a floor in an enclostd storacre area of building access area. FEW , ­Vs post -disaster investiffa- tions have COHSiStC11tlV C011CILOC(l tl]�Lt I'Cillfcn-CC(l concrete slabs dricker than 1 inclies can act as obsti-irctions to the free flow of -water and waves under- elevated buildin,,s and can (,ransfer flood loads tea the foundation if the slabs Marc undcrinined., displaced from a horizontal oncli- tation., or fail to break into small pieces (see Fi,';-ures 11 and 12) 1 The experience gained in post -storm evall-Lations suggests that slabs should either: ZD n Be frangible (break away), "floating,-" slabs that are supported by conipacted soil, are riot ari.ached to the buildin'-o'= ('ovindation, and are desi-ned and consiructcd wiih a maxinuirn I thicktic.ss (traditionally 4 inclics'), without reinforcenient and Without turned dOW11 Cd.17CS, or Technical Bu I I eTin 5 — auGu ST 2008 15 n Be desigyned and constructed to be. Self'SUIDPOI-61-10- SLI-11CLUI-al Slabs capable of reinainlufr 0 -71 if-IL21CL MICI CLHIctional undcr- base flood conditions, inctuding expected erosion. Building I foundaLiOIIS must be capable of' resisting any added loads due to the presence of these slabs, and any increase in local scour clue to the presence of the slal.-)s. For mos( circurnstances and for sinall, low-rise V zone structures (including residences), the first alternative ot'fran.gible slabs ShOLLId be employed. This alternative is also appropriate for 00-Iff use, of' -dabs such as pool decks, sidewalks, and patios. Figtire 13 illIIS(raLeS one possible design [01- SLIcIi a slab. Figure 12, NFIP- rj:LffItIj2aaUI[PMf nwle-d slab broke apart and performed well. 16 Technical Bul I eTin 5 — auGuST 2008 Pile/Column (Typical) Tooted Contraction Joint Contraction Joint (Typi'cal- See Detail) , T <-_4"Max. Crack Resulting From Concrete Curing Process Sawcut Contraction Joint Sawcut Joint 4"Max. -j— Crack Resulting From Concrete Curing Process N=- INSTALL EXPANSION AND ISOLATION JOINT -SAS APPROPRIATE IN ACCORDANCE WITH STANDARD PRACTICE OR AS REQUIRED BY STATE AND LOCAL CODES. Technical Bul I eTin 8 - auGuST 2008 17 For larcer tuld- and high-rise structures, hoth alternatives could be considered, although the second option of self-supporting structural slabs will likely inean a significant increase in NTIP flood I'nSLLI_M_ICC PVC1111LIMS (.since the bouorn of the slab —car the bottom of the lmvesi hori- zontal men-iber supporting the slab — will become ehe lowest, floor Cor flood insurance rating purposes). Reinforced, self'-stippoi-tirigsti-itct,iii-aI slabs maybe: appropriate for large structures that are supporte.cl on large concretc piles and columns, since these stVUCtLLR-.S are typically much heavier and are less prone to damage frorn flood loads, If a frangible parking slab is conS[I_UC(ed beneath such a structure, timely- reoccupation after a severe coastal storm event — of an otherivise intact and Usable SL1._LLCtU)_C — bray be prevented. A sell-supporring structural'n slab could be considered in such sfl.uatiems Reinforced, self -.supporting Ing structural slabs and beams beneath large buildings ShOUld be de- signed to be only as thick as necessary- to support vehicle loads and other design loads, but no thicker. The slabs and bean -is should be connected and IIILC-Fal to the FOLIndations, arid all I below ME components should be, designed to act together to resist flood loads and other de. - sign �) , sign loads. Obstructive effects will he i-ninimized as long its the slab systems remain intact and horizontal so that flood-,valers and waves pass above and beloW the slabs. The sections that l'ollow diSCLISS common site dekelopt-neritpFactices and issues that 11-lay signif- wantly affect the Cree passage of flood flow and a,,Faves under elevated buildinlgs. By following the guidance below, potential obstructive effects are trininnZCd and the practices arc judged to comply with the NFIP free -of -obstruction reqttirernem. U1 nless elevated on piles or columns, accessory structures III V runes Should be IIIIII[Cel to low-cost and small sn-Liciures such as metal, plastic, or woodert sheets that are "disposable," Guidance available from the NFIP suggests the terns -small" mearis less than or equal to 100 S(Inare feet in size, and cost" means $1,000 or less. Sornu States and communities rccom- mend other values. Ilan acccsson= StTUCLUre does not Meet the criteria established to allow below-11FE Installation, or if it is of, to significant size and nature that It WOUld likely crcatc either damaging debris or flow and wave diversion problems, it should be constructed and elevated in full compliancc, with the NTIP requirements. Examples of's Lruc tu res that excced size and value litnus, or con- tain eqLLiPI1ICII[ prohibited below the BFE, or tfacilitate LISeS prohibited below the 11)FE, include detached garages and I'eSLI'Oorn bLUlding comfort stations (see sections that. follow). 