This study presents the results of the flow regime evaluation, by means of computational fluid dynamics (CFD), of a vegetated detention pond located at Waterlooville, Hampshire, UK. Alternative pond layouts were assessed for the same flow conditions on the basis of recommendations made in the literature. The results were validated by comparing the maximum computational velocities for the same case using different numbers of mesh elements. It was found that the development of a CFD model of detention ponds is intricate but feasible. The main findings were: (i) The present design performed well in terms of flood risk management, but the flow patterns could result in questionable treatment efficiency; (ii) vegetation seems to promote horizontal recirculation and turbulence; (iii) triangular and elliptical pond designs showed very poor performance; (iv) the most appropriate design for the given location and hydrological regime is an elliptical pond with a central emergent/submerged island.

Road runoff contains a variety of contaminants that threaten aquatic systems. Pollutant mitigation is therefore an important function of sustainable drainage systems such as vegetated ponds. Vegetated ponds have a variety of treatment mechanisms that potentially can remove different pollutants. However, design is predominantly based on “black box” approaches. This study monitored a swale and vegetated pond receiving road runoff over two years to investigate the interaction of various pollutant removal processes. Storm runoff, pond water, and sediments were monitored for general water quality, metals, hexane extractable hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). A non‐exponential “first flush” was apparent for biochemical oxygen demand, chemical oxygen demand, and solids with higher concentrations seen during the early stages of storms; however, for hydrocarbons and PAHs peak concentrations were often seen later in storm events. Due to interference from natural compounds, PAHs are probably more appropriate than hexane extracts for tracking runoff pollutant fate. Pyrene, despite having low concentrations in water, accumulated in soils and sediments (median = 850 µg/g). Naphthalene was more mobile, but was effectively removed in the pond. Metals had similar concentrations to other studies, with large removals of particularly Cu and Zn. However, metals exhibited different deposition patterns, with Zn and Cu accumulating in pond inlet sediments and Ni and Cr accumulating at the outlet. The different behaviors and fates of pollutants means that refining design guidance is difficult and requires consideration of how specific mechanisms may be enhanced for prioritizing removal of pollutants that pose the greatest risk.

Temporary flood barriers can be used to create short-term, artificial walls blocking water flow across a floodplain as an alternative to permanent heavy-engineering solutions. However, to be successful, there needs to be an effective plan for the deployment of temporary flood defences. The authors of this paper highlight the lessons learned and knowledge gained through producing site-specific temporary flood defence deployment plans at Torksey Lock and St Neots in the UK. A deployment plan should operate at operational, strategic and tactical levels, with limitations at each level considered. It should also aim to resolve the risks associated with previous experiences of operational failure of temporary barriers. Limitations nevertheless remain, including awareness of and response to a structural failure. Testing of deployment plans is beneficial to flood risk engineers, emergency planning practitioners and the wider community.

This paper investigates the behaviour of certain water and sediment quality indicators of a vegetated detention pond system located at Waterlooville, Hampshire, UK. The period of study was 2 years (March 2011-March 2013) with sampling carried out once a month. Statistical analysis was performed using Minitab™. The aim of the study was to examine the changes in quality of various constituents with time and possible linear associations between them. Pond sediments and pond water quality were monitored for a range of variables at each monthly visit. Results indicate that the system demonstrates low levels of pollution while not having a direct impact on the oxygen balance of the receiving water-body. Oxygen demanding substances along with suspended matter and certain metals/elements were found to accumulate in the system with time. Significant linear associations were observed for road salts (containing Na, Cl, Mg) and certain pollutants, suggesting that road salts have a major impact on SuDS water/sediment quality. Sorption characteristics of specific metals were also evaluated by means of adsorption isotherm equations. Three widely used sorption isotherms were employed in this study. It was found that the sorption behaviour of metals is highly variable. This study highlights the dynamic nature of vegetated ponds and the importance of understanding the behaviour of different pollutants for SuDS design.

This paper investigates the behaviour of certain water and sediment quality indicators of a vegetated detention pond system located at Waterlooville, Hampshire, UK. The period of study was 2 years (March 2011-March 2013) with sampling carried out once a month. Statistical analysis was performed using Minitab™. The aim of the study was to examine the changes in quality of various constituents with time and possible linear associations between them. Pond sediments and pond water quality were monitored for a range of variables at each monthly visit. Results indicate that the system demonstrates low levels of pollution while not having a direct impact on the oxygen balance of the receiving water-body. Oxygen demanding substances along with suspended matter and certain metals/elements were found to accumulate in the system with time. Significant linear associations were observed for road salts (containing Na, Cl, Mg) and certain pollutants, suggesting that road salts have a major impact on SuDS water/sediment quality. Sorption characteristics of specific metals were also evaluated by means of adsorption isotherm equations. Three widely used sorption isotherms were employed in this study. It was found that the sorption behaviour of metals is highly variable. This study highlights the dynamic nature of vegetated ponds and the importance of understanding the behaviour of different pollutants for SuDS design.