Sediment Transport Modelling on the River Bandon

The River Bandon is located west of Cork City in the South Western River Basin District with a catchment area of 608km2. The town of Bandon, the largest urban settlement within the river catchment, has a history of flooding... [ view full abstract ]

The River Bandon is located west of Cork City in the South Western River Basin District with a catchment area of 608km2. The town of Bandon, the largest urban settlement within the river catchment, has a history of flooding with significant river improvement works planned for the summers of 2016 and 2017.

This paper presents an analysis of sediment behaviour and transport in the river system in the context of the overall river improvement project. A one dimensional hydrological software modelling package, HEC-RAS, has been applied to the river system. The model simulates hydraulic and sediment transport conditions and covers a 10.5km stretch of the river with 239 cross -sections from upstream of the town of Bandon to approximately 6.5km downstream. The model includes the river’s main tributaries (Bridewell, Millstream and Brinny) and various river structures. Calibration of the hydraulics of the model was undertaken for both in-bank and out of bank flow at the two hydrometric stations located within the model boundary (Bandon Bridge and Curranure). Satisfactory water level calibration was achieved by adjusting the Manning roughness coefficient to produce the lowest root mean square error for flows ranging from 148m3/sec to 330m3/sec (return periods of 2 to 100 years respectively using the L-moments approach). The hydraulic model was successfully validated using annual flow data. Calibration of sediment conditions in the model has involved the analysis of field suspended sediment concentration data at a turbidity measurement sensor at the Curranure hydrometric station and bed sediment data collected.

The HEC-RAS model is used to assess sediment transport and potential bed level change in the river system. The model is applied to simulate potential sediment transport impacts of the river improvement works on the river system.