Estimation of sediment volumes due to rainfall erosion using RUSLE model in basins of the province of Manabí, Ecuador

Abstract

Sediment production due to rainfall erosion is a topic of great interest because its lack of knowledge can represent serious dangers for nearby communities and infrastructures. Several methods have been developed in recent years to quantify sediments, but their complexity, precision, and accuracy vary depending on the approach used. However, many of these models require the use of extensive precipitation time series, but in Ecuador, the meteorological stations present a worrying lack of data and their spatial distribution is not homogeneous, which generates an incorrect rainfall estimation in the analyzed territory. To solve this problem, it is possible to implement methodologies that use satellite raster information. The objective of the present investigation was to estimate the volumes of sediments in the hydrographic basins of the province of Manabí, through the implementation of the RUSLE model and an empirical procedure that requires the use of the apparent density of the soil in its three main textures (sand, clay and silt). The methodology considered the delimitation of the analyzed basins, the evaluation of satellite raster data to determine the six parameters of the RUSLE model between 2001 and 2020, and the estimation of apparent density through an innovative method. The delimitation of the basins was obtained through regional sources; the satellite information was obtained from official web sources; the typical values of the apparent density were obtained from sources at global scale; and the validation of the apparent density data was carried out by means of on-site sampling. The results allowed identifying soil erosion rates that vary between 0.10 ton ha-1 and 3252.22 ton ha-1, which generated an estimate of sediments between 0.06 m3 year-1 and 692.43 m3 year-1 at the pixel level. The average apparent density was 1.49 ton m-3, which demonstrates a high sand content in the basins of Manabí. The data validation revealed an excellent compatibility between the proposed methodology and the conventional on-site analysis, which is reflected in an average difference of less than 3%. The information obtained will allow the competent government entities to establish mitigation programs to deal with the loss of soil due to rainfall erosion and to control the sediments production.