Sedimentomorphic geodiversity in response to depositional environments: remote sensing application along the coastal plain between Ummlujj and Al-Wajh, Red Sea, Saudi Arabia

In the framework of the Saudi Vision 2030, which intends to develop the coastal areas along the Red Sea to establish some of the
world’s most attractive tourism destinations, we conducted this study to offer decision makers with one case study illustrating the
role of geoscience while planning for such mega projects. The coastal strip between the cities of Ummlujj and Al-Wajh was
selected for the present study due to its suitability for construction of such resort project due to the wide coast reaches (10 km),
low slope ranges from 0.1 to 5 with slope of the plateau less than 15°, and a general slope trend of the area toward the W,NW, and
SW with a subordinated trend to E-NE. Environmental assessment of the study area reflects sedimentomorphic geodiversity
relevant to three different depositional environments. These are the colluvium, coastal marine, and aeolian geodiversity. The
sedimentomorphic geodiversity of the colluvium environment is associated with the major wadis in the area. It comprises
mangroves, mudflats, nebkhas, and alluvial terraces. The sedimentomorphic geodiversity of the coastal marine environment
comprises coral reef terraces of two levels at 1 m and 3–5 m ASL, coastal lagoons, marine sands, and coastal sabkhas. The
sedimentomorphic geodiversity of the aeolian environment comprises sand dunes and sand sheets 9–20 km away from the coast.
Assessment of environmental hazards that may threaten the area includes the vulnerability of the northern part of the area to flash
floods at Wadi Al-Hamd basin with an approximate area of 41,897 km2. This allows alluvial fan, tidal flat, and mangrove
growing areas. Another hazard factor is the fast growing dune movement in a high-energy aeolian environment eastward of the
area shows a mean annual rate of 15.7 m. A sedimentomorphic map is developed based on the obtained results with further
recommendations to consider the sedimentomorphic elements while planning coastal zones.