1-,S//' Small, loi-\�-cosr accessory structures that M-C not elevated must be designed and anchored to resist wind loads (see Ficrurt 14) , and to resist flotation that may occur even under relatively shallop flood depths. However, becaLISe srn all accessory structures are unlikely to wiLlIsLanci wave loads, their loss should be anticipated slurring the base flood, and the effects ghat the re- sultant debris i-nav have on nearby StrUCtUrCS MUSt be considered. In addition, small accessory 18 Technical Bul I eTin 5 — auGuST 2008 StftICtUFCS Must he ILI-IfIrliSI-ICCI On the interior, constructed of flood darnage-resistantnia[erl- als, used only- for storaae, and, if pr(Mded with electricity, the service inust be elevated above the BFE. Figure 14, Small accessory structure anchored to resist displace tent by wind An alternative to an accessory structure is to cl elue srorage space Belo-w the elevated structure by c.nclosing an area with brcakawav walls, However, creation of such an enclosure illay result in higher flood insurance preinivinis. Owners and cornniunItICS Should Weigh the alternatives carefully. Detached garages, such as those t-ypically built, for single-Caln- ilv hornes Or 1111-116-falf.-IiIV structures, are rc)o lar(re and roo COSLIV LO be considered accessory structures that. inav be a.1- lowed below the BFE (see Ign.1clance I -Or Accessory Strucatres) Therefore, detached garages niusL be properIv elevated on Plies 01' COILIIIIIIS alld Coniply with other requireinents for so-ticturcs ill V zollcs. Garages may be construct- ed under elevated buildings and enclosed with break- away walls (see Technical Bulletin 9). Note that large, billy -engineered, free-standing parking garages that sau.isfy NFIP V zone de- n slo-n and consirl-I.C11011 rCqnirCrnCnts are I-WI-MIUCCI, CVCTI if' portions he WOW the BFE (e.g,, vehicle ramps, PS, stairi-vells, elevator shafts, and parking spaces). These structures are not.walled and, roofed in the tl_<Idlt]'Olial sense, and can be designed to allow the frec passage of flooclwa- Lers and waves, (111-OLI(,Yll the Structures. Erosion control structures such as bulkheads, -seawalls, retaining walls, or revetinents that are installed beneath elevated coastal buildings are obstructions and are prohibited, even if they are not attached to the building Couilda [ions. These erosion c(-)nrroI structures earl. transfer daniarino- flood loads tc) bUildillff fOUTICIaLi0i'lS, and o-reaft increase the potential for �n 111� Technical Bul I eTin 5 — auGuST 2008 19 redirecting flood flow and wave action onto the cleated por- tions of coastal buildings. Figure 15 shows an exarriple of binbers attaCI_Wd (0 a Pile I61HICLUion (constituting a bulk- head) that are not perinitted. N,Tiile the NFIP does not prohibit bulkheads, seawalls, retain - in(, walls, or revetnicnis that are: OULSide a buildin-'s, footprint and that are not attached to the building, cornillunities and desi,un profcssionals roust carefully consider the potentially is: the greater the horlzotlLal distance between the CrOS10111 control structure and the building-, the less likely , - - L aLl%Me runup 0�_- 1_k, 1 1'-Ili till ak4 e1 Neis., aff1- L U11 I­ bulld1n(,. NVhile sine local or State regulations inay prohibit the constritction of are erosion control struc- LLIFe Ulltl a *1 erosion is within few f* er of the building; foundation (to rnaxii-nize the recreational beach area seaward of the device), the close proxiiuittl of the de- vice to the building may contribute to flood damage. FEMA's coastal inapping guldancc sug0 gists that a 0-too(. wide "N`F, splash zone" (the area where al-aves bt-caking on or runnin" LIP the Se.I M_d face of' an erosion control structure will land or splash down) Should be mapped landward of erosion control struc- MFeS, but provides for site -specific calculations that can lead to a narroNver splash /.one w1clLh. For flood - plain trianagernent, Purposes, aL ')O-f(.)Ot S[)LISh ZOO widt.h is desirable for new construction landward of existing istin(, erosion colitrol SLUICLUIVS. IMI 11MV 110t bC fc-asible wherc an crc)sion C01-ILF01 Sti-tICLUre is con- SLI-tiCted seaward cif' an existing; building. There Is no established Illillil-flUrn distance: bet`vccn a building and an erosion control sti-LICtLIFe, but LL reasonable n-uniinurri width would tw on the order of 10 to 15 feet. States and C01111-11LIAlitiCS shOLLId take local con- difions and observed building chunages into account when such detcrininarforis are inade. Guidance for evaluating po- tential effects of erosion control structures on waves is contained in the U.S. Army Corps