Coastal and Other Hazards

Date: 2007 February 10th Saturday
Location: along the coast of Eastern Jamaica
Presenters: Mr. Rafi Ahmad and Richard Coutou

On the road to Kingston Habour

There are noticeable disasters related to earthquakes. Financial institutions, industrial plants and quarries are present in this area where earthquakes occur. In 1907 an earthquake caused landslides to be triggered. Earthquakes in the past have caused changes in the emissions of springs. On the left hand side the Habour View Community is built on an alluvial fan which is prone to flooding. After the airport round about on the right hand side, a school is built (Donald High) on an area which is known to suffer from liquefaction caused by the 1907 earthquake. Further down a community was affected by storm surge. Why do these communities set up on these hazardous areas?

Eastern edge of Habour View Community.

The area between the mouth of the Hope River to the tilted house, have been affected by Hurricane Ivan in 2004.The force of the water damaged the houses on the coast. Caribbean Terrace was affected as well. The government had to relocate persons and forbid any house construction. However, construction at Caribbean Terrace was under taken to prevent flooding from the Hope River. It cost 3-4 million dollars to build each house.

Studying this area has brought forth questions about what is being done to reduce the effects of storm surges in the Caribbean. Between the years 1995-1999 Disaster Mitigation was set up in the Caribbean. P.A.S Module was set up to predict the type of storm surge. A map was prepared for this area in Habour View since 2000 but it has not been in used.

An area like this is susceptible to liquefaction, storm surges, possible tsunami and flooding of the alluvial fan. Hence it is known as a multiple hazard area. The storm surge was about 2.5m high and the concavity of the coast line is favourable for high waves.

Driving along the road on the left hand side there were some unconsolidated (unstable) rocks at the end of the Dallas Mountains. The earthquake in 1907 caused landslides and quarry workers used this to their advantage. The water supply from Yallahs is being affected by houses being above and below the pipeline. It is one of the main sources of domestic supply in Kingston/St Andrew.

Chalky River in Bull Bay is full of sediments which causes flooding on either side of the river. Bull bay is affected by sediment floods by the river or by the cement company. Nine Mile Bridge in Bull Bay is inefficient for sediment to go through it. When the bridge is choked water has no where to go but to flood the community. The river crosses the road folding. The design of the bridge needs to change. However, making any changes now would cause traffic congestion and chaos. It was noted that material dredged from the river was placed on the side of the bank and a school was built on the sediment. This is a cause for a major disaster.

The area which is considered to be the “most driest” part of Jamaica, is witnessing house construction. Where are these people going to get water? Lack of water can cause hygiene problems. The land being cleared for theses houses is on limestone rocks and bare limestone reflects radiation.

On the way we were driving through spurs and valleys. It was noted that heavy loads of trucks destroys the road. Many load bearing trucks were noted as we drove on. Scales were to be put to restrict the amount of load a truck can hold. Gravel and sand are mined from the Yallahs River by big companies for building industries. These are transported on the road, damaging it. The roads are usually dusty because of the sand.

An excellent outcrop of Pliocene Limestone (on the right hand side) in Grant’s Pen, with clear bedding planes and noticeable dip direction was observed.

Yallahs River

We stopped at the distilled part of the Yallahs fan- delta. The river carries a tremendous amount of sediments. These sediments originated from landslides from the catchment area further upstream. The raised areas are built up sediment. Years ago the concrete we were standing on was a folding but did not last. A bridge was built but that was knocked down in 1992. The area is affected by sediment flooding on the alluvial fan. A very expensive bridge is going to be constructed so that vehicles would not have to cross the river itself.

Judgment Cliff landslide was seen on the left hand side. To the right as we drove on, there was a salt pond, brackish with high salt content. It was once part of the sea and has been enclosed by longshore drift forming a spit. There is no life in the pond but it is suggested that shrimps might be able to live in this environment. There is a special bacterium that gives off a foul smell in pond. To the left hand side a satellite was titled by the 1978 earthquake which was 4.2 on the Richter Scale.

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