In August 1997, Water Studies Ply Ltd was requested by Clarence River County Council (CRCC) to undertake a flood study to investigate flooding behaviour in the Alipou Basin (i.e. areas bounded by Heber Street, Alipou Basin and Clarenza Levees) in South Grafton in general, and determine the impact of the recently constructed Heber Street Levee on flood levels in the above area in particular. This report is in response to the above request. Alipou Creek, a minor tributary of the Clarence River, drains a 32 square kilometres rural catchment to the east of South Grafton. The lower reaches of Alipou Creek are subject to both 'regional' flooding from the Clerence River and 'local' flooding from the Alipou Creek catchment itself. Numerous levees constructed over the years in North and South Grafton, including Heber Street and Alipou Basin Levees, have modified both regional and local flooding behaviour in the area of interest of this study. This report is structured as follows:
- Section 2 describes the adopted method of analysis for the study and the range of local and regional flooding combinations investigated.
- Section 3 describes the runoff - routing model used to estimate local flood inflows to Alipou Basin from Alipou and Musk Valley Creeks.
- Section 4 describes the development and calibration of two hydraulic models (a regional 'coarse' model and a 'fine' local model) used to investigate flooding behaviour in the area of interest.
- Section 5 describes the results of the investigation of various local and regional design event combinations.
- Section 6 presents the conclusions of the study.
- Section 7 provides a list of references.