Evolving waterlogged identification system to assess spatiotemporal impact of the new Suez Canal corridor, Egypt

Abstract

This study was designed to assess how accurately waterlogged areas can be detected from medium-resolution satellite images. The objective of this paper is to propose an automated extraction system to identify and map waterlogged areas around new Suez Canal in Egypt. Three Landsat-8 imagery (2014–2015) and topographical maps (1:50,000) had been used along with field observations. The applicability of different satellite-derived indices, including normalized difference water index (NDWI), modified NDWI (MNDWI), normalized difference moisture index (NDMI), water ratio index (WRI), normalized difference vegetation index (NDVI), and automated water extraction index (AWEI) were investigated for the identification of waterlogged areas from Landsat-8 data. The results indicated that the MNDWI and NDWI are good indices. Evolving waterlogged identification system (EWIS) was proposed as a simple automated method to identify and extract the waterlogged areas. It was found superior to other indices and hence it was used to model the spatiotemporal changes in the waterlogged areas around the new Suez Canal. The results also showed that the waterlogged areas have been increased (positive change, +1, 453 ha) and lands have been decreased (negative change, −1,449 ha). Three-thousand, four-hundred and sixty-three (3463 ha) Hectare were identified as waterlogged areas after excluding the other water sources in the period from 06/08/2014 to 05/05/2015. In order to determine the dominant topographic factors in the study area, high-resolution digital elevation model (DEM) was created. Out of five terrain analysis (elevation, contour, relief, slope and curvature), two factors (elevation and contour) were considered as important. Finally, to figure out the relevance of this technique toward mapping of the waterlogged areas, a correlation matrix had been prepared. The results were acceptable for an understanding of waterlogged areas, which are significantly correlated with topographic factors. Based on different maps, it was observed that the factors like relief, slope and curvature have a disproportionate relationship, while elevation and contour have direct proportion with the spatial distribution of waterlogged areas.