Flooding in the downstream regions of many coastal catchments is the result of the interaction between runoff generated by a weather event that elevates sea levels and/or estuary water levels. Historically assumptions have been made regarding either the independence of these events or the timing of rainfall or flood peaks and peak ocean and/or estuarine conditions eg. peak runoff and peak ocean or estuary levels coinciding. Assuming that the weather events that generated elevated ocean or estuary conditions and significant catchment runoff are independent can underestimate flood levels in coastal areas. Conversely an assumption that the flood peak coincides with the peak elevated ocean or estuary conditions can overestimate flood levels in coastal areas. In order to better understand flooding in coastal areas it is necessary to have an understanding of the role that severe weather conditions that create elevated ocean or estuary condition have in generating catchment runoff that floods coastal areas.

The importance of this understanding will increase in time as existing coastal communities are threatened increasingly by rising sea level as a result of climate change.

Thanks to the Port Authorities of Australia who have provided their tidal data at no cost to the project for use in Project 18.

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