Flood risk zoning in the Rio Grande, Mosquito, Garrapata subwaters contributing to the Rio Chone

Investigation article

Abstract

One of the natural events that is especially important in the city of Chone, province of Manabí, due to its frequency and accumulative damage in winter, are the floods, some of the most significant, are those caused by the Phenomenon of the Child, which increase the maximum flows of the three Río Grande, Mosquito and Garrapata River sub-basins, contributing to the Chone River, causing the river to overflow, in the lower basins, a situation that exposes the populated areas such as: Miraflores, Guabal, San Andrés, El Pueblito , Roca de Platanales, La Alianza, El Aguacate, Garrapata and Garrapatilla at a high risk of vulnerability and the onslaught of serious floods. The procedure used for this work was the realization of a map algebra, applying GIS tools, through univariate geo-statistical analyzes, to obtain maps of specific weighted risks, of each study variable (lithology, geoform, precipitation, use and land cover, pending), and then multivariate, to obtain the final risk map; All of these data statistics, through the application of the SAATY Analytical Hierarchy Method, which allowed zoning the flood risk in the study area. The results obtained for the proposed zoning were first given through 5 categories with the following values: Very high risk area: 25 km2 (5%), High risk area: 22 km2 (5%), Moderate risk area: 144 km2 (31%), Low risk area: 224 km2 (48%) and Very low risk area 49 km2 (11%); Regarding the validation of the research generated, the zoning proposed by the tutors of this work was compared and the zoning published by INAMHI in 2007, whose proposed zoning results were: High risk area: 47 km2 (10 %), Moderate risk area: 144km2 (31%), Low risk area 273 km2 (59%) and the results of the zoning presented by INAMHI were: High risk area 60 km2 (13%), Risk area Moderate 71 km2 (15%) and Risk Area under 335 km2 (72%). Therefore, it was determined that the proposed zoning in low-risk areas coincides with 92%; High risk areas have a coincidence of 87%. And the zone of moderate risk is the one that over passed the percentage of coincidence with 207%, in such a way, with this technique, it will be possible to guide the territorial planning and facilitate the risk management to the competent authorities.

Keywords: Risks, floods, environmental management.