FLOOD06691 - Laserfiche WebLink

Home Browse Search

SECTION IV FlOOD PLA INS GENERAL COMMENTS Once the flood flows were determined for future conditions, the flood plain could be determined. The basic procedure In determinIng the flood plain was the HEC-2 backwater program develop,~d by the U. S. Army Corps of Engineers (USACE). A hack\.ater p,'ogram Is necessary to determIne the flow depth upstream of the multitude of bridge, culvert and various channel constrictions of Lena Gulch. The data base required for this program consIsts of cross-sectional channel shapes, roughness, and survey Informatfon about culverts and bridges. The majority of the InformatIon Is provided by 1 Inch to 100 foot scale aerial topographic mapping and surveyed culvert Information provided by Olympus Aertal Surveys, Inc. This was supplemented by a Held trip In whIch detailed notes we"re taken to note various so11, channel and culvert condItIons. WATER SURFACE PROFILES (U.S. ARMY CORPS OF ENGINEERS - THE HYDROLOG I C ENG I NEER I NG CENTER CO~'IPUTER PROGRAM 723-x6-L202A) Origin of Program. The program used Is a modification of program 723- G2-L214A, developed In the Hydrologl(;: En!llneerlng Clmter, Corps of Engineers, 609 Second Street, DavIs, CalifornIa, by BIll S. Elchert (1964 version of 723-G2-L214A was from the Tulsa DIstl"lct by same auth- or). The Input requirements have been modified to al Tow the use of many additional options, to provIde for future expansIon and to sImplI- fy Input preparatIon. A supplementary p,'ogram (?23.-GT-L202B) Is avail- able to convert data from the old program 723-G2-L214J\ to the new pro- gram. Other changes have been made to Increase the program's flexlb11lty to handle a wide variety of ~~ater surface profile prol,lems. A data edit program (723-Gl-L202C) wh1ch reads the data cards for pro- gram 723-x6-L202A and checks the dat., for vllrlous Input errors Is a 1 so ava 11 ab 1 e. Purpose of Programs. A basic descriptIon of the purpose of the back- water program Is summarized In the HEC-2 Water SurfaCE' Profiles Manual. The program computes and plots the welt'.r surface profile for river channels of any cross section for flows !jreater or less than critical. The effects of varIous hydraulIc structures such as brIdges, culverts, weirs, embankments, and dams may be (:o'1sl dered In the computation. RIver conditions such as varIable channel roughness, Islands, bends, levee overflow, rIver confluences, and waterfalls melY also be Included. Jnvestlgatlng channel roughness from k110>m high wate,r marks is one of several specIal program applIcatIons. Input may be In either English or Metric units.