The Lower Macleay River floodplain occupies approximately 500km2 of coastal floodplain downstream of Kempsey, to the Macleay River’s main outlet at South West Rocks. The floodplain drains a catchment area of 11,500km2, has several secondary outlets to the ocean at Hat Head and Crescent Head and a hydraulic link to the Hastings River to the south, all owing to improved channel linkages constructed during implementation of historic flood mitigation schemes between 1955 and mid-1970s.
Kempsey Shire Council has engaged Jacobs to undertake the Lower Macleay River Floodplain Risk Management Study and Plan. The study will build on the previous Lower Macleay Flood Study Update (Jacobs, 2022) which provided information on flood behaviour in the Lower Macleay floodplain based on detailed hydraulic modelling developed for this Floodplain Risk Management Study (FRMS) project. This report is the FRMS which defines the flooding behaviour and its impact on the community, identifies and appraises potential management measures to reduce existing and future flood risk. Based on the study findings, a list of prioritised measures for consideration and implementation by Council is outlined in the Floodplain Risk Management Plan (FRMP).
Key objectives of this study are summarised below.
• Update of previous flood study modelling including extension of TUFLOW hydraulic model upstream to Turners Flat and southward to the Kempsey LGA boundary to include the Maria River floodplain. utilising revised main catchment hydrologic modelling and update local catchment hydrologic modelling to Australian Rainfall and Runoff (ARR) 2019. Redefine design flood conditions.
• Understanding of impacts and consequences of flooding on the community. This includes knowledge of properties (numbers of properties, flood damages), roads, infrastructure and critical services impacted by current and future flooding conditions, which will inform town planning, emergency management and evaluation of feasibility of mitigation works.
• Develop a list of recommended and prioritised physical works and strategic planning flood risk mitigation measures to improve current and future flood risk.
• Assistance with development of guidelines to manage future and proposed developments on the floodplain.
