Established Surge in An Impervious Vegetation Bed

Theoretical and experimental determinations are made of the steady flow of a surge of water onto a dry, impervious bed studded with artificial vegetation—wires—protruding through the flow at densities of 7.5, 29 and 116 wires per sq ft. The pertinent differential equation of the flow profile implies movement on a broad front, hydrostatic pressure distribution, no interference between the wakes of the individual resistance elements and constant bottom shear between the elements. Experimental data on profile shape and tip speed are gathered and recorded electrically by a combination of parallel-wire resistance probes, a scanner, an a. c. resistance bridge, and Sanborne recorder. Comparison of these data, brought to nondimensional form, with an analytic solution of the differential equation in similar form shows good agreement when the measured tip velocity has decreased from its initial value to within 5% of its terminal value, the flow velocity at normal depth.