of Engineers (2002) Coastal Engineering Manual. Generally, those devices with a steep face (1:2 [vertical to horizontal] or steeper) will result in the greatest wave runup. Figure 15. Shore�parallel timbers attaGhe-d to a pile foundation were intended to act as a bulkhead, but constitute an obstruction and are prohibited, Options are 11111ILed wherl erosion threatens coastal buildings that are supported by shallow foundations Of pile fOLIndat-ions with insufficient ernbedr-net-lL. Beast -disaster investilgauions indicate diai'low-cost and st-nall erosion control structures offer no real protection to ero- sion -threatened buildings since they are easily overtopped or fail when exposed to severe coastal flooding. Without, substantial erosion control structures, foundations rnay be an- derrnined an([ buildings may collapse. iVith substantial erosion control structures in place, building foundations are less likely be Undern-tincd, but nearby buildings rnay be sub' 'JeCL to in creased diniao-e From wave runup and reflection. More lasung and less daniaging sol-LiLions to 20 Technical Bul I eTin 5 — auGuST 2008 hripending erosion daniaInge include landivard relocation of bUildings171 and widening and rail- ing beaches through m.)urishinera. Fences and privacy walls (I uCI Udin'p, walls separating one property froin another) rnay obstruct or divert flood flow and waves. Thev must be analvzed for then- effects oil flood conditions and the effects of debris generated 1)�; fence,/wall failure Burin- Hood events. For flood],jain njanagementpLLiT()scs, it can be preSLUned that ODCII fences (c.o,., good/plastic/metal slat fencing, ividi gencrous oL)emngs, et.c.) will not lead to harmful diversion -of I'loodwalers or wave runup and reflection. Fences with smaller opcnM(, i , and sold ferices and -v,%-alls, may be "S Prone to trappin- debris. Solid fences and privacy ivalls, and fences prone to trappiric, debris, mast be designed and coil- SIVIR-ted to Ell] Under base flood conditionsividlout cansinu d acent. NFTP-conipliani ,In liarm to a'i buildings. Where building or fire codes require ground level walls for tenant fire separations, elforts should be made tosatlsf�- code requirements while muntruzint, poterinal adverse effects due to flood diversion. Siting of new buildings tiem- existing fences or walls should be reviewed carefuliv, Figure 16 shows an example of a shore -perpendicular solid wall that failed durnig- a coastal flood event and darnaged die pile foundation of an adjacent elevated building. M NFIP regulations prohibit the Use Of ['111 fOF StIlICtIll'al stip- port of buildings In V zones, However, ininor grading and the placement ofannor quantities of fill, is allowed, but only Figure 16. Shore - perpendicular reinforced masonry wail failed and collapsed into the building, contributing to failure of the cornet, cap/beam. Non-structural fill described in this Technical Bulletin must be ignored for load calculation and foundation design purposes. Technical Bu I I eTin 5 — au GuST 2008 `? I lot- landscaping, drainage under and around buildings, and support of parking slabs, pool decks, patios. walkways, and sinillar site elements. Fill rnust not. prevent the free passalge of floo(hvaters and waves beneath elevated buildings. Fill nIL1,St not Cll%'Cl-t floodwaters or deflect waves such that increased clainage is sustained by adjacentFbv buildillo-s. or nea Given the difficuln., that rnauNT corninunibes and designers ha-vc had in determining whether the placement and shaping Of Il0rl-StrUCtU1UI fill will be. dernnienual, sorrie State and local regulations essentially prohibiL, placeinent. of any non-structur- al fill ill V zones. This approach rriay, itself lead to problems, such as ponding of rainfall around or under buildings. 0111- er States and corninuniLies rnav accept sonie (unspecified) a1­1101-lut Of 1101-1-StFUCtUt-al lilt, provided all engineerinic, analy- sis is perfornied and all engineer will ccrtiR, that the fill will not, lead to chunaglng e -arnping and de - flow diAr rsion or wave I Z flecLion. Given the state of engineering methods and rnodels, �D credible and defensible analvses are ali-nost impossible to per- forni for small CILl"Ill 66CS of fill. The following evaluation criteria are reconiniended for -deter- inining acceptable placement of non-structural fill ill N, ;,.ones. Note diat there are several criteria listed, and ii is possible that SOMC MAY be in conflict, depending on specific circUrn.sLances. The local official is expected to use discretion in such cases to achieve the desired perforrnance while giving deference to the general intent of these criteria. n Type of 11. Fill placed on V zone SiICS ShOLAId be sirnilar [,o natural soils in the area. In nianv coastal areas, this