Dinámica de las terrazas fluviales en la subcuenca Grijalva-Villahermosa, México.

Geospatial analysis, based on comparative studies of satellite images through geographical information systems, has allowed to highlight territorial changes generated by the interaction between natural morphological processes and anthropogenic activities. The Grijalva-Villahermosa sub-basin is part of one of the largest watersheds in Mexico, the Grijalva-Usumacinta basin. Based on geographical location and geological characteristics Grijalva River is formed by sediments of recent quaternary alluvial Holocene. Geomorphology corresponds to the fluviodeltaic plain with an almost flat slope, so floods are constant. In order to evaluate the effect of water control systems in the dynamics of the fluvial terraces an environmental assessment was developed, taking into account the effect of flood mitigation structures. The fluvial terraces were identified through spectral analysis of 2011 LiDAR images and verified through photo-interpretation and field visits. The environmental assessment was based on Landsat images 1986 and 2016, to which the analysis of change trend with Markov chains was applied. The environmental criterion of the analysis was based on the evaluation of change on the vegetation coverage, wetlands, water bodies, soil and anthropic infrastructure. The most significant results on the dynamics of the fluvial terraces in terms of surface gain occurred in wetlands with 13034 ha and a loss of 6475 ha, in anthropic infrastructure gaining was 3242 ha and losing 3793 ha, as well as a gain of 1145 ha and a loss of 3519 ha in water bodies. The results showed an intensive change trend in wetlands coverage on the analysis period. The current dynamics in the Subbasin shows a regular behavior in the formation of the fluvial terraces, but a negative impact due to anthropic factors. [ABSTRACT FROM AUTHOR]