Stormwater Management Plan

SC5594 – Walter Hay Dr, Noosaville                                                               10




4.0 Stormwater Quantity Management
4.1      Background
The proposed development has the potential to alter the existing hydrologic and hydraulic characteristics of
the subject site unless suitable mitigation is achieved via careful hydraulic design of the proposed
stormwater management drainage system. With urbanisation there is potential for sites to create or
exacerbate drainage problems to downstream areas and/or drainage infrastructure. The purpose of this
section of the SWMP is to determine the general requirements for bulk stormwater management for the
proposed development. The design shall ensure that rainfall event discharges are mitigated and conveyed
from the site in a manner that complies with Council’s Urban Stormwater Planning Guidelines and does not
result in a worsened drainage situation to downstream infrastructure, without causing a nuisance or
annoyance to residents/property owners.


4.2      Site Drainage Constraints and Opportunities
4.2.1    Drainage Constraints
The increase of impervious areas will impact on the existing downstream boundary condition compared to
pre-development peak flows. Therefore, a volume of detention will be required to limit flows to that of pre-
development. This will required an detention volume over and above the bio-retention basin.


4.2.2    Drainage Opportunities
The second existing swale off the western boundary is deemed the lawful point of discharge for the site as
this is where the majority of site surface flows concentrate. The swale has adequate depth for Bio-retention
basin and detention volume.