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Flood Hazard Study
°. g."° '��'��rs-,fag e��_s���.� s see '�a�'r '��' x %�a`.� a•:.''%��,."� .�` � �. g•' � -g� ...-�,. €��' �a 'e._�, g �`r,1 , �4g, �, �� - f e��F-ax r s�� .^g' gg''�n••. ��sP�ga z� gg��sggs�-,�z�a�s�b%"a "'aa�-.:'g� �. g°� %�;8���'..�° '��f °a:y � 'fie '.fig' � %� �' l ' a �;,._' H-,= �« % g 9 ai t a S x a MA ' - - g a'5" ON, g gg Y s a zsa v x a a - OP", ": ....... g gak e t„s e;` g as sa g6 g as ra"a g- a AN 'a 6 MOM Kills x g ue g g a ~a gz it.• e pit € q e 4 ark tq- 3 gW"gg gaag g aag ix ® rsai+ :gI 055MASM 9¢r �I � I g.. aae '.as. s. a a % a e gg ag re a aag -. gy a"�s -xga a�?"•,-- g� a r$ ¢ g, a' >e- a a 3 €:. s t at r• y .,, y.;,a x 1 ia' at• 9 . .�Qsr g � % g;.s� �a-.:g � � .;�,�a g �3g.g k°>s'g g ,g g "§ '�;� � �. �; �•� s gsa-^ - t _ w -,a e� a aag a�z-a�ga�ss z�.g�p� �S� �b_ �� �a � � � g � Sa ��$ '�e ��• - ; 1 CALIF. tllll1�41#G;f;t?;�r_ . 30 1,17 1h Ali 1 1 1 •- 1 1 CITY OF HUNTINGTON BEACH CITY COUNCIL ALVIN M.Coen,Mayor NORMA BRANDEL GIBBS, Vice-Mayor TED W. BARTLETT, HENRY H. DUKE, JERRY A.MATNEY, DONALD D.SHIPLEY, HARRIETT WIEDER DAVID D. ROWLANDS, City Administrator PLANNING COMMISSION EDWARD H. KERINS,Chairman FRANK P. HIGGINS,Vice-Chairman ROBERT D. BAZIL, JOSEPH P.BOYLE, WILLIAM J.GEIGER, , MARCUS M.PORTER, KATHERINE L.WALLIN, RICHARD A. HARLOW, Secretary 1 CITV OF HUNTINGTONBEACH INTER-DEPARTMENT COMMUNICATION HUWNG"LEACH To All Department Heads From Ed Selich, 'Planning Dept. Subject RECENT PLANNING DEPARTMENT Date May 10, 1974 REPORTS Enclosed are copies of three recent Planning Department reports: Policy Plan, Final Report, Geotechnical Inputs Report; and Flood Hazard Study. These are being sent to you for your Departments' , . use and information. If for any reason you require additional copies please contact the Planning Department. We hope you find these reports of some use. • j EDS:mc I 1 3 i 1 , FLOOD HAZARD STUDY APRIL 1974 At"a :. 0 huntington beach planning department FLOOD HAZARD STUDY TABLE OF CONTENTS 1. 0 INTRODUC`1'ION 1 1. 1 Intent 1 1. 2 Seismic-Safety Element 2 2 . 0 FLOOD POTENTIAL 3 2. 1 Santa Ana River Flood Plain 3 2 .2 historic Floods 4 2. 3 Flood Projections G 3. 0 CONTROL MEASURES 15 3. 1 Corps of Engineers 15 3. 2 orange County Flood Control District 17 3. 3 Huntington Beach Public Works 18 4. 0 LAND USE HAZARDS 21 4 .1 Special Flood hazard Area 21 4. 2 Standard Project Flood 22 5. 0 aAZARD ABATEMENT 31 5. 1 Disaster Plans 31 5. 2 Flood Insurance 35 5. 3 Land Use Controls 38 1 1 1 1 1 Section 1 introduction 1 .0 INTRODUCTION Water is a vital element in the survival of man and his society; but water uncontrolled by natural processes or human works can be one of the earth' s most destructive forces. Situated on a low- lying plain and bounded by the Santa Ana River, this potential water hazard should be of major concern to the City of Huntington Beach. 1. 1 Intent 1 The degree of threat faced by the City from flood hazard is the subject of this report. Drainage and flooding have always posed problems for the community. In fact, only 100 years ago much of the area below the bluffs was marshland. And in the east side of the City, the Santa Ana River Channel is at a higher level than the surrounding drainage areas. It is the purpose of this document to compile what is known about actual flood potential in the City, to identify existing control measures, examine land use hazards, and investigate hazard abatement alternatives. 1 L 1 i 1 . 2 Seismic-Safety Element This Flood Hazard Study is a background report for the City' s co,abined Seisiaic-Safety Element of the General Plan. Along with Geotechnical Inputs and a special fire hazard study, this report will supply a data base for development of a comprehensive plan for co<<uuunity safety. The subject of seismic and public safety is a highly complicated one. In like manner , development of comprehensive seismic and safety plans requires not only the skills of the planner but many technical specialists , as well. To insure that the Element is prepared with an in-depth understanding of the natural hazards that confront the community, the City will rely on a five-member interdisciplinary team to supervise all safety planning activities. Representing Planning, Building and Safety, Public Works, fire, and Civil Defense Departments , the team will consist of two registered civil engineers , a fire marshall, a civil defense coordinator, and a planner. Coordinated by the Planning Department, the team will be responsible for reviewing and/or conducting the research, site investigation, inspection, plan formulation and ordinance proposals necessary to complete the Seismic-Safety Element. Pertinent General Plan laws and element guidelines developed by the � uncil on Intergovernmental Relations are presented in the Appendix. Section 2 flood potential 1 / 2. 0 FLOOD POTENTIAL of first concern is actual flood potential; that is, how much danger does the City face. And to present an overview of the problem, the following pages examine the Santa Ana River, historic 1 floods, and current flood projections. 2. 1 Santa Ana River Flood Plain The Santa Ana River originates near the summit of Mt. San Gorgorio 1 in the San iernardino Mountains at an elevation of over 8, 000 feet. Its 90-mile course drains both the San Bernardino and Santa Ana ranges; and 27 miles of the river course flow through Orange County to the sea. The 3,200 square mile Santa Ana River watershed is illustrated in Figure 2-1. The Santa Ana was once the largest river in Southern California, and flow through Orange County was perennial. With construction of Prado Dam in Riverside County, increasing upstream usage, and development of settling basins, the river is dry most of the year riow. Seasonal flows -- mostly storm runoff which deteriorates in quality as it approaches the ocean -- are used for irrigation, for 1 recharging the underground water basin, and thereby for domestic water. 3 1 1 F� aS V /1T 1! � - ((11 CHINO y,;` v`�'yr•�'� wAry +���W ir. �.,' �:1• l�:n�' 's'�+�j1,:•!�I' �p�d-'k .N Source : Physical Environment of s,...M Orange County 1 f FIGURE 2-1 SANTA ANA RIVER WATE RSHED huntington beach planning department 'The river has not maintained its present course through time. In fact, it rambled over the County cutting through sedimentary deposits gradually uplifted along the Newport-Inglewood Structural Zone thus forming the mesas and gaps of Huntington Beach.l It is within the last 9, 000 years that the Santa Ana River abandoned its previous course through Bolsa Chica and became established close to its present location in the Santa Ana Gap. More recent altera- tions in the river' s path are responsible for carving out the cliffs of Upper Newport Bay and depositing the sands of the Newport- Balboa Peninsula. Water flow was contained in 1940 with completion of Prado Dam and channelization of the river. Through Orange County, only one third of the river course is natural canyon while the remainder -- including that bordering Huntington Beach -- is leveed, sand bottom channel. From the mouth of the Santa Ana Canyon, the topography adjoining the river slopes gently toward the sea with few interruptions by hills or mesas. This character is also reflected in the topography of duntington Beach where only two mesa areas disrupt the steady slope of the land toward the ocean. Figure 2-2 depicts elevations within the Huntington Beach Planning Area and illustrates that a considerable portion of the community is less than ten feet above sea level . Some areas are, in fact, below sea level; and eastern portions of the City are lower than the Santa Ana River channel. 2. 2 Historic Floods The gentle topography of Orange County and the vastness of the three-County Santa Ana River watershed have combined on numerous occasions to spawn disastrous floods which ravaged farmlands, swept away structures, and eroded stream banks. The earliest of these recorded events was 1810, and in 1825, the rampaging Santa Ana changed its course, raging through Newport Bay with gravel and sand to form what is now Balboa Peninsula. Storms in 1862 accounted for a peak flow of 320,000 cubic feet per second in the upper river and created an inland sea in Orange County. Lasting about three weeks with water standing four feet deep up to four miles from the river, this disaster almost equalled a 200-year or worst possible flood. Again in 1884, the river cut a new channel; and serious flooding occurred in 1889, too. r 1 Geotechnical Inputs, Leighton-Yen and Associates, September 28, 1973 , p. 12. r 5 r 1916 witnessed the worst flooding of this century as the river ran wild through most of western Orange County causing a half million dollars in damage and four deaths. Other floods were recorded i.n 1925 and 1937 , but they did not match the flooding disaster_ in 1938 when an eight-foot wall of water swept out of the Santa Ana Canyon leaving 19 dead. Flows in the Santa Ana River measured 100 , 000 cubic feet per second. Most recently, the twin floods of 1969 resulted in $21 million in damages and five deaths. Peak velocities above Prado Dam reached 77, 000 cubic feet per second and 6 , 000 cubic feet per second below the dam. Only emergency sandbagging efforts, however, kept the river in its channel as it approached Huntington teach and the- ocean. 2. 