Overland Flow Assessments
Flood Smart Engineering provides overland flow assessments for residential, commercial, industrial and subdivision developments throughout South East Queensland. Using advanced TUFLOW hydraulic modelling, we identify overland flow paths, flood depths, flow velocities and flood hazards to support council approvals and practical engineering design.
What is Overland Flow?
Overland flow is the movement of stormwater across the ground surface during heavy rainfall when drainage systems are unable to capture all runoff or where natural drainage paths direct water across the land. Unlike creek or river flooding, overland flow is generated by local rainfall and can occur almost anywhere, including residential suburbs, commercial developments and industrial estates.
Although overland flow events are often short in duration, they can produce significant flood depths, high flow velocities and hazardous conditions capable of affecting buildings, roads and surrounding properties. Understanding how stormwater moves across a site is essential when planning new development, as even relatively small changes to ground levels or building locations can alter existing flow paths.
At Flood Smart Engineering, we utilise advanced TUFLOW hydraulic modelling to identify overland flow paths, determine flood depths and velocities, assess flood hazards and provide practical engineering solutions that support council approval.
When is an Overland Flow Assessment Required?
Overland flow assessments are commonly required where stormwater runoff may affect an existing or proposed development or where council planning schemes identify overland flow constraints.
Assessmnts are regularly undertaken for:
New dwellings
House raises
Home extensions
Knockdown rebuilds
Duplexes and townhouses
Residential subdivisions
Commercial developments
Industrial developments
Councils may also require an overland flow assessment where filling, retaining walls, buildings or other proposed works have the potential to alter existing stormwater flow paths or increase flood impacts on neighbouring properties.
Undertaking an overland flow assessment early in the design process helps identify potential development constraints, allowing practical engineering solutions to be incorporated before construction begins.
How We Assess Overland Flow
Every property has unique drainage characteristics. Our overland flow assessments combine council flood information, site survey data and advanced TUFLOW hydraulic modelling to simulate how stormwater moves across a site during major rainfall events.
Our assessments typically evaluate:
Existing overland flow paths
Flood depths
Flow velocities
Flood hazards
Potential impacts on neighbouring properties
Development constraints
Practical engineering solutions
The results provide a detailed understanding of flood behaviour and assist homeowners, developers and councils in making informed planning and design decisions.
What Does an Overland Flow Assessment Include?
Depending on the project, an overland flow assessment may include:
Review of council flood mapping
Existing survey and site information
TUFLOW hydraulic modelling
Identification of overland flow paths
Flood depth assessment
Flow velocity assessment
Flood hazard assessment
Assessment of flood impacts
Minimum floor level recommendations
Engineering recommendations
Preparation of an engineering report to support council approval
Every assessment is tailored to the individual site and proposed development, ensuring practical engineering solutions are provided for each project.
Overland Flow Assessments Throughout South East Queensland
Flood Smart Engineering undertakes overland flow assessments throughout South East Queensland, regularly assisting homeowners, builders, developers and consultants with projects requiring flood-related engineering advice and council approval.
We regularly work within the following local government areas:
Frequently Asked Questions
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Overland flow is stormwater that travels across the ground surface during heavy rainfall when drainage systems cannot accommodate all runoff or where natural drainage paths direct water across the land. Unlike creek flooding, overland flow is generated by local rainfall and can occur almost anywhere.
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Overland flow is caused by localised rainfall and generally follows the natural terrain, roads and drainage paths across a site. Creek flooding occurs when rivers, creeks or waterways exceed their banks and typically affects much larger catchments. A property may be affected by one or both flooding mechanisms depending on its location.
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An overland flow assessment may be required if your property is located within an overland flow path, flood overlay or flood-affected area, or if your proposed development has the potential to alter existing stormwater flow paths. We can review your property and advise whether an assessment is required.
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Yes. Overland flow may influence building locations, finished floor levels, driveway layouts, retaining walls and site earthworks. Understanding these constraints early in the design process can help avoid costly redesigns and support council approval.
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In many cases, overland flow can be managed through appropriate engineering design. However, developments must not create adverse flood impacts on neighbouring properties or significantly alter existing flow behaviour. An overland flow assessment helps identify practical engineering solutions that satisfy council planning requirements.