A prototype decision support system for streambank rehabilitation.
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Date
2001
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Abstract
The condition of a stream is often judged by the state of its banks. This, the lack of adequate
advice for streambank rehabilitation, and the drive by legislation, particularly the National Water
Act, 1998 (RSA Act no. 36 of 1998) and the National Environmental Management Act, 1998
(RSA Act no. 107 of 1998), to restore South African riparian areas, created a need for more
information into such systems. Identifying a gap in what we know about rehabilitating degraded
streambanks led to the development of a decision support system for the selection of
streambank rehabilitation techniques. The Streambank Rehabilitation Decision Support System,
or SR-DSS, aims to provide riparian managers with advice on choice of technique at degraded
streambank locations along a river system. Techniques were sought from the scientific literature
and organised to recommend appropriate techniques for combating certain erosive processes.
Rutherford et al. (1999) conclude that placing priority on sites of lower importance may be an
inefficient manner of spending the resources at hand. Foreseeing this likelihood, a priority setting
system was developed and based on the principles of Rutherfurd et al. (1999). These principles
aim to prioritise human interests without compromising ecological interests. Along a given
stream, the areas of degradation that compromise property will nearly always have the highest
priority. Once these have been addressed, sites of ecological value are taken into consideration
followed by sites that require substantial effort to restore. It is argued that sites taking substantial
effort to restore have the least to 'loose' should they degrade further.
To enable the use of these principles a site scoring system was developed, so that sites could
be prioritised. This was based on the value and threat rating tables developed by Heron et al.
(1999). It was soon realised that a framework was needed within which the above could be set.
For this purpose, Kapitzke's (1999) planning and design procedure was adapted to form an
eleven-step framework which would guide the rehabilitation venture from priority setting, to the
treatment outcome. The rehabilitation approach was tested in the case of the Foxhill Spruit. The
small size of the catchment allowed the different segments of the approach (framework, priority
setting model, field assessment sheet and SR-DSS) to be tested in real world conditions. The
approach was found to have a number of strengths. The framework brought to the attention of
the user, the dominant forces at play at each site, and was useful in determining the
recommendation given by SR-DSS. The priority setting model allowed sites to be arranged in
order of priority, that, according to Rutherfurd et al. (1999), would be the most efficient in terms
of ecological value maintained, and resources saved. The field assessment sheet was
consistent in rating the degree of intervention required, and in each case directed the user to the
appropriate sections in SR-DSS. SR-DSS recommended appropriate techniques that would
match the erosive forces occurring at each site. Comparing the technique chosen by SR-DSS
to techniques that may have been recommended instead substantiated this finding. The
techniques chosen by SR-DSS were found to be superior. This approach considers all aspects
of sound streambank rehabilitation and may be used to gain advice on small streams in South
Africa.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.
Keywords
Water resources development--South Africa., Freshwater ecology., Stream conservation., Stream restoration., Geographic information systems., Riparian ecology., Theses--Environmental science.