2 PURPOSE AND NEED & PROPOSED ACTION 2.1 The Purpose of the Proposed Actions is to improve the ecosystem integrity and functionality of the Holetown/Trent area watersheds in order to promote effective drainage in an environmentally sound manner. The Need is to reduce flooding in target areas while maintaining or improving the health of the coastal and marine environment. The Specific Needs are to: 1. Increase conveyance capacity in key watershed points to reduce flooding; 2. Reduce runoff volumes and velocity while capturing more groundwater through retention measures where practical; 3. Improve water quality through the reduction of pollutants (chemical and sedimentation) from runoff on the Folkstone Marine Reserve; 4. Protect endangered and threatened species and critical habitat in the FMR; 5. Help safeguard the thriving tourism industry. 2.2 PROPOSED ACTION Flooding has become an acute problem in a number of areas due to rapid development on the west coast of Barbados especially in the 1970s and 1980s, inappropriate land use practices and changing rainfall patterns. Conveyance structures (culverts, canals, swales) and retention measures (ponds, dry well, rain gardens, check dams, etc.) are either undersized or too few in number. The proposed action focuses on the conveyance structures in the lower watersheds of the Holetown/Trent area. The Holetown/Trent area watersheds have been identified as a priority target area in the recently updated Stormwater Management Plan (AMCECC Study). While the mapped boundary limits of each watershed end at the waters edge, in fact the FMR is the terminal component of all proposed watersheds, and must be considered as such. The AMCECC Study highlights the importance of using Integrated Water Resource Management (IRWM) as an approach to stormwater management and recommends viewing watersheds in a holistic, ridge to reef manner. As noted in Figures 1, all watershed gullies are contiguous and part of a larger watershed area that includes Holetown/Trents and the FMR (FMR boundaries within Figure 1 are the coast and areas outlined in red). The Proposed Actions include: Watershed 23, W23a, W24 – Culvert enlargement, new culvert installation, a new concrete drain channel, and extending and deepening grass swales.
upscale and/or complex the damaged structure, the more expensive repairs will be for Barbados conditions. For example, the reconstruction unit cost of a Chattel and a Villa are $38/sq-ft and $250/sq-ft, respectively. Table 1: Estimates of flood damages to structures (Source: Guidelines for Analysis, US Federal Emergency Management Agency (2009) Flood Depth in Feet % of Damage to Structure 1 Story Building, No Basement 2 Story Building, No Basement 0 to < 1 9% 5% 1 to < 2 14% 9% 2 to < 3 22% 13% 3 to < 4 27% 18% 4 to < 5 29% 20% 5 to < 6 30% 22% 6 to < 7 40% 24% 7 to < 8 43% 26% 8 to < 9 44% 29% 9 + 45% 33% Table 2: Cost of rebuilding or repairing a damaged Structure ($BBD) Structure Type Cost of New Structure Repair cost (approximately 50% of the cost to reconstruct/ rebuild in Barbados) Residential $ 250/sq ft $ 125 / sq ft Chattel $ 75 / sq ft $ 38 / sq ft Commercial $ 300 to $ 600 / sq ft $ 150 / sq ft Hotel/Resort $ 500 / sq ft $ 250 / sq ft