ODPEM says retaining walls may not prevent landslides

THE Office of Disaster Preparedness and Emergency Management (ODPEM) is warning that the practice of erecting retaining walls as a solution to landslides may not be the best option.

Project Manager for the Community Based Landslide Risk Reduction Mitigation Project (CBLRRMP), at ODPEM, Kirk Frankson, pointed out that retaining walls actually make the problem of landslides worse, because in many cases the actual volume of soil and water builds up behind the walls.

CBLRRMP is a low-cost slope mitigation pilot plan to be implemented in four test areas in Jamaica. It is funded by the World Bank at a cost of US$2.375 million.

He explained that when a retaining wall is built, oftentimes it is not properly constructed and so frequently, during heavy rainfall, water builds up resulting in the collapse of the structure.

Underscoring the point, Research Analyst at the ODPEM, Christopher Gayle, explained why retaining walls fail.

“Retaining walls, if not constructed properly, act as a dam or a holding mechanism for (excess) water, which may fail if adequate provision is not made for draining within the retaining walls. So, we’re saying if you’re looking at cost effectiveness, drainage solutions are better than the more expensive retaining [wall] solutions,” he said.

He added that in a lot of cases, the walls are usually thinner than what is required for an “adequate” retaining wall, hence they bulge, slant, flip or break up from the force of the contained water.

Meanwhile, Frankson said that various low-cost strategies are being investigated under the Management of Slope Stabilisation in Communities project (MoSSIC).

These strategies include traditional terracing, benching of slopes, planting of grass and the implementation of drains and gutters.

The first community test case, Harbour Heights, a former Operation PRIDE settlement, is now a regularised community which overlooks Harbour View, where some $50 million is to be spent erecting a network of drains, channels and rainwater harvesting strategies that will act as natural hazard intervention techniques.

The strategies being tested under the MoSSIC were developed by geologists, Professor Malcolm Anderson and Dr Elizabeth Holcombe of the University of Bristol, in the United Kingdom, and funded by the World Bank.

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ODPEM says retaining walls may not prevent landslides