Aerial photographs taken near the Thames Estuary show a newly constructed sea wall protecting low-lying farmland. Fig. 1 shows the wall, the salt marsh on i...
Question 1 Report
Aerial photographs taken near the Thames Estuary show a newly constructed sea wall protecting low-lying farmland. Fig. 1 shows the wall, the salt marsh on its seaward side and a drainage ditch behind it. The farmers want to reduce flooding during storm surges, but an environmental group has asked for the salt marsh to be retained because it provides habitat for wading birds.
(a) State one purpose of a sea wall. [1]
(b) Explain how a salt marsh can reduce the impact of waves on the sea wall. [2]
Coastal rangers at Flamborough Head have mapped an area where a cave roof collapsed last winter. Fig. 1 shows the present cliff profile, including a small inlet and a detached rock feature. The rangers need a simple explanation for visitors about why erosion is strongest where waves are focused against the rock. They also inspect the area after high tides to keep walkers away from unstable ground.
(a) State the name of the narrow inlet in the headland shown in Fig. 1. [1]
(b) Explain why wave energy is concentrated on a headland. [2]
Answer Details
Sea wall and salt marsh
(a) A sea wall is built to prevent flooding and protect land or property from the sea. [1]
(b) Salt-marsh vegetation and muddy sediment create friction, slowing incoming water. This dissipates wave energy before waves reach the sea wall, reducing its exposure to damaging wave force. [2]
Headland erosion
(a) The narrow inlet in the headland is a cave. [1]
(b) As waves enter shallower water around a projecting headland, they are refracted. The wave fronts converge and become closer together at the headland, concentrating wave energy there and increasing erosion. [2]
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