Source: Chiun, Ming L. 1985. Impact of check dams on steep mountain channels in northeastern Taiwan. p. 540-548. In S.A. El-Swaify, W.C. Moldenhauer, and A. Lo (ed.) Soil erosion and conservation. Soil Conservation Society of America, Ankeny, IA.

Ming L. Chiun summarizes his ideas about the construction and utility of check-dams. His study determines the changes in channel cross-sections, channel gradient, and bedload size composition after check-dam construction and evaluates the effectiveness of check-dams. Mr. Chiun referred to previous measurements of channel morphology and cross-sectioned dam sites to analyze sediment accumulation and particle size. Each year for three years rain of 100 mm or more fell during Chiun's study. These rainfalls were representative of the averages for Taiwan during the preceding 25 years. Average sediment yields from three different watersheds studied were about 26, 59, and 79 cubic meters respectively. The construction of check dams appeared to reduce sediment erosion. Each check dam blocked sediment flow significantly within two or three years. Chiun used channel profile to show the gradient above check dam sites was much steeper before than after the dam was built. Depending on the slope, the check dams changed the size composition of the substrate in the stream channel. The measurement of particle size was found through the comparison of sediment mean diameter before and after deposition occurred. The bedload deposited behind check dams ranged from fine, well-sorted sand to coarse gravel mixed with large cobbles. The mean particle diameter was much finer in higher dams (higher channel slope) while coarser in lower dams (lower channel slope). Prior to the construction of the dams, about 24,000 cubic meters of sediment were removed from 90 meters of channel in two years. The depth of the removal averaged from 1.2 m to 6 m. Before the check dams were installed, the channels of all three watersheds had been severely elevated so that the waterway openings of bridges could not drain a big storm flow. Therefore sediment was carried away at a high rate. Through a system of check dams, sediment yield rates can be decreased. The check dams serve as a stabilizing agent. Now, dam construction in upstream channels has become a common tool of sediment control in this area.

Abstract author: Michelle A. Russell, 12 November 1996.

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