will he clean sand or sand), soils, free of large clUUTIMICS 0f'Cla-V, silt, and organic niaterial. Non-structural fill should riot I For floodplain management purposes, this Technical Bulletin describes ac- ceptable placements of non-structural fill in V zones, which can be assumed not to lead to damaging flood and wave conditions on a site or adjacent sites. "Minor grading" shall be that required or allowed by com- munity regulations, subject to the limitations described herein. "Minor quantities of fill" shall mean the minimum quan- tity required for: adequate drainage of areas be ow and around elevated build- ings; support of parking slabs, in -ground pool decks, patios, walkways, etc.; and for site landscaping, subject to the limitations described herein. cc)ntain large rocks and debris. If the fill Is similar to and compatible a\ith natural soils, there is no need for coninik-11-li-IiC5. LO.LcLqLllre designers to In- vestiLyate or certifv whether the fill has as tendencv I -or ­e\cessive natural coinIXICtion" (a in many floodplain reg)-Matrons). If the fill marcrial is trift similar to natural soils, its behavior under flood conditions should be similar to the behavior of natural soils, and should not be a subject of debate. n Height or elevation of 11 at building. Generally, it is unreasonable to expect that the ad- dition Of I (o 2 feet of site -compatible, non-,sLru.cLural fill in a V zone will lead tea adverse effects on buildings. Thus, placement of up to.2..feet of fill tinder or around an elevated buildin� can be aSSUined to be acceptal-le (Mthout, eiiOneerirlp- arialvsis of CCrtifiCatiOl-1) provided basic site drainage principles and vertical clearance liMitatiOrIS al-(' not violat- e (sec Wow); and provided there are no site -specific conditions or charactcrisbcs that �voulcl render- the placenletAL (-)('the fill as darnagirif'Y to NFIP-cornpliant. construction (e.g., il' local officials have obsei-e,ed the placenient of similar qUanutles of' suitable fill has led to building darria-c durino, coastal storrn events). If additional fill height Is proposed for a site, the proposed Final grade should be compared to local topography. If proposed 22 Technical Bul I eTin 5 — auGuST 2008 final fill configuration is similar to grades acid slopes in the iryinie(liatc vicirtit�:, a detailed analysis of'Llic, effects on flood flow and waves needriot, be required. If more than 2 feet of fill is proposed and the proposect fill configuration excee(ts local grade heights ancl varia- tions, an analysis must be per-forniecl. n Grading to prevent ponding. In adclition to reqUil-Cments to elevate bUildin(YS to or above the BFE, ITIOSt cornn,itinities have establislie(I inuninurn floor elevations ro ensure that wa- ter sloes riot Collect at or tinder buildings. The floor elevation requircuients frcqucluly are tied to nearbv road elevations and, ou low-lying or level parcels, the quantity- of fill reqU I Fe(L tea raise bt.liklilhy footprint areas ty 2-foot fill height allow- ance nientioned above, Even though these floor clevau'011 i-cquireirtents are impleineilLed across eubl-e J'UCiSChCtionS, there is no reason to autornaticallv assurrie that application in a V zone will be (letrimental- Even if habitable portions of a bUil(ling arc elevated to Sabsc- ' V floodplain trtanakl,,cnient requirements (Usually several feet above grade in most V zones), there is no compelling reason to restrict the PLICCulent of site-cornpatible nori-structural fill beneath those buildings if it will prevent ponding and/or saturated soil conditions, an(I as long as other drainage reqUirerrients fo,r- grades and slopes can be sansfie(l, n Site drainage requirements, Nlost corninUnitles halve: established rninin-iurn slopes for building sites to facilitate drainage away froin buildings (Lypicatly 5 percent [one unit. %!(-r-- Lical to 20 units horizontal]). Shallow slopes such as these will not lead to wave ramping, rLITIL11), or, (teflection. In(lee(l, nitich steeper slopes (gener-al1v one unit vertical to three units horizontal, or steeper) are required to enhance wave runup. For floodela.111 nian- a(,,emcriL jxirposes, site slopes shallower than one unit. VfftiUll to five units horizontal (regardless of fill height). are. asSUrriecl not to cause or worsen wave runup, or reflection cap able.