Mabouya Valley Drainage Project
OverviewIn moist climates, soils may be adequate for cropping with the exception that they become waterlogged from from heavy rains for brief periods each year. Many soils have poor natural internal drainage and can remain waterlogged for several days after excess rain if there is no artificial drainage. This prolonged wetness prevents timely fieldwork and causes stress to growing crops because saturated soils do not provide sufficient ventilation for crop root development. The roots of most crops cannot tolerate excessively wet conditions for more than a couple of days. Soil conditions that make drainage a necessity for some agricultural lands include those with slow water permeability or dense soil layers that restrict water movement, flat or digressional topography and, in some areas, high levels of salts at the soil surface.
Other soils may have an impervious layer of mineralized soil, called a hardpan, or relatively impervious rock layers may underlie shallow soils. Drainage is especially important in tree fruit production. Soils that are otherwise excellent may be waterlogged for a week of the year, which is sufficient to kill fruit trees and cost the productivity of the land until replacements can be established. In each of these cases appropriate drainage carries off temporary flushes of water to prevent damage to annual or perennial crops.
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The drainage of banana lands in the Mabouya Valley was done in two (2) phases. The first phase was the drainage in 200 acres, which entailed the widening and deepening of 6.1km of drains, the sloping and building of embankments and the replacement of box and pipe culverts on the Dennery Main Drain, the Grand Ravine Drain and the Derrière Morne Drains. The second phase was inclusive of the reinforcement of the weir and replacement of the Petite Rivière culvert. This arrangement was not in the original draft plan of funded ventures, but was pitched and implemented near the end of the Programme completion with the unutilised resources from Phase I of the project. The projects works were carried out by various Saint Lucian contractors – Phase I, Northern Supplies and Phase II, Construction and Industrial Equipment Ltd. The BIT oversaw the project to completion, managing the allocation of EC$0.8 million and the project had the end dates of the two phases as August 2002 and October 2006 respectively.
An Agricultural Drainage System is one used in surface ditches, subsurface permeable pipes, or both, to remove standing or excess water from poorly drained lands. When installing a sub- surface drainage system, pipes are either strategically placed in a field to remove water from isolated wet areas or installed in a pattern to drain an entire field. In some areas, surface inlets or intakes (risers extended from underground pipes to the surface) remove excess surface water from low spots in fields.
The installation of an agricultural drainage system is a significant financial investment. The decision to make this investment was determined for two major reasons, which have improved agricultural production significantly:
- Agricultural drainage systems usually increase crop yields on poorly drained soils by providing a better environment for plants to grow, especially in wet seasons
- The systems generally help improve field conditions for timely tillage, planting and harvesting.
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At the commencement of the project, all farmers were notified and a public awareness campaign was launched to sensitise the public on the positive attributes to the works as access route and bridges would temporarily be affected along the path of construction. Throughout the project, farmers were notified when access routes were affected, particularly on banana harvest days.
Although large in scale, the implementation of the phases of the Mabouya Drainage Project did not take long. The workers’ operational hours were from 7am-10pm and monthly valuations were completed diligently. Works on site of Phase I were finished within a five (5) month time frame. The second phase of the project was completed in stages over a fourteen (14) month period, due to various unforeseeable delays, mainly adverse weather conditions.
Phase II of the project extended a little past October 2006 due to the late commencement. However, the works were an overall success celebrated by all involved. The maintenance of the systems where soil and trash deposits constantly need to be cleaned, have been sufficiently maintained by the IMU yielding the desired results for the farmers in the area, and the public in general.