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HomeMy WebLinkAboutA003 - necessary changes needed for Rock Island District Corps of Engineers FEDERAL EMERGENCY MANAGEMENT AGENCY FEDERAL,Old Federaluding TION 911 Walnut Street, Room 405 Kansas Cityp Missouri 64106 VEVEI �"w... y;e September 28, 1979 Mr. Ron Wooldridge J Y� Planning Commission lt'-''' t City of Ames 21g79 Depot Annex OCT Ames, Iowa 50010 Dear Mr, to ool.dridge: E�, eta This office has received a copy of gal's letter dated September 17, 1979 requesting some changes in the floodway on College Creek and Squaw Creek. In order to show such a floodway change in the Ames, Iowa Flood Insurance Study (FIS) , the proposed changes will have to be furnished to our study contractor, Rock Island District Corps of Engineers, by the City of Ames. Upon receipt of a request for a floodway shift, the study contractor will do hydraulic analysis of the proposed change to determine if it will meet the minimum criteria of no more than a one foot increase in the 100-year flood elevation. If the analysis indicates that such a shift is possible, then the City of Ames will be expected to coordinate the shift with all adversely affected property owners to ensure that they have no objections. In addition, this should be accomplished prior to the start of the six-month conversion period to the Regular Program phase of the National Flood Insurance Program in order to enable a floodway change to appear in the Ames, Iowa FIS. If you have any questions concerning the above, please contact Mr. Eric Jenkins of this office at 816/374-2161. Sincerely, Francis X. Tobin Regional Director Emergency Management Agency en Stephenson Dir etor Federal. Insuanc x . dministration FLOOD INSURANCE STUDY CITY OF AMES, STORY COUNTY, IOWA 1.0 INTRODUCTION 1.1 Purpose of Study The purpose of this Flood Insurance Study is to investigate the existence and severity of flood hazards in the City of Ames, Story County, Iowa, and to aid in the administration of the National Flood Insurance Act of 1968 and the Flood Disaster Protection Act of 1973. Initial use of this information will be to convert the City of Ames to the regular program of flood insurance by the Federal Insurance Administration. Further use of the information will be made by local and regional planners in their efforts to promote sound land use and flood plain management. }> 1.2 Coordination Prior to initiation of the study, a time and cost meeting was scheduled with the Federal Insurance Administration, city officials, the State Flood Insurance Coordinator. and the U.S. Army Corps of Engineers (COE), Rock Island District, to determine the streams to be studied by detailed or approximate method,. The tVDe of study for each stream :%:as mutually agreed on by those present. The identification of streams requiring detailed study was performed in a meeting attended by personnel of the COE, the Federal Insurance Administration, and the City of Ames in February 1976. Flow-frequency values used in the study were coordinated with the Iowa Natural Resource Council. On , the results of this Flood Insurance Study were reviewed and accepted at a final coordination meeting attended by personnel of the COE, the Federal Insurance Administration. and the City of Ames. 1.3 Authority and Acknowledgements The source of authority for this Flood Insurance Study is the National Flood Insurance Act of 1968, as amended. The hydrologic and hydraulic analyses for this study were performed by the U.S. Army Corps of Engineers, Rock Island District, for the Federal Insurance Administration. under Inter-Agency Agreement No. IAA-H-7-76, Project Order No. 24, and Inter-Agency Agreement No. IAA-H-10-77, Project Order No. 2. This work, which was completed in April 1978, covered all significant flooding sources affecting the City of Ames. 2.0 AREA STUDIED 2.1 Scope of Study This Flood Insurance Study covers the incorporated area of the City of Ames. The area of study is shown on the Vicinity Map (Figure 1). The areas studied by detailed methods were selected with priority given to all known flood hazard areas, areas of projected development and proposed construction until 1983. Approximate methods of analysis were used to study those areas having low development potential and/or minimal flood hazards as identified at the initiation of the study. The scope and methods of study were proposed to and agreed upon by the Federal Insurance Administration and the community. The Skunk River, Squaw Creek, Worle Creek, College Creek, Clear Creek, Onion Creek, Unnamed Creek A, and Unnamed Creek B were studied in detail. An unnamed tributary to Worle Creek was studied by approximate methods. 