Assessing coastal erosion and accretion trends along two contrasting subtropical rivers based on remote sensing data

The temporal shoreline position is a key indicator of coastal development and provides information on beach dynamics. Previous studies have indicated that there is a strong relationship between riverine sediment fluxes and beach volume. As such, worldwide hydroelectric projects and the associated damming infrastructure have decreased suspended sediment loads, and consequently increasing coastal erosion and deterioration of wetlands. The study was conducted along the coastline of the San Pedro River and the Santiago River on the Pacific coast of Mexico. Both rivers discharge into the ocean separated by 12 km of coastline, however the San Pedro River does not present dams through its watershed. Contrary, six dams had been constructed along the Santiago River since 1976. Results indicated that after 45 years, the San Pedro River coastline presented minimum variability and a total of 379 ha of accretion. Contrary, the Santiago River coastline showed major erosion trends with a total of 669 ha of beach and wetland losses. Our study highlights the feasibility of combining historical remote sensing data and GIS analysis in order to assess coastal variability trends when field-based surveys are not available.