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Urban Drainage
The risk of flooding is defined as a function of both the probability of a flood happening and its impact. In urban areas, the impact can be very high because the areas affected are densely populated and contain vital infrastructure. The reason for increased flooding in urban areas is twofold. Firstly, increased urbanisation has resulted in developments encroaching on floodplains, obstructing floodways and the loss of natural flood storage. Secondly, increased urbanisation has resulted in increased impervious areas such as roads, roofs and paving which create more rainwater water run-off.
To establish the flood risk associated with individual sites or catchments PUNCH Consulting Engineers can undertake Flood Risk Assessments in conjunction with River Flow Modeling.
Traditional drainage systems were designed to move rainwater as rapidly as possible from the point at which it has fallen to a discharge point, via a piped system to either a watercourse or soakaway. During periods of wet weather this approach can result in the increased risk of flooding downstream, sudden rises in water levels and flow rates in watercourses, By diverting rainfall to piped systems, water is stopped from soaking into the ground, depleting ground water and reducing flows in watercourses in dry weather. In addition, surface water run-off can contain contaminants such as oil, organic matter and toxic metals. Although often at low levels, cumulatively they can result in poor water quality in rivers and groundwater, affecting biodiversity, amenity value and potential water abstraction.
PUNCH Consulting Engineers recognise that the Sustainable Urban Drainage System (SUDS) approach to drainage reduces flood risk, minimises diffuse pollution, maintains or restores natural flow regimes and improves water resources while enhancing amenity. PUNCH have varied and extensive experience in the design of SUDS systems.