Dutch team proposes flood hazard maps as 1st step to risk management

Although Guyana is not in a position to set up a full risk management system to solve its drainage problem and alleviate the impact of flooding, Dutch experts have proposed that Guyana develop flood hazard maps as a small step towards a full-fledged risk management system.
The report, titled “Risk Approach”, indicated that a full risk management approach was not possible in Guyana at the moment, owing to a lack of data and modelling capacities, but a good first step would be to consider the various elements of the drainage system as interconnected elements of a system, and to look for its weakest elements.

It stated that it would also be a good step to consider drainage system improvements (concrete projects) as investments that need to be in accord with the value of what is being protected. Adding that it makes no sense to invest in protecting an area that has little value, the report suggested that it was more beneficial to invest in protecting high-value areas.
In addition to these more general requirements, a first step towards working with a risk management approach would be to prepare flood hazard maps. These are maps of certain floodprone areas showing what could happen under 1/10, 1/50, or 1/100 years conditions (rainfall, river and sea levels). It will provide information for now and for the future on a number of climate change scenarios.
“Flood hazard maps differ from flood maps such that they are projections for what can be expected under extreme conditions with a specific frequency of occurrence. It is a first step towards a risk approach in decision-making. Flood hazard maps can be used for planning purposes and to compare areas. They can also be used for investment purposes as they show which areas may be more favourable than others,” the report said.
It added that after local personnel has gained experience in working with flood hazard mapping, “a next step can be made towards the development of a full risk approach for the drainage system of Georgetown and other low-lying coastal areas in Guyana”.
Without drainage systems, flood damage will occur multiple times per year and the avoidance of this damage is the monetary benefit of the drainage system. These benefits are not only monetary, but also refer to health and safety issues. Under extreme flood events, resulting in rapidly rising water or strong flow velocities, deaths may occur as a result of drowning and during inundation, water from the sewerage system may get mixed with the surface drainage water and result in serious health threats.
The report purported that having an adequate and well-functioning drainage system thus prevents economic damage and reduces the number of casualties.
It stated that Guyana’s practice in proposing improvement measures seemed to be primarily project-based, without an assessment of the whole drainage system, implying that the chosen measures may in the end not have the largest reduction of the flood risks.
The Netherlands has developed a Rational Risk Approach to deal with their drainage system. It is a consistent method that analyses all elements of the flood defence system; it computes failure probabilities of each element under a wide variety of extreme conditions and computes the (monetary and non-monetary) consequences of any such failure.
“ Either way, it has proven to be an effective method to steer spatial developments and to prioritise measures that have the largest contribution to flood risk reduction,” the report indicated, referencing that the Flood Risk document (FLORIS) prepared by the Dutch government on how a Rational Risk Approach has been developed and applied on all water defences in The Netherlands.