Factors contributing to the Vulnerability of the City to Flooding

East Dry River Port of Spain

The East Dry River gets its name due to the fact that during the dry season, the river is merely trickling in flow. This river before it was paved as seen in the picture; it was seen as a stream that had severe erosion cutting into its bank.  This River was once a social space in which children were seen to play amongst the roots of trees exposed due to erosion and women used the upper river where the water was the cleanest to do laundry. This was until the river became a garbage disposal, a sewer and in the end it posed serious health risk to people.  It was only in 1934 that the river was paved due to its erosion properties that threatened the households on Piccadilly Street, Port of Spain. This river came about due to the diversion of the St. Ann’s River which previously caused the town to flood during the rainy season. As such to prevent the flooding, and to aid in urban planning it was decided that the river be diverted. Read more on East Dry River's history here

Do you think that diverting the water flow will prevent the East Dry River from causing flooding as well?  The answer to this question is “No”. The East Dry River as well overflows its banks during the rainy season and this contributes to the main areas of Port of Spain flooding: The South Quay which is the main transportation hub, the Brian Lara Promenade/Independence Square and the network of streets which all makes up part of the Central Business District (CBD). Therefore when this flooding occurs, the main area that is affected is the highly populated city that is densely concentrated with businesses as well as households. This poses a serious threat to the economic gains of these businesses both of the formal and informal industries as well as affect the livelihoods of persons living in the area who become at risk to diseases from the flooded water.

 Why do you think the River overflows and contributes significantly to flooding in the city? This is as a result of not only the polluted waterways from garbage being disposed of in the river, but it has to do with the level of denudation taking place higher up in the hills. These elevated regions such as St. Anns, Laventille and Glenco in which development is taking place in terms of housing, are examples of areas that contributes to the amount of sediment being brought down during the rainy season. 

 Even though channel capacity can be increased to help in drainage, all this does is facilitate in moving greater volumes of water at a faster speed. When deforestation occurs by housing developments or unplanned developments or agricultural squatters and a rainfall event occurs, the run-off due to it being on a slope is removed quickly as there is no trees to intercept or infiltrate this water. As such the water under gravity is pulled down faster into the city. Due to the city being found in a low lying area, there is little to no vegetation for the water to infiltrate here and so the water stays on the surface and contributes to the widespread flooding within the city.Also contributing to the flooding of the city is natural degradation of the land which occurs during the dry season where bush fires are usually a serious problem. Due to the burning of these areas during the months of 'drought' the land becomes cleared and its surface is vulnerable to run-off as it is with deforestation.The level of deforestation or degradation seen can also lead to severe landslides which can contribute to the loss of property. This was a serious issue taking place in Diego Martin a few years ago. Read more on the disaster caused by Landslides in Diego Martin here.

Many years ago when planners decided to divert the river due to flooding, this was definitely a mistake because what they actually did was remove the problem of flooding from one area and directed it towards another. Therefore this type of flood management was unsuccessful because this created another flooding problem.

 Furthermore, flooding occurs due to several contributing factors that all play a role in blocking the easy flow of water. In order to prevent this, not only is the role Governments play by ensuring that there are numerous drains constructed to facilitate in the fast drainage of the low lying city important but also individuals as well needs to take a single handed vow preventing themselves as well as others from littering in these waterways. As the old saying goes, "Prevention is better than cure".

For future prevention of flooding of the East Dry river, what can be done by Governments or planners is firstly the erosional features of the uppermost bank of the river should be evaluated so that its impact can be prevented. This can be done by  building dams and detention basins on the steeper regions of the river so that the rate of water flow is reduced and hence during the rainy season  the volumes of water that would have entered the city quickly is prohibited and the flooding slowly but surely would be prevented.

As such, it was found that it is difficult to educate people on taking measures to prevent their own waste from blocking waterways. This is due to the fact that people once they are not affected by the problem they are blind to the hazard they are contributing to. Thus it is somewhat inevitable that waste will be disposed of in waterways so therefore what can be done is that when planning for urban growth, planners should carefully assess slope stability and take into consideration the negative outcomes that can be associated with improper planning. Therefore once these factors are considered, the most viable decision could be made so that little to no mass movement can occur. For each building plan, certain priorities must be met and a general consensus should be made so that planning along slopes does not create future problems such as floods (Pacione, 2009,400).

Reference:

Michael Pacione. 2009. Urban Geography: A Global Perspective Third edition. London and New York: Routeledge.