2.2 Community Description The Cite of Ames is located in Story County, in the central part of the state, approximately 30 miles north of Des ,Moines, the state capitol of Iowa. Ames has a population of 43,561 with approximately half the population being students at Iowa State University. Ames is presently served by three major highways: U.S. Highway 30, U.S. Highway 69, and Interstate Highway 35. In addition to these three highways, Ames is served by the Chicago and North Western railroad. The climate of the study area is continental in character with cold winters and warm. humid summers. The temperatures of the area ran(ze from -30 degrees Fahrenheit (F.) in the winter to 110 degrees F. in the summer, with an average annual temperature of 50 degrees F. The average annual precipitation is about 31.5 inches, with a maximum of 56.8 inches in 1881 to a minimum of 17.1 inches in 1966. The average seasonal snowfall is 32 inches, with a minimum of 8.3 inches in the winter of 1965-1966 to a maximum of 72.0 inches in the winter of 1911-12. The soils in the area consist primarily of glacial drift in the channel bed. and deep black loam in the valley. This is considered the best agricultural land in the state. 2 Air�nca ,stisr�r. t --- - ' --� -- - AJirnw. o� W I� 0 G� °t • 6 B ♦ L _ w I I c - ' 1 X cc V _ _- • _ �,_ Z ' ;-_ � L I NIA _ e d • 9I Lu us uj O C — - — — — — - - c C LAJ O w 1 0O 3NDbS _ A1l^3 3N .B N _ Q r v C Li. C J o �— . z z s � -40, c a i Q � V a W v �'acr.r +is NO FIGURE 1 The Skunk River flows south through the eastern part of Ames. Squaw Creek flows in a southeasterly direction through the center of Ames and discharges into the Skunk River. Worle, College, Clear, and Onion Creeks all flow through the western part of Ames and discharge into Squaw Creek. The two Unnamed Creeks flow through the southeastern part of Ames and discharge into the Skunk River. Much of the Skunk River flood plain consists of agricultural land with a few farm buildings. Some development has occurred; however, at the present time it has engulfed only a small portion of the flood plain. The Squaw Creek flood plain is relatively undeveloped. There are a few residential developments near South Riverside Drive and commerical developments exist near Duff Avenue. Iowa State University lies along the right bank of Squaw Creek with some development in the flood plain along Elmwood Drive. The Onion Creek and Worle Creek flood plains are presently undeveloped. College Creek, which flows through Iowa State University, and Clear Creek have relatively confined flood plains with little development within the flood plains themselves. The unnamed tributary to Worle Creek flows through a new development area with most of the houses lying outside the flood plain. 2.3 Principal Flood Problems The low-lying areas of Ames are subject to periodic flooding from the Skunk River, Squaw Creek, Worle Creek,: College Creek Clear Creek, Onion Creek, Unnamed Creek A, and Unnamed Creek B. Flooding in the Ames area is most often caused by rainfall on snow covered or saturated ground. The floods occur most often in the late winter, spring, or early summer. On June 27, 1975, the City of Ames sustained severe flooding from Squaw Creek and the Skunk River. In terms of magnitude of discharge and damage, this was the most severe flood on record, with losses estimated by city and Iowa state officials at over a million dollars. The peak discharge on Squaw Creek was measured at 11,300 cubic feet per second (cfs). In comparison, the 500-year flood is 11.600 cfs. The peak discharge on the Skunk River below the confluence with Sauaw Creek was 14,700 efs, compared to a 50- year flood of 15.530 cfs. This flood is discussed in detail in a report entitled, "Flood of June 27, 1975, in City of Ames, Iowa" (Reference 1). Other floods of varying magnitude occurred on the Skunk River and Squaw Creek in the years 1918. 1944, 1947, 1954, 1958, 1960, and 1965. 2.4 Flood Protection Measures There are no flood protection devices in the City of Ames and none are planned for near future. A multiple-purpose reservoir, proposed to be located on the Skunk River approximately five miles upstream from Ames, Iowa, was authorized under the 1965 Flood Control Act. The report on the proposed Ames reservoir is published as House Document No. 267, 89th Congress, 1st Session. The project has not been constructed and was reclassified as inactive in June 1974 due to state and local opposition. 