Abstract: Submerged rigid aquatic vegetation can be found in a large number of water bodies, such as oceans, rivers, reservoirs, lakes, and canals. Vegetation could impose a great impact on flow structure, riverbed scour and silting, flood process, and navigation; and a systematic study of river flows with vegetation is fundamental to better understand the impact of aquatic vegetation on river flows. In this work, we model rigid aquatic vegetation with arrays of glass rods, and measure the open-channel flows on a laboratory flume using a three-dimensional laser Doppler velocimeter (LDV). Four vegetation arrangements are examined ? parallel arrangements with full-coverage and semi-coverage, staggered arrangements with full-coverage and semi-coverage ? with each being tested under four submergences. Systematic analysis of the measurements reveals that the density, arrangement and submergence of vegetation are closely related to water surface gradient, head loss, flow velocity, and turbulence intensity.

Key words: rigid vegetation, LDV, water surface gradient, head loss, flow velocity