Identification of permanent surface water in Bengawan Solo River downstream area, Indonesia using Sentinel-1 imagery

Permanent surface water is defined as area of the Earth continental surface corresponding to an accumulation of water, showing slight variations in water levels, retaining most of their volumes over the year and that do not dry up. Bengawan Solo watershed, especially in the downstream area is situated in East Java, Indonesia and is recorded as the longest and the largest river on Java Island. Thus, this river becomes one of the biggest water resources in Java, Indonesia. As a water resources, it is important to identify spatial distribution of permanent surface water in Bengawan Solo River. Synthetic Aperture Radar (SAR) is an effective way to detect surface water over large areas. Sentinel-1 is a new available SAR and its spatial resolution and short temporal baselines have the potential to identify permanent surface water. Thus, we propose an identification of permanent surface water using Sentinel-1 data. The quantitative evaluation shows relevant results with overall accuracy of more than 97%, F-measure provides value 0.79, also very low False Positive Rate and commission error. There are also morphological and land use change detected in the area. These results are encouraging and the first step for monitoring Bengawan Solo River.