Soils in Catchment System Dynamics: Measuring Sediment Connectivity on Catchment Scale with Case Studies from Temperate and Mediterranean Climates.

Soils are a precious resource threatened by many degradation processes. Water erosion is the world’s most important soil threat as identified by FAO. To be able to understand the implications of soil erosion at different scales well developed techniques for measuring and modelling are needed. It is important to look at the soil erosion threat in an holistic way, on the scale of a catchment, with the sources, transfer paths and sinks incorporated. We need to understand the catchment system dynamics by incorporating both processes on hillslopes, in the river channel. Process knowledge enables explanation of the impact of natural and human drivers on the catchment systems, and which consequences these drivers have for water and sediment connectivity. Improved understanding of the catchment sediment and water dynamics will empower sustainable land and river management and mitigate soil threats like erosion and off-side water and sediment accumulation with the help of nature’s forces. Understanding the catchment system from a hydrological and sediment transport point of view enables us to predict the reaction of this system when it is influenced by an external driver. Drivers can be divided into natural; such as wild fires, and human drivers, such as agricultural soil management. This presentation gives an overview of techniques we use in measuring sediment transport and related connectivity on catchment scale. Emphasis will be on how available data sources can be used to model soil erosion and associated sediment transport. Furthermore, sediment sources, transport paths and sinks within a catchment will be explained using the concept of connectivity with examples of measuring using innovative field methodologies to assess this spatial distribution. Examples of different climatic situations will be touched upon and new field methodologies will be shown such as rainfall simulations, water repellency measurements, runoff detectors, high temporal and spatial resolution remote sensing techniques (UAV based DEM interpretation). The importance of well measured and monitored data will be highlighted as measured data are usually taken as the truth, used for calibrating models executing scenario analysis and in the end for decision making. However, the value of data lies in the experimental set up, the sampling scheme and the methodology of the measurement technique itself. Too often data are used without considering the above mentioned constraints. To be able to transfer data from one research to the next it is important to harmonize technologies and methodologies, and standardize the information generated to achieve sound science and translating this into relevant information for stakeholders. Lastly, implications of these new data sources for modeling tools will be discussed, and how these new insights are used in the concept of catchment system dynamics for connectivity of water and sediment. Undergoes