4 3.0 ENGINEERING METHODS For flooding sources studied in detail in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Floods having recurrence intervals of 10-, 50-, 100-, and 500-years have ' ement and for been se s having nce premium special significance um rates. The analyses rep000d rted here ma insure hereagreflect current flood insurance p conditions in the watersheds of the streams. 3.1 Hydrologic Analyses Hydrologic analyses were carried out to establish the peak discharge- frequency relationships for floods of the selected recurrence intervals for each flooding source studied in detail in the community. Two streamflow records for gages are available at Ames. One is on the Skunk River near Ames (drainage area: 315 square miles), which lies above the confluence of Squaw Creek and has 51 years of record; and the second is on the Skunk River below Squaw Creek (drainage area: 556 square miles), which has a systematic record of 22 years and a historic record of 32 years. Two frequency curves were developed in accordance with the techniques below described in Bulletin No. 17 (Reference 2). Since the Skunk River, Squaw Creek, has only 20 years of continuous record, a correlation was run with the longer station record of the Skunk River near Ames. The Extended record equals 40 years. This gage analysis was delineated using the log- Pearson Type III analysis. Streamflov. records are available for Squaw Creek at Ames. Iowa (drainage area: 204 square mile), v.ith a length of record of -20 years. a frequency curve was developed in accordance with the techniques described in Bulletin No. 17 (Reference 2). Since Squaw Creek has a short record of 20 vears and a gap of 37 years between the two halves of data, a regional correlation was run with the Skunk River near Ames, and the missing years were reconstituted. Since there was little difference in the results of the two analyses, the original analysis with the systematic record of 20 years was adopted for the study. No now records are available for the other streams studied in detail. Therefore, a regional analysis of neighboring streams was used to compute average statistics (Reference 3). To check the validity of the regional analysis, a comparison was made with the Squaw Creek gage. Since the Squaw Creek frequency curve could be correctly developed using the regional data, the regional data were taken to be correct, and were used for the ungaged streams. Peak discharges for the 10-, 50-, 100-, and 500-year floods of each flooding source studied in detail in the community are shown in Table 1. 5 i o0 0 0 0 0 0 W 0 Cl ClM O e+� V� o cN to O t to to M to 1 O N N .� O tf� , wa 00 0 0 0 0 0 0 0 W � cc.� o � CD ., ti ., >4 O Cl co qw to I "• !V • • cn c Ca t- Q) C) N rl kn rW o .-4 Vy � W d U) o0 0 0 0 0 o O o m M O to Co r WA W rr O M O O QC o0 � tp N N •-1 d' � rl d ` a r' U A o0 0 0 0 0 0 0 0 f=+ d m o M o to co oD eM ti O W m m c- a M ao o to to pd o -4 d W fn �I CC CD M L`� N d' C: .--i L: N •� •-d M V5 N a cr z_ F ¢ A z o C U a o w A o c) r d d U U d y a0 U (m W C tY-7 to .Le y r~.. w .Mi 0 m a En O W > w E E E w E U a) o O z d z w O CD m O U U 3 D D 6 3.2 Hydraulic Analyses Analyses of the hydraulic characteristics of the streams in the community are carried out to provide estimates of the elevations of the floods of the selected recurrence intervals along each flooding source studied in detail. The cross section shown for Squaw Creek and the Skunk River were those used in a previous report, entitled "Flood Plain Information Report, Skunk River and Squaw Creek, Story County, Iowa, Technical Appendix" (Reference 4). Additional surveys were taken as needed. Channel surveys for the other streams studied were surveyed during completion of this report. Detailed topographic ma6s were used for the overbanks to supplement the channel surveys (Reference 5). All bridges were surveyed to obtain elevation data and structural geometry. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway is computed (Section 4.2), selected cross section locations are shown on the Flood Boundary and Floodway Map (Exhibit 2). Channel and overbank roughness factors (19anning's "n") for Squaw Creek and the Skunk River below the confluence with Squaw Creek were determined by reproducing the flood of June 27, 1975. The profile for this h,storic flood was obtained from "Flood of June 27, 1975, in City of fames, Iowa" (Reference 1). Roughness factors for the remainder of the streams studied were selected by field selection and aerial photographs (Reference 6). The roughness factors selected for the flooding sources studied range from 0.04 to 0.05 in the channel and from 0.05 to 0.085 in the