Author(s): Masakazu Fujikane; Takahiko Chino; Shiro Maeno
Keywords: River improvement; Flood control plan; Hydraulic alnalysis
Abstract: The Hyakken River, a diversion channel of the Asahi River, is an artificial flood control channel constructed about three hundred years ago during the Edo period to protect Okayama castle town from flooding. Three fixed overflow weirs were constructed at the bifurcation point. Two of them, the first weir and second weir, remain at their original locations. The first and second weirs still play an important flood control role, although its shape and structure have changed somewhat because of repairs conducted after repeated failures by frequent floods. A plan exists to reform the remaining fixed weirs into a movable weir, but residents have voiced strong demands for conservation of the fixed weirs. To satisfy those demands, hydraulic model experiments and analyses were conducted to evaluate the possibility of conserving the remaining structures. Hydraulic model experiments and numerical analyses related to the distributary structure under the design flood condition show that conservation of the remaining fixed weirs from the Edo period is possible. Furthermore, based on expert committee recommendations, a flood control plan has been developed to include the use of the remaining fixed weirs with minimum reinforcement.