Flood mitigation measures were investigated for eliminating flood problems for the 1% annual exceedance probability flood for: Greystanes Creek from Fox Hills Golf Course to Fitzwilliam Road, Toongabbi e, Pendle Hill Creek from the Great Western Highway to Fitzwilliam Road, Toongabbie, and The Confluence Area extending from Fitzwilliam Road, on both creeks, to Toongabbie Creek, including the confluence of Greystanes Creek with Pendle Hill Creek. The capacities of all channels, bridges and culverts in the Study Area were assessed and compared with the 1% flood estimate for existing conditions and for conditions with the upstream retarding basins completed. On the basis of the comparison those structures which were inadequate.