The quantification and understanding of hydrological, erosive, and biogeochemical processes in catchments are essential to the sustainable management of water and soil resources. Soil-erosion studies and hydrological simulation models comprise a large range of scopes and objects of investigation with different levels of spatial and temporal scales and/or innovative approaches that are important tools to address environmental problems in a cost-effective way. Thus, for example, analyses may range from absence-presence inventories of erosion features in large areas, -such as badlands-, to detailed studies of rill and ephemeral gullies; or focus on the assessment of the overall expansion of permanent gullies and their evolution; characterization of headcut migration; or identification of downstream deposition areas after intense sheet/rill erosion; among others. Assessment of the environmental impact of economic activities in catchments should be based on the acquisition of experimental data to implement and/or to evaluate conservation practices at different scales. However, monitoring systems can be restricted by technological, economic and legal factors, spatial and temporal sampling strategies and availability, and are rarely conceived in the long term.
Remote sensing is increasingly being utilized to address a plethora of hydrological and soil erosion issues, providing highly valuable information both on surface reflection and surface heights. In fact, the continued improvement of remote sensing techniques has allowed the study of a large range of erosive processes at varying spatial and temporal scales. More sensitive and accurate sensors are available every day. In addition, the frequency of observations is rapidly increasing and new statistical analysis techniques are increasingly used.
Here, the authors are encouraged to present new environmental challenges related with the use of models, remote sensing techniques and new experiments to address hydrological and erosive issues. In addition to classical modeling procedures such as evaluation of models; new conceptualizations to address current environmental problems facing society, tools and techniques aimed to conserve water, soil and nutrients, and evaluate degradation processes of soil and water as well as analyses concerning the ways and potential of using remote-sensing techniques to assess soil erosion are also expected.