摘要:

The disconnection of sewered impervious areas is a measure to reduce the overflow frequency and hydraulic load of both combined and improved separate sewer systems. In this article the sizing of disconnection facilities is elaborated. The usual procedures for determining the required dimensions of the facilities contain some spurious assumptions. These assumptions have been removed, resulting in a more realistic design procedure for disconnection facilities to make sure that the discharge of stormwater is guaranteed. With the use of simulations various design graphs have been constructed. In the graphs the permeability of the soil (K value) is plotted against the required construction length of the facility (L value) scaled to the amount of connected impervious area. For a known K value, a known amount of impervious area and a chosen cross-section of the facility, the required construction length can be assessed directly from the graphs. The effect of a discharge drain at the bottom of a percolation trench has also been investigated. It appeared that, compared to a facility without a drain, the required dimensions of a facility with a drain decrease significantly. Consequently, soils with low permeability allow the application of percolation facilities, provided that a discharge drain is installed at the bottom of the facility. As the drain prevents groundwater filling the facility, the facility with a drain can be applied in areas with relatively high groundwater levels, as occur in many cities in the delta and polder areas of The Netherlands.

ISSN:0262-6667    

DOI:10.1080/02626669809492116

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Bayesian Generalised Likelihood Uncertainty Estimation (GLUE) methodology, previously used in rainfall-runoff modelling, is applied to the distributed problem of predicting the space and time varying probabilities of inundation of all points on a flood plain. Probability estimates are based on conditioning predictions of Monte Carlo realizations of a distributed quasi-two-dimensional flood routing model using known levels at sites along the reach. The methodology can be applied in the flood forecasting context for which the N-step ahead inundation probability estimates can be updated in real time using telemetered information on water levels. It is also shown that it is possible to condition the Nstep ahead forecasts in real time using the (uncertain) on-line predictions of the downstream water levels at the end of the reach obtained from an adaptive transfer function model calibrated on reach scale inflow and outflow data.

ISSN:0262-6667    

DOI:10.1080/02626669809492117

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An important aspect of flood management is the estimation of catchment response to storm events by simulation of flood wave propagation through the catchment storage. A derivation of the wave speed (c) is presented in terms of discharge (Q) and the exponent (m) in the storage (S)-discharge relationship S = kQm. The wave speed-discharge relationship has the form c = (αmc/m)Q1-m, where αcis a parameter in the kinematic wave model. The parameters in this relationship, however, change with flow conditions in the cross section, especially as flow leaves the main channel to inundate the floodplain. This finding confirms that the parameters in the single storage-discharge relationship do not have discrete values as used in many runoff-routing models, and hence the use of single parameter values is not suitable for estimating floods in many situations. It is shown that a more reasonable relationship is S = Sc+ k1LQ1/b, where Scis a threshold storage, and the other parameters are functions of the flow conditions. The parameters k, L, b and also the parameters in the wave speed-discharge relationship change between inbank, overbank, and fully developed floodplain flow situations. This paper investigates the relationship between the kinematic wave exponent (l/βc) and discharge that gives an estimate of (1/b) which is not provided by the wave speed-discharge relationship. This estimate is shown to be approximately equal to m, the exponent conventionally used in the storage-discharge relationship S = kQm. Further, the kinematic wave exponent (1/βc) can be approximated by the ratio between the water velocity and the flood wave speed. This analysis is used to explain the complicated behaviour of wave speed and water velocity in channel, overbank, and fully developed floodplain flows.

ISSN:0262-6667    

DOI:10.1080/02626669809492118

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To avoid flooding of the cities on the lower reach of the River Lenne, the main tributary of the Ruhr River, an adaptive on-line flood forecasting model has been developed based on a distributed deterministic catchment model. With the help of this model optimal strategies for the operation of the Bigge Reservoir during floods can be derived. The model was implemented in March 1995.