-o[clarnaging acljaceni builcling-s. Figure 17 shows an example of' fill placernerit ID that is consdcicrccl acccptahtc; Hic fill hell -lit is nio(lestt arA the side slopes are (-Tcxitic. At- LhOUCIA-t air adjacent pi-e-FIR-NI building is lower, the pre-FLIZA1 building would likely susLair-1 SUFUCtUral (.lanial(lyc during a coastal floo(l, every if the rill was riot preseni. SwalCs and con- ventional site rlraiiia(,c practices should be usecl tra mitigate potential effects of' runoff fi-otu the fill area. Figure 17. Post - hurricane photo showing elevated building surrounded by gently sloping fill, with adjacent damaged pre -FIRM building (the presence and configuration of the fill were judged by the damage inspection team not to have led to flood or wave damage to the elevated building or the Technical Bul I eTin 5 — auGuST 2008 2 3 n Vertical clearance between top of 11 and the elevated lowest oor. RegardIcss of whether fill is Used for drain- age or landscaping put -poses, it should not be placed to an elevation that. hLLI_IeS arrV portion of the lowest floor systcm (i.e., bCMIIS, girders, trusses, orJoisLs supporting the walk- in sm-Cace of the floor). While the likelihood of'such fill le.actilIG, to S[rUct.ttral, dama-e is deenied to be small, it is considered good pracnc(. to provide sorne vertical clear- ance between the top of the fill and the botton-I of the lowest floor systern. This clearance will allow for sheet flow (such as that Caused bv waves overtopping a dune or barri- er) to a- beneath the Tlitro ,are na7 t­zrijijid-ifel rules as to what constimtes acceptable vertical cleara.11cc beat, for floodplain management purposes, a vertical clearance of 2 feet is considered ad- equate in most cases. n Compaction of 11. The NFIP regulations are very explicit - fill shall not be used for su-tic- tUral sLipporr, of buildings In V, zones. However, for floodptain nianagcnicnt purposes, cortmaction cif fill below and around clevaLect, btrildim:)s in order to SUDDOFt narkinL, slabs. m-gyround pool decks, patios, sidewalks, and similar site arneint.les is consistent xvith the in- tent of the rczttlations. n Mine construction, repair, or reconstruction. Dt,mcs arc MIUMAI features in manN2 coast- al areas, and they can erocle during storms and recover nati.traliv over time. The natural 1 7 recoNICIA., process can be accelerated I)v replacing the eroded dtinc with compatible sand, Plal-ItifIg dune: grasses, and installing sand fences, (see (,-Iiapter 5 of Roo-ers and Nash, 2003). fn -encral, these activities Should not be ccmsic1cred as (Ictrimcmal, even if part of the dune lies tender as building's footprint.. The addition of sand to restore a site Lo its pre-stolln '91'ades arid stabilization xvlLh (ILHIC vegetation will likely do more good than potential harrn in terms of flood damag-c rcductioii. Concerns .about placement of non - Structural, Structural, Clean sand under and arounct beaclifront. buildings should not be the basis for prohibiting dUne inalliterrance and construction, beach nom-Islinicin, or similar activities, Dune construction, repair, and reconstruction under or around an elevated building may he assurned to be acceptable (Wid-IOUtengineering analysis or certification) as long as: 1) the scale and location of the dune work is Consistent. With local beach -dune morphology, and 2) verrical clearance is maintained beta,veen the lop of' the clone and the building's floor- system, Note, however, this guidance is not intended to give license to violate the other limitations on use of fill where buildings are disLani fr,otri the shoreline and where clunes would not. othenvise occur riacuraliv. Tn some V zones, it. is not Uncommon to have ;round elevations at or- above the BFE, particu- larly along sliortlines avith well -developed dune fields. Having a inappcd V zotie with a RFF at OF bclok,�j gradc sccms COLIMC611LUiLiVe, IDUL it is possible because of taro N' zone mapping con- siderations; 24 Technical Bul I eTin 5 - auGu ST 2008 n Duric erosion. Dunes cari erode ClUrIn'g the base flood (or lesser floods), resulting in a substantial lowering of the pre-stornn grade to a lex-el below the rnapptd VjFF. The BFE is 11 mapped based oil surge and ��avcs passing over the lowered around SUrfaCe. I I n The presence of a primary frontal dune. Vzories are snapped to tyre inland extent (heel) of the PI-i III MT frontal clone. The BFE on the seaward face of the dune wl I I be exterided as a horizontal line from the seaward toe, through the dune teati-II-C, to the location of the heel, Having grade elevations at or above the BFE Illav COrnplicaLe, but does not ehuninate, the need to comply with V zone design and construction require vents. But this prompts -,I question: how does the free-of­obstruCU Oil reclUfferneilL apply in this Sit- uatiori: Because the soil at the site Ynay erode during a severe coastal flood event, the area Under the building i4i11 be ex- posed — this exposed area must be free ofoY)structions, Excavation to place the low- est floor at the BFE is not recommended, and may in fact violate the NFIP regula- tion not to alter sand dunes if such alteration increases potential flood hazards. The sarne free-ofobstruction considerations