A simple method for estimating flood discharge in gravel-bed channels with varied riverbed level

The information of flow discharge in channels is crucial for river planning and regulation, weir and reservoir operation, river crossing and encroachment remediation, and river restoration. It also affects the degree of erosion on the channel bed and river bank, and scour around structures in the riverine environment. During a flood event, large scour on the channel bed and rapid sediment transport along the channel reach occur at the flood rising stages. Significant changes of riverbed level appear consequently. However, the conventional method of on-site measurements is time-consuming and dangerous for the investigators. A simple method utilizing non-contact water-surface velocity radar (SVR) and ground-penetrating radar (GPR) was developed. Two rating curves, the relationships for the stream mean velocity and river cross section to the stream surface velocity, were investigated. The resultant stream discharge shows great improvement of the estimation of entire flood hydrograph, indicating that the proposed method has the capability to reasonably estimate the flood discharges of gravel channels with mobile bed