Annual Report 2009/2010 - Hawkesbury City Council - NSW ...

oad network has not evolved or been designed for the purpose of evacuating the floodplain's
communities. Under existing conditions, many of the local roads are cut early by mainstream flooding
and/or local catchment flooding.
The present urban and rural population of the valley has had no experience of severe flooding, having
only suffered events up to approximately a 1 in 40 chance per year flood since 1867. This lack of
awareness will make evacuation all the more difficult and could increase the trauma that may be
experienced by the floodplain communities in the event of a severe flood.
Response to the issue
Council has established a Floodplain Risk Management Committee. The Committee generally meets
once every 2 months.
Council relies on flood related data and flood studies prepared by Sydney Water, internally by Council
staff and external consultants. This includes flood levels and studies for the Hawkesbury-Nepean, Colo,
and Lower MacDonald River. A Digital Terrain Model of the flood prone areas of the Hawkesbury was
completed in 2008 with grant funding provided to Council under the Natural Disaster Mitigation Program.
Council has been successful in obtaining a grant under the State Floodplain Management Program to
assist in the preparation of the Floodplain Risk Management Study and Plan.
Council has engaged a consultant to prepare a Flood Risk Management Study and Plan for the
Hawkesbury River within the Hawkesbury LGA.
Council does have flood related development controls in the Hawkesbury Local Environmental Plan 1989
(HLEP 1989) and Hawkesbury Development Control Plan 2002 (HDCP) which have been developed
overtime and prior to the Floodplain Development Manual: the management of flood liable land. The
current flood related development controls are substantially based on the 1 in 100 year flood event being
the flood planning level.
Future directions
Floodplain Risk Management Study and Plan to be prepared and implemented.
Introduction
River Health
The Hawkesbury-Nepean River is one of the longest rivers in Eastern Australia. The Nepean River rises
near the Robertson in the Illawarra Range, 100km south of Sydney. Downstream from the junction of the
Nepean and the Grose River, the river is called the Hawkesbury. Uses of water from the Nepean River
and its tributaries include water for Sydney's domestic purposes, water supply for land holders along the
river, irrigation, stock watering, recreation, habitats for aquatic flora and fauna and waste disposal.
Waterways of the Hawkesbury-Nepean are also adversely impacted by a wide range of land uses. Storm
water runoff from urban areas along with sediment and nutrient runoff from rural areas contribute to
reduced water quality. Water quality is also adversely impacted by on-site waste water management
systems as well as through discharges from sewerage treatment plants. Licensed surface water
extraction to support agricultural production contributes to reduced stream flows.
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2009/2010 Annual Report