Linkage between river dynamic patterns and deforestation at gold mining activities in the Madre de Dios (MdD) River, Peru

Abstract:

Alluvial gold mining activities in the Madre de Dios River (MdD), Peru, have intensified exponentially over the last thirty years, resulting in progressive deforestation of its floodplain. Along this floodplain, complex river-geomorphic structures, related to historical migration patterns, have resulted in the formation of fine and coarse sediment patches.

This study aims to understand the link between the past dynamics of the MdD river and the deforestation caused by gold mining activity along the river. The area of study is the Madre de Dios River from Boca Colorado to Puerto Maldonado. We used deforestation data from 1985 to 2018, complemented with remote sensing techniques using satellite images to digitize complex river geomorphic structures (e.g., paleo-channels, oxbow lakes, scroll bars), and physically-based analyses regarding known patterns of migration processes.

In the reach of the Madre de Dios River between Boca Colorado and the Los Amigos River, the river has migrated across a wide floodplain, imprinting a broad range of river-geomorphic features. 47% of the total number of river-geomorphic features found were paleo-channels. 62% of the paleo channels exhibited upstream meander migration and orientation. This area coincides with the greatest area of deforestation.

The analysis shows that deforestation areas are correlated to the meander bend skewness along the paleochannel. In general, along all the study the areas with most deforestation were found on the upstream section which is represented by 58%.

Understanding how deforestation patterns relate to river-geomorphic structures will help us identify future areas that will be impacted by mining activity, and develop targeted mitigation plans.