3 Flood Projections Though more recent floods have not been as severe as earlier ones, damage has increased. This is a natural result of continued devel- opment in the affected area. First, as open spaces are replaced by population, flood waters can do more damage; and secondly, as ground cover and watershed are paved and urbanization spreads, rainwater can no longer filter into the soils but gathers as run- off and must be collected and redistributed thus adding to the burden of natural drainage systems. These factors are a prime reason the Army Corps of Engineers has concluded that chances for a devastating flood in Orange County are greater than ever. "With today' s development of the watershed, the Standard Project Flood, a flood magnitude frequently used for design of urban flood control improvements would, with the present reservoir capacity, result in large, uncontrolled spillway flows that would breach the Santa Ana River levees near Anaheim and flood about 100, 000 acres in the Orange County urbanized flood plain, Total damages to homes, businesses, industries, transportation, work lost, and other economic entities would be an estimated $2 ,200, 000, 000 under 1973 conditions of development. As time goes on, this amount would increase due to more intense development in the flood plain, further upstream urbanization, and shrinking reservoir capacity. The existing level of protection is such that the odds are about 1 in 70 each season on uncontrolled flows going over Prado Dam spillway, and about 1 in 35 for the Santa Ana River channel capacity being overtaxed in spills from Prado Reservoir or by tributary drainage in the urban areas of Santa Ana, Fountain Valley, Costa Mesa, or Huntington Beach. "2 2 Alternative Proposals for Flood Control and Allied Purposes, Army Corps of Engineers, May, 1973, P. 3 . --- `. . !q•LO fiE0 14 BF =OVER 100 FEET p �leL !^, "ems t„ ♦ 75-100 FT .i \>``,: :'i:♦ pP o ®50-75 FT. 25-50 FT. M 15-2 5 FT. 2 w. O IS FT. Go 5 E� M1 P s M O- 5 FT. t c P ................... : ................ BELOW O FT. ....................... 4 E0. P 1 0 O T P_ P ...................... ..._... .'J. 9 - I ............. ............: ............. : C ti } Y 9 �4: l II .r.c i- 1. :t •:\' P Y:} - b C IIIf t'`t X. I 4•• ER' P 7 I I:r.:� I � •:}•gr•:•}?::•}:?fir:{:}::??'1 `vr=,: '%.'�� - p. fit•,.;::::•:.::�::::;:.I r ' :`�I I ,I I i 'a ' ..•t;.;-�`� ,��' �� • ' :3y*::•' '.:li I III � I II. r 2�^'` `-'r. ''�v'��.}. �` "'.'^ {.'�� ,ko i a3. }vr I o.L }�ti I I l I y. { rl `I a I t" $;: iE`i?i?�w-i,•:`• I `TII k`*.�..: �'\. U`2=,. vi r. '•�•. 'S• �v. ^� ''�',�' _- .q '; 'c- _ �i:" 1'W'` •t,ham t, \ .} `1.�,�`a �L r I � I I ..�''� I I I I III - ;.r:•:�;, ,�; ;.t{: P I I� t IL I I y� I �1 I I � � - 4T I I I I I II I I�I I I I it I I I i I I I' � I I I I I i I I I II s, 4 III I I I fi.lI III I I I� :✓ 1 I t� I r"I'I I . 'II 'I I I ✓�- I I I 'I I. .......;.::. I ,I,III IIIIILI ,',I''��'•.�:: .. ,,��:zw ,l ';�,.�,11,�'s,—;:I: ,li�, I':� il. �I I I , rl 1111. � tlr fit• - -= t I „i; plll�• "I :�= ,,A;�y Tp,w,:��':�^ `s I,I „1 I.0' I;;III liii' II '*k I ��� I ill �I�, 'I '.r, II..I�� .'I• 4:� - ���.#ar`-.a. ,::m" I I� �I I I I .I �.;i� •I 'I I ' �I�` � �'�' •�ri' i�,II I.II Ili I � I IIII .I R� l I � I I _ I I, I I I �• r' _ �IIi +tb, I 'I I t' I �I''II, '•�.III II Aarlc •- 1 r fn1111 SOURCE-8 PLANNING 9-1-73 Figure 2-1 BEACH CALIFORNIA PLANNING DEPARTMENT TOPOGRAPHY:RELIEF BY ELEVATION PLANNI 'tia to- WATER LEVEL (STD PROJECT FLOOD) �>� Y — CITY BOUNDARY _ �`� 25 ELEVATION Fjiq FLOOD PLAIN T a �R X 4 ,. WNW- AT, .'marti p a s �, Jr w - t err � .� �A�. �. :*�w b�9 #Ta. >'r-II'gyp* . '_ v a '.,, P^,� 9-4 NOW � � �w -` are 7, 0ITS r. � __ IN Wx ,#, ' s '4� ,, _-s ' .-- t � %� --•�` �aRee'. �,d " a " �E ` �r tt�n ter# fSs+�:r F'k � g: ,"'' ems i ^> tie i tic � -- �'mxJs'ktp �a�i erA� ==�A_-r_y - �+ .{ - ,�' �,p- _ 't. , - ) YE .�` \i - _ - - `W*,,,1E�'f Cj� — .. _ -s.. Yam , SOURCE S.ARMY CORPS OF ENGINEERS 9-1-1973 HUNTINGTON BEACH CALIFORNIA FLOOD PLAINS PLANNING DEPARTMENT s In a 200-year flood, water would stand two to seven feet deep over 156 square miles, and about 300, 000 homes would be destroyed. . Figure 2-3 depicts the extent of such a standard project flood. Even a flood of lesser magnitude would cause considerable damage. As defined by the Army Corps of Engineers, a 100-year or "inter- mediate regional" flood would inundate 27,000 acres south of the Garden Grove Freeway including parts of Santa Ana, Fountain Valley, Costa Mesa, and Huntington Beach causing $330 million in damages. Tne 100-year flood is the minimum criteria for flood safety set by the Federal Insurance Administration, and in 1971 the Corps of Engineers delineated the limits of such a flood specifically for the City of Huntington Beach. 3 As shown in Figure 2-4, areas subject to flooding are depicted by specific reaches. (The reach number refers to the specific reach of stream for which the eleva- tion-frequency characteristics are similar. ) The frequency of flood stages was developed from historical data and hydrologic studies by the Corps of Engineers modified to allow for the effect of existing drainage systems and obstructions such as block walls, elevated freeways, and debris. The elevation-frequency zones identified within the City and a summary of flood data for each zone is presented below. FIGURE 2-5 • ELEVATION-FREQUENCY DATA4 Recurrence Zone & Zone & Zone & Interval in Reach Reach Reach Years Al A2 B3 Elevation Elevation Depth 10 25 6. 0 10. 0 . 5 50 9 . 0 13 . 0 1. G 100 (Base Flood) 9. 0 13. 5 1 .5 500 9 . 0 14. 0 2. 5 FEET DIFFERENCE 10 & 100 years** 5. 0 5. 5 1. 5 *Lesser flows carried by flood control channels, streets, and storm drains **Due to the presence of below ground drains, the difference given is a synthetic value suitable for flood insurance rates. 3 Flood Insurance Study, Los Angeles District, Corps of .Engineers, December, 1971. 4 Flood Insurance Study, Los les District, Corps of E•'ngineers, December, 1971, p. 3. 9 Flood zones were delineated by determining overflow limits for a specific flood and extending the zone to the next higher identifi- able line (i.e. , street or city boundary) . The zone designations, defined below, are in accordance with Federal Insurance Administra- tion criteria: 5 (1) Zone A. This zone is utilized where the land is subject to floodflows up to and including the base flood (100-year- frequency flood) and when sufficient data are available to calculate a reasonably accurate flood profile. (2) Zone B. This zone is utilized where an area is not subject to flooding from the base flood, but would be flooded by greater floodflows. it is also utilized for areas that are subject to sheet flooding from the base flood and lesser floodflows. (3) Zone V. This zone is equivalent to Zone A except that high velocity flows or wave action are present which would cause greater damages than a similar Zone A. (4) Zone D. This zone is utilized where flooding is a distinct possibility; however, either detailed information such as suitable topography is lacking or time available was insuffi- cient for the detailed studies required for development of adequate flood profiles. Some hydraulic calculations are made to insure that the area would be subject to flooding. In this report, Zone Dl was used for coastal areas and Zone D2 was used in local depression areas. (5) Zone C . This zone contains the remainder of the study area not included in the above listed zones and has a very low average flood damage potential. Many of the. streets and intersections would be flooded by the base flood (100 year- frequency flood) and it would be possible for some places to experience minor flood damage. However, the majority of the area would be free from damaging floods. The time and cost to single out the few points of possible damage are beyond the scope of this study. It is considered that the minimum rate would take care of the few minor damages that may occur. (6) Zone P. In combination with any above zone refers to potential mudslide activity. 5 Flood Insurance Study, Los Angeles District, Corps of Engineers, December, 1971, pp. 4-5. lU v -}:?•J}..�:::ter.::�. ... ...:.:. }. :x���r - :: c:{:: ::;:w t:y.:s� .:;};}:;:?f} : r r{'`'r{:, •: :.L.:: :<,;::vr y;::c,�-••.•�:�:-rt••;'-;:� :1r�:��•k�:�:�•. 4 t4 .r b'.v:•:r. .t .4 1 kM ........:.:. ::........:.;::•:.}'i:.;{:::J::v:::riff v .4 }}.�y'•:f•,;}..?•ems X - n }'${::=5}`v''ir'Y' fl �':'JYCi{•: •':iti:��.���i''.}}}•r};.;•: ..•'i(?::-:{}.i?V"h.',}'�`i��•.'C;:r-:fJi.• };:+s3ir}:' ^i:;i'�}::: :.:.. •. .{�. i F {.5.: i7LN51Y1 - i • • • � Section 3 cont rol measures. r r r r r 3. 0 CONTROL MEASURES Over the years an extensive flood control system has been developed throughout the Santa Ana River watershed. However, as presented in Section 2. 0 unpredicted development in the flood plain and decreased capacity of older projects leave the City -- and all of Orange County -- inadequately protected. 3.1 Corps of Engineers Figure 3-1 diagrams the flood control system developed by the Army Corps of hngineers to capture flood flows in the watershed and direct them safely through developed areas. One of the major control facilities in the Santa Ana River Basin is Prado Reservoir in Riverside County. Completed in 1941, the darn and reservoir were designed in the 1930' s to control floods expected to occur under anticipated future development of the watershed. Originally, this facility had a storage capacity to spillway crest (543 feet) of 223,000 acre-feet. Capacity has diminished 11 percent over the past 30 years due to sediment deposit. Current capacity is 198, 000 acre-feet and total reservoir 15 \ 1 0 S 10 SCALE MILS z4% RIVER v 0 / /l• p I 1 1 \ I ��..; SAN HERNAROIN6 I PCNt;•1A ` r O�TARIO - !'7 SAN_RERNI RCIN0 CO. ANERSIDE _CO^ LG RN ERSIDE one -� `\ ��� V `��1� 1 a-" i ("--- -� \ �' ,1r iW.. ,nf,•dai,q i�L �I'l�� 1�� \ - MARCH SOBloss r + R\vER f t v��s � \ �� moo,•! � � SOS* 0�0 L41Q MATHEWS RESERVOIR oL/�u' �� F F � 'A / �L + SANTA 4NA \� R I 7C �SC •....4 I , / / •;��I� inl� \ I, fir.