{"help": "https://data.gov.au/data/en/api/3/action/help_show?name=package_show", "success": true, "result": {"archived": false, "author": "Hawkesbury City Council", "author_email": null, "contact_point": "council@hawkesbury.nsw.gov.au", "creator_user_id": "c2fbbe4a-4ba0-4945-808b-67454605a4cf", "duplicate_score": 2, "geospatial_topic": [], "id": "af2ded03-419f-47da-934c-b10cf60ba94e", "isopen": false, "license_id": "cc-by", "license_title": "Creative Commons Attribution 3.0 Australia", "license_url": "http://creativecommons.org/licenses/by/3.0/au/", "maintainer": null, "maintainer_email": null, "metadata_created": "2026-01-10T17:00:27.339764", "metadata_modified": "2026-03-01T18:45:20.753422", "name": "nsw-fdp-hawkesbury-floodplain-risk-management-study-plan-report", "notes": "The study area of the Hawkesbury Floodplain Risk Management Study & Plan comprises all\nof the Hawkesbury River and its immediate surrounds that fall within the Hawkesbury Local\nGovernment Area. It extends from Agnes Banks/Yarramundi in the south to Wisemans\nFerry in the north, representing a river distance of approximately 83 km and an area of some\n220 km2 subject to inundation in the Probable Maximum Flood (PMF). The main area of\nfocus is for the area from Agnes Banks/Yarramundi to Wilberforce, including the flood?prone\ncommunities of Richmond and Windsor (see Figure 1.2).\n\nThe Hawkesbury?Nepean catchment covers about 22,500 km2 and is one of the largest of all\ncoastal rivers in New South Wales (see Figure 1.3). It includes extensive grazing areas in\nthe south?west and large National Parks in the Blue Mountains to the north?west. Urban\ndevelopment in the catchment area includes towns such as Goulburn and Lithgow and outer\nsuburbs of western Sydney including Camden and Penrith (ERM Mitchell McCotter, 1995).\n\nMore than 40% of the total Hawkesbury?Nepean catchment \u0096 about 9,000 km2 \u0096 is upstream\nof Warragamba Dam. Half of this area comes from the Wollondilly River. The Warragamba\nRiver joins the Nepean River 3.5 km below the dam. The Grose River is a major tributary\nwhich joins the Nepean at Yarramundi, after which the Nepean is known as the Hawkesbury.\nWhilst the Grose has a catchment of only 650 km2, it drains a high rainfall area and can\nhave a significant effect on flooding at Windsor. In particular, it can cause flood levels to rise\nquickly in the early part of major storms (ERM Mitchell McCotter, 1995).\n\nThe catchment area at the Windsor gauge is about 12,800 km2. South Creek joins just\ndownstream of the Windsor gauge. Whilst its catchment area of 640 km2 is virtually the\nsame as the Grose, it receives less rainfall and thus has less impact on Hawkesbury River\nflooding. At Lower Portland the Hawkesbury is joined by the Colo River, which drains an\narea of 4,640 km2 (ERM Mitchell McCotter, 1995). The Colo can influence flooding in the\nHawkesbury River depending on the movement of flood producing rainfall over the\nHawkesbury and Colo River catchments. The Colo has a shorter response time to rainfall\nand as shown in the 1978 flood, it can have a large impact on Hawkesbury River levels,\nparticularly downstream of Sackville. A study of the joint probabilities of floods originating\nfrom the Hawkesbury and the Colo has been carried out (AWACS, 1997). AWACS found\nthat the 100 year design flood levels in the Hawkesbury downstream of the Colo confluence\nwere relatively insensitive to the assumed Colo contributions. Nevertheless in some events,\nflooding in the Hawkesbury River within the lower portions of the study area can be\nsignificantly influenced by the Colo subject to the spatial and temporal distribution of the\nrainfall.\n\nWhen measured in 2000, the Hawkesbury River was subject to tidal influence up to\nYarramundi Bridge (MHL, 2005). However, the limit of tidal influence is rarely constant.\nThere are short?term cyclical changes in response to the ever?changing ocean tides, and\nchanges over long time spans according to both natural processes and artificial disturbance.\nSand extraction in the vicinity of the limit of tidal influence in the Hawkesbury River is\nreported to have caused the tidal limit to move a further 10 km upstream over the 20th\ncentury (Estuaries Branch, 2010).\n\nRECOMMENDATIONS\n\nThe Floodplain Risk Management Plan (FRMP) showing the preferred floodplain risk\nmanagement measures for the Hawkesbury study area is presented in this chapter. The recommended measures have been selected from the range of measures discussed in\nChapter 6, after an assessment of each measure\u0092s impact on flood risk, as well as\nconsideration of environmental, social, and economic factors. The recommended measures\nare presented in Table 9.1. The principal components of the Plan are presented below\naccording to priority, which is assessed on the basis of how easily (quickly) each measure\ncan be implemented and on value for money. The timing of the proposed works will depend\non Council\u0092s overall budgetary commitments, and the availability of funds from other\nsources.\n\nPRIORITISED MEASURES\n\nHigh Priority Measures\n\n- Item 1: Community Flood Education
\n- Item 2(a): Dual Outbound Lanes on Jim Anderson Bridge
\n- Item 2(c): Construction of Community Refuges
\n- Item 2(d): Flood Emergency Plans for Special Uses and Utilities
\n- Item 2(e): Flood Emergency Plan Templates for Caravan Parks
\n- Item 2(f): Review and Update Hawkesbury?Nepean Flood Emergency Sub Plan and\nNSW State Flood Sub Plan (Annex C)
\n- Item 2(i): Investigation of Road Duplication Options at the Eastern End of the Jim\nAnderson Bridge
\n- Item 3(a): Provision of Evacuation Risk Advice for Existing Development Proposals
\n- Item 4: A range of Town Planning Measures including revisions to the Flood Risk\nchapter of Council\u0092s DCP
\n
\n\nMedium Priority Measures\n\n- Item 2(b): Enhance Emergency Management Assessment Tools
\n- Item 5: Study of Voluntary House Raising and Redevelopment Options
\n- Item 6: Assessment of a Levee and Refuge Mound for McGraths Hill
\n
\n\nLow Priority Measures\n\n- Item 2(g): Provide additional crossing of South Creek
\n- Item 7: Update Flood Behaviour Data for Valley
\n
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