overbanks. The starting water-surface elevations for Squaw Creek and the Skunk River were determined using the slope-area method. The 100-year elevation was used as the starting point for the 50-, 100-, and 500-year flood, and the 2- year elevation was used as the 10-year flood for the remaining detailed study streams. Water-surface elevations for the detailed study streams were computed using the COE HEC-2 step-backwater computer program (Reference 7). Flood profiles were drawn showing computed water-surface elevations to an accuracy of 0.5 foot for floods of the selected recurrence intervals (Exhibit 1). The water-surface elevation for the unnamed creek in the approximate studv was determined by using normal depth analysis and then applying Manning's equation to a 100-year flood. Flood elevations are often increased due to various obstructions to flow, such as ice and debris jams. The hydraulic analysis for this study, however. is based on the effects of unobstructed flow. The flood elevation. as shown on the profiles, are thus considered valid only if the hydraulic structures in general remain unobstructed. 7 All elevations are referenced from National Geodetic Vertical Datum of 1929 (NGVD); elevation reference marks used in the study are shown on the maps. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS A prime purpose of the National Flood Insurance Program is to encourage state and local governments to adopt sound flood plain management programs. Each Flood Insurance Study, therefore, includes a flood boundary map designed to assist communities in developing sound flood plain management measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimination, the 100-year flood has been adopted by the Federal "Insurance Administration as the base flood for purposes of flood plain management measures. The 500- year flood is emploved to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the 100- year and the 500-year floods have been delineated using the elevations determined at each cross section; between cross sections the boundaries were interpolated using detailed topographic maps at a scale of 1:4800. with a contour interval of two feet (Reference 5). The boundaries of the approximate study determined by using the above-mentioned topographic maps. All areas that are shown on the Flood Hazard Boundary Map have been included in this study (Reference 8). The boundaries of the 100-year and 500-year floods are shown on the Flood Boundary and Floodway flap (Exhibit 2). Small areas within the flood boundaries may lie above the flood elevations. and. therefore. not be subject to flooding; owing to lack of detailed topographical information or to limitations of the map scale, such areas are not shown. In cases where the 100-year and the 500-year flood boundaries are close together, only the 100- year boundary has been shown. 4.2 Floodways Encroachment on flood plains, such as artificial fill, reduces the flood- carrying capacity and increases flood heights. thus increasing flood hazard in areas bevond the encroachment itself. One aspect of flood plain management involves balancing the economic gain from flood plain development against the resulting increase in flood hazard. For purposes of the Flood Insurance Program. the concept of a floodway is used as a tool to assist local communities in this aspect of flood plain management. Under this concept, the area of the 100-year flood is divided into a floodway and a floodway fringe. The floodway is the channel of a stream, plus any adjacent flood plain areas, that must be kept free of encroachment in order that the 100-year flood be carried without substantial increases in flood heights. As minimum standards, the Federal Insurance Administration limits such increases in flood heights to 1.0 foot, provided that hazardous velocities are not produced. S The recommended floodways were determined using the HEC-2 computer program and the equal conveyance method. The flood recommended for this study was based on the hydraulic conveyances characteristics of the streams surveyed sections. The effect of a structure, such as a bridge, is reflected in the hydraulic computations. No encroachment was allowed in the hydraulic influence of bridges or the natural channel. Outside of the bridge's hydraulic influence, the floodway was determined using the equal degree of conveyance reduction method for a maximum of 1.0 foot rise. The results of the floodway computations were tabulated at selected cross sections for each stream segment for which a floodway was computed (Table 2). As shown on the Flood Boundary and