Appendix C - Stormwater Management Plan

     2.3. Proposed Development Drainage Pattern

          2.3.1 Stormwater Concept
All run-off from the development will continue to drain and be discharged by the existing stormwater inlet pit within
the site. In order to maintain existing peak flow rates, roof-water from the proposed building will be drained via
attenuation tanks sized to ensure run-off resulting from the development won’t increase flows to the downstream
receiving environment. Discharge from the attenuation tank will be piped with a connection to the existing
stormwater inlet as the lawful point of discharge from the site

The overland flow paths within the development will be as the driveway is well graded to collect surface run-off at
the existing pit. A spoon drain will be provided along the northern boundary to intercept flows discharged from the
adjacent shed building, which will convey the run-off to the existing pit to maintain existing conditions.

The roof and allotment drainage system for the proposed site shall be designed to comply with:

     1. Noosa Shire Council Planning Scheme Policy (PSP) - Engineering Design Standards – Roads, drainage and
        earthworks;

     2. The Queensland Urban Drainage Manual (QUDM); and

     3. AS/NZS 3500.3:2015 - Plumbing and Drainage Part 3: Stormwater Drainage.

Refer to Appendix A Proposed Development Plan for the proposed stormwater drainage layout plan illustrating
the concept described above.



          2.3.2 Lawful Point of Discharge
The existing site drains to the east, with run-off from the property captured within an existing stormwater inlet
within the property. The inlet is connected to a kerb inlet pit in Station Street which is under authority of Noosa
Shire Council. This is proposed to remain as the lawful point of discharge for the development. The lawful point of
discharge test, as described in Section 3.9.1 of QUDM, requires:

      •     The development does not change the flow characteristics leaving the site; or
      •     The proposed development will not alter the sites stormwater discharge in a way that may substantially
            damage a third-party property; or
      •     The location of the discharge from the site is under lawful control of the government or other statutory
            authority from whom permission to discharge has been received; or
      •     An authority to discharge has been obtained.

An assessment of the sites peak run-off generation under the range of storm events has found that on site
detention of the new roof area is able to ensure no worsening to the downstream conditions. Refer to Section 3.1
Pre-Post Comparison for further details.

The proposed discharge from the site using the existing infrastructure will therefore not alter run-off conditions in a
way that may substantially damage third party property and remains consistent with the existing drainage
characteristics. The existing stormwater inlet pit is therefore able to achieve a lawful point of discharge for the
development.




Project number 20220213
File 20220213 Reserve St SWMP.docx, 2022-09-19 Revision 1                                               Page 6 of 16

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