Sound of the Flow over Groundsels and Sabo-dams

Abstract

Various trials have been performed to harmonize the sabo structures with the surrounding Nature. Mild slopes with rough masonry roughness attached to groundsels are among these structures. They look better than ordinary drop structures. What makes them better? How can we improve them? We focuses on the sound of the flow over groundsels and sabo-dams. A series of model experiments was carried out. The levels of sound and frequency distributions were measured and analyzed and the sound of the actual flow was analyzed using similar procedures. The actual flow sounds include some in a compact disk commercially recorded and our own material recorded in the field.
The noise level was higher for ordinary drop-type structures than for slope-type structures. Flows with large quantities entrained air showed higher noise levels. The predominant frequency was high for small discharges and low for large discharges. The power spectrum of ordinary drop structures was similar to that of natural waterfalls in some parts. The flow on slopes had a wide spectrum. The similarity was confirmed in terms of the differences of noise levels between models and fields. The noise level increased with the drop number.