NAVIGABLE BRAIDED CHANNEL CHARACTERISTICS WITH THE EFFECTS OF NARROW PASS

Abstract

 This study presents bed deformation phenomena in the braided stream by experiment first and the effects of a narrow pass on navigable channel characteristics in braided stream are discussed. Two 10 cm x 10 cm timber posts are set at both sides of the flume to make a narrow pass section. The depth integrated two dimensional flow calculation was conducted to evaluate horizontal distribution of water depth in the experimental flume to clarify the effects of a narrow pass on the water depth along thalweg. The narrow pass makes channel geometry more stable and the difference of bed elevation between channel bed and bar crest is larger. As a result, the flow depth tends to be deeper and it is easier to keep the navigation flow depth. Therefore, the deep-water depth could keep for navigation on braided channel and maintenance of a fairway after some years. It could be effectively reduced the dredging frequency as much as possible to keep the deep flow depth for the navigation due to the effect of a narrow pass.