Computation of resistance coefficient and conveyance capacity in compound channels

Stage-discharge curves are particularly important in river basin management.For compound channel,it is difficult to produce the stage-discharge curve.In computing conveyance capacity,adopting either the single channel method or the conventional divided cross section method will result in enormous error.In this paper,a compound channel is divided into four subregions:the flood-plain-side-slope region,the flood-plain region,the main-channel-side-slope region and the main-channel region.By analyzing a large numbers of experimental data from the Science and Engineering Research Council Flood Channel Facility(SERC-FCF),the Darcy-Weisbach resistance coefficient relationships among them are established.The experimental data from SERC-FCF show that the resistance coefficient in main-channel region is related to the relative depth(Dr),the ratio between the resistance coefficient in flood-plain region and that in main-channel region varies exponentially with Dr,and the resistance coefficients in flood-plain-side-slope region and the main- channel-side-slope region can be expressed by those of the flood-plain region and the main-channel region.Finally,by computing the discharge in every sub region on the basis of the resistance coefficient relationships,the total discharge can be obtained.The experimental data show that the computed discharge is in close agreement with the measured one.