How to make a connection across the landscape: interactions between topography, weather and hydrological connectivity at the landscape scale.

S. M. Reaney, L. J. Bracken and C Williams

Institute of Hazard, Risk and Resilience and Department of Geography, Durham University, Durham, UK

Hydrological connectivity describes the ease with which water can move across the landscape and is a central factor in determining catchment hydrological and water quality behaviour. The strength of the connectivity is determined by the interactions between the driving rain storm events and the physical structure of the landscape.Being able to determine the connectivity is key to predicting: 1. how the catchment will respond to storms events to generate flood events and 2. the distribution of critical source areas for diffuse pollution. If it was possible to read a topographic connectivity signature from the landscape, it would help make predictions in ungauged basins for both flood and water quality risk.  Through the use of flow path tracing algorithms, it is possible to make predictions of hydrological connectivity at the landscape scale. These predictions are made with the Network Index coupled with field measurements, a topographic wetness index or with the spatial output from a fully distributed hydrological model, such as CRUM3. This work utilises these different approaches. The model gives a time series of predictions and the soil moisture patterns are able to develop in response to the local topographic driving forces. With these predictions, it is possible to relate the connectivity strength to the nature of the topography. The relationships between hydrological connectivity, slope lengths, slope gradient and slope profile variability and how these relationship vary seasonally with the different storm events have been investigated with the aim to develop a topographic connectivity signature.

Presentated at the IUGG meeting in Melbourne July 2011

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