Year

2012

Degree Name

Bachelor of Environmental Science (Honours)

ANZSRC / FoR Code

0406 PHYSICAL GEOGRAPHY AND ENVIRONMENTAL GEOSCIENCE, 040601 Geomorphology and Regolith and Landscape Evolution

Department

School of Earth & Environmental Sciences

Advisor(s)

Colin Murray‐Wallace

Abstract

The cutting of Berry’s Canal in 1822 between the Shoalhaven River and the Crookhaven River system has significantly contributed to the erosion of the Comerong Island Nature Reserve banks. Since the excavation of Berrys Canal in 1822 and the semi-permanent closure of Shoalhaven Heads, Berrys Canal is now the main pathway for both river and tidal flows for the Shoalhaven River. This intensification of hydraulic forces has created a river system that is unstable. This thesis demonstrates that engineering in estuaries can have unpredictable long-term impacts on levels of erosion, tidal circulation and intensifying flood and ebb patterns.

This paper aims to analyse the evolution of Berrys Canal through historical records and contemporary case studies to assess the recent dynamic channel adjustments. The causes of erosion in Berrys Canal are complex and have been identified as predominantly fluvial and tidally scoured. However thalweg location, riparian vegetation and bank material type are influencing erosion resistance and forcing variables. Currently a decrease in the rate of erosion suggests Berrys Canal is adjusting towards a dynamic equilibrium point. Whilst gradual decreases in rates of erosion in the Berrys Canal may reflect an evolving state of equilibrium, it is however unlikely to reach stability for some decades, if not centuries to come.

Through understanding the driving forces and resistance variables influencing the evolving morphology of Berry’s Canal, NPWS can make informed decisions regarding its bank management strategy for Comerong Island nature reserve.

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