Upstream Flood Lowering in Reservoirs

Dams can lower flood levels near upstream limits of their reservoirs. This lowering has been observed at four Tennessee Valley locations. The phenomenon is called upstream flood lowering. It results from increased flow carrying capacity primarily due to deep longstanding reservoir waters in alluvial valleys. This smooths channel linings and eliminates vegetation. The effect occurs early in reservoir life and is permanent. Added quantitative documentation elsewhere is invited worldwide toward identifying parameters which will allow advance prediction of upstream flood lowering in the project planning stage. Major reservoir cost savings can result. The basic paper was presented at the September 8-10, 1954, ASCE Hydraulics Division meeting at Austin, Tex. but was not published. In a l974 addition, 20 yr. of added data confirm upstream flood lowering but show that the lowering was underestimated significantly at one and somewhat at two of the four locations.