Floodplain stability indices for sustainable waterfront development by spatial identification of erosion and deposition

Abstract

The abrupt rises of water level in rivers by torrential rain or storm repeatedly cause inundation damage, such as erosion and deposition in floodplains. However, studies on identifying the abrasion of waterfront facilities or the accumulation of sediment near rivers under extreme flow conditions are seldom found because floodplains are utilized in various ways in each country. In this study, novel floodplain sustainability indices by spatial classification of erosion and deposition were developed for sustainable waterfront development. The indices can provide the relative spatial distribution of erosion and deposition in a floodplain by using only kinematic flow information, such as flow depth and velocity obtained by 2D numerical analysis. Accordingly, applying a complex sediment transport model that involves numerous assumptions and parameters can be moderately replaced with the present approach. The suitability of developed indices was tested in several flow problems by comparing the predicted erosional or depositional region with measured data. In addition, the developed indices were applied to a floodplain in a natural river to examine the relative spatial distribution of the erosion and deposition for a typhoon event, and the results were compared with field monitoring data. It was found that deposition was more likely to occur than erosion in most floodplains, and the developed floodplain sustainability indices accurately quantified the erosion and deposition phenomena.