Saturday 21 September, 2019

Flood categories in T&T

While Trinidad and Tobago may be experiencing a hot wet season with increased daytime and nightime temperatures forecast until December, this does not diminish the likelihood of flooding events.

According to the Meteorological Service (Met Office), the risk for flash and riverine flooding, landslips and landslides remains high for the remainder of 2017 with above normal accumulated rainfall totals likely for the next three months.

October is likely to see wetter than usual conditions, while November is forecast to be the wettest month during the October, November, December period.

The Met Office advised that flooding occurs when the inflow of water into an area is faster than the outflow. Four types of flooding typically affect Trinidad and Tobago:  

Riverine flooding is an overflow of water from rivers, which happens when a river’s water holding capacity is exceeded in an area and the river banks are overtopped. Riverine flooding usually occurs after extended periods of rainfall.

Flash flooding is a rapid onslaught of raging waters caused by heavy rainfall in relatively short periods - within a period of minutes to hours (usually less than 2-3 hours in T&T). Flash flood events are very unpredictable as they can occur with little or no warning. Flash floods can develop in water courses as well as over land.

Street flooding is a local term used to describe accumulation of water along the streets of urban areas that are commonly lower than the pavement areas. This typically happens in Trinidad along the east-west corridor due to runoff from the elevated areas of the nearby northern range.

In Tobago, it favours Bon Accord and Scarborough. Street flooding may also occur in other areas such as those where debris or litter block the outflow of street water or where the drainage is inadequate alongside streets.

Coastal Flooding occurs in coastal regions that are not normally inundated with water. Coastal floods may originate from inland due to excessive or heavy rainfall that collects within or runs off into coastal areas. Coastal flooding may also occur due to inundation by higher than normal tides -such as spring tides, storm surges - associated with tropical cyclones or wind driven seas forced into the coastal areas.

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