Effect of Submerged Weeds on the design: Procedure of earthen Egyptian canals

Abstract

It is usual practice, in good conditioned earthen Egyptian canal design, to assume that Manning's roughness coefficient is equal to 0.025. Field monitoring showed that more than 40% of the canals are infested by Submerged Weeds (Potamogeton pectinatus, Potamogeton nodosus andPotamogeton crispus), in which case Manning's n-vlaues are higher than in the design. A numerical procedure for the design of canals with submerged weeds in Egypt is presented. The procedure is based on the Manning formula and the n-vR relationships, vegetation density and different types of distribution of submerged weeds along the canal cross-section. The presented numerical solution is an iteration process within the capabilities of a scientific pocket calculator.