ISSN:0262-6667    

DOI:10.1080/02626669809492119

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A confined finite fractured aquifer bounded by a stream on one side and by an impervious boundary on the other is considered. Unsteady flow in the aquifer resulting from a sudden rise (or drop) of water level in the river stage is analysed. The governing differential equations are based on the double porosity conceptual model with the assumption of pseudo-steady state fracture-to-block flow. By applying finite Fourier sine and Laplace transform techniques to the governing equations, analytical solutions for the piezometric head distribution are obtained. By applying Darcy's law the time-dependent flow rate to (or from) the aquifer per unit length of the stream is evaluated. For negligible storage coefficient or hydraulic conductivity of the blocks, the new solutions reduce to known forms. The proposed analytical solutions may be useful in predicting the variations in the water levels in the aquifer as well as evaluating the time-dependent flow rates especially in the analysis of recession hydrographs in the streams. The solutions may also be used for the identification of the aquifer properties and for numerical model validation.

ISSN:0262-6667    

DOI:10.1080/02626669809492120

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Les observations tensiométriques et piézométriques au voisinage du ruisseau des Maurets, dans le bassin du Réal Collobrier, fournissent des informations intéressantes sur les mécanismes hydrologiques en cas de crue. Des mesures au pas de temps hebdomadaire montrent une bonne corrélation entre le débit dans la rivière et le niveau piézométrique au voisinage de celle-ci. D'autre part, on observe que ce niveau ne peut monter que si la pression d'eau dans le sol avant la crue est voisines de zéro. D'autres observations tensiométriques plus détaillées ont été effectuées au pas de temps de la demi-heure. Elles montrent que seules les pluies de fortes intensités peuvent provoquer une montée rapide de la pression positive d'eau du sol (saturation), à condition que cette pression soit très voisine de zéro avant la pluie. Dans ce cas, le gradient vertical de la charge hydraulique est quasi-nul, et des zones saturées contributives apparaissent et se développent, accompagnées de forts débits de crue dans la rivière. Ainsi, même dans des conditions méditerranéennes, les crues peuvent être provoquées par le développement des surfaces saturées contributives au voisinage des rivières. Dans ce cas, sur le bassin étudié, ces surfaces saturées ont une durée de vie très courte.

ISSN:0262-6667    

DOI:10.1080/02626669809492121

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Three monthly rainfall-runoff models have been applied to semiarid catchments within Namibia under the Southern African FRIEND (Flow Regimes from International Experimental and Network Data) programme. These are the Namrom model, developed specifically for Namibia, and two versions of the Pitman model, developed in South Africa and applied throughout the southern African region. The models were all calibrated on about 20 years of observed flow data and the calibrated parameters used to generate 68 years of simulated inflows to reservoirs located at the catchment outlets. A reservoir water balance simulation model was used with the three inflow series to assess the differences resulting from the application of the three models, with respect to estimates of the reliable yield. The calibration results for the three models were not very different and suggested that the yield estimates would be similar. However, the results based on the 68-year inflow records produced greater differences in yield which could have serious implications for the planning and management of water supply schemes.

ISSN:0262-6667    

DOI:10.1080/02626669809492122

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A multicomponent reactive transport model, MIN3KIN, has been developed. MIN3KIN handles both multiple chemical equilibrium and multiple component chemical kinetic reactions. A two-dimensional transport code has been coupled with a chemical equilibrium code and a chemical kinetic subroutine. A finite element method is used to solve the transport equations. Different coupling methods between transport and equilibrium calculations are evaluated and chemical equilibrium may be solved sequentially or iteratively. MIN3KIN has been evaluated against an analytical solution and applications for different coupling schemes and temporal discretization. It is shown that the chemical kinetic flux should not exceed 10% of the mass depletion for a given time step. Systems with both chemical equilibrium and irreversible chemical kinetics reach a condition, where the concentration quotient does not correspond with the equilibrium constant. The model is finally applied to a two-dimensional case study to illustrate the presence of an intermediate aqueous state governed by transport and irreversible chemical kinetics.

ISSN:0262-6667    

DOI:10.1080/02626669809492123

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492124

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669809492125

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor