Sensitivity Analysis Assessing the Impact of Gabion Dams and Vegetation on Flood Flows in the Ravine Millett in Haiti

Location: Haiti
Sponsors: University Corporation for Atmospheric Research (NOAA Grant)

As a follow-up to the  project “Evaluate the Effectiveness of Check Dams in the Millet and Brise Tout Ravines in Haiti Using Hydrologic/Hydraulic Modeling”, HRC used the methodologies and models developed and applied for the previous Ravine Millet study, conduct a sensitivity analysis to quantify the downstream flood impact of the size and location of gabion dams and of the vegetation coverage applications in the flow contributing areas. The sensitivity study was then a basis to determine guidelines for the management of flood flows through effective design of gabion dams and vegetation planting.  This sensitivity analyses described above was then used to inform a case study that will concern a second ravine in Haiti to evaluate the establishment of gabion dams along the ravine to attenuate peak flow levels. In addition, the available vegetation-cover options were examined to develop recommendations for contributing area cover that will contribute to reducing downstream peak flows and sediment transport.  The optimal solutions were adjusted to respect the available constraints in this case study so that the recommendations may be appropriate for prototype implementation in the selected ravine.  At the conclusion of the sensitivity analysis and case study, HRC developed a reference guide appropriate for use by donor agencies and NGOs to design and implement an approach to mitigate impacts on population centers from floods in steep flashy mountainous streams that receive high rainfall amounts.  The focus was on mitigation efforts involving dams (of various sizes and locations) and vegetation.  The guide addressed background information regarding the methodology to be applied, applicability of the methodology, the steps taken to design and implement the mitigation program, the required technical tools and their application and an example of the application of the methodology.  The guide was written for a primarily non-technical audience.  The Guide can be downloaded here.