Assessment of the design of stormwater ponds for flow attenuation and water quality treatment
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(n order to reduce the impact of flooding and water quality degradation in urban areas sustainable urban drainage systems (SUDS) are increasingly being implemented throughout the UK. The thesis is concerned with one such type of system, namely retention ponds. With an absence of continuous long-term monitoring data to demonstrate how well these ponds perform in practice, a mathematical model was developed to investigate their flow attenuation and water quality enhancement characteristics. Simulations obtained with the model aimed to quantify how well ponds, designed using current UK guidance, are likely to perform now and under climate change scenarios. Furthermore, the model was used to study the effect of innovations in pond design. Initial modelling concerned ideal, generic ponds, with the knowledge gained being used to guide a case study on Linbum Pond in Scotland. Results show that the volume of temporary storage and the design of the outlet device are both of critical importance in meeting both flow attenuation and water quality enhancement targets. Furthermore, results also indicate the importance of dilution in achieving water quality targets. Simulations show that not only should a large permanent pool be provided but that water quality performance improves significantly when ~his volume is provided using larger surface areas as opposed to by deeper permanent pools. The assimilation of the knowledge gained in the study has enabled a set of improvements to current retention pond design to be proposed.