Floodwav Map (Exhibit 2), the floodway boundaries were determined at cross sections; between cross sections, the boundaries were interpolated. In caVs where the boundaries of the floodwav and the 100-year flood are either close together or collinear, only the floodway boundary has been shown. The area between the floodway and the boundary of the 100-year flood is termed the floodway fringe. The floodway fringe thus encompasses the portion of the flood plain that could be completely obstructed without increasing the water-surface elevation of the 100-vear flood more than 1.0 foot at any point. Typical relationships between the floodway and the floodwav fringe and their significance to flood plain development are shown in Figure 2. -100-YEAR FLOOD PLAIN - I F -r,•JvAv I FLC�Da A� 1 F LGCOW 4Y FRINGE �I j - IV`C .._ I FLOOD ELEVATION WHEN I CONFINED W ITHIN F L'CCWAY ENCROACHMENT I ENCROACHMENT `I -=-=- SURCHAPGE' .I !\ i �• 1 ARE40F FLOOD,LA THAT COULD _\- 9E USED FOR DE�ELOPMENT BI FLOOD ELEVATION PAISI%G BEFORE ENCROACHMENT .F_GOO PLAIN U r.E CC IS'-E EL?-C•ELE.A" •S�P[.ARGE IS NOT TO E ECEEO :)F9GT'E'A FEC,R`YE 1Ti OR LESSEE cvCUNT IF SPECIFIED BY STATE FIGURE 2 - Floodwav Schematic The floodways in this report are recommended to local agencies as minimum standards that can be adopted or that can be used as a basis for additional studies. 9 Date ect Ac /O,EpFi�£5 M Kr-H /979 r�asEo o Sheet of s Checked Gompuledbp n /ooYX /doYR .7EC T/od STAT onl NATaRA1 r1voroAcH I NCf EASE M/C ES 3 +30 O, GS" SB 3. 0 9113.0 0140 1/3 tG0 0.93 g 8S. S 885. G 0• l C 56-vn O 406, 987.8 887• 8 0.0 D 61-too 1.31 888.3 888.it 0. 1 �o-tZo 15.3 889 a. 889.3 O•/ F q5t o c A 80 8 FR.0 892./ 0 • / G 1054 o C, 1.99 8 9,�. / 8 9�.2 0. r H 113+ 20 .74 $93.9 89 0 D•/ 1 19-?190 a.Vz s9y.8 89�. 9 6. l 139i.3o . •(oil 895.9 89 G•0 0• / K 144+70 .?.7/ 89G•3 S9G. D.1 L 16 21 C c 3.08 899.4 898.'� D.D M 1-7I16o 3.25 899.0 8m / 0•l N 1$9-t -70 3.50 899-G 899.7 04 0 194tgo S 9v0.a 900.3 0• 1 aog� 3 9� 90/.0 90/./ o.l Q �t� f s o 90/. 9 9 0 A.o a . 1 S 2 i:so y.GS i T a6I-t �o y,9s 9oS�i 905,7 0• ! 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Z p Y � Z0 O w 0 y o in U f c � v W3 0 — c�i O Z O e I 0 w Q o 0 U J NLLJ 3 < W J J LU J cr f U C W 0 I ------------- — -- TABLE 2 W C7 Z W !'faf M -e0t" 0000 W W OOOOOOO OOOO LLB LL cc 0 LL o CD Q m > W Ow �> W • QW 030 h0 a)-1 McoCD 00)0(7 Q :E LLU OO> unONuiO) Ct0 m1- (DN I-- 'Q Q 1 0 0 r- m m m m 0)0) m 0)0)O Q ©� 30Z mmmmmmm mmm0) O Z 2 Q Sao 0cn Lnr-- mc7 c0)0Cl) O W 3 o> co1C-icciOivt; c6 •-6ci O Li 0 r- m m m m D)(M m (M m 0 O? cocommmmm mmmrn —J C.3 J `i LL 0 >v W 2r=N I m w o w yn to COQ r` to M (D m r- Q C7 [ W ('7 O f to LC) •- to In tD O ( Z >LL Z i Q Z �uj3 OQ 0 Q (Dlnmm CT) CDcnm O U¢ cI C7NNc7 tt R •- NON O W a.; LL 7 _ S� 0uj 0Lnr4N rTOCD OsT CDw W V rN n c r LLam. 3 v N f- z — W d O W J . ti LU CV to r\ (D m (D t\ r` r\ m Q r-OwmC) r14 mV, O — r.4M W .y I 000 - -- •- ^ 00CD p c Z cr .� N — 0 --- o Q m I z a > `� MCC at 0 0 w LIJ w z W r�- COY U Q O N w U U O — Q Qm0pUiLL 0 Qco j W W 0 O e (rQ Q i•� U. v z z N W z zLU cc -- -- U 96 W � O --------- ------ TABLE 2 5.0 INSURANCE APPLICATION In order to establish actuarial insurance rates, the Federal Insurance Administra- tion has developed a process to transform the data from the engineering study into flood insurance criteria. This process includes the determination of reaches, Flood Hazard Factors, and flood insurance zone designations for each flooding source affecting the City of Ames. 5.1 Reach Determinations Reaches are defined as lengths of watercourses having relatively the same flood hazard, based on the average weighted difference in water-surface elevations between the 10- and 100-vear floods. This difference does not have a variation greater than that indicated in the following table for more than 20 percent of the reach. Average Difference Between 10- and 100-year Floods Variation Less than 2 feet 0.5 foot 2 to 7 feet 1.0 foot 7.1 to 12 feet 2.0 feet More than 12 feet 3.0 feet The locations of the reaches determined for the City of Ames are shown on the Flood Profiles (Exhibit 1) and are summarized in the Flood Insurance Zone Data Table (Table 3). 