Overland Flow Path

An overland flow path is the route that rainwater takes across the ground surface when it rains harder than the piped stormwater system can handle. Every property sits within a catchment, and water naturally flows downhill through these paths towards streams, rivers, or the coast.

In urban areas, councils map overland flow paths as part of their stormwater management planning. Properties located on or near an overland flow path may experience surface flooding during heavy rain events — even if they're not in a mapped flood zone. This is different from river flooding; overland flow flooding can occur quickly during intense rainfall.

Councils typically impose restrictions on building within overland flow paths. You may not be able to build fences, walls, or structures that would obstruct the flow of water. Existing buildings on flow paths may experience regular surface water entering garages, basements, or ground-floor living areas during storms.

Properties on overland flow paths can experience repeated surface flooding during heavy rainfall, even in areas not mapped as flood zones. This can damage property, disrupt daily life, and affect insurance premiums. It's a risk that many buyers overlook because it's not as obvious as river flooding.

Check the LIM report and council stormwater maps for overland flow paths. If the property is on or near a flow path, inspect it during or after heavy rain to see how water moves across the site. Consider whether ground-floor rooms, garages, or driveways are vulnerable.

The LIM report will typically note whether the property is affected by a mapped overland flow path. Council GIS mapping portals often show stormwater overland flow paths. You can also ask the council's stormwater team for specific information about flow paths affecting a property. A practical check is to visit the property during or immediately after heavy rain.