The role of vegetation in mitigating the effects of landscape clearing upon dryland stream response trajectory and restoration potential

Dryland rivers are recognized for limited research and high uncertainties with respect to understanding biogeomorphic processes. This study uses aerial photography, sediment analysis, palynology indicators and hydraulic modelling to investigate the role of riparian vegetation in influencing the response of systems to disturbance, the trajectory of channel evolution and the potential for management. The study focuses on cleared and uncleared sites in the Yerritup catchment, along the south coast of Western Australia, that occur along a transect with a consistent stream gradient and landscape topographic setting. Downstream reaches show no gross botanical change, but gradual sediment deposition across the floodplain of up to 40cm based on palynological and sedimentary indicators. Channel response in the cleared section by incision, widening and floodplain degradation began rapidly after land clearing, but is driven by large flood events. Degradation of riparian vegetation has significantly increased the sensitivity of the system. The cleared reaches have transformed from a low-capacity channel, under-adjusted to the prevailing flow regime, to the large present channel that is now over-adjusted to the predominantly low to moderate seasonal (occasional flood) flow regime. Modelling of pre-settlement erosive potential reveals that the entire system was naturally sensitive to change, and was primed to erode once riparian vegetation was removed. The trajectory of channel evolution and the role of riparian vegetation is examined in relation to undisturbed reaches in the system and an appreciation of the historical range of variability in geomorphic response. Analysis of the patterns of contemporary vegetation growth identify the potential to re-establish vegetation where it is elevated from saline baseflow. However, the system is assessed as being close to a threshold where restoration is no longer possible and remediation options become more limited as eco-hydraulic and hydrochemical changes continue

Land and water governance on the shores of the Laurentian Great Lakes

© 2014 International Water Resources Association. The Laurentian Great Lakes Basin is large and complex, as is its institutional setting. Given these characteristics, Great Lakes boundaries are both horizontal and fluid, and governance at the Great Lakes water/land interface implicates at least four different frontiers of planning and management. While substantial multinational and sub-national policy regimes have formed over the last century to improve Great Lakes water quantity and water quality management, parallel arrangements have not formed to manage better shoreland boundaries and frontiers