Attachment 6 - Stormwater Management Plan and Engineering Response. · MCU23/0078

CONTENTS

1.     INTRODUCTION ............................................................................................................................................................................. 1

2.     SITE CHARACTERISTICS ................................................................................................................................................................ 1
2.1 LOCATION AND EXISTING FEATURES ........................................................................................................................................ 1
2.2 PROPOSED DEVELOPMENT .......................................................................................................................................................... 2
2.3 TOPOGRAPHY AND CATCHMENT CHARACTERISTICS ............................................................................................................ 3
       2.3.1         Lot 3 – Western Lot ........................................................................................................................................................ 3
       2.3.2         Lot 7 – Eastern Lot .......................................................................................................................................................... 3
2.4 EXISTING FLOODING CONDITIONS ............................................................................................................................................ 3

3.     EXISTING AND PROPOSED STORMWATER INFRASTRUCTURE .............................................................................................. 4
3.1 EXISTING INFRASTRUCTURE ....................................................................................................................................................... 4
3.2 PROPOSED STORMWATER DRAINAGE ...................................................................................................................................... 5

4.     STORMWATER QUANTITY ANALYSIS ........................................................................................................................................ 5
4.1 EXISTING NATURAL DRAINAGE CHANNEL FLOOD ASSESSMENT – XP STORM .................................................................. 6
       4.1.1         Flood Assessment – Existing Scenario ......................................................................................................................... 6
       4.1.2         Flood Assessment – Developed Scenario .................................................................................................................... 7
4.2 DETAILED HYDRAULIC MODELLING – XP STORM – DETENTION SIZING.............................................................................. 8
       4.2.1         Existing Scenario Model ................................................................................................................................................ 8
       4.2.2         Results for Existing Scenario ........................................................................................................................................ 8
       4.2.3         XP Storm and Rational Method Comparison ...........................................................................................................10
       4.2.4         Developed Scenario Model .........................................................................................................................................10
       4.2.5         Results for Developed Unmitigated Scenario ..........................................................................................................11
       4.2.6         Detention Basin Design ...............................................................................................................................................12
       4.2.7         Results for Developed Scenario .................................................................................................................................13
       4.2.8         Hydraulic Impacts on Downstream Waterway Corridor .........................................................................................14

5.     STORMWATER QUALITY ............................................................................................................................................................16
5.1 CONSTRUCTION PHASE .............................................................................................................................................................16
5.2 OPERATIONAL PHASE.................................................................................................................................................................16
       5.2.1         Pollutants of Concern ..................................................................................................................................................16
       5.2.2         Modelling/Assessment Approach ..............................................................................................................................16
       5.2.3         Meteorological Data ....................................................................................................................................................16
       5.2.4         Source Nodes ................................................................................................................................................................17
       5.2.5         Treatment Methodology .............................................................................................................................................17
       5.2.6         Treatment Nodes .........................................................................................................................................................18
       5.2.7         Proposed Treatment Train ..........................................................................................................................................19
       5.2.8         Results............................................................................................................................................................................19

6.     NOOSA SHIRE COUNCIL CODES ................................................................................................................................................20

7.     SUMMARY ....................................................................................................................................................................................20




                                                                              www.bornhorstward.com.au