Characterization of the bed roughness of the Cavaillon River, Haïti: an application of the Pebble Count Method.

Olivier Carlier, Adermus Joseph, Yves Zech, Nyankona Gonomy, Sandra Soares-Frazão

Wednesday 1 july 2015

12:54 - 12:57h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling, Poster pitches

Parallel session: Poster pitches: 8A. Sediment - Erosion

The definition of the bed roughness of a natural river remains a key element in the characterization of a fluvial system in order to achieve a 1-D modeling of the flow. The Cavaillon River is a Southern Haiti River causing considerable management problems since its behavior is uncertain and likely to cause serious damage to local populations living along its banks. This paper presents an in-situ study of the roughness of the river by an application of the Pebble Count method (Wolman, 1954). The advantage of using this method in a context such as Haiti, is the relative ease of implementation, requiring very little equipment. Indeed, the procedure consists in randomly picking up 100 pebbles along a river cross section and measuring the length of their intermediate axis. These samples are then recorded according to this measured length in different size classes to draw a frequency distribution curve of bed materials, from which the desired parameters can be read. Through a regular monitoring of the bed roughness of several sections along the river, it will be possible to observe the evolution of the parameters, for example following a flood. Also, an analysis of sediment distributions of several consecutive sections might provide useful information about the behavior of affluents during flood events, and especially the solid discharge brought by these.