Assessment of changes in overland time of concentration for two opposing urbanization sequences

Wong, Tommy S. W.; Li, Yunjie

doi:10.1080/02626669809492106

Cited by 8 publications

(2 citation statements)

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“…For practical applications, the formula is further developed in terms of the Manning resistance coefficient. In fact, the kinematic wave theory has also been used to derive the time of concentration and the peak discharge formulae for a series of planes (Wong, 1996(Wong, , 1998Wong & Li, 1998.…”

Section: Open For Discussion Until I April 2001mentioning

confidence: 99%

Determination of equilibrium detention storage for a series of planes

Wong

2000

Hydrological Sciences Journal

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The detention storage in a drainage basin under the equilibrium condition is an important parameter in rainfall-runoff modelling. As this parameter is an efficient measure of the basin response to rainfall, it is commonly used as a basis of approximation of a complex basin by a simpler one. For flows on an overland plane, the equilibrium storage has also been used as a basis of determining the resistance coefficient of the overland surface. A formula is derived, based on the kinematic wave theory, for the equilibrium detention storage for a series of planes. For practical applications, the formula is further developed in terms of the Manning resistance coefficient. The derived formulae are all consistent with the published formulae for a single plane. Détermination du stockage temporaire à l'équilibre pour un ensemble de surfaces planes Résumé Le stockage temporaire à l'équilibre d'un bassin versant est un paramètre important pour la modélisation pluie-débit. Comme ce paramètre mesure bien la réponse du bassin à une pluie, il est couramment utilisé pour donner une image simple d'un bassin complexe. Pour les écoulements sur une surface plane, le stockage temporaire à l'équilibre a également été utilisé pour déterminer le coefficient de rugosité de cette surface. Dans cet article, nous établissons, sur la base de la théorie de l'onde cinématique, une formule permettant de calculer le stockage temporaire d'un ensemble de surfaces planes. Pour les applications pratiques, la formule a été établie en utilisant le coefficient de rugosité de Manning. La formule établie est cohérente avec les formules publiées pour un plan unique.

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Section: Open For Discussion Until I April 2001mentioning

confidence: 99%

Determination of equilibrium detention storage for a series of planes

Wong

2000

Hydrological Sciences Journal

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“…For the planes with a low degree of urbanization (small L i /L), Figure 5 shows that for all three n i /n p ratios, the design¯ood peak ratio is less than one indicating that the¯ood peak for planes with the downstream portion urbanized is less than that for planes with the upstream portion urbanized. This phenomenon can be attributed to the longer time of concentration for planes with the downstream portion urbanized (Wong and Li, 1998) thereby resulting in a smaller design rainfall intensity. The Q md /Q mu ratio decreases with increasing degree of urbanization.…”

Section: Eect Of the Manning Resistance Coecientmentioning

confidence: 94%

Theoretical assessment of changes in design flood peak of an overland plane for two opposing urbanization sequences

Wong

Li²

1999

Hydrol. Process.

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Abstract:By considering urbanization on an overland plane as a process whereby a relatively rough, permeable surface is gradually replaced by a relatively smooth, less permeable surface, the eect of urbanization sequence on the¯ood peak is theoretically assessed by the kinematic wave method. In the assessment, two opposing urbanization sequences are considered: one from downstream to upstream, and the other from upstream to downstream. The assessment is carried out in terms of the individual eect as well as the combined eect of the Manning resistance coecient and the runo coecient. For both urbanization sequences and for all degrees of urbanization, the assessment shows that surface conversion from rough to smooth, or from permeable to less permeable causes the¯ood peak to increase. A comparison of the individual eects shows that for equal reductions in surface roughness and permeability, the reduction in permeability causes greater increases in thē ood peak compared with the reduction in surface roughness. For a partially urbanized plane and for the same degree of urbanization, due to the partial area eect, urbanization at the downstream end generally causes greater increases in the¯ood peak. In terms of urbanization sequence, the downstream to upstream urbanization sequence generally causes greater increases in the¯ood peak. The eect of urbanization sequence on thē ood peak, however, is only signi®cant for the larger reductions in surface roughness and permeability. Finally, a comparison of the results of this study with those obtained from drainage basins shows that for most of the results from the basins, they correspond to those for the small reductions in surface roughness and permeability on an overland plane. For these cases, the eect of urbanization sequence on the¯ood peak is small. Copyright # 1999 John Wiley & Sons, Ltd.KEY WORDS design discharge;¯ood peak; kinematic wave; overland¯ow; urbanization location; urbanization sequence NOTATIONThe following symbols are used in this paper.

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