Spur dike layouts impact on upstream flow conditions during flood wave movement

Despite the widespread application of spur dikes in river training projects, the performance of the structure during flood events and its impacts on unsteady flow conditions have rarely been studied. In this experimental investigation, the influences of twelve unsubmerged unilateral and bilateral spur dike layouts on upstream flow conditions during flood movements were examined. Three hydrographs with varying unsteadiness intensities were generated and applied to all layout tests, including the no-spur condition for comparison purposes. The results revealed that discharge directly affected changes in flow depth upstream of the spur dike, while the flow rate trend exerted inverse influences. The Keulegan-Carpenter number was modified to assess the impact of unsteadiness intensity on the rating curve loop. Stage hysteresis analysis demonstrated an increase of more than thirty times compared to the no-spur scenario, highlighting the elevated risk of flooding in the upstream reach while delaying peak flood arrival time. This has implications for flood risk management and warning programs. The results underscore the significance of considering not only peak discharge but also unsteadiness intensity in spur dike design.