Managing flooding in Guyana

Jun 11, 2021 Letters

---

DEAR EDITOR,

Two weeks of flooding has been unbearable. The flooding will soon abate, and another one will come, even at an accelerated rate due to climate change. Unfortunately, this natural disaster of unusually high rainfall is coinciding with a high tide worsening the consequences. Based on some understanding of the flooding in Guyana, this commentary humbly offers some thoughts on the situation, causes, and mitigation.
Water resources engineer and UG lecturer, Ram Dharamdial, was asked to explain flooding in Guyana in 1982 in a Chronicle article. Mr. Ram Dharamdial said, “when it does not rain, it’s a drought, and when it rains, it’s a flood”. That was 40 years ago, and little has changed in handling water management and planning for flooding.
In a concise way, the problem of flooding is presented after interactions with civil engineers specialised in flood control so that readers without the relevant engineering training and experience understand what is happening. The coast landscape is such that 90 percent of the population is on a flood prone zone having been reclaimed by the Dutch and other colonisers for mainly sugar cultivation. Like all floodplain lands, the drainage for these lands is not natural. Hence, a gravity drainage system was constructed that works with the tidal influence, capable of discharging 2 – 3 inches of rainfall over a 24-hour period. This functions acceptably good for low intensity high frequency storms (typically, a heavy downpour lasting 3-4 hours. However, the long duration events (over a few days), typically experienced in December-January and May-June periods when as much as 12 inches of rain fall, the natural runoff accumulates on the vulnerable parts of the coastlands. Therefore, even at the highest drainage efficiency and capacity, flooding will occur. A good example of an area that illustrates this is Black Bush Polder , which was built from reclaimed swamp, and the gravity drainage capacity can handle just about 2 inches. Thus, there must be the following planning and mitigation measures.
Flood management structure
There must be a strong institutional structure to co-ordinate the management, functioning and maintenance of the gravity drainage system. The Drainage and Irrigation Authority, GuySuCo, Ministries of Infrastructure and Agriculture, and the 10 Administrative Regions (operating independently) have to integrate and coordinate their functions under a single comprehensive management structure to create policies, processes and establish responsibilities, not during the flood but before the floods, i.e. during the six (6) months when those long duration storms do not occur. For a functional institutional framework, the legal authority, probably a Water Resources Act should be a guiding document.
Flood management engineers
Flood management is mostly an application of hydrology to estimate the flood volumes, and hydraulics to convey the flows to a safe and adequate outlet. With the volumes and conveyance capacities known, a flood management plan is typically created. The President should work with the Diaspora to create a pool of Guyanese engineers, who have served North American governments well in managing flooding adequately and competently. He should assemble these guys and work on a flood management plan and master drainage plans for each drainage catchment area, and an acceptable hydrological/flooding modelling.
Water management policy
With policy, the objective is to establish protection and safety rules. Policies on the development of all floodplain lands – coastlands and in-lands, and riverain areas should be enforced. For example, for a major housing development, a clear rule should be established as to the level of the first floor for each dwelling. Further, main streets should be constructed above the known maximum flood level. With regards to the riverain areas, farmers/ miners, etc., should be informed that they are trespassing on the floodplain of a river, and how to protect themselves.
Financial support
There is a cost to the economy for this current flood, perhaps, in billions of dollars. There is disruption of lives, damage to properties, livelihood, loss of crops, etc. estimated in the billions of dollars. The President recognises this and is promising some investment. The investment ought to be focused on short term and long-term measures. The national budget ought to identify flood prevention projects. No spending should be done without a water management plan. It is known that the present drainage capacity is inadequate. In the short term, the capacities of all the canals, sluices, kokers, outfalls, etc. should be improved to at least the design capacity. Where there is incapacity, the discharge of the rainfall should be supplemented with pumps, temporary ponding, control structures, etc.
As stated above, once rainfall exceeds the maximum drainage capacity of a dysfunctional gravity drainage system, flooding will occur. It may not be possible to eliminate flooding completely, as it takes time for even the most efficient system to drain off excessive floodwater. However, getting water off the lands in the shortest possible time requires a flood management plan. The thoughts expressed are not meant to disparage anyone, but to find solutions.

Respectfully submitted,
Vishnu Bisram,
Ram Dharamdial

---

---