that apply to buildings clevat.ed far- above grade apply to clevated buildings where the lowest floors are at or near grade. The builclings niust, still be desi,(,;-ned and constructed on pile or column foundations that are. ernbedded deep into the 'CIround, and the bottoms of the lowest horizontal supporting members rust still be at or above the BFE. As rioted in the sc.ct.iori oil Fill, to 2-foot vertical CICaFMICC I)Ct-wCCII the bot- torn ol'ifie lowest horizontal supporting - niernYwr and the grovind is recorriniended. The soil around such buildings should be graded to, drain a,vawr a,,vay ['roll] the, f"OundaitOrls. )ne question that arises is whether vestroorri buildings or comfort staL'oiis can be treated d'['- I I fc,renLly than other i%lpcs ot'N' zone sti-LICtUIVS and he Co1ISt1_LICtCd below the BVE, particularly when those facilities are situated in public parks or recreation areas. The answer is no. These StIJXCLUI'C,S MUSt Meet the same V zone design and construction reels n_CHICIItS its Other build- i n gs. Post -disaster assessments show that buried septic systems and Moundd eseptic systems in. V ZOIACS 1`17C(ILteritly arc exposed and/or displaced. In addition to cornpI_O1ni.Sin0- their subse- quent use, damage to these systerns can release their contents. Septic systems frequently are destroyed it they are near the shoreline. Therefore, septic sysLenIs should be located Cilher outside areas subject to CFOSi011 during the base flood or, if placed in an area subje ct to ero s siri i nflict widi septicon, lwlox\, the depth of expectcd crosion. '['his lacteI , s IIAarion niav co I sysi.ein groundwater COTISideraLiOr.IS, in WhICII Case a .septic Systeri-i is not appropriate for the area. Sepic system tanks ryinst riot, he st'nicnirally all ached to building (oundations. Plumbing MId I he required, and these. Items are allowed in V zones. However, [)ILLinb- plplri�y connect ons wl I I I ing and piping cornponerits niusc not be attached to or pass th.1-OLIOD-11 breakaway ,vall panels. Technical Bul I eTin 5 — auGuST 2008 25 Mounded septic SN'SUCTIFIS can requtre significant volunics of fill, which, if placed Under or irn- inediawly adjacciu, to buildings, likelyaAdll constitute an ObSMIC6011 that, diverts flood flow and waves. Mounded sepric WSICIIIS rnay he allowed in V zones if then will not Nvorsen flood and wave conditions for the buildings they serve, or for other nearby buildings (see the dISCUSS1011 '7� in the section on Fill for guidance on evaltuttirig mounded systems near elevated buildings). An additional consideration forsepitic sysLenis HiVzones is addressed by Section 60.3(a) (6) (ii) of the NFIP red ;-ulations, which requires "on -site w7aste disposal systerns to be located to avoid itripairnient to them or contarninarion froni them clitrino- flooding." FEMA 348 prop. -ides acl- clitional guidance. MM1 M Tivo) priuiar�, considerations are related tea the placernent of swininling, pools acid spas under or adJacent, to buildings in V zones: n AVIiether the pool and,/or spa COTARIcruration is sul)' JecL to NFIP use limitations for enclosed areas under elevated buildings, and n Whether the pool or spa will lead to increased flood loads on buildings or- exacerbat.e scour and erosion near buildings. The NFIP perniits a swiminin ' g- pool of- spa to he placed be- ticath an clevatcA building only if the top of the pool/spa and accoinpanying deck or walkway are flush with the exist - Pools and spas are allowed adjacent to coastal build- ings only if these amenities will not act as obstruc- tions that lead to damage to nearby buildings. This ef- fectively means that most pools and spas must be in- stalled in -ground (either frangible or immovable), or completely elevated above the BFE. This constraint ap- plies where the ground level is below, at, or above the BFE. ing grade, and only if (lie space aFOUIIC1 the pool/spa reinairis unenclosed. However, SOJIIC states MId conirriurii ties inav prohibit restrict pools and spas heneath elevated buildings — designers should check with [hCJLIF1,SdICtIOII (-or anV additiOMII requircrueriLs. The NFTP limits the use of enclosures to parking of vehicles, building access, and storage. Because pools and spas are fir recreational use, 0-icy are not allowed to be enclosed, evert if enclosed by glass or- hrcaka,,vaywalls, I.Tse oflattice and insect screening around pools and spas is peurnitted. Registered design pre f.essiorials rrul.St cert.if�, to local officials thata pool or spa beneath or near a V zone building will not be subject to floLation or displacement that will dairlage build- ing Coundations dLIr_inI(.T a coastal flood. Figure 18 shows a, case where a spa was displaced and likely caused failure of two piles that supported pan. elevated deck. Pools, pool clerks, and kvalk- ways thatare placed under or adjacent t.ct coastal buildings irnist be SITIICHIF�LIIV Hidependent of the building and Its foundation. 