| Summary: | Thesis (MScEng)--Stellenbosch University, 2002. === ENGLISH ABSTRACT: This investigation arose out of the pressing need for alternatives to ineffective existing
methodologies for low flow measurement in boulder bed rivers, with particular focus
on the mountain streams in the Western Cape.
Both empirical and mathematical verification were regarded as important if progress
was to be made towards identifying a suitable approach. Historically the inability to
determine the frictional effect of the streambed on the flow rate has been a major
obstacle limiting the accuracy of flow calculations. From literature, the most likely
relationship appears to be a power function, utilising hydraulic variables derived from
physical parameters characteristic of a section of stream.
Local Western Cape data was thus collected from various typical mountain streams,
so that relevant analysis could be done. Testing of existing equations from literature
sources on this set of data revealed limited applicability.
Subsequent empirical experimentation has shown that particle size is a dominant
variable in determining boulder bed flow resistance under low flow conditions.
A mathematical approach was sought to provide a more suitable base for a locally
applicable formula. Sediment transport theory, based on simple power conservation
laws, was successfully implemented, partially bridging the gap between the
applications for sand bed and boulder bed flow conditions respectively.
After a certain degree of empirical adjustment, an equation form was finalised that is
believed to be the most suitable for Western Cape mountain streams, with definite
potential for wider application, provided further research is done. === AFRIKAANSE OPSOMMING: Hierdie ondersoek spruit uit die dringende behoefte aan bruikbare alternatiewe vir bestaande laagvloei meetmetodes in riviere met bodems bestaande uit spoelklip, met
spesifieke klem op die bergstrome van die Wes Kaap.
Dit is as belangrik beskou om beide empiriese en wiskundige bevestiging te vind vir
'n verbeterde metode. Histories is die akkuraatheid van vloeitempo berekeninge
hoofsaaklik beperk deur die onvoorspelbaarheid van die ruheidseffek van die
rivierbodem op die vloei. Uit bestaande literatuur blyk dit dat die mees geskikte
verwantskap waarskynlik 'n magsfunksie is, wat saamgestel is uit hidrouliese
veranderlikes verkry vanaf fisiese parameters kenmerkend aan die spesifieke
riviersnit.
Plaaslike Wes-Kaapse data is dus versamelop verskeie tipiese bergstrome in die
gebied sodat geskikte ontledings gedoen kon word. Verskeie bestaande formules is
getoets teen hierdie stel data en ongeskik gevind vir direkte aanwending.
Empiriese toetse het gevolg en getoon dat partikel grootte 'n dominante invloed het
op die vloeiweerstand van spoelklip bodems onder laagvloei omstandighede.
'n Wiskundige benadering is daarna gevolg om 'n beter basis te verskaf waaruit 'n
plaaslik bruikbare vergelyking kon volg. Sedimentvervoer beginsels, wat gebaseer is
op basiese drywingsteorie, is suksesvol aangewend vir hierdie doel, en het in 'n mate
die gaping tussen aanwending op sand en klip bodems oorbrug.
Na afloop van empiriese verstelling is 'n formule gefinaliseer wat beskou word as die
mees geskikte vir Wes-Kaapse bergstrome, maar wat ook die potensiaal besit vir wyer
aanwending, mits verdere navorsing gedoen sou word.
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