Flood study urges US$123M works

-says fragile part of EDWC dam in need of rehab

A five-year study of coastal drainage in the aftermath of the 2005 Great Flood has recommended US$123 million in remedial work – including to the key East Demerara conservancy – but the government says it only has US$11 million at the moment.

One positive finding for the government from the World Bank-funded project is that the soon-to-be commissioned Hope Canal is expected to spare the region from flooding in extreme weather events.

The government yesterday said it plans to undertake a US$11 million initiative which it believes will allow it to better manage the East Demerara Water Conservancy (EDWC), overtopping of which was seen as key factor in the weeks-long flood along the coast in 2005.

The US$11 million initiative stems from the findings of “The Conservancy Adaptation Project,” or “CAP 1” according to Agriculture Minister Leslie Ramsammy.

CAP 1 was implemented at a cost of US$3.8 million and was executed by a variety of consultants, including Mott MacDonald out of the United Kingdom, in collaboration with the Ministry of Agriculture (MOA).

The Project was financed by the Global Environmental Facility’s Special Climate Change Fund grant, and ran for about five and a half years – January 2008-August 2013.

Speaking to reporters at a seminar on the findings at the Regency Suites Hotel, Fredrick Flatts, Senior Engineer with the Agriculture Sector Development Unit (ASDU), said the consultants “made a number of recommendations on (improving) the EDWC, as well as (on) improving drainage down the stream of the conservancy, that is on the east coast.”

Flatts said the consultants recommended works to the total  of US$123 million. Unfortunately, he noted, the ministry does not have all of the necessary funding, and will therefore seek to carry out works equivalent to US$11 million.

“We don’t have all the funds and that is the reason we have this meeting here. We have donors and the donors will become aware of what are some of the needs.”

The various initiatives which will be undertaken pursuant to the consultants’ recommendations is being referred to as CAP 2, the minister explained yesterday.

National Drainage and Irrigation Authority (NDIA) CEO Lionel Wordsworth said that the consultants recommended the construction of pump stations at several East Coast locations – Liliendaal, Ogle, Enterprise, Mon Repos, Paradise and Lusignan. Flatts also mentioned plans to construct a pump station in Buxton.

He also said that the consultants recommended improved discharge into the Demerara River, which is to be achieved via improving the operational capacity of the Kofi and Cunha sluices. According to Wordsworth, the ministry will likely start this section of improvements with works to the Cunha Sluice, East Bank Demerara, since there are more peripheral benefits to be had with this option.

“As it were in the past, there were lands which were drained when the Cunha was at optimal capacity,” he told Stabroek News. However, the NDIA CEO explained that when rerouting work was done some areas were disconnected from drainage outlets.

A large part of the initiative will also target the EDWC itself for rehabilitation – from Hope, East Coast Demerara, according to Flatts. Wordsworth continued that there are plans to increase the conservancy’s width and depth to increase its water-holding capacity.

The EDWC’s banks will also be strengthened and built higher to better guard against the water overtopping or breaking the dam. Flatts admitted there is no way to know for sure if the initiatives the ministry plans to implement will prevent all future overtopping and breaking of the conservancy’s banks, but he argued that the ministry, in the meantime, will attempt the best engineering solutions at its disposal to mitigate any such future occurrences.

Wordsworth also explained that the ministry will seek to strengthen certain sections of the conservancy which runs behind villages along the East Coast embankment, particularly areas in Non Pariel. He said that in 2005 10% of the length of the conservancy behind Non Pariel was overtopped, leading to widespread flooding.

The US$11 million the ministry has been able to secure thus far has been made available by the International Develop-ment Association (IDA) of the World Bank.

Dam

Underpinning the proposed US$123m works is the concern that the consultants clearly have about the integrity of the 130-year-old EDWC dam. As part of the CAP, a geotechnical stability analysis was conducted on the dam. The presentation on the findings of CAP said it found that for most of the dam the historical evidence suggests that earthwork stability is reasonable “but falls marginally short of international standards”.

It added that under certain conditions, the stability of the dam becomes marginal as demonstrated by incidences of localised instability. One such was the 2011 slippage at the old Shanks sluice location. The results of the study state that the north east dam between Annandale and Flagstaff, Mahaica is “the most fragile part of the dam and in need of rehabilitation”. The CAP findings said that this part of the dam is founded on pegasse to a depth of up to 4m and is made of soft clays with high pegasse content.

Further, the north dam between Nancy and Annandale and the east dam between Flagstaff, Mahaica and the Maduni Creek, have also been determined to have “marginal stability”. The findings also say that the west dam from Nancy to the Cunha Canal on the East Bank is made of better clays but the side slopes are very steep and the crest is very narrow and overgrown.

“It therefore does not meet international standards, but it still considered stable,” the study said.  It added that possible designs have been drawn up along with the recommendation that work on the north east dam be done first.

The study also said that computer modelling has projected that the long-planned Hope-Dochfour canal once in operation will significantly improve drainage from the EDWC and “the models show that even for an extreme 10,000 year rainfall event (an event much more severe than in 2005), water levels will not reach the top of the dam.” The Hope canal was meant to be operational already but two of its key components have been significantly delayed.

The computer modelling also demonstrated that water levels in the conservancy are shallowest in the vicinity of Land of Canaan on the East Bank and therefore increasing the conveyance of internal channels along with upping the discharge capacity to the Demerara River will help to lower water levels in the rest of the conservancy.

Since the 2005 Great Flood, hydrologists and engineers have been arguing that the efficiency of the internal drains in the EDWC have to be vastly improved and had this been done consistently there may not have been a need for the Hope Canal.

Hydraulic modelling was also done of communities in Region Four. The findings said that it became evident that many of the key existing drainage facilities were made for agricultural drainage and not for mixed urban and agricultural use.

“The results of the cost-benefit analysis shows therefore, that in most cases, separation of urban and agricultural drainage areas, providing different levels of service to both, would be most beneficial”, the findings said. Other recommendations relate to additional pumping capacity and the resizing of outlet systems and culverts.

In addition to the studies, the US$3.8m CAP funded the complete rehabilitation and upgrading of  the two sluices at Lama on the eastern side of the conservancy. A long-boom excavator was also procured and a floating punt and pontoon were designed and constructed.

“This has improved drainage and helped to rapidly mobilize equipment to areas of the dam in need of repair and respond to dam breaches…”, the findings said. It added that the purchase and installation of hydrological instruments has also helped to manage the conservancy’s water levels.

Representatives from donor agencies at the seminar included Sophia Makonnen, the Inter-American Development Bank’s representative to Guyana, Benedikt Madl, EU’s Head of Bilateral Development Section, and the World Bank’s Armando Guzman.

Madl, while making remarks at yesterday’s meeting, announced that the EU will be offering funding for projects in the area of disaster risk management quite shortly and he invited the MOA to submit proposals.

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