5.2 Flood Hazard Factors The Flood Hazard Factor (FHF) is the Federal Insurance Administration device used to correlate flood information with insurance rate tables. Correlations between property damage from floods and their Flood Hazard Factors are used to set actuarial insurance premium rate tables based on Flood Hazard Factors from 005 to 200. The Flood Hazard Factor for a reach is the average weighted difference between the 10- and 100-vear flood water-surface elevations expressed to the nearest one-half foot. and shorn as a three-digit code. For example. if the difference between water-surface elevations of the 10- and 100-vear floods is 0.7 foot, the Flood Hazard Factor is 005; if the difference is 1.4 feet, the Flood Hazard Factor is 015; if the difference is 5.0 feet. the Flood Hazard Factor is 050. When the difference between the 10- and 100-vear water-surface elevations is greater than 10.0 feet, accuracy for the Flood Hazard Factor is to the nearest foot. 5.3 Flood Insurance Zones After the determination of reaches and their respective Flood Hazard Factors, the entire incorporated area of the City of Ames was divided into 16 zones, each having a specific flood potential or hazard. Each zone was assigned one of the following flood insurance zone designations: Zone A: Special Flood Hazard Areas inundated by the 100-year flood, determined by approx- imate methods; no base flood elevations shown or Flood Hazard Factors deter- mined. Zones A2-A4, A8, Special Flood Hazard Areas inundated by Al2, A15, A17: the 100-year flood, determined by de- tailed methods; base flood elevations shown, and zones subdivided according to Flood Hazard Factor. Zone B: Areas between the Special Flood Hazard Area and the limits of the 500-year flood, including areas of the 500-year flood plain that are protected from the 100-veer flood by dike, levee, or other water control structure; or areas subject to 1�_ certain types of 100-year shallow flooding where depths are less than 1.0 foot; and areas subject to 100-year flooding from sources with drainage areas less than 1 square mile. Zone B is not subdivided. Zone C: Areas of minimal flooding. Table 3, "Flood Insurance Zone Data," summarizes the flood elevation differences, Flood Hazard Factors, flood insurance zones, and base flood elevations for each flooding source studied in detail in the communitv�. 5.4 Flood Insurance Rate Map Description The Flood Insurance Rate Map for the City of Ames is, for insurance purposes, the principal result of the Flood Insurance Study. This map (published separately) conU�ins the official delineation of flood insurance zones and base flood elevation lines. Base flood elevation lines show the locations of the expected whole-foot water-surface elevations of the base (100-year) flood. This map is developed in accordance with the latest flood insurance map preparation guidelines published by the Federal Insurance Administration. 6.0 OTHER STUDIES A Flood Plain Information Report was prepared in June 1966 by the COE (Reference 4). Discrepancies between the Flood Plain Information Report and this 17 study exist due to development changes and updated hydrologic and hydraulic procedures. These profiles therefore supersede those in the Flood Plain Information Report. A Flood Hazard Boundary Map for the Citv of Ames has been Published using approximate methods to determine flooding (Reference 8). This report either supersedes or is compatible with all previous studies published on streams studied in this report and should be considered authoritative for the purposes of the National Flood Insurance Program. 7.0 LOCATION OF DATA Survey, hydrologic, hydraulic and other pertinent data used in this study can be obtained by contacting the office of the Federal Insurance Administration, Regional Director, Room 305, 911 Walnut Street, Kansas City, Missouri 64106. 8.0 REFERENCES AND BIBLIOGRAPHY 1. U.S. Geological Survey, "Flood of June 27, 1975, in City of Ames, Iowa," Oscar G. Lara and Albert J. Heinitz, October 1976. 2. U.S. Water Resources Council. Bulletin No. 17. Guidelines for Determi Flood Flow Frequency, March 1976. nin 2 3• U.S. Army Corps of Engineers, Rock Island District. "Skunk River, Iowa- Review of Reports for Flood Control and Major Drainage," August 27, 1971, (unpublished). 4. "Flood Plain Information Report, Skunk River and Squaw Creek, Story County, Iowa, Technical Appendix." June 1966. 5. City of Ames, Topographic INaps 1954 and 1961 Aerials. Scale 1:4800, Contour Interval two feet. City of Ames, lowa, Elevation based on City of Ames datum 0.00 = ,MSL Datum 823.55. 6• Tri-State Aero-Engineering Co. of Bettendorf, Iowa, Aerial Photographs; Scale 1:18000: Ames, lowa, April 249 1977. 7. U.S. Army Corps of Engineers, Hydrologic Engineering Center. 11HEC-2 Water-Surface Profiles," (updated) 1976. modifications through 59. 8. U.S. Department of Housing and Urban Development,Administration. Flood Hazard Boundary Ma Federal Insurance 1974, (revised) .4pri1 1977. p, City of Ames, Iowa, August 20