Connectivity describes the ease with which something may move through the landscape. The strength of the connectivity between two points in the landscape depends on many factors both regarding the nature of the landscape and the substance of interest, e.g. water or nitrogen.

The SCIMAP risk mapping framework has developed a distributed treatment of surface hydrological connectivity based on the analysis of the potential pattern of soil moisture and saturation within the landscape. For each point in the landscape, the probability of continuous flow to the river channel network is assessed. This is achieved through the prediction of the spatial pattern of soil moisture and hence the susceptibly of each point in the landscape to generate saturated overland flow.

For a point in the landscape to export risk in surface flow, every other point along the flow path to the channel must be capable of transporting the risk. If a down slope point is not also saturated, the upslope risk will be captured at this point and not reach the river channel, the cell is disconnected. The total risk that a point represents is a function of the point scale risk and the risk of connectivity to the river channel. These risks are accumulated through the river catchment to show the points in the landscape where there is a greater or lower risk of diffuse pollution impacting on the aquatic ecosystem.

The above animation shows the how hydrological connectivity develops along a hillslope. Once runoff is generated, it will move down slope. This water may infiltrate further down slope and hence the sediments eroded upslope are deposited. If runoff is generated further downslope and flows into the river channel, then this lower part of the slope will be connected whereas the upper part of the slope will not be connected.

 

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