EIS 1361 I:Js)!Z,Isisi1 Forster/Tuncurry Floodplain Management Plan For
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EIS 1361 i:js)!Z,IsIsI1 Forster/Tuncurry floodplain management plan for Great Lakes Council. EL5 u I ABO2 0006 LND&WATER I CONSERVATION I I I FORSTER/TUNCURRY I FLOODPLAIN MANAGEMENT PLAN for I GREAT LAKES COUNCIL I April 1998 I I I I I I U H L J I N S W D e p a r t m e n t of L a n d and Water Conservation I FORSTER/TUNCURRY FLOODPLAIN MANAGEMENT PLAN for GREAT LAKES COUNCIL April 1998 NSW Department of Land and Water Conservation FOREWORD The State Government's Flood Policy aims to reduce the impacts of flooding and flood liability on individual owners and occupiers, and to reduce private and public losses resulting from flooding. The Policy encourages the development of solutions to existing flood problems in developed areas, and strategies for ensuring that new development is compatible with the flood hazard and does not create additional flooding problems in other areas. Under the Policy, local government has responsibility for managing flood liable land. The Great Lakes Council Floodplain Management Committee has assisted Great Lakes Council in this task. The Committee membership comprises a wide range of technical and community based skills. The Policy provides for technical and financial support by the State Government for a number of activities that include: Preparation of a Flood Study to determine the nature and extent of the flood problem. The Forster/Tuncurry Flood Study was prepared by the Public Works Department in 1989. Preparation of a Floodplain Management Study to evaluate management options for the floodplain in respect of both existing and future development. The Department of Land and Water Conservation, in conjunction with Great Lakes Council, prepared the Forster/Tuncurry Floodplain Management Study in April 1998. Preparation of a Floodplain Management Plan that involves formal adoption by Council. The plan may include provision for structural and non-structural options. Implementation of the Plan. The Forster/Tuncurry Floodplain Management Plan constitutes the third stage of the floodplain management process for Forster and Tuncurry. This plan has been prepared by the Department of Land and Water Conservation in conjunction with Great Lakes Council. It provides the basis for the future management of flood liable lands and the management of development within the Forster and Tuncurry floodplain areas. I I SUMMARY I Great Lakes Council sought to examine a range of floodplain management options for Forster and Tuncurry. These options were intended firstly, to protect the existing I development as far as possible, and secondly, to ensure that any new development would be reasonably protected and would not create major adverse flood impacts on existing development. Council's design standard for the Forster/Tuncurry area is the 1% AEP I (annual exceedance probability) flood. In accordance with the State Government's Floodplain Development Manual, Council's Floodplain Management Committee assisted in the examination of floodplain management options (Forster/Tuncurry Floodplain Management Study, April 1998). The options I considered by the Committee and the community included structural measures such as levees and dredging, as well as non-structural measures to reduce the impacts of flooding. I Structural options would not be economically effective in reducing flood damages. In some ' cases, levees would also lead to significant flood level increases in adjoining developed areas. Non-structural options, particularly an effective flood warning and evacuation system, would reduce the potential damages from flooding in the study area. The Forster/Tuncurry Floodplain Management Plan was prepared with the assistance of the I Committee, and a Draft of the Plan was made available for public comment over a 5 week period. Ten letters were received from the public, with comments mainly indicating I opposition to levees. The Forster/Tuncurry Floodplain Management Plan contains the following key measures, I with estimated implementation costs as indicated: Flood forecasting system (including feasibility study $ 130,000 I and installation) I Preparation of detailed evacuation plan $ 5,000 ' Flood awareness and public education program $ 10,000 Voluntary house raising $1,000,000 I Planning and development controls (including - Development Control Plan for flooding) I TOTAL $1,145,000 I I I ii I I TABLE OF CONTENTS I FOREWORD I I SUMMARY I BACKGROUND 1 FLOODPLAIN MANAGEMENT PLAN 3 I 2.1 THE PREFERRED MEASURES 3 2.2 FLOOD WARNiNG SYSTEM 3 2.2.1 Description 3 I 2.2.2 Benefits 5 2.2.3 Costing 5 2.2.4 Implementation 5 I 2.3 VOLUNTARY HOUSE RAISING SCHEME 6 2.3.1 Description 6 2.3.2 Benefits 6 I 2.3.3 Costing 6 2.3.4 Implementation 6 2.4 PLANNING AND DEVELOPMENT CONTROLS 7 I 2.4.1 Description 7 2.4.2 Benefits 7 2.4.3 Costing 8 I 2.4.4 Implementation 