Abstract

NAVARRO LOZANO, José Octavio; NAVA SANCHEZ, Enrique; TROYO DIEGUEZ, Enrique  and  CADENA ZAMUDIO, José Luis. Erosion rates and geomorphological indexes in three coastal basins south of the Baja California peninsula, Mexico. Bol. Soc. Geol. Mex [online]. 2012, vol.64, n.2, pp.229-241. ISSN 1405-3322.

Coastal drainage basins in the southern part of the peninsula of Baja California are an important part for the stability of the littoral cell system of the coast in Baja California, because they are the major sediment sources. Migriño, El Salto and El Tule watersheds are vulnerable to erosion due to the steep slopes and geographic location because in this part of the peninsula rainfall associated with summer hurricanes has a mayor influence. Using the RUSLE equation (Revised Universal Soil Loss Equation) and geomorphologic indexes, obtained by GIS techniques, we assessed the spatial distribution of erosion rates and its relationship to lithology, geomorphic features, soil distribution and structural patterns. This allowed us to know the control that soil distribution and geomorphic features exert on the distribution of erosion rates within each drainage basin. Moderate (0.1 to 0.5 Mg ha^-1 year^-1) to high (0.5 to 2 Mg ha^-1 year^-1) erosion rates are associated to slopes equal to or greater than 15°(mountain slopes), and Litosol-Regosol types; low erosion rates (0 - 0.1 Mg ha^-1 year^-1) are associated to slopes of less than 5º (gentle hill slopes and plains), and Regosol types. Analyses of geomorphologic indexes show that river drainage basins are young, and are associated to moderate or negligible neotectonic activity, as evidenced primarily by structural control in the upper basin. Changes in geomorphologic indexes in the middle and lower basins, where erosion and depositional processes are occurring, indicate little structural control.

Keywords : Erosion rates; structural control; San Lucas Bay; RUSLE; sediments.

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