Runoff Source Areas
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
Commercial & institutional resilience
Commercial site drainage should move water safely without shifting risk elsewhere.
Review grades, inlets, roof discharge, storage, conveyance, overflow routes and maintenance at Ontario commercial sites.
- Ontario depth
- Canada-wide learning
- Standards-informed
- Risk reduction, not guarantees
The practical answer
Start with the property, the operations and the consequence.
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
System view
Four areas that should be reviewed together
Each area needs a defined purpose, owner, evidence trail and review cycle.
Surface And Pipe Conveyance
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
Storage And Outlet Controls
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
Safe Exceedance Routes
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
Guidance 1
Runoff Source Areas
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
For this topic, the organization should collect current grading and servicing information. The decision should be recorded with the responsible owner, evidence used, limitations, review date and any need for qualified technical, legal, insurance or municipal advice.
Commercial resilience depends on connected decisions. Building systems, site drainage, occupancy, maintenance, emergency response, continuity and capital planning should not be evaluated as isolated programmes.
Guidance 2
Surface And Pipe Conveyance
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
For this topic, the organization should trace roof and surface drainage. The decision should be recorded with the responsible owner, evidence used, limitations, review date and any need for qualified technical, legal, insurance or municipal advice.
Commercial resilience depends on connected decisions. Building systems, site drainage, occupancy, maintenance, emergency response, continuity and capital planning should not be evaluated as isolated programmes.
Guidance 3
Storage And Outlet Controls
Roofs, pavement, landscaping, loading areas, snow storage and private drainage operate as one site system. The review should identify intended routes, blockages, low points, overflow behaviour and downstream consequences.
For this topic, the organization should inspect low points, catch basins and outlets. The decision should be recorded with the responsible owner, evidence used, limitations, review date and any need for qualified technical, legal, insurance or municipal advice.
Commercial resilience depends on connected decisions. Building systems, site drainage, occupancy, maintenance, emergency response, continuity and capital planning should not be evaluated as isolated programmes.
Implementation workflow
Move from concern to governed action
A useful commercial workflow identifies decisions, accountabilities and verification rather than producing an isolated report.
- 1
Collect Current Grading And Servicing Information
Assign an accountable owner, document the evidence and define what completion and verification will look like.
- 2
Trace Roof And Surface Drainage
Assign an accountable owner, document the evidence and define what completion and verification will look like.
- 3
Inspect Low Points, Catch Basins And Outlets
Assign an accountable owner, document the evidence and define what completion and verification will look like.
- 4
Observe Conditions During Or After Rainfall When Safe
Assign an accountable owner, document the evidence and define what completion and verification will look like.
- 5
Correct Operational Obstructions
Assign an accountable owner, document the evidence and define what completion and verification will look like.
- 6
Scope Professional Analysis Where Capacity Is Uncertain
Assign an accountable owner, document the evidence and define what completion and verification will look like.
Readiness check
Use this page as a working review
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Common failure points
Avoid incomplete planning
- Assuming Old Drawings Match Current Grades
- Blocking Inlets With Vehicles, Storage Or Snow
- Redirecting Water Toward Neighbours
- Cleaning Drains Without Investigating Repeated Overload
Connected pathways
Continue with the next useful decision
Frequently asked questions
Questions organizations commonly ask
Does ponding always mean failure?
No. Some systems store water temporarily, but depth, duration, location and overflow need to be understood.
Can maintenance staff redesign drainage?
Maintenance and design are different scopes; changes may require professional design and municipal approval.
Should roof and site drainage be reviewed together?
Yes, because they can share receiving systems and low points.
Can RSM approve a design?
No. RSM provides education and pathways, not engineering or municipal approval.
Official source basis
Use current public and professional requirements
RSM summarizes concepts for education. Confirm design, legal, insurance, code, permit, funding and emergency requirements with the responsible authority or qualified professional.
Next step
Turn commercial flood-resilience knowledge into an owned programme.
Connect the building, site, people, records and investment decisions through one accountable pathway.
Published: July 19, 2026 Last reviewed: July 19, 2026
Prepared by Regional Stormwater Management for public and professional education. RSM does not certify buildings, guarantee flood prevention, determine insurance coverage or replace engineering, legal, municipal or emergency advice.
Next steps
Build the property resilience pathway
Connect this topic to assessment, planning, maintenance and organizational learning.