No description available.

Urban drainage models are examined in terms of model purpose, type and usage. Model usage for the prediction of flooding behaviour in the UK adopts the design storm approach, which assumes that flood frequency equals rainfall frequency. This equation is shown to be affected by antecedent moisture conditions and rainfall spatial variability. Data collected from three small urban catchments (0.3 ha, 0.7 ha and 3.2 ha) in Southampton are used to calibrate and verify three urban drainage models: namely WASSP-SIM, WALLRUS-SIM and USGS-DR3M. A probabilistic approach to model verification is used and demonstrates that accepted bounds to model accuracy associated with the use of these models are difficult to justify if consideration is given to the possible errors in rainfall and discharge measurement. Comparison of the results from storms collected during 1985 on these catchments shows that the DR3M performs better than either of the other models in terms of a number of standard indices of model accuracy. Soil moisture observations collected over a two year period using the neutron probe method are then used to calibrate and test a number of simple soil moisture models including the soil moisture algorithm incorporated in the MORECS procedure and that included in the DR3M. These models are found to predict catchment average soil moisture conditions to within 20 mm, using local rainfall information and standard evapotranspiration curves as inputs. Using the MORECS soil moisture model it is shown that antecedent soil moisture conditions do have an impact on observed percentage runoff values, but that the relationship is confused by seasonal factors. The soil moisture model is then used together with WASSP-SIM to derive discharge-frequency curves using a continuous simulation approach. Comparisons with the design storm approach confirm the assumptions of the approach, although they do not prove that either approach produces the correct answers.

No description available.

No description available.

No description available.

The objective of this research was to investigate the sediment behaviour in a compound channel and, in particular, the transfer of sediment between a main channel and its flood plain. A review of the literature on compound channels showed that, whilst research on fixed boundaries had been carried out or was in hand, there was no evidence that the loose boundary situation had previously been studied.Experiments were conducted in a loose boundary, outdoor sand channel of symmetrical compound section. The channel was of straight alignment, 50 m long, with an overall width of 3 m. Pumping equipment was available for recirculation of the water and the sediment.Samples of suspended sediment were collected from the shallow and deep sections and analysed by Coulter Counter to obtain the particle size distributions. The distribution curves were found to be very similar for the main channel and the flood plains.Sand from the channel was labelled by fluorescent dye and inserted in the bed of the main channel so as to simulate a point release. Bed samples were collected at sections 5 m and 10 m downstream of the injection point and examined under UV light for their tracer proportions. It was found that the cross-sectional distribution of tracer concentration was approximately Gaussian indicating that there had been some sediment transfer to the flood plains.A two-dimensional diffusion model, which accounts for the movement in the longitudinal and lateral directions, has been applied to describe the transport and dispersion of the tracer particles. A best-fit overlay with the experimental results enabled the longitudinal and lateral dispersion coefficients to be established. The model results, for the distribution of tracer, are depicted in 2 and 3-dimensional form at a sequence of time intervals for up to 2 hours after tracer release.It was concluded that under steady state conditions there would be a constant transfer of sediment from the main channel to the flood plains; in fact, analysis showed that approximately 40% of a continuous tracer injection in the main channel would be transferred to the flood plains.

No description available.

No description available.

No description available.

No description available.