Q. Kerb overflow weirs – horizontal bars vs. vertical bars?
Overflow weirs must be provided for steep roads (longitudinal gradient>5%), flat roads (longitudinal gradient<0.5%), sag points and blockage black spots. For steep roads the flow is rapid and overflow weirs must be provided to accommodate the excess flow. For flat roads, probability of accumulation of rubbish increases. So overflow weirs must be provided in these locations to avoid the stormwater flow just in case of blockage of gullies caused by trapping of rubbish.
Essentially kerb overflow weirs suffer from the disadvantage that it provides another passage for debris to enter the gullies and so bars (either vertical orhorizontal) must be provided to prevent the entry of debris into the weirs. For steep roads, as main concern is to provide an alternative route for excess flow, horizontal bars must be provided in this case to sustain better drainage efficiency. For flat roads, purpose of overflow weirs is to trap rubbish,so vertical bars must be provided since it is more effective in prevention of entry of debris.