Sustainable opening of Adayar River mouth

Adayar river flows through Chennai city of India. A portion of the sewage from Chennai city drains into the Adayar, which needs flushing into the sea to avoid pollution due to stagnation. The river mouth is characterized by the formation of sand bars at the confluence with the sea, thereby resulting in negligible exchange. A detailed scientific study was carried out for the sustainable opening of the Adayar River mouth consisting of field data collection (during July 2019) for bathymetry, beach profiling and sediment characteristics and desk studies, including analysis of satellite imageries (2007-2016) using ARCGIS and numerical model study using DELFT 3D. Studies conducted using satellite imageries (2007-2016) and field measurements indicate that the mouth remained closed due to the sand bar formation up to the onset of the northeast monsoon in October. Assessment studies have been carried out using satellite data to understand the inlet closure problem and the behavior of the Adyar river mouth. The data analysis shows that the reversal in the current direction and its impact on the accretion/erosion pattern is typical of the phenomenon observed along the East coast of India. To devise a suitable scheme for sustainable mouth opening, dredging of the river mouth and sediment nourishment scheme is evaluated using the numerical model study. The model has been calibrated and validated using the data from the field data collection during July 2019. The model run with the proposed scheme was carried out from July 2017 to August 2018, during which continuously measured wave data was available. From the results, dredging of river mouth and nourishment of eroded northern coast is found to be suitable for the Adyar river mouth, considering the positive impacts on the adjacent shoreline