Short-term analysis on shoreline morphological changes due to coastal structures

Numerical modeling of shoreline morphological changes due to groin field along Muttukadu, Chennai coast, is exposed to extensive erosion. Hydrodynamic analysis is carried out by using Delft3D and DETRAN modeling software. The WAVE and FLOW modules are coupled online models, used for the numerical simulations. The model domain considered for the study is 16km along the shoreline and 7 km seawards up to approximately 30m water depth. Bathymetry for the model is obtained using National Hydrographic Chart (NHO). Numerical Modeling is carried out for various combinations of the groin configurations viz., variation in height of groins, providing gaps of groins and groins with different widths. The model consists of two domains as shown in Fig. 1, an inner domain, with finer grid (15m x 15m), nested in outer domain, having coarser grids (70m x160m). The inner domain with finer grids is required to model the groins having a width of 15m. Simulation period is taken from January 2018 to December 2018 (1 year). And also, the studies have been carried out using remote sensing and geospatial technologies. The land sat images acquired from 2016 and 2018 were used to demarcate the rate of shoreline dynamics using GIS based Digital Shoreline Analysis System (DSAS) tool. In this study area, data has been processed in Arc GIS software. It is used as an effective platform to evaluate the shoreline changes from 2016 to 2018. The model calibration and validation are carried out using Digital Shoreline Analysis (DSAS) software, based on Geographical Information System (GIS) as shown in Fig. 2. Comparisons of shoreline changes before and after construction of groins are taken as satellite images as shown in Fig. 3. For hydrodynamic morphological analysis, a time series measured wave data is used along the Chennai coast and tidal data also measured at Kovalam coast. The Delft 3D model and DSAS, GIS result has been compared and the comparison showed a very good agreement. The study area shows, during last two years (2016 and 2018), erosion rates are more than the accretion of the shoreline occurred over the earlier periods. This hydrodynamic analysis, further emphasis the need for an integrated coastal management approach, so as to have proactive measures. This paper will give a detailed analysis and research outcomes on this numerical modeling.