Coastal land degradation severely affects low-lying shorelines along the Gulf of Guinea in southern Nigeria. Which of the following represents the correct chronological sequence of physical processes that lead to coastal cliff and beachfront retreat?
- 1Hydraulic action and wave abrasion continuously erode the base of coastal slopes.
- 2Basal notches develop along the shoreline face, removing structural support from upper material.
- 3Unsupported overhanging rock and soil collapse under gravity onto the beachfront.
- 4Wave backwash transports collapsed debris seaward, exposing a bare slope face further inland.
Answer
The correct sequence of coastal land degradation begins with hydraulic undercutting at the slope base, followed by basal notch development, mass collapse of unsupported overhangs, and finally seaward removal of debris by wave backwash.
Coastal degradation progresses systematically: wave energy concentrated at the shoreline base causes hydraulic undercutting, leading to notch formation. The loss of underlying support causes gravitational mass failure of unsupported overhanging material, and subsequent wave backwash carries the debris seaward, resulting in permanent shoreline retreat.
Step-by-Step Solution
Key Concept
Sequential Stages of Coastal Erosion and Shoreline Retreat