Application of 2d electrical resistivity imaging (eri) to geomorphological research in complex groundwater flow patterns

In recent decades, techniques supporting geomorphological research have undergone significant development to meet the demand of "quantitative" information, essential for the research focusing on "applied" aspects on the geomorphological processes. One of the most spectacular quantifying advances regards to the development of wide-ranging data-gathering tools, devoted to ensure a high density of data with a suitable spatial-temporal resolution. Electrical Resistivity Imaging (ERI) is one of such techniques that better reflects this trend. The number of reported geomorphological investigations involving ERI surveys has developed exponentially and encompass 2D, 3D and 4D surveys applied to geomorphological processes investigation. However, despite the geomorphologists community is increasingly incorporating ERI as a subsurface surveying technique some questions still remain about the proper implementation of this method. This thesis attempts to fill the gap between geophysicists and geomorphologists and contribute to the knowledge of ERI application on the field of geomorphological investigation: in particular on the study of geomorphological processes comprising complex groundwater flow patterns, being this issue very weakly addressed in literature. The thesis is outlined as a compendium of 5 field investigations encompassing several geomorphological processes: littoral environments and salinization; focused groundwater discharges of a karstic regional aquifer -thermal and radionuclide-enriched- into a marsh area; a seismically active fault -circulated by endogenous gases; subsurface weathering of granite massif and tafoni initiation; and a translational slide, likely coseismic, and conditioned by a larger-scale gravitational movement. All the geomorphological processes researched are similar in that involve several converging ground flows: local, intermediate and regional groundwater flows and, occasionally, gas flows. ERI imaging capability and suitability to solve geomorphological problems in such complex settings has been thoroughly assessed. Additionally, strategies have been developed for combining and overlapping different geophysical methods and calibrating geophysical datasets with true data obtained from direct methods and other geomorphological information. The research has concluded that despite the ERI technique comprehends some limitations of associated with "accurate" quantitative analysis, it is has significant potential for surveys aimed constructing qualitative models of the subsurface. ERI is an excellent method for depicting the continuity at depth of key geomorphological features and probably is the geophysical surveying technique encompassing a wider range of applications for the subsurface geomorphological characterization. Additionally, ERI is currently the most capable geophysical surveying technique for gathering information on the groundwater flow pattern, showing proficiency at imaging groundwater flow-paths and distinguish between groundwater with different hydrochemistry. Elucidating groundwater flow pattern -which often is an essential topic- improves meaningfully the understanding of the geomorphological system and its geodynamics.