There is some merit in the idea of designing roads as emergency flood relief channels (NCE last week), not least because some of them already act as such.
In one incident, for example, a road fed by surface flow and a spring, discharged into another road which was already receiving water coming up out of its drains.
The resulting flow was forced onto an old lady's garden and the water entered her undercroft and rose to lap at her floor boards before stabilising.
In another incident, two roads discharged water, this time containing raw sewage, onto a roundabout, which flooded. While cautious drivers picked a route through, a gung ho driver dashed past, inundating two children whose route home lay along the footpath.
Leaving aside the problems of signing and parking on emergency flood relief roads, people get ill, accidents happen and houses catch fire even if it is raining. If one set of roads becomes impassable to anything except water, another set will be needed for the emergency services.
Obviously, roads do act both as water courses and as detention ponds and this aspect of their design does need careful consideration.
Peter Smart, civil engineering department, Glasgow University, Glasgow G12 8QQ