Processes and Trend of Gully Development in a Forest Environment in Australia

摘要

A catastrophic gully erosion has occurred during pine plantations in and around Bombala in southeast of NSW in recent years. This research aimed at finding the dominant hydrologic and erosional processes of gully development. An extensive field survey, three and half years of monitoring and historic and anecdotal evidence were used to determine the trend of gully development and its hydrologic and erosional processes. Characteristics of a single gully such as view plan, long profile, soil of the head and banks were surveyed. Rainfall, the depth of the water table just uphill of the gully head, surface runoff and channel flow, and seepage were monitored. The results of the research indicate that the trend of gully growth is exponential and that there is a rainfall threshold above which significant surface runoff, channel flow and water table rise. It is also indicated that a mixture of processes such as seepage, soil creeping, block failure and scour were acting on gully development and that two hydrological processes, seepage and overland flow are important. Furthermore, seepage is the dominant process involved in headcut erosion but to maintain the headcut retreat, overland flow is necessary.