⚡ Quick Answer: A stormwater flood management plan is an engineering report that combines stormwater drainage design with flood risk assessment for your development site. It addresses how stormwater is collected and discharged from your property while ensuring the site meets council flood planning requirements. RI ENG PTY LTD prepares stormwater flood management plans for residential and commercial developments across NSW and Queensland.
Find out more about our Flood Management Plan services for stormwater and drainage projects.
What Is a Stormwater Flood Management Plan?
A stormwater flood management plan is a technical engineering document that addresses two related but distinct issues: the drainage of stormwater from your development site during rainfall events, and the flood risk posed to your site by overland flow or waterway flooding during major storm events.
Most residential and commercial developments in NSW and Queensland require both a stormwater management plan and a flood assessment as part of the development application (DA) process. Councils often accept a combined stormwater flood management plan that addresses both requirements in a single report.
The stormwater component covers roof drainage, driveway drainage, subsoil drainage, on-site detention (OSD) where required, and connection to council drainage infrastructure. The flood component covers the flood planning level (FPL), habitable floor levels, and flood construction standards applicable to the site.
RI ENG PTY LTD prepares combined stormwater flood management plans for residential, duplex, townhouse, and commercial DA applications.
All reports are prepared by a practising civil engineer and are ready for lodgement with your council as part of your DA documentation package.
When Do You Need a Stormwater Flood Management Plan?
Your council’s Development Control Plan (DCP) will specify when a stormwater management plan, a flood management plan, or a combined report is required. Generally, any new dwelling, dual occupancy, multi-dwelling housing, or commercial development triggers at least a stormwater management plan.
A flood assessment is required when the site is located within a Flood Planning Area (FPA) as mapped in the council’s Local Environmental Plan (LEP) or flood maps. Many sites in Sydney, the Hunter Valley, Illawarra, Central Coast, and South East Queensland fall within FPAs.
Even where a flood assessment is not formally required, RI ENG PTY LTD recommends having one where a property is in a low-lying area, near a drainage line, or in a catchment with a history of flooding — these factors can affect your building design and your ability to obtain flood insurance.
For townhouse and multi-dwelling developments, the stormwater flood management plan needs to cover site drainage for the entire development, including common areas, driveways, and individual dwelling connections.
Our team reviews the applicable council DCP requirements before preparing your plan to ensure the report addresses every required element.
What Our Stormwater Flood Management Plan Covers
Our stormwater flood management plan includes a site drainage assessment, stormwater system design including pipe sizing, on-site detention calculations where required, connection details to council infrastructure, and a flood hazard and risk assessment for the site.
The flood component includes the applicable 1% AEP and PMF flood levels from the council’s adopted flood study, the Flood Planning Level (FPL) with relevant freeboard, recommended habitable and garage floor levels, and flood construction requirements for the development.
Where the council requires an OSD system, we calculate the required storage volume and design an appropriate detention structure. We also address overflow paths and confirm that stormwater discharge from the site does not increase flood risk for neighbouring properties.
The report is structured to match the council’s assessment checklist and is delivered in a format that supports a smooth DA assessment.
Delivery is typically within 3–5 business days of receiving the site details and development drawings.
Frequently Asked Questions
What is the difference between a stormwater management plan and a flood management plan?
A stormwater management plan addresses the collection and disposal of rainwater from the development site. A flood management plan assesses the risk to the site from external flooding (overland flow or waterway flooding) and specifies how the development must be designed to meet flood planning standards. Many councils require both; RI ENG PTY LTD combines them in a single report.
Do I need on-site detention (OSD) for my development?
OSD is required by many NSW councils where a new development increases the impervious area of a site, which increases the rate of stormwater runoff. The council DCP sets the OSD requirement. We calculate the required detention volume and design an appropriate system.
How long does it take to get a stormwater flood management plan?
Most plans are delivered within 3–5 business days of receiving the required site and development details.
Do you cover councils in Queensland as well as NSW?
Yes. RI ENG PTY LTD prepares stormwater flood management plans for developments in both NSW and Queensland councils.
Can the stormwater flood management plan be used for a townhouse or multi-dwelling development?
Yes. We prepare plans for all residential development types, including single dwellings, duplexes, townhouses, and larger multi-dwelling housing projects.