�C^l A'II \ - r 1 CAN7JH i nKc'LAKE b� SEI E n,Ni NG1Oh` �- N J4CIN'O � 1 \ �.. 1ELSINOR L�" SEAL. / ` 1., ` NE WPC:r %% HENET ACH AN i_• I RIVER..^.IDE ,,1p •1�� 'I 1 JUAN / ^M 4 ,r'f '�C.•tl7 A�rAPI,TRAND SAN DIE60 l\ '^'1r,, r LEGEND F J 8CU OARY OF DRAINAGE AREA q �+ © EXISTING RESERVOIR 2 >f CONSIDERED RESERVOIR �ll FLOOD CONTROL DAM, PROPOSED d DEBRIS BASIN, PROPOSED ■N1Hf2CHANNEL UNDER CONSIDERATIM LEVEE UNDER CONSIDERATION CNAPNEL-CONSTRUCTED OR CONSTRUCTION IN PROGRESS LEVEE-CONSTRUCTED 1111 1 =CHANNEL-CONSTRUCTION NOT YET STARTED FIGURE 3-1 \�: CORPS OF, ENGINEERS FLOOD h \ma`s`•. \�� a CONTROL SYSTEM huntington beach planning department area is about 9 , 741 acres. 6 Though designed to contain a standard project flood, the reservoir (and the downstream river facilities) were barely able to contain the 35-year floods which occurred in 1969. Using more reliable analysis methodology and reflecting the intensive urbanization of the drainage area, the Corps concluded in 1973 "that neither Prado Reservoir nor the Santa Ana River downstream could contain the large floods . . . "7 expected to occur. Several proposals have been made by the Corps of Engineers to make the Santa Ana River Basin "flood safe" . A short-range plan would raise Prado Dam ten to 12 feet and rebuild the spillway to avert "wash outs" . While expense would be limited, disaster potential during very large floods would be generally unaffected. Another proposal calls for great enlargement of Prado Reservoir and some widening of downstream channels. This proposal would provide for the standard project flood and cost about $33, 000, 000. However, an additional 6 , 000 acres would be inundated behind the dam in Riverside County; and homes and dairies would be displaced. Other proposals outline widening the downstream channel 300 feet from Imperial Highway to the San Diego Freeway and 500 feet from there to the ocean. Such projects would require reconstruction of 35 bridges and condemn 3, 210 homes. A final plan, and one that appears most acceptable to the three Counties involved -- San Bernardino, Riverside, and Orange -- is a compromise among several individual proposals. It projects some enlargement of Prado Reservoir, some widening of the lower channel (200 feet from the San Diego Freeway to the ocean) and eventual construction of a new dam in San Bernardino County. The Mentone Dam would be 3. 5 miles long, 300 feet high, with a storage capacity of 200, 000 acre-feet. Total cost of the entire project would be $374 million, most of which would be covered by federal funds . Construction could begin in 1980, and completion would take eight to ten years. This proposal has been approved by both Orange and San Bernardino Counties. Before the design stage can begin, however, . the plan must also be acceptable to Riverside County. 3 .2 Orange County Flood Control District The Orange County Flood Control District owns 408 acres in fee and has easements on 20 acres of flood control channels in Huntington Beach which provide storm drainage for the City and inland areas. 6 Alternative Pro osals for Flood Control and Allied Purposes, ' Army Corps ot Engineers, May, 1973, p. 2. 7 Alternative Proposals for Flood Control and Allied Puri2oses, Army Corps of Engineers, ;Wtx 973, p. 3. 17 Judging the current flood control network (illustrated in Figure 3-2) inadequate and unwilling to wait the 20 or more years required to complete planned Corps of Engineers project, the District has ei,ibarked on a 3-year interim program to increase protection for downstream areas. 'rile brunt of this $8 million project will affect the Santa Ana River whose current capacity of 35, 000 cubic feet per second is far below the 150, 000 cubic feet per second required to hold a 200-year storm. Though achieving such maximum capacity is impossible at this time, the District hopes to reinforce the river enough to contain a 75-year storm. Last year a $1 million project to line the river channel upstream between the San Diego Freeway and First Street was completed. In June, the program will be continued downstream from the freeway to Garfield with $1 . 6 million budgeted to strengthen and cement the channel. The remaining portion of the river (through Huntington Beach) will be improved in subsequent years. The County Flood Control District is also improving its facilities in the Adams and Yorktown area -- a project that will cost more Lia,i one million dollars. 3. 3 Huntington Beach Public Works The City owns over 20 acres of flood control channels as indicated on Figure 3-2. 14o special additional projects are planned at this I 18 i ftR F �P COUNTY PERMANENT CHANNELS COUNTY PERMANENT UNDERGROUND CHANNEL CITY CHANNEL y��tt ♦ CmUsEu HANNEL F NW* MCUK COASS SOURCE;N B PLANNING 9-1-73 m Figure 3-2 HUNTINGTON 8154CH CaLIFORNIA FLOOD CONTROL CHANNELS PLANNING DEPARTMENT Section 4 land use ha rds 4 .0 LAND USE HAZARDS While it i2 the role of the Seismic-Safety Element to specifically designate lance use hazards, this section presents a reliminar identification of possible land use problems and flood damages to the City. 4.1 Special Flood Hazard Area Within the special flood hazard area -- which would be inundated by the 100-year flood (Figure 2-4) -- damage would be incurred by government, public, and private structures. Of first concern are goverrunent facilities vital to the continuation of comulunity life. Flooding in the special hazard area would jeopardize the sewage treatment plant, two fire stations, two r major highways (Pacific Coast Highway and Beach Boulevardl , one high school, and thirteen elementary schools of the Fountain Valley and Huntington Beach School Districts. Additionally, there are three proposed school sites and 22 existing and proposed park and recreation areas in the danger zone. r ACOL 21 ARM Public facilities (privately-owned but operated for public use) endangered include the Edison Plant, major utility corridors, and several neighborhood and community commercial areas. Because private uses predominate in the hazard zone, damage in the 100-year flood would be suffered primarily by residential units. Much of the vicinity is single-family construction; but there are several high-density condominium projects and mobile home parks as well as some apartment complexes. 4 .2 Standard Project Flood tis depicted in Figure 2-3, a standard project or 200-year flood would cause significant damage to most of the City. Except for those located on the mesa areas, almost all government, public, and private structures and facilities would be affected by flood waters. In July, 1973, an estimate of this potential flood damage was prepared by the City' s Civil Defense Office and excerpts from this study follow. 8 "Water damage is the principal item resulting from a flood that can be estimated and cost figures are based on estimated loss, repair and renovation of facilities in the flooded area. it is estimated that all commercial and industrial facilities would be incapacitated partially or totally for a period of one to four weeks. "The ;aajority of the residents in the flooded areas of Huntington 1 Beach would be left homeless for at least a month and in some cases, much longer. Loss of life should be minimal with sufficient advance notice. All telephone communications, electricity, gas and water in the flooded areas would be disrupted. Helicopters and boats would be the only means of access to flooded areas. Food could be transported from other locations into the city. 1 "Disruption of schools in the flooded areas would present a major problem that can only be solved by outside classroom instruction. Damage to schools used as Red Cross Evacuation Centers cannot be estimated but would probably be considerable. " 1 Figure 4-1 presents a summary of estimated damage costs resulting from flooding and the following paragraphs detail more specific cost factors by use and by area. 1 8 "Potential Results of a Major Flood" , Office of Civil Defense, Huntington Beach, July, 1973. 1 22 Adftk Inp 4 • FIGURE 4-1 ESTIMATED DOLLAR DAMAGES RESULTING FROM FLOODING Streets------------------------------------------- $ 13,493,332 • Street Lighting----------------------------------- 10, 000 Traffic Signals----------------------------------- 945,000 Water--------------------------------------------- 4 ,125,000 • Street Trees and L" andscaping---------------------- 1,825,000 Parks--------------------------------------------- 12,300,000 Block Walls---------------- 2,125,000 • Sewers and Storm Drains--------------------------- 9,160, 000 Public Buildings---------------------------------- 5,000,000 Agric,-, itural Land--------------------------------- 847,000 • Single and Multiple Family Residences------------- 443,800,000 Sales Tax Revenue--------------------------------- 470,000 Southern California Gas Company Services---------- 750,000 • Telephone Communications-------------------------- 21,500,000 Edison Electric Company--------------------------- 3,000, 000 Schools------------------------------------------- Ocean View School District------------------- 900, 000 Fountain Valley School District-------------- 2,100, 000 Huntington Beach High School District-------- 7,518r000 TOTAL $519,308,332 Aft 23 I STREETS Street physical facilities such as sidewalks, curbs, gutters, and 1 paving will be affected primarily by silt and debris deposits requiring extensive cleanup. It is estimated an average depth of six inches of material will have to be removed from 150 miles of streets in each area. Last of Beach Blvd. 1 733 ,333 cubic yards @$2 . 00 $1,466,666 West of Beach Blvd. 733 , 333 cubic yards @$2 . 