RFI - Attachment B - Stormwater management Report · MCU20/0026

2. 2       Law ful poi nt of d i sch ar ge

There is existing Council stormwater drainage infrastructure traversing the site adjacent to the western
boundary, which conveys runoff from an upstream catchment and exits the site across the northern
property boundary via a 600mm dia RCP. It is assumed that minor flows from the roof of the existing
dwelling report to this existing infrastructure. Stormwater runoff from ground areas of the existing site
and major flows from the roof area appear to initially fall northeast as overland flow, prior to
concentrating and discharging to across the site boundary to the adjoining Council pathway, eventually
reporting to Sunshine Beach.

Stormwater runoff from roof areas of the proposed dwelling are proposed to be conveyed to the existing
stormwater drainage infrastructure traversing the site via the construction on new on site drainage.
Major flows from roof areas & runoff from ground areas is proposed to be directed to an underground
infiltration tank located at the rear of the site. Runoff from the tank shall discharge via infiltration or,
when at capacity, shall surcharge and discharge across the northeast property boundary per existing
conditions in a manner that results in no adverse impact to adjoining properties. Refer to Appendix B
for further information.

2. 3       Ups tr e am d ra in ag e c onne ct ion

There are no undeveloped lots upstream of the development. The provision of an upstream drainage
connection is therefore not considered to be required.

2. 4       Floo din g

According to the NSC planning scheme flood hazard overlay mapping the development site is not
subject to flooding from any sources.

3      ST O RM W AT E R Q U AN T IT Y M AN AG EM E NT

The stormwater quantity analysis of the existing and developed site conditions has been undertaken
with reference to the requirements and procedure outlined by:

           Queensland Urban Drainage Manual (QUDM)

           Australian Rainfall and Runoff Volumes 1 & 2 (Aust R&R)

The following section of the report discusses the proposed development’s impact on peak stormwater
runoff and total runoff volume from the site and compares the existing site condition to ensure a no
worsening effect to downstream land.

3. 1       Cat ch me nt Su mm a r y

Pre-Developed Site

The existing site consists of an existing dwelling. Stormwater runoff from roof areas of the existing
dwelling is assumed to report to the existing stormwater drainage infrastructure traversing the site, and
runoff from ground areas initially falls northeast as overland flow prior to concentrating and discharging
across the site boundary.
The existing site area is approximately 550m2 and is has approximately 44% impervious area (fi=0.44).

Post-Developed Site

The development involves the construction of a new dwelling and ground level features. Runoff from
roof areas of the development is proposed to discharge to the existing Council stormwater infrastructure
traversing the site. Major flows from roof areas and runoff from ground areas is proposed to be conveyed




11 June 2020                             Stormwater Management Report                                     2
S20-023                                40 Park Crescent, Sunrise Beach