Geomorphological change detection of an urban meander loop caused by an extreme flood using remote sensing and bathymetry measurements (a case study of Karoon River, Iran)

Abstract

Flooding and flood inundation are key hydrological characteristics of meander Loop Rivers. However, the effects of extreme floods on river morphology and spatial patterns of erosion and deposition are poorly understood. A detailed geomorphologic change detection and sediment/erosion process caused by an extreme flood (more than 100-year recurrence interval discharge) on 14 Apr 2016 was surveyed for a single urban meander loop of the Karoon River, Iran. The studied meander loop is located next to the city of the Ahavz and has a centerline length of about 14 km. The bathymetry in 8892 stable points was measured, also the detailed bathymetry layers for before (8 Apr 2016) and after (24 Apr 2016) the extreme flood event were compared. Geomorphological change detection (GCD) results show that in the studied reach about 106 ha of bank erosion was detected, with a total volume of approximately 450,600 m3. Furthermore, total volume of surface lowering and the total volume of surface rising volumes that were obtained were 95421.6 m3 and 98619.0 m3, respectively. The talweg length of the studied meander loop decreased about 126 m, and the average depth decreased from 3.71 m to 3.14 m after the flood event. Channel widening as a consequence of the extreme flood was found to be about 21 m (17%). The findings of this study indicate that extreme floods play an important role in the sediment budget and morphological evolution of meandering rivers.