00 1, 466,666 The east of Beach area would experience destruction of 1 approximately 50 miles of streets costing $10,560,00.0 to replace. Total Streets $13 ,493 ,332 STRELT LIGHTING 1 The majority of street lighting within the City is property of Southern California Edison Company. City owned lighting west of Beach would be affected only in cleanup of pull boxes, blown lamps,, and repair of any connections failing under water satura- tion. 1 Total Street Lighting $ 10 ,000 TRAFFIC SIGNALS Huntington Beach presently has 29 traffic signals east of Beach 1 and 34 west of Beach. A traffic controller under water subject to silt and corrosion would be a complete loss and cost $15,000 each to replace. Flooding east of Beach will also destroy 10 intersections for a replacement cost of $40,000 each. 1 East of Beach Blvd. $435, 000 West of Beach Blvd. 510, 000 Total $9A5,00.0 1 WATER Damage to water systems is estimated to require .a general cleanup of well and reservoir sites and meter settings; together with_ 1 flushing and re-chlorinating all lines due to safety needs after 24 Adft I lip all backflow devices have been under water. General cleanup for each area is estimated to cost $125,000. It is estimated 50 miles of water systems will be destroyed and replacement will cost 44,000,000 . .East of Beach Blvd. $4 ,000,000 West of Leach Blvd. 125,000 Total $4 ,125,000 STREET TREES AND LANDSCAPING The City has approximately 7,500 street trees in the east of Beach- area and 13 ,500 in area west of Beach which suffer approximately one-third mortality due to being under water. Each replacement is estimated to cost $150. East of ;Leach "Blvd. $ 750,000 West of Beach Blvd. 675,000 All landscaping will be destroyed east and west of Beach and is estimated to cost $200,000 for each area. 'ASt of Beach Blvd. $ 200,000 West of Beach Blvd. 200,000 Total Street Trees and Landscaping $1,825,000 PARKS All parks will be virtually destroyed by submersion except for a few trees which may survive. 110 acres of parks lie east of Beach and 300 acres of parks are located west of Beach which will cost $30,000 per acre to clean and replace. Last of Beach Blvd. $3,300,000 West of Beach Blvd. 9,000,000 Total $12,300, 000 b1LUCK WALLS An estimated 100 miles of block walls will be severely damaged and require replacement at a cost of $40,000 per mile. / 25 elm 1 Last of Beach Blvd. $2 ,000, 000 West of beach Blvd. 125, 000 1 Total $2 , 125, 000 SEWLRS AND STORM DRAINS Cleanup, clearing of pipes and repair and replacement of pumping 1 facilities will cost: East of Beach Bivd. $8 ,500 ,000 West of Beach Blvd. 660, 000 1 Total $ 9, 160, 000 PUBLIC BUILDIAGS Public building damages will occur to an estimated $25,000,000 worth of structures which include recreation centers, fire stations, / pump stations, reservoirs, restroom facilities and others. The cleanup costs are estimated to be 20% of the building costs. East of Beach Blvd. $2 , 000, 000 West of Beach Blvd. 3, 000,000 1 Total $ 5 ,000, 000 SUMMARY OF COSTS TO PUBLIC FACILITIES East of Beach Blvd. $22, 656,666 1 West of Beach Blvd. 15,766, 666 Total City Owned Public Facilities $38,423,332 AGRICULTURAL LAND / Potential agricultural loss in a standard project flood is estimated to be a total of $847, 000. This is based on the 800 acres on the flood plain that are in production. This total is potential loss of value to the land by flood water action such as silt deposition or erosion of topsoil. 1 The following method was used to determine flood damage to agri- cultural acreage: 1 26 1 Total acres of land in agricultural production in flood plain. 880 acres Acres east of Beach Blvd. 350 acres Acres west of Beach Blvd. 530 acres Assumed average value of crops $27.50/ton Assumed average yield per acre 35 tons Assuming value of crops as total loss and all land in simultaneous agricultural production, the potential loss in a standard project flood would be as follows: East of Beach Blvd. $27.50 X 35 tons X 350 acres $336,875 West of Beach Blvd. $27. 50 X 35 tons X 530 acres 510,125 TOTAL $847,000 SIAGLE AND MULTIPLE FAMILY RESIDE14C;LS There ure approximately 31,700 dwelling units on the flood plain in Huntington Beach. This is an estimate. of existing units as of July 1973. These units are single family, multiple family and mobile homes. Median value as reported in the 1970 Federal Census was $28,700. The costs resulting from flooding would include provision for removal of mud and silt, replacement of carpets, drapes, furniture, clothing, automobiles, appliances, etc. Cost per unit is estimated to be approximately one-half the median value of $28,700 or $14,000. Total residential losses would be approximately $443 . 8 million. Last of Beach Blvd. 16,100 units X $14,000/unit $225,400,00.0 West of Beach Blvd. 15,600 units X $14, 000/unit 218,400,000 Total 31, 700 units X $14, 000/unit $443,800,000 SALES TAX RLVENUE Based on a current population of approximately 150,000 it is assumed that about 100, 000 persons would be affected according to U. S. Census figures (1970) , plus 23% increase since then. AM& 27 One month ' s purchasing equals $47 per person or $4 . 70 per person in sales tax loss to the city (1% return from State) . Therefore, a total loss to the city would be $470,000 in sales tax revenue. i Since some 35% of the population live east of Beach Blvd. we estimate the loss as follows : East of Beach Blvd. $164,500 West of Beach Blvd. 305,500 Total loss of sales tax revenue to City $470 000 SOUTHERN CALIFORNIA GAS COMPANY SERVICLS 1 Estimated expenditures by the Gas Company to restore service in the flooded areas are: East of Beach Blvd. $250, 000 West of reach Blvd. 500, 000 I Estimated Gas Company total expenditures in Huntington Beach will be approximately $750, 000 ri`ELEPNUNE COMMUNICATIONS I There would be minor damage to cable facilities as underground splices and cable are watertight. Terminal boxes and crossconnect points located at the base of telephone poles would be damaged in addition to home and building protectors mounted near ground level. The estimated cleanup and repair costs east of Beach is $500, 000 and west of Beach is $1 , 000, 000. Major damage to the central offices, toll office and numerous PABX-PBX installations scattered throughout the city would result in probable disruption of service for an indefinite period with 1 damage costs that could exceed $20,000, 000. Estimate of damage east of Beach is $7, 000, 000 and west of Beach is $14,500,000. RESTORATION COSTS East of Beach Blvd. $ 7 ,000, 000 West of Beach Blvd. 14,500,000 Total $21,500,000 1 28 1 • EDISON ELECTRIC COMPANY The damages to Southern California Edison Company facilities are subject to considerable variations depending on the severity and scope of the flood. The interruption of electric service and its attendant difficulties cannot be accurately estimated in advance. The damages to S.C.E. facilities would approach $2. 44 niillioil in • a one to three foot flood situation and $5.24 million if a four to five foot flood were experienced. Estimated total damages to S.C.E. would be between $2,400,000 and $5,240, 000 for an average total of: $3,000,000. SCHOOLS Ocean View School District This school district has two schools, a district office and a school site, in the huntington Reach flood plain. The dist. .ic:t, would experience the same problems as the other school districts, resulting in estimated total damages of $900,000. Total $ 900,000 Fountain Valley School District • The Fountain Valley School District has seven schools within the Huntington Beach flood plain. Based on an estimate of $300, 000 per school an anticipated loss of $2,100,000 may be expected as the result of a flood. • Total $2,100,000 Huntington .Beach Union High School District In the event of a major flood in the City of Huntington Beach, the damage estimate for Huntingtion Beach Union High School District • would be: Damage to Plant and Equipment East of Beach Blvd. • Edison High School Capital Equipment Losses $1,670,000 Plant 700,000 Equipment 1,150,000 Total AC $3,520,000 aim in P 29 1 West of Beach Blvd. Marina High School / Capital Equipment Losses $1, 750,000 Plant 575,000 Equipment 1 ,375,000 1 Total $3, 700,000 Wintersburg High School Plant and Capital Equipment Losses $ 268,000 Equipment 304000 Total $ 298,000 , Total for Huntington Beach Union High School District $7,518,000 1 1 1 1 1 30 1 Section 5 hazard abatement • 5.0 HAZARD ABATEMENT The preceding pages of this report have identified flood potentials, evaluated existing control facilities, and specified land use hazards in the City. This section is concerned with programs designed to shorten municipal reaction times during a flood emergency, speed recovery after disaster, and (in the long run) decrease flood hazards through land use controls. 5. 1 Disaster Plans Though the City's long-range goal is to minimize flood risk, its short-range concern must be to prepare for the disaster that could strike now. In response to this need for disaster preparedness, the Huntington Beach office of Civil Defense has developed a five- step contingency plan for floods.9 This emergency program is outlined below: 9 "Operations Plan Four - Floods", Huntington Beach Office of Civil Defense. Adak 31 1 OPERATIONS PLAN FOUR - FLOODS (O-PLAN-4) 1 CITY OF HUNTINGTON BEACH CIVIL DEFEASE/EMERGENCY SERVICES PLAN I. MISSION: A. The City of Huntington Beach, in coordination with the Orange County Flood Control District, will conduct operations to: (Plan "A") . 1. Reinforce the Santa Ana River levees and flood control channels to prevent flooding. 