Flooding & Drainage

Catchment assessments, stormwater calculations, culvert design and integration of LiDAR / DTM data for accurate and resilient outcomes.

Design Verification & Peer Review

Independent design checks for councils and contractors, ensuring compliance, constructability and value for money.

Drainage is both overland and subsurface. Kerb & channel carry major overland flow; pits & pipes handle the minor events. In renewals, capacity is often replaced like-for-like and the overland path gets ignored. We design the minor network to work with the major route—rather than trying to build a separate “1% AEP system”, which is rarely economical.

What we fix

• Missing or blocked overland flowpaths (kerb & channel grades, sags without relief).
• Under-sized inlets/bypass causing ponding at crossings and intersections.
• Renewals that swap assets without checking capacity or downstream impacts.
• Disconnected major/minor systems leading to nuisance flooding.

How we design

• Map major flowpaths and set safe relief routes; confirm sag vs grade locations within survey domain.
• Size pits/inlets & pipes to the local minor-event standard, then test performance under a major event (e.g. ~1% AEP) with controlled overland conveyance.
• Coordinate road levels, pram crossings, driveways and kerb & channel upgrades.
• Provide headwalls/wingwalls, scour protection and constructable staging.

DDA crossings — grades first, TGSI only if still needed

On brownfield sites, TGSI is often added as a shortcut to “show compliance”. Our approach is to achieve compliant grades first and reserve TGSI for genuine residual hazards. With proper grade design, compliant outcomes are achievable on the majority of sites (often ~80%).

Deliverables

• Drainage concept showing integrated major/minor network and constraints.
• Kerb & channel plus pit/pipe layouts with grading and inlet capacity notes.
• Crossing layouts with grade checks and a DDA compliance summary (TGSI rationale if used).
• Quantities, staged estimates, drawings and construction notes to relevant standards.