Thesis (PhDEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The interaction between moving water and the physical attributes of a river, as displayed by
the channel morphology, determines the availability of physical habitat for aquatic species
and thus also the condition of the ecosystem. As such, the environmental flow assessment
process requires knowledge on how changes in the flow regime will affect both the
morphological and hydraulic conditions within a river channel. With the increasing
development of water-related infrastructure in mountain regions, knowledge of the
morphological and hydraulic characteristics of rivers in the upper catchment areas is very
important. Cobble and boulder bed rivers in the Western Cape are typical examples. They are
characterized by steep gradients, great variability in sediment size and relatively low flow
depths. The bed configuration contains a series of pools, steps, rapids, riffles and plane beds,
while energy losses are high as a result of turbulence and hydraulic jumps. Due to their wideranging
morphological and associated hydraulic attributes, the physical habitats within these
rivers are extremely diverse, both on a spatial and temporal scale. This study addresses the
interaction between moving water and the physical attributes of cobble and boulder bed
rivers. Empirical, semi-empirical and theoretically based models are developed which define
the hydraulic and morphological related characteristics of environmental flow components in
cobble and boulder bed rivers. They cover macro scale channel deformation, the scouring of
sand from the interstitial spaces between the cobbles as well as velocity-depth relationships,
which prove to be key components in the assessment of environmental flow requirements in
cobble and boulder bed rivers. / AFRIKAANSE OPSOMMING: Die wisselwerking tussen die vloeiende water en die fisiese eienskappe van 'n rivier, soos
beskryf deur die morfologie, bepaal die beskikbaarheid van habitat vir akwatiese spesies en
gevolglik ook die welstand van die ekosisteem. Kennis omtrent die impak van 'n veranderde
vloei regime op beide die morfologiese en die hidrouliese toestande in 'n rivierloop is dus
nodig vir die bepaling van omgewingsvloeibehoeftes. Met die toenemende ontwikkeling van
water-verwante infrastruktuur in bergagtige gebiede is 'n grondige kennis van die
morfologiese en hidrouliese eienskappe van riviere in hierdie bo-opvanggebiede gebiededend
noodsaaklik. Spoelklip riviere in die Wes-Kaap is tipiese voorbeelde van sulke riviere.
Hierdie riviere word gekenmerk deur steil hellings, 'n wye verskeidenheid sedimentgroottes,
relatiewe lae vloeidieptes en hoë energieverliese as gevolg van turbulensie. Verder bevat die
ri vierbed afwisselend poele en stroomversnellings en gevolglik word 'n wye verskeidenheid
habitat tipes in hierdie riviere aangetref. Hierdie studie fokus op die interaksie tussen
bewegende water en die fisiese eienskappe van spoelklip riviere. Met behulp van empiriese,
semi-empiriese en teoretiese modelle word die morfologiese en hidrouliese eienskappe van
omgewingsvloeibehoeftes in spoelklip riviere aangespreek. Dit sluit makroskaal kanaal
vervorming, die uitskuur van sand tusen die spoelklippe asook die verwantskap tussen
vloeisnelheid en vloeidiepte in. Hierdie aspekte kan beskou word as van die sleutel elemente
vir die bepaling van omgewingsvloeibehoeftes in spoelklip riviere.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52826 |
| Date | 12 1900 |
| Creators | Jonker, V. (Verno) |
| Contributors | Rooseboom, A., Gorgens, A. H. M., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 177 p. : ill. |
| Rights | Stellenbosch University |
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