1 2. Inform the residents in the flood danger areas of the situation. B. In event the Santa Ana River or the flood channels over- flow, the City of Huntington Beach will: 1 1. Direct and coordinate the evacuation of residents in low-lying danger areas, and provide security in the evacuated areas. (Plan "B" ) 2. Conduct Search and Rescue Operations for residents stranded by the flood. (Plan "C") 1 3. Provide, in coordination with the Red Cross, for the mass care of individuals and families displaced by a flood. (Plan "D") 4. Provide for a rapid recovery of City services, 1 utilities, schools, commerce and industry. (Plan "E") 5. Coordinate the return of residents to their homes and assist in return to normalcy. (Plan "E") II. ASSIGNMENT OF RESPONSIBILITIES : 1 A. Flood operations have been sub-divided into five (5) plans. Each plan covers a major phase of the operations. 1. Plan A-Flood Prevention - Public works 1 2. Plan B-Evacuation of threatened areas - Police 3. Plan C-Search and Rescue - Harbors and Beaches. 4. Plan D-Mass Care of displaced families - Parks and Recreation / 32 AM& I lip • 5. Plan E-Recovery - Public Works B. The Departments designated in paragraph "A" will prepare a detailed plan to carry out each of the phases. III. CONCEPT OF OPERATIONS: A. GENERAL • 1. The build-up of flood waters, of the magnitude to threaten the Santa Ana River and the flood control channels, will probably be a relatively slow process with adequate warning. The build-up to flood conditions will normally take from several days to • a week. 2. The National Weather Service provides flood fore- casts and warnings which are received by Harbors and Beaches. Harbors and Beaches will disseminate the warnings to the City Administration and interested • departments. Warnings are also broadcast by radio and television stations. 3. The Army Corps of Engineers and the Orange County Flood Control District will maintain surveillance of the Prado Dam, the Santa Ana River Channels and • the flood control channels during the build-up period. 4. A Flood Watch will be established in the Orange County Emergency Operating Center when the danger of a flood increases. • 5. Flood situation re orts will be issued by Orange County Flood Contro District to the Department of Public Works. Public Works will be responsible to disseminate flood reports to the City Administrator . and other City Departments as required. 6. A flood watch and patrols along the Huntington Beach Flood Contr-ol Channels will probably be estahlished in conjunction with Orange County Flood Watch. . 7. Orange County Flood Control District in coordination with the Army Corps of Engineers will progressively increase the size of the work-force to reinforce and maintain the river levees and flood control channels throughout the County. (The Flood Control District and the Army Corps of Engineers historically have employed all of the County resources, the National Guard and the Military before requesting mutual-ai-d. ) AM& 33 • BPI 1 8. Public Works will maintain and reinforce, as required, the Huntington Beach Flood Control Channels during this period. 9. As the threat of flood increases, Orange County Flood Control District will request the City of Huntington Beach for assistance under mutual-aid. 10. The City of Huntington Beach will, on request, provide maximum assistance to the Army Corps of Engineers and the Orange County Flood Control District for the maintenance of the River levees and flood control channels. 11. The Information Officer, in coordination with Orange 1 County will prepare information and warning notices to be broadcast over KWIZ 1480 and KEZY 1190 and T.V. Channel 50. 12 . It is anticipated that some individuals will leave the possible threatened areas within the City during the build-up period. 13 . The decision to direct residents to evacuate should be made as far in advance as possible. A heavy rainfall in San Bernardino or Riverside Counties, when the Prado Dam is filled to capacity and the 1 Santa Ana River is carrying capacity run-off, would create conditions which would necessitate an evacuation of low-lying areas. Several hours of advance notice would be available to conduct an evacuation. Little or no tune would be available for evacuation if the Santa Ana River west bank south of the San Diego Freeway collapses while the- river is at capacity. The varied conditions leading up to the necessity for a directed evacuation will probably reduce decision and warning time to a minimum. 1 14 . The evacuation of areas, due to actual or threatened flooding is a command responsibility. This decision will be made by the City Administrator or in his absence, his designated successor. It is anticipated that the declaration of a "local emergency" will be made prior to any evacuation of residents in the flooded or threatened flooded areas. 15. An announcement of the order to evacuate will be made over KWIZ 1480, KEZY 1190 and TV Channel 50. This will be augmented by detailed house-to-house notifi- cation, using loud-speakers and bull-horns of Police 34 AM%6 I I FIF 4 Department, Harbors and Beaches and the Fire Depart- ment. The City' s warning sirens will sound 3-minute steady blasts (repeated at 1-minute intervals) . 16 . Residents in the areas designated to be evacuated will be advised to go to the schools on the high- ground in the older part of the City. 17 . For flood control, see plan "A" . 18. For evacuation, see plan "B" . 19. For Search and Rescue, see plan "C" . 20. For iaass-care, see plan "D". 21. For recovery, see plan "E" . 5. 2 Flood Insurance A speedy recovery after disaster depends significantly on money available to both the public and private sectors for rehabilitation and reconstruction. Title XIII, National Flood Insurance, part of tha Housing and Urban Development Act of 1968 (Public law 90-448) , was initiated by the federal government to meet such needs for disaster funds. The law was conditional in nature as originally adopted with colnmsnity participation not mandatory. As amended in 19.73, however, coi,ununities with identified flood prone areas (such as ciuntington Beach) are required to participate in the insurance program by July 1, 1975 or be denied federally-related financing for projects that would be located in such areas. The long-range incentive to enter the program is to pravent, reduce, or control loss and damage due to flood and mudslide. The immediate incentive for members of the community is that they may purchase insurance against such loss under a Federally subsidized plan at a "reasonable, affordable cost".10 The purpose of the program is to offer states and local communities the chance to purchase protection against floods provided that they declare themselves participants in the program and express willing- ness to adopt appropriate land use controls. The original deadline 1 10 `1'ne Flood Insurance Guide, Professional Services Division, Canfield Press, pp. A-1-A-2. Ad*& for joining the program on an emerUeney basis and meeLinq minimum requirements was June, 1970. That date was later extended to December, 1973 , and has now been amended to December 31, 1975. Under the program, a federal subsidy was established to make basic flood anti mudslide protection available to property owners at a reasonable premium. The law provides that a maximum of $10 billion of insurance may be written. As explained in the Flood Insurance Guide: "The Federal government pays the difference between tl-ic so-called � affordable premium, which is charged to the policy holder, and the , actuarial premium. The actuarial premium would have to be charged if insurance were written based on the statistical likelihood of flooding combined with the potential severity of flood damage. In exchange for the 'reduced ' rate, the property owners, through their local and state governments , agree to adopt adequate land use and control measures for areas having special flood hazards. "ll After entering the program, it is the community' s responsibility to first declare its willingness to adopt and enact land use and control measures and second to implement and enforce those measures. Failure to do so may result in expulsion from the program. And once the special flood hazard areas (see Section 2 . 3) have been identified for a community, new development that occurs there may i)e uninsurable or required to pay actuarial rates for protection. C Essentially, the minimum eligibility requirements amount to planning and policy. As a check on future loss, building permits must be required and development in hazard areas must be "flood-proofed" . In reviewing subdivision proposals, too, attention must be given to flood safety. After the surface elevation for the 100-year flood has been identi- fied, however, community performance standards become more stringent. All new construction or substantial improvements in special hazard areas must be elevated above projected water levels, and a floodway must be designated in which development is restricted if the commu- nity is to remain eligible for the program.12 In April 1971, the City of Huntington Beach became eligible for Flood Insurance and was required to conform to minimum performance standards -- building permit procedures. In December, 1971, the Army Corps of Engineers completed its Flood Insurance Study and 11 The Flood Insurance Guide, Professional Services Division, Canfield Press, p. A-3. 12 The Flood Insurance Guide, Professional Services Division, Canfield Press, pp. C-4-C-10. 36 Acak I the city was required to fulfill additional responsibilities. These increased demands were met by the City' s existing Subdivision Map Act and by adoption of the Uniform Building Code. With the 100-year flood delineated and actuarial rates determined, the City is now obligated to adopt special land use control measures. As specifically outlined in Section 1910. 