Baseman posted:Who considered it an overnight issue? Flooding was increasingly for a long time. And Guyana had always been flood prone. The 2005 event was a watershed.
I’ve always contended the flooding has origins in the Pnc development thrust of the early 70’s and continued under the PPP!
The guilty parties know who they are, their conscience will be their guide.
The question again is what has the govt done with regard to the outcome of the Netherlands study? Did they implement the recommendations from 2016?
RECOMMENDATIONS
After the extensive time that was spent in Georgetown for the execution of this project several recommendations were formulated. These focus mainly on the improvement of knowledge on the system and improving the capacity of knowledge based decision making. First some general recommendations will be given which apply to the whole drainage system
(9.1). Afterwards more in depth advices are formulated on the local drainage system
(9.2), primary drainage channels
(9.3) and outfall structures
(9.4). 9.1
General recommendations Some of the recommendations can be applied on all the three elements of the project. Therefore they are added separately below.
1. Upgrade modelling capacity in order to use model outcomes for knowledge based decision making to come up with the best measure to improve the drainage system.
2. Use the capacity at the University of Guyana to start building models of the city of Georgetown. Different catchment areas can easily be modelled during a graduation topic, and can subsequently be used in a larger model.
3. Assure that authorities take into account the effect on drainage whilst deciding on interventions in and around the drainage system to prevent negative effects of these interventions on the conveyance and discharge capacity.
4. Develop new mapping and information systems of Georgetown’s catchment areas. Make a sound analysis of interconnected areas between catchment areas. Identify culverts, siphons and channels between areas to get a complete overview. Map all these observations in one new general map of Georgetown and one map per catchment area.
5. Gather more information on the distribution of rainfall over space by using rainfall measurement stations spread around the city. The distribution of rainfall intensity over space can then be analysed and used in the modelling.
6. Most of the additional observations could be a direct consequence of a lack of awareness. This has already been treated extensively in the report written after the DRR mission of 2015 and was not a major subject of this project. However, it should be noted that whatever measure is taken, awareness of people for their drainage system is essential for successful implementation.
9.2 Local drainage system
A spreadsheet model was made of a specific catchment area in the local drainage system. Multiple
2. Since the current model assumes a flat system with no gradient, the influence of the natural slope of the wards is not taken into account. This should be done by measuring the surface elevations of the wards and implement it into the model.
3. The model should be improved by taking into account the overflow of banks in order to make the inundation predictions more accurately. The present model only works within the volume of the local channels. Once the water level reaches the maximum depth of the channels, the water level will keep on rising as it was contained by the initial channels.
4. Accurate rainfall data and storm cases are necessary. In this report a single design storm was determined. However it could be that other types of rain showers pose a higher load on the local drainage system. Therefore the rainfall analysis has to be evaluated with relevant stakeholders in order to find the most leading cases for local drainage systems.
5. Damages of floods need to be determined, both in terms of the economic and the social aspects. It is recommended that an additional socio-economical study is performed to investigate which damages are actually present.
6. The analysis with the developed model of catchment area 7 of the South-Ruimveldt area should be finished on short term. This can be done by including the costs for each measure into the model, and evaluate which measure to execute, taking into account costs, effectiveness and feasibility.
7. The analysis with the developed model should be extended to other zones of South-Ruimveldt. The following steps should be taken: - Make a full system analysis of each area to be included, including geometry (heights) and failure mechanisms - Determine the possible measures to improve drainage - Check the costs, feasibility and effectiveness of the possible measures with the calibrated spreadsheet model
9.3 Primary drainage channels
The analysis on the primary drainage channels mainly consisted of the development of a modelling approach for a catchment area in Georgetown. During the analysis the following recommendations were developed. They consist of recommendations for improving the example model of South-Ruimveldt (9.3.10) and of recommendations for implementing hydraulic modelling in other catchment areas (9.3.2). 9.3.1 Improve the existing model of South-Ruimveldt The model that was made on the catchment area South-Ruimveldt and consists of all steps needed to make a model which can be used to estimate the effect of different interventions. However, for further use or more accurate estimations the following recommendations are advised:
1. Expand geometric data of the most upstream part of the South-Ruimveldt channel. Furthermore, the geometric data (heights) of the connections between secondary and primary channels should be measured.
2. Implement the Liliendaal catchment area in the model. Currently, a basic assumption is made on the influence of the Liliendaal pump station on the South-Ruimveldt channel. This can be made more reliable by implementing the Liliendaal catchment area. 68
3. More calibration steps should be performed in order to make a more reliable model Especially calibration with measurements made during high discharge (4.3.4).
4. Execute sensitivity analyses after the model has been expanded. This can help verifying the strength of the basic assumptions that were made initially (4.3.3). 9.3.2 Implementation of model in other catchment areas The same approach that has been used in the catchment South-Ruimveldt can be used for other catchment areas as well.
The following recommendations are advised:
1. Set a clear goal for the model before the actual modelling starts. The making of a model is not a goal on itself. The goal can be to understand the system and find the weak spots. It can also be used to estimate the effect of possible interventions in the system.
2. Build the model in a structured manner. The first set up should be simple (steady flow) to get an idea of the system. After that a more complex model can be build (unsteady flow) and can be calibrated. More information can be found in the provided modelling manual with this report.
3. The user should be able to criticize the results. Exact data from the hydraulic models output might not be reliable and therefore the model might be more useful in comparing the effect of different interventions. In APPENDIX H a full plan was made for implementing the modelling approach in different catchment areas. In combination with the provided manual document this appendix can be used for the development of hydraulic models in other areas.
9.4 Outfall structures
During the project a structural assessment tool was made for the kokers in Georgetown along the Demerara river. Effective improvements on the structural design of the kokers should be the result of the use of the assessment tool. A couple of recommendations are given for improvement of this tool:
1. Gather data on the total lifespan of koker elements and implement these in the tool to improve the prediction of remaining lifespan.
2. Expand the tool by including missing elements like the wood works leading to the wing walls, steel beams and brick work elements.
3. Analyse the cost of replacements and maintenance and implement them in the current method to investigate the most cost effective improvements.
4. Consider the design of protective elements and cleaning of the koker door. This could result in an extended lifespan of the koker elements. This can be examined with the structural assessment tool.
5. Consider the tactically scheduling of maintenance in periods where the probability of failure is lowest (for instance during dry season). Take this into account while using the structural assessment tool.