This page is dedicated to outlining the simple types and causes of flooding. Please be reminded that areas have different characteristics that make them susceptible to flooding and, at times, some flood events can have multiple causes. There are also some instances where the below flood types can all occur at once in one area which further compounds the problem and requires a holistic approach to flood risk management.
Coastal Flooding can be broadly categorized as Surge Flooding or Sea Level Rise Flooding. These flood events affect areas in close proximity to an open body of water. As Trinidad is a (relatively small) island, coastal flooding can affect a large proportion of our population, especially as much of our industrial and production areas are situated on the coast. The below map was taken from the Sea Level Rise and Storm Surges: Vulnerability Mapping presentation (Professor Dr. Bhawan Singh and Dr. Calin Obretin (Sea Level Rise and Storm Surges-Trinidad)) and depicts Sea Level Rise and Storm Surge predictions. The areas in blue are flooded areas while the dotted areas are tidally inundated zones.
Storm surge can be defined as the action of water being pushed onshore by high wind activity from a storm weather event. Coastal flooding can be mild to severe depending on the strength of the storm activity, speed of storm, size of storm, direction of storm, onshore and offshore topography and the presence of human activity on the coastline.
Also termed Fluvial Flooding, riverine flooding occurs when rivers overflow their banks. This can be due to excessive flooding and/or to river courses being blocked through soil erosion, improper waste disposal or other blockages. A single river flooding can cause cascading riverine flooding in smaller branch rivers. The severity of a river flood varies and is factored by presence of human activity, amount of precipitation, length of precipitation event, relief, and the existing soil saturation levels of river floodplain.
Pluvial or Surface Water Flooding is flooding primarily generated through the direct effect of precipitation (heavy rainfall) on an area. The most common types of Pluvial Flooding are:
- Water runoff from steep hillside areas which cannot absorb the water either through weak soil or impervious surfaces (such as those created by hillside development). This water eventually accumulates and floods areas at the base of the hill.
- Drainage Overflow Flooding- this occurs when the existing drainage capacity cannot properly manage the water from intense rainfall, either through inadequate capacity or through poor maintenance of drainage systems allowing them to become blocked and ineffective.
Causes of Flooding
The major causes of flooding have been described by the TTWeatherCenter as either Natural or Human.
See link below for further information:
Each of these above causes can be further subdivided and are extremely location specific. There may be similar causes across all flooded areas, however, each area has its unique set of causes which lead to a flood event. Proper flood risk management involves a comprehensive understanding of the specific causes of flooding in an area, analysis of these, and then targeted interventions (prevention, resistance and resilience measures) in order to minimize or eliminate entirely the negative impact of future flood events. This understanding and action is the responsibility of all stakeholders and information must be openly shared for the most effective results.