2d of the National Flood Insurance Program, these control measures must: * Require new construction or substantial improvements of resi- dential structures within the area of special flood hazards to have the lowest floor (including basement) elevated to or above the level of the 100-year flood. * Require new construction or substantial improvements of non- residential structures within the area of special flood hazards to have the lowest floor (including basement) elevated to or above the level of the 100-year flood or together with attend- ant utility and sanitary facilities, to be floodproofed up to the level of the 100-year flood. * Designate a floodway for passage of the water of the 100-year flood. The selection of the floodway shall be based on the principle that the area chosen for the floodway must be designed to carry the waters of the 100-year flood, without increasing the water surface elevation of that flood more than 1 foot at any point. * Provide that existing nonconforming uses in the floodway shall not be expanded but may be modified, altered, or repaired to incorporate floodproofing measures, provided such measures do not raise the level of the 100-year flood; and * Prohibit fill or encroachments within the designated floodway that would impair its ability to carry and discharge the waters resulting from the 100-year flood, except where the effect on flood heights is fully offset by stream improvements. Failure to meet these requirements may make the entire community ineligible for continued insurance, federally-related grants and loans, and disaster assistance. Tile deadline for implementing such measures was recently extended to December, 1975, by the Flood Disaster Protection Act of 1973 (Public law 93-234) . This new law substantially increases the limits of flood insurance available to all types of properties and extends emergency flood insurance programs until December 31, 1975, while eliminating the 1968 provision that would have denied disaster relief (as of December 31, 1973) to those who cosld have purchased flood insurance for a year or more but had failed to do so. ACOL AM 37 The new act requires the purchasing of flood insurance for any building located in the "special flood hazard" area of a participat- ing community (API and AP2 in Huntington Beach as shown on Figure 2-4) as a condition for receiving any form of Federal financial assistance or loan from a Federally supervised lending institution after I-larch 1, 1974. Federal financial assistance for acquisition or construction of projects within a "special hazard zone" are prohibited unless : A. It is covered by flood insurance for its full development costs (less land costs) or the new limit of available coverage, whichever is less; or B. Federal instrumentalities responsible for supervision of j lending institutions direct such institutions to require I flood insurance in connection with real estate or mobilehome and personal property loans in such identified areas up to the maximum limit or balance of the loan, whichever is less. These provisions take effect 60 days after enactment of the bill (i.e. , I-larch 1, 1974) . The act also defers, until December 31, 1974, the application of actuarial pre;nium rates on "first layer" coverage on all construc- tion and increases available limits of both subsidized and unsub- sidize,; flood insurance coverage for all types of properties as follows : Subsidized Unsubsidized Single-family Residence $ 35, 000 @ $. 25/$100 $700,000 Other Residential 100,000 @ $. 25/$100 200 ,000 Non-residential 100, 000 @ $. 40/$100 200, 000 Contents - Residential 10, 000 @ $. 35/$100 20, 000 Contents - Non-residential 100,000 @ $. 75/$100 200,000 It will be the responsibility of the Seismic-Safety Element to determine the most adequate and desirable land use and control measures needed by the City to comply with the flood insurance requirements and maintain its eligibility in the program. 5. 3 Land Use Controls The previous paragraphs have dealt primarily with identifying and moderating flood damage in the City. This section identifies several alternative land use controls designed to prevent flood problems . The following discussion, therefore, presents four possible approaches that might be utilized to make the community "flood safe" in the future. 38 xwh6 5. 3.1 Flood Plain Zoning Because zoning is concerned with the separation of incompatible land uses, it is a natural tool for protecting the integrity of watercourses and flood plains from urban encroachment. The purpose of flood plain zoning is to restrict development in flood hazard areas to uses which will neither obstruct water flow or jeopardize life and property. In most cases, flood plain zones designate severe hazard areas in which human habitation is forbidden and use is limited to flood control facilities, open space, agriculture, and temporary structures. Flood plain zones may also designate less severe hazard areas which permit urban development if adequately flood-proofed and if bottom elevations are at or above the level of the design flood. In all designated flood plain zones landfills which unduly obstruct flow of flood waters and excavations which widen the flood plain are prohibited. 5. 3. 2 Subdivision Regulations Subdivision regulations can reduce flood damage in several ways: a. prohibiting the subdivision of lands subject to serious flooding; b. requiring restrictions on purchase deeds to control lands unsuitable for dwellings or other uses; C. prohibiting encroachment in floodway areas by fill or structures; d. requiring a building site at an elevation above flood heights; and e. requiring installation of flood-proofed public facilities. 5. 3.3 Building Codes Building code regulations can establish the special design and construction provisions that should be required for structures and facilities subject to flooding. Such provisions may include: anchorage 'of structures to prevent floatation, installation of water-tight barriers Acak 39 over openings, reinforcement of walls to resist water pressures, use of materials to reduce wall seepage, construction or modification of water supply and waste disposal systems to prevent entry of flood waters, place- ment of essential utilities above the flood protection elevation, and installation of pumping facilities for internal and subsurface drainage. 5. 3.4 Flood Plain Management A flood plain management system is simply a coordinated method for dealing with flood hazards. It includes the three types of land use controls listed above in combi- nation with disaster preparedness programs, insurance programs, and flood control projects. The intent is to use each tool to its maximum in an effort to reduce obstruction of natural drainage areas in the future, increase protection to development already located in hazard areas, and to prepare for swift defensive action and speedy recovery in the event of flooding. 40 ACWk appendix SEISMIC SAFETY ELEMENT A. Authority Government Code Section 65302(f) requires a seismic safety element of . all city and county general plans, as follows: A seismic safety element consisting of an identification and appraisal of seismic hazards such as susceptibility to surface ruptures from faulting, to ground shaking, to ground failures, or to the effects of seismically induced waves such as tsunamis and seiches. The seismic safety element shall also include an appraisal of mudslides, landslides, and slope stability as necessary geologic hazards that must be considered simultaneously with other hazards such as possible surface ruptures from faulting, ground shaking, ground failure and seismically induced waves. The effect of this section is to require cities and counties to take seismic hazards into account in their planning programs. All seismic hazards need to be considered, even though only ground and water effects are given as specific examples. The basic andeeconomic andrsocialldislocations resulting fromgfuturerearthquakes. B. Background Earthquake losses in California through the remainder of this century, assuming that additional significant counter-measures are not taken, have recently been estimated at approximately $20 billion (Urban Geology Master Plan, California Division of Mines and Geology) . Estimates of potential loss of life for this period range well up into the thousands and most of this loss is preventable. ' The most widespread effect of an earthquake is ground shaking. This is 1 also usually (but not always) the greatest cause of damage. Structures of all types, including engineered structures and public utility facilities, if inadequately constructed or designed to withstand the shaking force, may suffer severe damage or collapse. The vast majority of deaths during earthquakes are the result of structural failure due to ground shaking. Most such deaths are preventable, even with present knowledge. New construction can and should be designed and built to withstand probable shaking without collapse. The greatest existing hazard in the State is the continued use of tens of thousands of older structures incapable of withstanding earthquake forces. Knowledge of earthquake-resistant design and construction has increased greatly in recent years, though much remains to be learned. 