26 Technical Bull eTin 5 — auGuST2008 Figure 18. Movement of a spa likely caused failure of two piles supporting an elevated deck. Itifl, M-11191 'The U.S. Congi,ess established the NFIP -,vith the passalge of the National Flood Insurance Act of 1968, Tli(--,, INFIP is as Federal prograrn enablil-10- prOperty owriers in participating corn- Inanities tar PLII-ChaSC. inSLII_aIlCC as protccl,ioll against flood losses, in exchan1ge for State and cornryninity floodplain inariagenient reo-Wa[ions that, redtice future flood damages. Par -tic Ipa- tion in the NFJ P is based oil an agrecluent betwecti connn tuni Lies and the Federal Government, If cornintinity adopts arid enCorces adequate floodplain rnanagerrient regulations, FENfAwlll make flood instirance available within the coinniUnity. Title f l caJ- the J'T, S (' o(Le offederal Regulations contains the NFIP ci-neria for floodplain man- agernent, inchiding, design and C011SMIC6011 standards fi..)r new and SUbsLandally iinproved bitildings located in SFFTAs idenfified oil the NFIP's Flood hisin-anco Rate Ntaps. FE-NfA eri- COUrages corninnn I ties Io adopt f I oodplal H [Mi I I a(YeRIC. I I L reo'nlatiol is that exceed dic In iiiiiilLl I I I NFIP criteria. As an insurance all.erlladVe to disaster assistance, the NFIP reduces the esca-lat- in(),- cosis of repairing daniage to bUildings and Llicir contents CaLISCd 1))000&S, This is one of"a series of'Technical Biffletins that FENNIA has produced to provide guidance COnce I'll I ng the building pel-forinance reclLtirements of the NFIR These requirements are con- tained in Title 44 cif` the U.S. Code cafe Fe Reo-lilations at Section 60.3. The btilletins are intended for LISe by State and local officials responsible for interpreting; and enforcing the re- qUit-CITIcnts in their floodplain n:iana1(_;ernen(, regLilat.lons and building codes, and by incillbers Of the deVelOptnel-11 COITIHILLFIILA�, such as de.Si(1JTl Professionals arid bUilders. Neiv bulletins, as well as LIP(laces of , a existing Bulletin',, are isstled perlodicalhs necessarN, The bUllCtillS (10 not n I Y create regulations; rather, they provide specific gnidance for coinplying NVIth the requirements of existing NFIP rCYLILIIIOIVS. Users of' the Technical BLilletnis who need additic_)nal guiclance I Technical Bu I I eTin 5 —a uGuST 2008 27 should contact their NFIP State Coordinator or the appropriate FENIA regional office. The User's Guide to Technical Bulletins (liLLp:,//"NNi�i,�,.f-cma.gov/pdf%fiti-ia"c)-itidcOl..I-)df) lists the bul- letins issued to date. The quickest and easiest wav to acquire copies of' FFNLk's Technical Bulletins is to dod=n- load them ft-orn the FEMA wef)site sh till). Technical Bulletins also tnay be ordered free of charge troin the FEMA Publications Vare- house I)v calling 1-800-480-2520, of by faxing a request to 301-362-5355, Mondav throu-h Friday between 8 ami. and 5 p.m.. EST. Please provide the FEMA pi-Iblication nUnIber, title, and quantity oaf each puhlicatiori requested, along ilk-ith your name, address, zip code, and day - nine telephone number. AEI-nLen requests may be also be submitted bN: mail to the f6llowino address: FEMA Publications P.O. Box 2012 jessup, AID 20794 The f'011wvino- sources provide Itirdier hil'orniation concerning Iree-ol-obstruction re(jLIIrC.- Merits. 'rican Society of, Civil En;7o-eei in-S, SLFLICUHal FAI-ineefilIg IuSlitllte. 2005. Flood Resistant Design and Construction, ASCEII/SEI 2-4-05. FENI' 1993. NFIP Technical Bulletin 4-93, Elevator Installation for Buildings in Special Flood Hazard Areas. FENLN. 1999. Protecting Building Utilities fi-on-I Flood Damage. FENIA 348. C� FE-I\.IA- 2003). Guidelines and Spec] cations for Flood Hazard Mapping Partners, Appendix D: Guid- ance for Coastal Flooding Analyses and Mappin-I FEMA. 2005. Coastal Construction Manual, FENIA 55(D edition). FEMA. 2005. Home Builde-Cs Guideto Coastal Construction: Technical Fact Shed Series, FENLN 499 FE1\4A. 2008. NFIP Technical Bulletin 2-08, Flood Darnage-Resistant Material Requirements for Buildings Located in Special Flood Hazard Areas. 8 Technical Sul I eTin 5 — auGuST 2008 FENLA. 