The influence of groundwater conditions on streambank stability in the Wet Tropics

Sands, Leonard Brett (2008) The influence of groundwater conditions on streambank stability in the Wet Tropics. Masters (Research) thesis, James Cook University.

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Abstract

Streams are naturally dynamic, adjusting their form in response to changes in natural processes and human activity. Streambank mass movements (slumps) that affect human utilities such as land-use and infrastructure may occur as part of the natural stream processes, or may be accelerated by flow regulation or encroachment on the stream. Slumping commonly occurs when the subsurface water levels in the bank remain above the falling water levels in the stream. This condition is referred to as 'rapid drawdown', and typically develops when alluvial stream banks, saturated prior to or during flood inundation, are subject to a rapid recession of flood water levels. Rock revetment has been used traditionally in the treatment of bank slumps in order to surcharge the bank as well as to prevent fluvial erosion. Alternative treatments, incorporating subsurface drainage have been used successfully in north Queeensland, Australia, but more needs to be done to fully understand the attributes and mechanisms associated with slumping and to identify performance characteristics of existing drainage treatments. This study will provide practitioners with a better understanding of slumping and improved treatment methods. Subsurface water conditions affecting streambank slumping are a function of stratigraphy, local rainfall, flood infiltration, flood recession and regional water table levels. Pressure, moisture and raingauge instrumentation were installed at a streambank case study site on the Herbert River Anabranch in tropical north Queensland, to monitor subsurface water response to river flooding, site rainfall and regional water table heights. Monitoring results show bank stratigraphy and drainage treatments affect flood infiltration and regional water table inundation of the bank. Furthermore, subsurface water levels within the bank remain elevated during rapid flood recession and continue to be elevated until the regional water table has fallen. Modelling of various streambank and artificial drainage configurations has confirmed the response of subsurface water levels and seepage face progression to flood recession, has demonstrated that subsurface drainage lowers elevated water levels, and identified slumping thresholds associated with typical flood recession rates and bank permeabilities. This research provides an understanding of the attributes and mechanisms of slumping in tropical streams, illustrates the performance of subsurface drainage, and will lead to techniques for better management of slump failures.

Item ID: 32248
Item Type: Thesis (Masters (Research))
Keywords: subsurface drainage; slumping; streambank stability measures; Herbert River; Wet Tropics; North Queensland; stream management
Date Deposited: 30 Apr 2014 06:15
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050104 Landscape Ecology @ 30%
09 ENGINEERING > 0907 Environmental Engineering > 090702 Environmental Engineering Modelling @ 70%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960999 Land and Water Management of Environments not elsewhere classified @ 70%
96 ENVIRONMENT > 9609 Land and Water Management > 960905 Farmland, Arable Cropland and Permanent Cropland Water Management @ 30%
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