The objective of having freeboard is to provide assurance against overtopping resulting from wind set up and wave run up.

Other factors which may influence the selection of freeboard include:

– Reliability of design flood estimates. – Spillway gate reliability and the effect of a gate or gates failing to operate during

the flood. – Assumptions made in flood routing. – Potential changes in design flood estimates, either through changes in flood

estimation techniques or due to changed catchment conditions.