Thresholds, Scale and Connectivity in semi-arid Catchments: Implications for eco-engineering Strategies

Geomorphological processes in semi-arid environments are strongly influenced by the connectivity between different landscape units. This connectivity can either be established
through concentrated flow in rills, gullies and channels but can also have a more
diffuse flow character, where sheet flow can reach the channels. Whether connectivity
is established or not, is largely dependent on the properties of the landscape units involved.
Moreover, the actual connectivity is strongly dependent on the magnitude of
the events generating geomorphological processes.
From two semi-arid catchments in Southeast Spain examples of events with different
degrees of connectivity will be discussed. Fine, intermediate and broad scale aspects
will be integrated in relation to the recurrence period of the events and their consequences
for runoff generation and sediment delivery at the hillslope and catchment
scale will be discussed.
This knowledge can be used to apply sustainable strategies to reduce the undesirable
on- and off-site effects in order to mitigate land degradation. However, the effectiveness
of revegetation and soft engineering approaches are also site specific as well as
scale dependent and these aspects should be incorporated in their planning and expected
sustainability.