Floodplain Management Study Spring Street Drain, Muddy Creek and Scarborough Ponds - Volume 2

#APPENDICES\r\n* APPENDIX A STUDY BRIEF\r\n* APPENDIX B REVIEW OF MUDDY CREEK FLOOD STUDIES\r\n* APPENDIX C ADDITIONAL FLOOD MODELLING, MUDDY CREEK CATCHMENT\r\n* APPENDIX D ADDITIONAL FLOOD MODELLING, SPRING ST DRAIN\r\nCATCHMENT\r\n* APPENDIX E LOCAL STORMWATER FLOOD MODELLING\r\n* APPENDIX F ADOPTED 'DESIGN' FLOOD LEVELS\r\n* APPENDIX G FLOOD DAMAGES ESTIMATE\r\n* APPENDIX H ANALYSIS OF SELECTED OPTIONS, MUDDY CREEK CATCHMENT\r\n* APPENDIX I ANALYSIS OF SELECTED OPTIONS, SPRING ST DRAIN CATCHMENT\r\n* APPENDIX J COMMUNITY CONSULTATION\r\n* APPENDIX K SOCIAL AND ECONOMIC EVALUATION\r\n\r\n#Catchment Description\r\n#Spring Street Drain\r\nThe Spring Street Drain has a total catchment area of approximately 3.5 km2. The upper\r\nreaches of the catchment are in the suburbs of Rockdale and Bexley and are principally\r\nresidential. It flows through a pipe network towards the Illawarra Railway Line. The railway\r\nline is raised above the natural ground level for a considerable distance either side of the main\r\npipe network under the line which may restrict surface flows from the western side.\r\nImmediately east of the railway line the catchment comprises a Commercial area along\r\nPrinces Highway and incorporates most-of the Rockdale City Centre.\r\n\r\nThe pipe conduit network combines into an open concrete trapezoidal section at Short Street,\r\nBanksia. The section downstream is through a low level residential area built fairly close to\r\nthe channel. As the channel continues past West Botany Street it flows through an open park\r\narea with some adjacent wetland areas. It eventually drains into the Cooks river at the\r\nconfluence of the Cooks River with Muddy Creek.\r\n#Muddy Creek\r\nThe catchment area of Muddy Creek is about 5.6km2, its catchment area is heavily urbanised\r\nwith a mixture of residential, commercial and industrial development, and it drains into the\r\nCooks River near its entrance to Botany Bay. The residential development is mainly low\r\ndensity with some patches of medium to high density residential area consistent with urban\r\nconsolidation.\r\n\r\nMuddy Creek consists of a formed concrete channel from the Cooks River upstream to Frys\r\nReserve. There are a number of side channels, both open and piped, that laterally feed the\r\ntrunk flows into the creek. Upstream of Frys Reserve the trunk drainage system divides into a\r\nnumber of drainage systems combining open concrete channels with piped sections.\r\nThe section of Muddy Creek downstream of the Bestic Street bridge has been widened and\r\ndredged to form part of the lower Cooks River estuary. The tailwater level for Muddy Creek\r\nis controlled by the water level in the Cooks River.\r\n\r\nScarborough Ponds has a catchment area of about 4 km2 and a stream length of about 3.4 km.\r\nThere are three main ponds or wetlands, from England Street to President Avenue, from\r\nPresident Avenue to Barton Street, and downstream of Barton Street. The day-to-day water\r\nlevels of each pond are controlled at the downstream end by weirs at President Avenue,\r\nBarton Street and the outlet structure at Florence Street. The Florence Street outlet structure\r\nconnects the ponds to Botany Bay, allowing the tide to penetrate into the downstream ponds.\r\n\r\nThe Florence Street culvert consists of triple 1350 mm diameter pipes.\r\nDevelopment within the catchment is predominantly low to medium density residential\r\ndevelopment with localised commercial and industrial development. The areas adjacent to\r\nthe ponds have been landscaped into open spaces suitable for passive recreational activities.\r\nSome residential development on the eastern side of the ponds comes very close to the ponds.\r\n\r\n#Scarborough Ponds\r\nThe existing culvert under the railway line at Frys Reserve produces a throttling of the flows\r\nand causes Frys Reserve to act as an on-line retarding basin. The adjacent Warialda Street is\r\nexpected to be inundated in about a 20% AEP flood. Sydney Water has recently constructed\r\na new bypass culvert under the railway line to alleviate the hazard of floodwater through the\r\nHegarty Street underpass. The flood study examined flood behaviour for the original and\r\nnow existing culvert conditions under the railway line at Frys Reserve.\r\n\r\nThere are a large number of road and pedestrian bridges over Muddy Creek that may impact\r\non the flood behaviour. The major bridge crossings are at the Princes Highway, Bay Street and Bestic Street. In addition a sewer line crosses over Muddy Creek upstream of the Princes\r\nHighway. This sewer line would act as a major impediment to flood flows, ponding water\r\nagainst the concrete structure with no bypass arrangement. Some of the properties adjacent to\r\nthe creek have boundary fences located close to the Muddy Creek channel and these would\r\nimpact on flood flows by restricting the spread of water onto the floodplains.\r\n\r\nThe section of Muddy Creek downstream of the Bestic Street bridge has been widened and\r\ndredged to form part of the lower Cooks River estuary. The tailwater level for Muddy Creek\r\nis controlled by the water level in the Cooks River.\r\n\r\n#Scarborough Ponds\r\nScarborough Ponds has a catchment area of about 4 km2 and a stream length of about 3.4 km.\r\nThere are three main ponds or wetlands, from England Street to President Avenue, from\r\nPresident Avenue to Barton Street, and downstream of Barton Street. The day-to-day water\r\nlevels of each pond are controlled at the downstream end by weirs at President Avenue,\r\nBarton Street and the outlet structure at Florence Street. The Florence Street outlet structure\r\nconnects the ponds to Botany Bay, allowing the tide to penetrate into the downstream ponds.\r\nThe Florence Street culvert consists of triple 1350 mm diameter pipes.\r\n\r\nDevelopment within the catchment is predominantly low to medium density residential\r\ndevelopment with localised commercial and industrial development. The areas adjacent to\r\nthe ponds have been landscaped into open spaces suitable for passive recreational activities.\r\nSome residential development on the eastern side of the ponds comes very close to the ponds.