2018-05-14 GC Agenda Attachment 1 to Item 6 Lake MacDonald Dr Community Reference Group Investigations Report

Table of Contents
1.    Executive Summary ............................................................................................................. 3
2.    Introduction .......................................................................................................................... 4
3.    Catchment Description ........................................................................................................ 5
      3.1         Catchment Area to Highland Drive ........................................................................... 5
      3.2         Contributing Sub-Catchments .................................................................................. 5
      3.3         Contributing Catchment Land Use............................................................................ 5
4.    Historical Flooding and Flood Records ............................................................................. 7
      4.1         February 2012 Flood Event ...................................................................................... 8
5.    Six Mile Creek Flood Study ................................................................................................. 9
      5.1         Previous studies ....................................................................................................... 9
      5.2         Six Mile Creek Flood Study Upgrade........................................................................ 9
      5.3         Design Flood Events ................................................................................................ 9
6.    Ultimate Catchment Urbanisation..................................................................................... 11
      6.1         Discussion of results .............................................................................................. 19
7.    Flood Mitigation Scenarios for Lake MacDonald Drive ................................................... 20
      7.1         Mitigation Options .................................................................................................. 20
      7.2         Council considerations for mitigation options .......................................................... 31
      7.3         Flood storage & blockages ..................................................................................... 32
      7.4         Sensitivity of water supply pipe crossing ................................................................ 33
8.    Lake MacDonald Dam outflows ........................................................................................ 36
9.    Six Mile Creek Flood Warning Stations ............................................................................ 37
      9.1         Flood Warning - during a rainfall/flood event .......................................................... 38
10.   Conclusions ....................................................................................................................... 39
11.   Where to from here? .......................................................................................................... 40
      11.1        Catchment flood risk assessment. .......................................................................... 40
      11.2        Develop a catchment wide flood mitigation strategy. .............................................. 40
      11.3        Update flood emergency planning maps. ............................................................... 40
      11.4        Update planning overlays for new Planning Scheme .............................................. 40
      11.5        Continue to monitor rainfall and runoff records in catchment. ................................. 40




Lake McDonald Flooding Community Reference Group Report                                                                              Page 1