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, ' o . (~:") N "'-l o ~ to the Arkansas River preventing flooding of cropland between the Amity Canal and the Arkansas River. A reinforced concrete structure placed in the Amity Canal dike wDuld consist of seven radial gates each twelve feet wide. The gates would pass the 3,600 cubic feet per second (c.f.s.) flood- flows to the f1DDd channel. The seven gates will be Dpened and the head- gate closed on the ARkansas River priDr to flood flows reaching the Amity Cana 1 for proPElr operati Dn. Two reinfDrced concrete strai ght drop structures will control abDut 12 feet of excess grade from Amity Canal to the Arkansas River and keep velocities in channel to around five feet per second (f.p.s.). The channel bottDm width and weir length Df the drDp structures is 65 feet, with a channel depth of 10.5 feet. . Pleasant Valley Drainage , Three miles downstream Dn the Amity Canal is Crosses the Pleasant Valley drainage. F1DOd flows from this drainage has caused dike breakage also, and disruption of irrigation service. Structural wDrks prDpDsed for controlling floodwaters is similar to prDposal on the Wiley Drainage. Five radial gates installed in the Amity Canal dike would pass 2,500 c.f.s. to the floDd channel fDr transpDrting flDWS to the Arkansas River 5,300' feet from the Amity Canal. About 30 feet of excessive grade exists between the Amity Canal as it crosses Pleasant Valley drainage and the Arkansas River. Five reinfDrced concrete straight drop structures will , be requi red to remove the 30 feet Df excess grade and keep channel velocities belDw five f.p.s. , The bottDm width of the flood channel and weir length Df drop structures wou1dbe 60 feet with a channel depth of 9.0 feet. Controlling damaging flDOd flows from bDth Wiley and Pleasant Valley drainages depends on having gates to floDd channels open prior to flood flows entering the Amity Canal. N AT U R E AN DES T I MATE 0 F CO S T S Oi stances and e 1evati on difference acqui red from U.S. G. S. topographic 'maps were used in preliminary design of flood channels. Design of concrete structures and channel capacity were based Dn a 25-year frequency peak flow. Quantities along with up-dated costs were used in developing an estimated' constructiDn CDSt. Landrights CDSts were considered fDr approximately 25 acres of private land for channel right of way. Engineering, services and project administration are 14 percent and 17 percent, respectively, of the construction CDst. Average annual operati on and maintenance costs were estimated as a percentage of the cDnstructiDn cost. The total estimated installation, ' cost is $596,300 (Table II). The average annual cost which includes $2,300 for operation an~ maintenance is $44,200 (Table III). \ , '-, -3-'