Flow backup caused by structures within open channel

Abstract

With the introduction of the Active, Beautiful, Clean program, hydraulic structures such as piers may be required to be built within water channels to support decks built over the water channels. These hydraulic structures may cause excessive flow backup, resulting in flooding on the upstream. This study is done to study how to minimize the impact caused by these hydraulic structures.

A hydraulic modeling program, HEC-RAS has been used to model the plausible impacts different piers parameters may have on flow backup. Energy, momentum and Yarnell's method are used to arrive at the analytical results. The parameters being studied includes drag coefficients, shape factors, the number of piers in the transverse direction, shapes of piers, the percentage blockage,contraction/expansion coefficients, number of piers in longitudinal direction as well as using wall instead of series of closely packed piers.

Results have shown general trend of higher flow backup with increasing blockage and increasing number of piers in the flow direction. Wall has shown to cause lower flow backup compared to multiple closely packed piers. Changing number of piers in the transverse direction has shown little impact on flow backup.