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several storage reservoirs located on major tributaries of the Colorado River. Emergency actions have in the past been successful, but such actions do not guarantee success and are costly. These measures do not offer a sound and permanent solution and were, therefore, deleted from further consideration. . Flood proofing of structures could be performed either by constructing ring levees around the structures or by elevating the affected structures above flood stage. Ring levees in the Riverside community are not feasible due to the lack of space between structures. Any ring levee would take up much of the land around each residence. Clustering the houses within larger ring levees would result in the same problem since each city block is fully developed. The Rosevale community is more amenable to protection with ring levees due to its characteristic clumping of residential houses in less developed areas. However, flood proofing with ring levees was deleted from further consideration since such costs usually exceed those for a banks ide or setback levee due to the need for specialized equipment and additional rights-of-way. Elevating affected structures was retained for further consideration as being the most likely nonstructural measure. (2) Channel Modification. - Deepening the channel was considered but rejected for several reasons, including significant disruption to the environment during initial dredging, questionable effects on or lowering the flood stage, and future maintenance required due to the high sediment load of the river. Channel deepening would also require modifications to the Grand Avenue bridges at considerable cost. . (3) New Upstream storaae. - storage upstream of the study area would require costly dam and reservoir construction or enlargement of existing storage reservoirs for flood control. These options were well beyond the scope of flood control work required for the subject study both economically and environmentally and were, therefore, deleted from further consideration. (4) River Diversions. - Water diversion for flood control would likely be through the expansion of existing irrigation conveyance structures. In order to reduce the flood elevation in the Colorado River significantly enough to avoid damages, the conveyance structures would need to be enlarged to carry many times the flow they currently handle. Such actions are also beyond the economic and environmental scope of the subject project. (5) Levees and Floodwalls. - Bankside levees were initially considered but rejected for the following reasons. The cost of constructing banks ide levees would have to include significant costs for riprapprotection as well as establishment 10 .