Author(s): Rocky Talchabhadel, Hajime Nakagawa, Kenji Kawaike

Linked Author(s): Hajime Nakagawa, Kenji Kawaike

Keywords: Beel; Digital elevation model; Sediment deposition; Tidal river management;

Abstract: High-accuracy airborne digital elevation models (DEMs) are not always available esp. in developing countries. Relying on spaceborne DEMs is one of the popular approaches. Our objective is to best utilize the available spaceborne DEMs. This study focuses on the estimation of the sediment deposition by the operation of tidal river management (TRM) in southwestern Bangladesh (SWB) which is seriously suffering from perennial pluvial flooding. TRM is the process where the designated lowland (beel in Bengali term) is connected to the tidal river by opening/cutting the embankment and letting the natural tidal flow up-down for land-heightening, river deepening and managing drainage congestion. Better topographical data is necessary for the estimation of sediment deposition. This study uses the three spaceborne DEMs namely 1) AW3D, 2) SRTM, and 3) ASTER. We also used high accurate terrain elevations (Yamazaki et al., 2017), MERIT DEM, where multiple error components are removed from existing spaceborne DEMs (excluding ASTER). In the case of Polder 24 in SWB, MERIT DEM also shows that almost whole areas in two eastern beels are with same elevation values, which is not realistic. We considered the use of ASTER to fill the gaps of MERIT DEM. Raw and improved DEMs were then used for the simulation. The simulation model is a two-dimensional unsteady flow model based. MERIT DEM shows higher applicability than raw DEMS and improved DEM is found to be superior. Our results showed that the error of one DEM could be reduced by using another DEM or locally surveyed information.

DOI: https://doi.org/10.3850/38WC092019-1268

Year: 2019