61 1 A second effect of earthquakes is ground failure in the form of land- slides , rock falls , subsidence and other surface and near-surface around movements. This is often the result of complete loss of strength of water-saturated sub-surface foundation soils ("liquefaction") , such as occurred near the Juvenile Hall in the 1971 San Fernando 1 earthquake, and -in the massive Turnagain Arm landslide in Anchorage, (luring the 1964 Alaska earthquake. Most such hazardous sites can be either avoided or stabilized if adequate geologic and soil investigations are utilized. Another damaging effect of earthquakes is ground displacement (surface 1 rupture) along faults . Such displacement of the earth 's crust may be vertical , horizontal or both and may offset the ground by as much as 30 feet (as in 1857 in Southern California) . It is not economically feasible to design and build foundations of structures (dams, 'buildings , bridges , etc. ) to remain. intact across such zones. Fault zones subject to displacement are best avoided in construction. In addition to regional 1 investigations necessary to the basic understanding of faults and their histories, detailed site investigations are needed prior to the approval of construction in any suspected active fault zone. Utilities, roads , canals and other linear futures are particularly vulnerable to damage as the result of ground displacement. 1 Other damaging effects of earthquakes include tsunamis (seismic sea waves , often called "tidal waves") , such as the one which struck Crescent City and other coastal areas in 1964; and seiches (waves in lakes and reservoirs due to tilting or displacement of the bottom or margin) . The failure of dams due to shaking, fault displacement or overtopping (from seiches or massive landsliding into the reservoir) can be particularly disastrous. 1 Most modern dams are designed and constructed to be earthquake-resistant; some older dams were not. In addition' to man-made dams , temporary darns may be created by earthquake-triggered landslides. Such inadvertently created dams are certain to fail within a relatively short time.. CFi7;' COP L' AND NATURE OL' Y'LL/s SI'1;>M1G' SAFETY EI;AMENT A. A general policy statement that: 1 . Recognizes seismic hazards and their possible effect on the community. 2. Identifies general goals for reducing seismic risk. 3. Specifies the level or nature of acceptable risk to life and property (see safety element guidelines for the concept of "acceptable risk") . .4• Specifies seismic safety objectives for land use. S. Specifies objectives for reducing seismic hazard as related to existing and new structures. ., / u. Identification, delineation and evaluation of natural seismic hazards. C., Consideration of existing structural hazards. Generally, existing substandard structures of all kinds (including . ' substandard dams and public utility facilities) pose the greatest hazard to a community. 1 t D. I'valuation of disaster planning prograii: for near-term earthquakes, the most immediately useful thing that a community can do is to plan and prepare to respond to and recover • from an earthquake as quickly and effectively as possible, given Lhe existing condition of the area. The seismic safety element can provide guidance in disaster planning. E. Determination of specific land use standards related to level of hazard aril risk. • As an initial step, it may be helpful to determine what aspects of the element creed greater emphasis . If a community is largely developed, emphasis on struc- Uiral hazards and disaster planning would be most appropriate. This would • .0 so be the ca.�e for, corrn,iuni ties whose greatest hazard will be from ground On the other hand, communities with extensive open areas and areas ,rabjr,,-t to ;orbanization may wish to focus on natural seismic hazards and the forlrilation of land use policies and development regulations to insure that row development is not hazardous. Aildit !onally, local planning agencies may wish to consider the preparation of the element or portions of the element in joint action. This would be particularly practical for the study of natural seismic hazards. A. Initial organization • ( 1 ) Focus on formulating and adopting interim policy based on very general evaluation of earth science information readily available. (2) Evaluate adequacy of existing information in relation to the identi- fied range and severity of problems. (3) Define specific nature and magnitude of work program needed to complete the element in a second stage. R. Identification of natural seismic hazards ' ( 1 ) General structural geology and geologic history. (2) Location of all active or potentially active faults, with evaluation regarding past displacement and probability of future movement. ( 3) Evaluation of slope stability, soils subject to liquefaction and differential subsidence. (4) Assessment of potential for the occurrence and severity of damaging ground shaking and amplifying effects of unconsolidated materials. (5) Identification of areas subject to seiches and tsunamis. (6) Maps identifying location of the above characteristics. C. Identification and evaluation of present land use and circulation patterns should be recognized in the formulation of seismic safety-land use policies. D. Identification and evaluation of structural hazards relating structural characteristics , type of occupancy and geologic characteristics in order to formulate policies and programs to reduce structural hazard. i_. I ormuIation of se,,s,-Jc Safety poi ici_� and recuimuend'.ALiOils. I . Iormulation of an implementation program. A. Acceptable risk: The level of risk below which no specific action by local government is deemed necessary, other than making the risk known. Unacceptable risk: Level of risk above which specific action by government is deemed necessary to protect life and property. Avoidable risk: Risk not necessary to take because the individual or public goals can be achieved at the same or less total "cost" by other means without taking the risk. R. Technical Terminology: Tsunamis : Earthquake-induced ocean waves , commonly referred to as tidal waves. Seiches: Earthquake-induced waves in lakes or ponds. Seismic: Pertaining to or caused by earthquake. Soil Liquefaction: Change of water saturated cohesionless soil to liquid, usually from intense ground shaking; soil loses all strength. Tectonic forms forces, and movements resulting from deformation of the earth s crust: Movement may be rapid resulting in earthquake, or slow (tectonic creep) . Fault: A plane or surface in earth materials along which failure h :., occurred and materials on opposite sides have moved relative to one another in response to the accumulation of stress in the rocks. Active Fault: A fault that has moved in recent geologic time and which is likely to move again in the relatively near future. (For geologic purposes, there are no precise limits to recency of wovement or probable future movement that define an "active fault". Definitions for planning purposes extend on the order of 10,000 years or more back and 100 years or more forward. The exact time limits for planning purposes are usually defined in relation to contemplated uses and structures. ) Inactive Fault: A fault which shows no evidence of movement in recent geologic time and no evidence of potential movement in the relatively near future. oi%mic Iiozard;: Hazards related to seismic or earthquake activity. Ground Failures: Include mudslide, landslide, liquefaction, subsidence. Surface ruptures from faulting: Breaks in the ground surface resulting from fault moveruent. TI '% HJP1; • A. To Other Elements: The seismic safety element contributes information on the comparative safety of using lands for various purposes, types of structures, and occupancies. It provides primary policy inputs to the land use, housing, open space, circulation and safety elements. Because of the close relationship with the saFety element the local planning agency may wish to prepare these two elements simultaneously or combine the two elements into a single document. If combined, the required content and policies of each element should be clearly identifiable. The local jurisdiction may wish to include the seismic • safety element as a part of an environmental resources management element - ERME - as discussed previously. B. To Environmental Factors: (1 ) Physical : Geologic hazards can be a prime determinant of land use capability. (2) Social : May provi�e basis of evaluating costs of social disruptions, including the possible loss of life due to earthquake and identifies means of mitigating social impact. (3) Economic: Cost and benefits of using or not using various areas related to potential damage or cost of overcoming hazard. (4) Environmental Impact Report: Provides basis for evaluating environ- mental impact of proposed projects in relation to slope stability, possible structure failure, etc. C. To Other Agencies : The State Geologist is required by Chapter 7.5, Division 2 of the Public Resources Code to delineate by December 31 , 1973, special studies zones encompassing certain areas of earthquake hazard on maps and to submit such maps to affected cities, counties, and state agencies for review and comments. By December 31 , 1973, the Division of Mines and Geology will have delineated the special studies zones encompassing all potentially and recently ac*fl ve traces of the''San Andreas:. Cal c,-;.Z.,as . Hayward, and San Jacinto faults . The special studies zone, will ter, delineated on'U.S. Geological Survey quadrangle sheets. The Ill:: +: at►gles listed in Appendix F will be included in the initial distributio►i which will begin on or about ! October 1 , 1973, and be completed by Dece*.-nr 30 , 1971. In addition to the faults named above, all active or poten-: ;�l1v active faults within the quadrangles listed will be zoned. The iones are ordinarily 'about one-quarter mile in width. The State Mining and Geology Board is required by Chapter 7.5; Division � 2 of the Public Resources Code to develop policies and criteria by December 31 ,. 