The Formation and Persistence of the Matthieu Landslide-Dam Lake, Dominica, W.I

Abstract

Research shows that the majority of natural dams formed by landslides exist for only a matter of days or weeks. Thus, the persistence of the 11-year-old Matthieu landslide dam and its resulting lake in Dominica, West Indies, is atypical. In addition, its association with the two earlier landslide dams, which formed and failed within weeks of emplacement of the persistent dam, adds to the unusual circumstances surrounding the Matthieu landslide dam. The persistence of the lake is attributed to the size and composition of the Matthieu landslide dam and the rate of inflow from the Matthieu River. Based on end-of-the-year measurements, the water impounded behind the Matthieu landslide dam rose rapidly by 64 m for the first 7 years before stabilizing at the current level. The stabilized lake level may be the result of seepage discharge from an area of springs on the dam face that equals inflow from the Matthieu drainage basin. Unquantified lake evaporation and seepage discharge to the regional groundwater system may also be factors that contribute to stabilized lake levels. The persistence of the lake behind the Matthieu landslide dam will depend on whether the decreased threat of dam overtopping is replaced by an increased threat of failure by piping.