SLOPE FAILURE TYPES:

Marine undercutting

marine_undercutting1 marine_undercutting2

SLOPE FAILURE NAME:

Marine undercutting.

DEFINITION:

Erosion on the toe of a cliff due to waves during storm surges against that debris mantles.

MAIN CHARACTERISTICS:

Marine undercutting appears as scars on the toe of cliffs, revealing outcrops of the debris mantles and, in case of Port Ganny, an old asphalted road.

Marine undercutting could lead to a reactivation of slope movements and potentially the destabilization of cliff profiles. The potential for this is most evident in Port Ganny, where reactivation of the scree behind the road is a distinct possibility. At the western part of Portnaboe, near the remains of a small jetty, the slope is extremely unstable due to undercutting.

CAUSES:

Storm surges, which can be accentuated if they coincide with high tidal moments.

AREAS PRONE TO FAILURE:

Weak debris mantled slopes that can be attempted by waves during cited storm events. Two specific areas have been identified: At Port Ganny, on the Causeway Road near Giant’s Causeway, and on the western part of Portnaboe.

OCCURRENCE:

Storm surge events.

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