Abstract
The Ash Shuqayq coastline, is located (between latitudes 17 degrees 30' N and 17 degrees 45' N) along the Saudi Red Sea coast and was chosen for Landsat ETM investigations because it is a unique environment, being characterized by some of the most productive biological ecosystems and major geological environments (e.g. coastal reefs, mangrove stands, marshes, sabkhas, alluvial fans, sea cliffs. Landsat ETM data interpretation and analysis delineated seven major sedimentary environments: recent sediments sands dunes, sabkhas, sand beaches, lagoons, wadis, organic matter and vegetation areas. Coloured images from band 4 distinguished between classes (e.g. soil composition, vegetation, and moisture content) that have certain common characteristics in the unsupervised classification image. Coastline bathymetric mapping was undertaken using a mosaic of unsupervised image and true colour image bands 3, 2 and 1, and false colour images bands 7, 4 and 1, and 4, 5 and 7. Image interpretation and analysis enabled delineation of the main geological units: proterozoic rocks extending to the east, a north-northwest trending belt of Mesozoic to lower Tertiary rocks in the centre, and a large area of coastal plain (Tihama Plain) of middle Tertiary to Quaternary deposits. Four water depth zones (<10, 10-20, 20-30 and >30m) were identified and most of the Ash Shuqayq coastal area is considered shallow (<10m), although other deposits in greater water depths (20-30m) were subsequently classified. This investigation also demonstrated the influence of geology, coastal morphology, sediment distribution and longshore transport on low-lying rocky and plain shorelines. Results documented beach geomorphological characteristics, which tended to be more dissipative and have lower gradient shorefaces, than those along the most northern part of the study area coastline. Analysis also demonstrated the valuable contribution Landsat ETM data can make to long-term coastal management.