INVESTIGATING THE RELATIONSHIP BETWEEN RAINFALL INTENSITY, CATCHMENT VEGETATION AND DEBRIS MOBILITY

Abstract

Urbanisation creates the need for engineered hydraulic structures in catchments, floodplains and
watercourses. These include piped and open-channel drainage networks, flood control systems and waterway
crossings such as culverts and bridges. During larger storm events, debris and other material located higher in the
catchment can be mobilised and transported towards these hydraulic structures creating the potential for
blockages. This debris is often trapped by the hydraulic structures, causing partial or full blockage which can
reduce the flow capacity of the structure. This may cause upstream flooding during high intensity rainfall events.
This study investigated the debris transport behaviour in a natural channel. A model of an existing catchment and
culvert system in Australia was build based on Froude similitude scaling. Different sized twigs were used to
replicate natural debris of various sizes. The experimental results demonstrated that the mobility of debris during
rainfall events was dependent on a range of factors including stream depth and width, the size and availability of
debris, and on the condition of the riparian vegetation within the catchment. This could have significant
implications for culvert design and maintenance procedures.