8 I IMPLEMENTATION OF PLAN 9 ACKNOWLEDGMENTS 10 I I LIST OF FIGURES 1. Locality Plan I LIST OF TABLES I 1. Program to Implement the Forster/Tuncurry Floodplain Management Plan I I I I 111 I 1 1. BACKGROUND I Great Lakes Council, through its Floodplain Management Committee, is developing a Floodplain Management Plan for Forster and Tuncurry in accordance with the New South I Wales Government's Floodplain Development Manual (1986). The twin towns of Forster and Tuncurry are situated at the mouth of Wallis Lake on the mid- 1 north coast of New South Wales, about 120 km north of Newcastle. The location of the study area is shown on Figure 1. The towns form an important urban centre which has experienced rapid growth in recent years. Forster and Tuncurry have experienced flooding from Wallis I Lake in the past. The highest recorded flood level was 2.25m AHD in April 1927 at Point Road, Tuncurry, just upstream of the bridge over the lake. I A Flood Study was prepared in 1989 to investigate the flood behaviour of the study area. A Floodplain Management Study was prepared in 1998 to investigate flood mitigation and I development options for the area. Hydraulic analysis was undertaken to determine flood levels for the 1% annual exceedance 1 probability (AEP) event. The adopted flood levels at various locations for this event are as follows: Forster/Tuncurry Bridge 2.28m AHD I Forster Keys 2.1 7m AHD Darawank 2.65m AHD Wallingat River Junction 2.70m AHD I Wang Wauk River Junction 3.51 m AHD I It is estimated that under existing development conditions, about 1300 houses would be on flood liable land in the 1% AEP flood event, of which about 1000 houses would be inundated above floor level. However most of the flood liable properties would be in low hazard areas I where flow velocities are low and evacuation could be undertaken without undue risk as the floodwaters rise. The locations which are provisionally considered to be high hazard in the 1% AEP flood are low lying areas near Beach Street and Wharf Street, and near Point Road and I Bay Street, Tuncurry. Great Lakes Council has adopted the 1% AEP flood as the designated flood for the study area. 1 This flood standard was used for the analysis of flood mitigation and development options. The structural flood mitigation options considered in the Floodplain Management Study I included levees and dredging. It was found that structural options would not be economically effective in reducing flood damages. A deflector levee could be constructed along the north side of the Point Road peninsula to reduce flow velocities across the peninsula which is a high I hazard floodway area in the 1% AEP flood. However the levee would have high cost, would lead to significant flood level increases in adjoining developed areas, and is likely to be I opposed by the local community. I I I I Future development options considered in the Floodplain Management Study included broad scale landfill in various locations. Of the five development options considered, only landfill on the Point Road peninsula would create a significant adverse impact in terms of increased flood I levels in other developed areas. The adverse impact could be mitigated to some extent by retaining a floodway across the peninsula. I The following non-structural options were considered for the study area: Flood warning and evacuation planning I Public information and education Voluntary purchase scheme Voluntary house raising scheme I Planning and development controls I An effective flood warning system and evacuation plan, supported by a public education program, would enable residents to take appropriate actions to limit damages and to evacuate without undue risk to life and limb during the early stages of major floods. This option would I reduce the hazard to the residents of all flood prone areas, and is the preferred option for hazard reduction to the residents of the Point Road peninsula. I With an effective flood warning system and evacuation plan, voluntary purchase of properties in flood prone areas of Forster and Tuncurry would not be warranted and it would be acceptable I to continue the existing uses of all properties on the floodplain. A voluntary house raising scheme would have some merit for a relatively small number of houses which are of construction suitable for raising. Planning and development controls will be appropriate to ensure that new development is compatible with the flood hazard. A comprehensive community consultation program was undertaken as part of the Floodplain Management Study. The program included community participation through a resident survey, workshopsand opportunity for written comment. The outcomes of community consultation included opposition to large scale structural solutions such as major levees and some concerns about land filling for development. The need for appropriate stormwater drainage to be included in filled areas was identified.