Time for mitigation

Jun 20, 2022 Letters

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Dear Editor,
Flooding in Regions Five and Six has been occurring too frequently in the last decade and even more so in the last five years. Residents and farmers are faced with the situation on an annual basis either during the year end, mid-year or both rainy seasons and are forced to overcome serious socio-economic consequences every time they are flooded. Farmers are especially hard hit. Their daily battles with pests, diseases, rising prices of inputs and fluctuating markets are now compounded with flooding, crop destruction and death of farm animals. Most importantly, the frustration and despondency will definitely discourage both, current and future generations of farmers from continuing. Considering their suffering, there definitely, will be seriously deleterious economic, social and political consequences in the future should this continue unabated.
Why is the situation as it is today?
Historically, in Guyana, the drainage system was designed and built by the Dutch and which catered for one and a half inches of rainfall per day. It is upon this basis that all tertiary, secondary and even primary drainage structures are built and maintained up to today. At the time and until the late-80s that design was essentially sufficient and effective for several reasons:
a) The rainfall pattern had remained essentially the same as the 1800s.
b) There were large undeveloped land masses which served as seasonal reservoirs and which restricted the mass surface flow of water from the land and into the rivers to cause floods downstream.
c) There was little to no major economic development and expansion of cultivation.
d) Little to no media coverage.
What changed?
There are a number of factors that changed between the early 90s to now that are working in synchrony to create the situation as it is existing today; these include but are not limited to the following
a) There were small changes in the rainfall regime, both, in pattern and intensity.
b) The PPP came into government which encouraged investors’ confidence in the economy. That resulted in significant expansion and modernisation of agriculture in the regions. Both rice, cash crop, cattle and sugar made significant expansion in their respective cultivations and moved their operations to more modern technologies and methodologies with little or no soil conservation techniques employed.
c) The invasive species Antelope grass reached the waterways and invaded the creeks. This resulted in the occupation of large swaths along the banks of creeks and other waterways. While they occupy the shallow 20% of the waterway, it is the 20% most essential in the time of heavy rainfall since it is the upper 20% water column in the waterway which moves fastest and drains the longest.
d) Siltation – more land under cultivation means more siltation in surface runoffs which gets into Antelope clogged waterways. The grass’s subsurface root system forms a sieve in the water which slows down the flow resulting in deposition of sediments on the river or canal bed. With time, sediments become trapped in the root network forming ‘’bag’’, which further slows down the flow and increases deposition of sediments. This situation is more compounded by the fact that there are huge silt deposits at the mouths of the three creeks and the channel of some kokers in Region Five. These deposits effectively limit the velocity and volume of discharge into the sea. Again, a slowdown of the flow occurs and more deposits take place at critical points closest to the final discharge point. There is a third salient case of deposition occurring; when the tide rises and flows into the creek, it brings sediments into the creeks and deposits them as it reaches its peak but when the water is flowing out as the tide drops and it is at its last third, the stage of outflow when the greatest erosion should have taken place, the flow is restricted by the silt build up at the river mouth and the sediments brought into the river cannot go back out, hence a net deposition of sediments occurs. The cyclic occurrence of this phenomenon results in the gradual shallowing of the creek front and by extension a reduction of water discharge.
e) Electronic and print media flourished under the PPP government and these situations, no matter how benign, are broadcasted to all and sundry to finally shape the public opinion about a situation.
What can be done?
The situation has to be looked at on a macro perspective. First and foremost, a comprehensive study needs to be done to fully assess the situation, its dynamics, Economic, social, political and ecological implications.
From my perspective and limited evidence, the following are recommended?
1) The mouths of the three creeks must be gated to control the flow of water in one direction.
2) The best possible route for the flow of water through the marine sediment banks needs to be plotted, dredged and groins built to protect the dredged channels from re-sedimentation to offer effective flows.
3) A massive antelope control programme needs to be designed and implemented with a heavy chemical control component to manage the weed situation.
4) Two massive drainage canals (with relevant sluices) connecting the Mahaica, Mahaicony, Abary and Berbice rivers, conveniently located between the Public road and the MMA main canal needs to be established to divide the drainage basin and manage the water flow.
5) Additional works on secondary and Tertiary drainage systems will have to be enhanced on a case by case basis.
I am convinced that the implementation of the first three recommendations will practically reduce the frequency of flooding in the region by well more than half.
Sincerely,
Rohit Singh

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