Geostatistical Analysis of River Sedimentation Behavior in Kerala State

Abstract

Sediment transport is an important aspect of all fluvial systems like river flows. Sediment transportation depends on the flow conditions, ratio of densities of sediment and fluid, and the size of the particle. Analysis of sediment yield data is helpful in understanding the distributional characteristics of sedimentation in river basins. Evolving a sediment distribution relationship over the region, consisting of different catchments, may facilitate in estimating sedimentation rates at non-sampling locations. Such estimates based on geostatistical analyses would be better estimates of mass fluxes compared to those obtained through conventional methods. As processes like river sedimentation, with time-space variation, may be considered as regionalized variables, geostatistical techniques can be effectively utilized in analyzing such variables to bring out their spatial structure. In the present study, geostatistical analysis of sediment yield data from sixteen river basins of the State of Kerala has been undertaken with a view to reveal the spatial and temporal distribution pattern of sedimentation in the region. The mean annual rainfall in the region is above 3000 mm, and it varies from west to east as well as from south to north. Therefore, the sedimentation behavior also is expected to vary. Geostatistical analysis has been carried out for distinct cases based on regional and seasonal variations. Northern and southern regions were treated separately. Also, seasonal variations with regard to SW and NE monsoons were also considered. The geostatistical analyses revealed that the sedimentation characteristics in Kerala river catchments tend to increase from north to south during NE monsoon. However, during SW monsoon, northern region yielded more sediment. The quantitative increment in sediment yield toward the southern parts of the state may be attributed to the rainfall characteristics.