EVALUATION OF THE EFFICACY OF WATER CHANNEL PLANNING FOR THE NAGAOKA CITY AREA OF THE SHINANO RIVER

摘要

An effective flood-control strategy for mitigating flow attack points in a meandering river with a steep bed gradient and alternate bars is to preserve the floodchannel and stabilize the water course. In the Nagaoka City Area River Plan, main channel alignment was determined according to the results of hydraulic model tests, and training levees were built as the primary means of stabilizing the main channel. To assess the channel-improvement efficacy of these works over the 25 years that have passed since the project began, the authors used the results of field observations, model tests based on the adopted plan, and computational analysis. This paper compares and considers the actual observed effectiveness of the flood control works in the river and the results of model tests and numerical analysis with regard to main channel planning, bed evolution, flow attack point mitigation, and other factors.