2008. NFIPTechnical Bulletin 9-08, Design and Construction Guiclancefor BreakawayWalls Below Coastal Buildings. FEMA. 2008. Flood Insurance Manual. Rogers, S.M., jr. and D. Nash. 2003. The Dune Book. North Carolina Sea Grant Report SC,03-03. USA(.,',E, 2002. Coastal Engineering Manual. Accessory structure — AX structure that is on the same parcel of property as a principal struc- Lure, the use of'which is incidental LO the u,,,.,,c of they principal structure. Base ood —The flood havinga 1-percent chance ofbetna-equalcdorexceccled In any given near, commonly referred to as the "100-year flood." The base flood is the national standard Used by the and all Federal agencies for the PUrpOSCS 01"FC(IL111-Ing [11C PLU-chase of flood d �n insurance and regulating new development. Base ood elevation (BFE) — The heio,,-h[. of the base (I -percent annual cha]ICC Or I 00-year) flood in relation t.o the daturn spccified on the cominumi-y's flood hazard map, usually the Nadonal Geodetic Vertical Daturn of 1929 (NGIVD), or the North Anicrican Vertical Datum of'1988 (N.NVD). Coastal High Hazard Arca—An arcaof special flood hazard extending fi-om offshore to the inland limit ofa primary f-rontal dune alongmi opeii coast and high - velocity avave action from storms or seismic sources. Design ood elevation (DFE) — Elevation of the design flood, including c�lave effects, relative to the damin specified on a communit,y's flood hazard map. Enclosure or enclosed area — Areas created b\1 a crawlspace or solid walls that fully enclose areas below the BFE. Federal Emergency Management Agency (FEMA) — The Federal agency that, ill addition to carrvino- out other activities, administers the. National Flood Insurance Program. Flood 111SUrance Rate Map (FIRM) —The official map of'a C01_11111L.inity on which FENLA, has delineated both the special flood hazard areas (SFIfAs) and the risk PrCMILIM ZO11CS �IPPII_ cable t.o the conimunity, Flow diversion — Change in course of flood flow when it encounters an object or structure. Diversion can be accompanied by an increase in clue local flood level and./or flood velocitV when the block aue is large relative to the area thr-OLIgh Which the flOW WoUld (Aherwise pass. Technical Bul I aTin 5 — auGuST 2008 29 Hydrodynamic load — The load imposed oil all immersed object- such as a foundation element or enclosure c4all, b�. water flmvino- against and around it. The magnitude of the hv­ drodynarnic load vaiie,13 as a. function of'VeloCiLy and Other factors. Lowest oar — The lowest floor of the IONVeSL enclosed area of a building, including; a base- ment, Anv NFTP-comptiant unfinished or flood -resistant euCIOSLIVe usable SOleJV for parking of vehicles, building access, or storage (in all area other than a basemcriL) is not considered a building's lowest floor, provided the enclosure (toes not render the structure in violation of the applicable design re(JUH-CillenUS of the NFIR Mitigation Directorate —The component of'FENfA directly responsible for achninistering the flood hazard identification and floodplain rnanageineuL aspects of the NFIR Primary frontal dune — The PrInlary Frontal Dune is a continuous or nearly Coll till IIOLIS mound or ridge of'sand wlt.h relatively steep seaward and landward slopes iturnediatelv land- ward and adjacent to the beach and sul-)jest to erosion and overtopping from high tictes and Nvavcs dUrinICY 1114jor coastal storms. The landward limit of' the priinary frontal dune, also known as the toe or heel of -the. dune, occurs at as point where there is a distinct change Croni as I-Clativel): steep slope to a relativcly mild slope: The primary fronualdurte toe represents the tandivard extension of'Lhe Zone NT. coastal high hazard velocitv zone. Registered Design Professional — An individual who is registered or licensed to practice their respective design profession as defined by the statwory reqUIFenients of the professicmal registration lakes of State or Isdiction in ��:hich the project. is 0 J U I 'I i to be constructed. Special Flood Hazard Area (SFH A) — An area delineated on a Flood Insurance Raw Nlap as being subject to inundation b�! the base flood and dcsignat.cd as Zone A,AE, AI-A30, AR, AO, AT 1, A99, VI X`F, or VI N3 0 Substantial damage — Darnage of oriuin sustained by a SO-LICILIFe wlierebV the cost ofre- 'n 111) storinCT the structure to its before-danlao-ed condition mould equal or exceed 50 percent of the market value oft.he structure before the daniagc occurred. Structures that are determined to be suhstantlallv rLuuao-ed are considered to be substantial [I'll Provelnent's, re,(4-1-IiAless of the actual repair tvork performed Substantial improvement — Any reconstruction, rehabilitation, addition, or other Unprove- men[ ofastructure, the cost of which equals or exceeds 50 percent of the market value of'the structure (or Smaller percentage ifestahlished by the cornmunitv) before the "start of'con- .Stl_UCLIon" of' the improvement. This terns includes structures that have incurred "SUT)SI,1116A danlage," regardless of the actual repair N,%F-oFk perfori-ned. Wave re ect io n — Return or rech recilon of wa-ve striking an object. Wave runup — Rush of as vi,a\`e Lip .1 slope or SWUCLUr-c. 30 Technical Bul I eTin 5 - auGuST 2008