Reference Document - Flood & Stormwater Management Plan 28_8_2025

                 Executive Summary
                 Colliers Engineering and Design have been engaged by PSP Developments Pty Ltd to prepare a Stormwater
                 Management Plan (SMP) in support of a development application to Noosa Shire Council (NSC) over land located
                 at 33 Pavilion Street, Pomona (Lot 4 RP809059). This investigation supports the Operational Works (OPW) design
                 for 8 residential lots. The site has an existing building at Lot 1 and no works are required to create lot 1.

                 The location of the proposed development site has a total land holdings area covering 3.33ha. The site is
                 consistent with a rural residential land use type with some wooded vegetation cover over the site. The site is
                 accessed by Pavilion Street to the east and Majestic Place to the south and is bounded by private allotments to the
                 north, east and south. Cooroora Creek is located in the adjacent property to the west.

                 It can be seen from the results presented that the treatment measures proposed for the development site achieve
                 the performance criteria set by the NSC Planning Scheme (2020) and SPP (July 2017). Annual Load Reductions of
                 Total Suspended Solids (TSS), Total Phosphorus (TP), Total Nitrogen (TN) and Gross Pollutants (GP) between the
                 Mitigated and Unmitigated Scenarios have been achieved through the upgrade of the existing bioretention basin
                 from 80m2 to 130m2.

                 It has been demonstrated that non-worsening of peak flows has been achieved to the discharge point for events
                 up to the 1% AEP event. The results show that there is non-worsening for events up the 1% AEP. The intent of
                 sizing the detention basin is to mitigate flows up to the 10% AEP storm event to ensure non-worsening of
                 discharges into the downstream flow path. In larger events, flows from the site will start to sheet flow across the
                 rear of the site to Cooroora Creek. As the discharge point for the site becomes inundated from Cooroora Creek
                 flooding in the major storm event, it is considered non-worsening has been achieved. The catchment size of
                 Cooroora Creek reporting past the site is approximately 1,400 ha and it is considered that no quantifiable change
                 to downstream flooding conditions would result.

                 The development Is located above the regional 1% (2100) AEP flood extent with 500mm freeboard recommended
                 to future dwellings on the new allotments.




                 23-0167SMP01-V4 | Stormwater Management Plan | 33 Pavilion Street, Pomona

Document Set ID: 24092538
Version: 1, Version Date: 02/09/2025