PPS 15 Planning and Flood Risk (Revised)·Page 44·6.50
Flood risk impacts of culverting
Culverting may alleviate local flood risk but can increase downstream flood risk through flow accumulation. Protective grilles can become blocked and fail during intense rainfall, so culverting does not completely eliminate flooding potential.
Whilst culverting may in some instances alleviate local flood risk, it can increase flood risk downstream by the accumulation of higher flows. The installation of protective grilles at culvert inlets may reduce the incidence of blockages within the culvert, but can often become blocked themselves and cause flooding as a result of a high intensity rainfall event or lack of maintenance. Culverting therefore does not completely remove the potential for local flooding.
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