Cas historique de sédimentation du barrage Péligre, Haïti

The Péligre Dam in Haïti, on the Artibonite River, was built in 1956 for an expected life of about 180 years. Based on sedimentation data collected in 1925 and 1926, the average rate of silting in the reservoir was estimated at 3.45 × 106 m3/year. In 1979, however, an average sedimentation rate of 9.6 × 106 m3/year was established.Systematic observations were undertaken in 1961, 1977, and 1979 to explain the phenomenon and to predict the future rate of silting in the reservoir. The studies led to simulation, by means of a mathematical model, of the processes involved and have permitted reconstruction of the hydro-sedimentological events since 1956 as well as prediction of the future rate of sedimentation.In order to develop a methodology that has widespread applicability for predicting the rate of sedimentation, the main physical processes responsible for the patterns of deposition were used as common denominators: degradation of watershed and rivers, effects of deforestation, urbanisation, and agriculture, effects of flocculation and consolidation, effect of the reservoir geometry, expected sediment inflow, water inflow versus outflow, etc.On the whole, the model indicates very well the acceleration of the silting rate with an average increase of about 18% per year. The study thus shows that the sediment inflow took the form of a quadratic or exponential growth curve instead of a straight line. After 23 years the average silting is three times that of the design. The results show in conclusion how we must be careful in predicting long-term sedimentation rates in a reservoir since the lifetime of the dam is notably reduced. Keywords: erosion, sedimentation, reservoir, lifetime, simulation, degradation, watershed, design.