1973, concerning real estate developments or structures to be built within the special studies zones. F;, iWPLEMENTATION A. Concurrent or subsequent revision of other general plan elements to give specific recognition to seismic safety rr.,:sic .Qs and criteria. B. Inclusion of appropriate requirements and procedures in zoning, sub- division and site development regulations and building codes. Designation of special zones with special land development regulations such as ! "seismic hazards management zones". C. Preparation of renewal plans for areas where a change in use .and devel- opment pattern is necessary because of major se4_-mic damage or extreme hazard: D. Building inspection program to identify unsafe structures and instigate necessary corrective measures. E. Inclusion of potential earthquake destruction in contingency plans for major disasters and emergencies. Review and liaison with Emergency Preparedness Organizations and Police Departments of overall plans and major public facilities proposals as to their adequacy in emergency . situations. F. Educational programs to develop community awareness of seismic hazards. G. Updating the building code to reflect changes in techno.l-ogy. d NOTE: These guidelines drew extensively from: Suggested Interim Guidelines for the Seismic Safety El.emen't; ,in General Plans, prepared__by t e overnor s art quake. Counci u y, - Draft Guidelines for the Seismic Safety Element', prepared hy^Advisory Group on Land Use Planning for Joint Committee on Seismic ': ;afety, California State Legislature, September, 1972. Seismic Safety_ Concerns in CIR/OIM Pr�og�ram prepared far "C1k" y , Wil Liam Spangle & Associates, March 19727unpublished. ME Adft SAFETY ELEMENT 1. /11i771011 ry Government Code Section 65302.1 requires a safety element of all city and county general plans, as follows: A safety element for the protection of the community from fires and geologic hazards including features necessary for such pro- tection as evacuation routes, peak load water supply requirements, minimum road widths, clearances around structures, and geologic hazard mapping in areas of known geologic hazard. -. 7'Hls 5r'c�PF AND NATURE OF THE SAFETY ELEMENT The objective of this element is to introduce safety considerations in the planning process in order to reduce loss of life, injuries, damage to property, and economic and social dislocation resulting from fire and dangerous geologic occurences. A. General policy statement that: (1 ) Recognizes safety hazards (2) Identifies goals for reducing hazard (3) Specifies the level of acceptable risk (4) Specifies objectives to be attained in reducing safety hazards as related to existing and new structures. (5) Sets priorities for the abatement of safety hazards, recognizing 4 the variable frequency and occurrence of hazardous events. i B. A map shoeing the location and extent of known geologic hazards. C. Standards and general criteria for land use and circulation relating to: ( 1 ) 'Fire prevention and control (2) Geologic hazards D. Consideration may be given to the crime prevention aspects of land rise development such as planning for "defensible space". hfls11710001,0(;Y A. Identification, mapping and evaluation of existing and potential hazards, both as to severity and frequency of occurrence. Analysis of hazardous land use relationships. R With maximum citizen input "acceptable risk" should be determined. In ,Waking this determination, it should be kept in mind that any attempt to develop the appropriate planning response to potential hazard involves a judgement, either explicit or implicit, of how much risk is acceptable. There is no such thing as a perfectly hazard-free environment. Natural and man-made hazards of some kind and degree are always present. However, efforts can be productively undertaken to try to mitigate the consequences of known hazards. In the context of the Safety Element, the problem of risk is one of public policy and the appropriate allocation of public resources to mitigate hazards. The central question is, "how safe is safe enough?" The planner' s responsibility is to provide a framework in which a communitywide, as opposed to an individual , response to the question can be meaningful. The first of several essential steps is the rec- ognition of the presence of a hazard. Much of the planning of the past has proceeded without enough knowledge of the natural forces at play in a given area. Once a problem has been recognized, considerable effort is required to evaluate its likely severity, frequency, and the characteristics of the area involved. This step should take into account the bene- fit/cost ratio of reducing hazard, acknowleding the intangibles in- volved, and comparing it with that of other projects. The factors of voluntary and involuntary exposure to risk must be considered in reaching a decision. C. Define nature and magnitude of effort required to correct or mitigate S hazards. 3 D. Define general nature of regulations and programs needed to prevent t or mitigate the effects of hazards in the developed and natural environments. ixchange information and advice with fire, pulice and public works departments , other agencies, and specialty personnel in the formu- lation of the element. Ac_ceytable Risk: The level of risk below which no specific i - action by local government is deemed to be necessary. Unac:cepU ble Risk: revel of risk above which specific action by s government is deemed to be necessary to protect life and property. Avoidable Risk: Risk not necessary to take because individual i - MM f k or public goals can be achieved at the same or less total "cost" by other means without taking the risk. Defensible Space: Concept of urban space desig:ied to inhibit crime by utilizing the proprietary concerns of residents. Key ingredients in designing defensible space include: improving the natural capability of residents to visually survey the public areas of their residential environment; enhancing spheres of territorial influence within which residents can easily adopt proprietary attitude; and enhancing safety through the strategic geographic loca- tion of intensively used community facilities. UFLATIONSl1IPS OF THE SAFETY ELEMENT A. To Other Elements: . (1 ) The Safety Element contributes to developing land use standards and policies. These will relate type and intensity of use to the level of risk from fire and geologic hazard, to the effect of development upon that risk, and to the availability of services and facilities to combat them. . The Safety Element also contributes basic standards and requirements to the circulation and optional public utilities elements, and will have important implications for the open space and conservation elements. (2) Because of the strong relationship with the Seismic Safety Element, the local planning body may wish to prepare these two elements sirnul- taneously or to combine the two elements into a single document. D. To Other Factors: i - (1 ) Social : The element is directed at reducing social costs due to f injury, loss of life, or public or private dislocations increasing the sense of community security and well-being. (2) Economic: The element should be directed at reducing costs of direct property loss and economic dislocation. (3) f.nvironur ntal Impact: The Safety Element provides the policy dir•ect.ivu" . for reducing adverse impacts on both the built and natural environments of major safety hazards. C. to OVier Agent-ies : (1) The preparation of the Safety Element would also be facilitated by identifying, and securing the cooperation of major Federal , state regional and private owners of land in a largely natural state, which iaffects the potential fire hazard. Such agencies would include, j for example, the national and state parr services. (2) Local pidnning bodies are encouraged to enter into joint planning and the execution of mutual assistance pacts related to safety hazards materially affecting more than one planning jurisdiction. IMPLEMENT:IT ZON A. Concurrent or subsequent revision of other general plan elements to incorporate safety policies and criteria. B. Addition of capital improvements as may he necessary for the mitigation and control of safety hazards to the capit•i1 program. i C. Review and possible amendment of zoning, auhciivsinn end site development regulations to incorporate safety provi F 4c.n:. D. Formulate building and fire safety inspection programs of buildings and premises to identify fire and other safety hazards. E. Provide input to contingency. plans for m;+j,=-• J i s ds tr.t- or, emergencies. F. Provide for ongoing review of major public and private development proposals by fire and police departments to insure compatibility with safety objectives. t i f I F g 1 I 1 HUNTINGTON BEACH PLANNING DEPARTMENT *RICHARD HARLOW Director *EDWARD SELICH Senior Planner *MONICA FLORIAN Associate Planner DAVE EADIE Associate Planner AL MONTES Assistant Planner MAUREEN WILD Assistant Planner SAVOY BELLAVIA Assistant Planner FRED RITTER Assistant Planner JOHN COPE Assistant Planner *EMILIE JOHNSON Planning Aide CHARLES LAUMANN Planning Aide BOB KIRBY Planning Aide SERGIO MARTINEZ Planning Aide *THOM JACOBS Illustrator *GEORGE ERMIN Planning Draftsman . *BOB SIGMON Planning Draftsman *ALAN LEE Planning Draftsman JUNE ALLEN Administrative Secretary JANA HARTGE Principal Clerk SUSAN PIERCE Secretary-Typist GISELA CAMPAGNE Secretary *MARY CARDINAL Clerk-Typist *Participating Staff REPORT BY: ADVANCE PLANNING STAFF