Spatiotemporal variation of sedimentation in an agricultural drainage canal with eco-friendly physical structures: a case study

Excessive sediment deposition in eco-friendly physical structures introduced in agricultural canals sometimes damages the function of these structures as fish habitats. This study reports the spatial and temporal changes in bed elevation in a canal section where a set of six fish nests and one fish pool were installed. Field observations and numerical simulation using the two-dimensional hydrodynamic model, Nays2DH, were conducted to describe the circumstances in which sediment deposition and scouring occur in the structures. The bed topography of the canal section was surveyed 12 times during 2016–2019, at 19 transverse cross sections of the area. The measured bed elevation was interpolated to estimate its spatiotemporal variation, sedimentation timing, and change in sediment volume. The results of this work clarified that deposition and scouring occurred in a 1-year cycle in the fish nests. The accumulation of sediment in the whole study area was found to be lower than expected. These results could provide insight for designing fish pools and fish nests that require less maintenance in an eco-friendly canal influenced by soil transport from surrounding paddy fields.