I note the use of a 'box weir' to divert flood flows from the River Piddle (No piddling matter, NCE last week). The photograph in the article indicates long narrow slots to carry the flow into the box culvert.
I would be interested to know to what extent the designers have taken into account the possibility of the slots becoming blocked or obscured in a flood event.
My own experience of such arrangements is that a severe reduction in the flow capacity is possible when fl oating debris inevitably accumulates at the slots.
Charlie Rickard, independent consulting engineer, 4 Millards Lane, Lode, Cambridge CB5 9ES