Dear Editor,
It is my considered opinion that Georgetown and the coastal belt of Guyana need a comprehensive technical analysis of the drainage system. While the ‘cleanup campaign’ is a good one, that alone won’t alleviate flooding. It would only bring short-term and minor relief. This is evidenced by the continued flooding, caused by the recent heavy downpour of rain, despite the cleanup which was conducted in certain parts of the city. My own opinion is that the cleanup will address the drainage of normal runoff water from households and light rainfall, but certainly not storms and heavy seasonal rainfalls. I guess over time we will see the results of the cleanup.
The drainage system needs more than just a cleanup campaign; it needs a full technical understanding of the entire system. Our drainage is chiefly dependent on tide and gravity flow because of the low-lying nature of our coastline – 3 feet below high tide (this is a guesstimate since sea level has risen and is expected to rise even more, therefore we must be further below high tide). When the tide is at its lowest or close to that, the sluice gates are opened to drain the canals and trenches that would have accumulated water from rainfall, households and other sources, thus the canals and trenches act as holding reservoirs for water when the tide is high. At the turn of high tide the sluice gates are locked to avoid the intrusion of sea water onto the land. Also protecting us are the sea walls and river defence dams during high tide. At low tide we have approximately 2 to 3 hours (this is a rough estimate) or less for the drainage channels to drain since the tide changes every six hours approximately. It would therefore be prudent for us to ensure we get most of the water from the drainage channels out to the sea so that they will in turn have enough capacity to hold water in the event of storms, as well as waste water generated from humans and other sources. Is this happening? Is water being effectively drained from the channels during the limited time period at low tide? Do the channels have adequate slope to cause natural runoff from the backlands to the sea or are they sloping toward the backlands? Do the channels have enough capacity based on rainfall data and human generated waste water data etc? How much has the sea level risen locally (do we really know this accurately) and what are the impacts? What projections do we foresee that may warrant modifications/improvements to the drainage system? Could there be a possibility that the mean low water level has risen significantly thus causing water in the drainage channels not to adequately drain or drain as it once did? Have we been experiencing any subsidence/vertical land movement on the coastal belt? How are we getting hard facts to know for sure what is happening? In other words are we measuring, collecting, analysing/interpreting, combining and storing adequate scientific data to know, understand and pronounce on the aforementioned scenarios?
We can dig canals all year long but if we don’t understand the meaning and importance of elevations, sloping, sea level and rising sea level due to climate change then our work is baseless and becomes counterproductive. The elevations of land, sea level, canals and structures must be accurately and precisely known relative to each other, especially with the low-lying vulnerable nature of our coastline. The national elevation for mean low water must be accurately known, proven and monitored continuously so as to inform on the required elevations and slope of canals. The elevation of high water must also be accurately known, proven and monitored continuously to provide information on the height to which sea and river defence structures must be constructed. Measuring the sea level requires a series of measurements over a long period to accurately and precisely understand changes and the behaviour of the MSL (Mean Sea Level) and its relationship to our national level datum. This is important for our vulnerable low-lying populated coastline and the implications it has for coastal habitation.
Finally, I believe a 3D analysis of the main drainage system and the foreshore (and maybe further seawards) needs to be commissioned to provide date on, for example, the current and required capacity, elevations and sloping of the drainage channels, etc. I am contending that this is a small price to pay that will reap enormous benefits to the heavily invested coastal real estate of Guyana. Accurate topographic survey data need to be collected based on national level datum- GD (Georgetown Datum). Combining this data together with sea level measurements, rainfall data, storm water data, human waste water, backlands water from creeks/water bodies and the East Demerara Water conservancy, etc, can provide limitless possibilities when dealing with the drainage problem from a technical standpoint. 3D models, scenarios and predictions can be developed to check the severity of potential problems, plan forward and develop mitigation and adaptation plans/strategies, etc. We must not also neglect the need for proper drainage construction and monitoring of secondary and tertiary urban drainage systems and the issue of squatting along drainage reserves. In addition there is the improper disposal of solid waste and the management of same, especially in urban areas.
Yours faithfully,
N C Liu
Sworn Land Surveyor
