Landscape Connectivity in the Upper Mzimvubu River Catchment: An Assessment of Anthropogenic Influences on Sediment Connectivity

Abstract

Connectivity has been altered in many landscapes world‐wide and impacts the routing of water and sediment. Diminished ecological infrastructure can result in a reduced ability to retain water and soil that will impede ecosystem health and sustainable use of land and water resources. In the northern Eastern Cape Province of South Africa, the headwaters of the Mzimvubu River, land use change and land degradation over the past 50–100 years has initiated increased sediment connectivity through features such as gullies and incised river channels. The water resources of this catchment are largely undeveloped, but future development will be threatened by high suspended sediment loads. The Vuvu catchment, a headwater tributary of the larger Mzimvubu River system, is used as a case study to assess how hillslope–channel and channel–valley fill sediment connectivity has changed over the past 100 years. From detailed mapping of gullies, roads and livestock tracks, it was concluded that downslope connectivity added 22% and across‐slope drainage 159% to the drainage network. As a result of increased drainage efficiency, the main channel was incised and straightened, in turn reducing channel–valley fill connectivity. A conceptual model of changes to sediment connectivity is presented with recommendations for future restoration. Copyright © 2017 John Wiley & Sons, Ltd.

Integrating Sediment (dis)Connectivity into a Sediment Yield Model for Semi-Arid Catchments

“…Sinks can be reworked and become sediment sources during high magnitude events or once the storage capacity is effectively filled. Gully erosion is a common process responsible for reworking long-term hillslope or valley floor sinks, while at the same time, increasing connectivity within the landscape [30][31][32].…”