Pre-Request Response Application 132001.210310.1

Flood Investigation & Stormwater Quantity Management Plan                                                                                                 BROWN
Proposed Residential Development at Doonella Stage C         -
                                                                                                                                                                       SttUlrt Uitter




          FLOOD INVESTIGATION & STORMWATER QUANTITY
                                                      MANAGEMENT PLAN

                  PROPOSED RESIDENTIAL DEVELOPMENT AT
                                                   DOONELLA                             -
                                                                                            STAGE C

                                                    TABLE OF CONTENTS
1.0 INTRODUCTION .............................................................................................................1

        1.1     Past Studies.......................................................................................................................................1

2.0 SITE CHARACTERISTICS .............................................................................................2

        2.1     Location .............................................................................................................................................2

        2.2     Existing Topography and Drainage....................................................................................................2
3.0 HYDROLOGICAL ANALYSIS.........................................................................................3

        3.1     Catchment and Land Use ..................................................................................................................3

        3.2     Existing Scenario Model.....................................................................................................................4
                3.2.1     Rainfall Data                                                                                                                            ......4
                                               .....................................................................................................................




                3.2.2     Routing Factors.......          .............................................................
                                                                                                                       ............................................
                                                                                                                                                                   ......4

                3.2.3 Loss Model & Lag Parameter.                        ..........................................................................................
                                                                                                                                                                   ......4

                3.2.4     WBNM Calibration ..................................................................................................................5

                3.2.5     Existing Peak Flows................................................ ................................................................6
        3.3     Developed Scenario Model................................................................................................................ 6
        3.4     Management Strategy........................................................................................................................7
        3.5     Mitigated Scenario..          ...........................................................................................................................
                                                                                                                                                                          7

        3.6     Peak Flows for Hydraulic Analysis .....................................................................................................8

4.0 HYDRAULIC ANALYSIS ................................................................................................9

        4.1     Assessment Criteria...........................................................................................................................9

        4.2     HEC RAS Analysis.............................................................................................................................9

                4.2.1     Cross Sections........................................................................................................................9

                4.2.2     Manning’s Roughness ............................................................................................................9
                4.2.3     Boundary Conditions ..............................................................................................................9
                4.2.4     Hydraulic Structures........            ..................................................................................................
                                                                                                                                                                       ...1 0

                4.2.5     Peak Flows        ....................................................................................................................
                                                                                                                                                                .......10

                4.2.6 Results..................................................................................................................................1 0

                4.2.7     Sensitivity Check ..................................................................................................................10
5.0 CONCLUSIONS ............................................................................................................11

6.0 RECOMMENDATIONS .................................................................................................11

7.0 REFERENCES ..............................................................................................................12

8.0 DISCLAIMER ................................................................................................................12

9.0 APPENDICES ...............................................................................................................12


B09182.w-02A                                                                                                                                                                    Page ii