Home Letters Effects of flooding – lessons to be learnt
Please permit me to elucidate on the drainage requirements of Guyana. Watching the outcome of the recent flooding has precipitated these thoughts.
As an industry practitioner with 47 years’ experience in drainage, I offer the following recommendations:
* Global warming is here to stay. As a result, the moisture storage capacity of the atmosphere has increased over the past three decades. This means that when precipitation takes place, it’s more intense, as there is more water to fall as rain; hence the observed increase in rainfall over that corresponding period.
In reality, this means that floods are here to stay! The best we can do is engineer our drainage system to cope with such floods, and attenuate the adverse effects on our lives.
* The Drainage and Irrigation Department needs to be split into Drainage and Irrigation. A Drainage Director needs to be appointed. That person must report directly to the President or Prime Minister.
* ALL drainage canals need to be dredged immediately. Siltation has, over the years, restricted their capacity to effectively deal with floods and effectively drain the land.
* ALL outfall channels need to be dredged from the kokers to the sea. The contours of such channels must be cut/excavated to render them self-cleaning.
* Mangrove revegetation needs to be accelerated. Mangroves are our first line of defence from the onslaught of the sea.
* Vegetation covering 15 metres on each bank of every river from the water’s edge should be protected. Such growth of trees would arrest rainfall runoff, allowing that water to percolate down to the water table and recharge the table. During the dry season, that water would be released into the river as riparian springs. This would need legislation.
Where deforestation of this area has already occurred, revegetation must be embarked upon.
* Built-up areas such as buildings, car parks and industrial sites must have unbuilt areas adjacent to, and between, them. This would allow surface runoff to percolate down to the water table, rather than inundating drainage channels and roads. By-laws would need rewriting.
* Operation of kokers and drainage pumps need to be synchronised with the tides. Accurate level gauges need to be installed on both the landward and seaward sides of each koker to aid maximisation of drainage time.
* A check of the operation of all kokers and drainage pumps throughout the country needs to be made on a 24/7 basis.
* Hinterland rivers also need to be dredged. Irresponsible alluvial mining has culminated in fast-flowing rivers silting up and thus reducing their capacity to drain the land in their catchment areas. Recent flooding in the Mazaruni area is testimony to this.
* Each region needs a stock of portable pumps that can be mobilised at short notice for flooding emergencies.
Low-lying coastal Guyana is susceptible to the vagaries of the weather and rising sea level. As a result of this, about 15% of the annual budget over the next 3-5 years needs to be voted for sea defense and drainage.
If the above measures are implemented, it is estimated that about 70% of the type of flooding we recently experienced could be alleviated.