MTO Drainage Policy

The fundamental basis of MTO drainage policy is to ensure that water conveyed through highway drainage works will not infringe upon the riparian rights of landowners located upstream or downstream of the highway right-of-way. Accordingly, the proponent must recognise that MTO will not approve a land development proposal if the riparian rights of any landowner may be infringed upon by the proposed land development.

The primary sources for the above noted policy, and other MTO drainage policies are derived from two principle sources:

For specific information on MTO drainage policy, refer to the following sections.

The MTO Regional Highway Planning and Design Office or the local MTO District Office may alter requirements presented in this document, since an extensive SWM report is not always required. MTO may make provisions to accept a drainage impact analysis that has a lower level of detail associated with it, provided that the proponent submits a plan showing how stormwater runoff from the proposed land development will be conveyed to the receiving drainage system. The proponent must be able to demonstrate that drainage impacts to the highway right-of-way or upstream/downstream riparian landowners will not occur, and that the capacity of the highway drainage system will not be exceeded as a result of stormwater runoff discharging from the proposed land development.

Elements of Common Law

Common law is a matter of precedents that are modified by court rulings. Common law governs unless it is superseded by statute law. Common law is founded on the principle that water flows naturally and should be permitted thus to flow, and can be divided into three main categories:

  • natural watercourses;
  • surface or sheet flow; and
  • subsurface flow.

Refer to the "Drainage Management Manual" (MTO 1997), Chapter 2 Appendix 2B, for more details.

Natural Watercourses

A natural watercourse is:

  • formed by the flowing of water that must be present to the eye on casual examination with the unmistakable evidence of the frequent action of running water; or
  • constituted if there is sufficient natural flow of water to form and maintain a distinct and defined channel.

Therefore, a natural watercourse could be in the form of a stream, a ditch, concrete channel etc.

Aspects of common law that pertain to natural watercourses include the following.

  • Riparian Rights and Obligations: a riparian owner is one whose land is in actual contact with a natural watercourse. Specific riparian rights include:
    • the right to drain that land into the watercourse;
    • where it traverses that land, the right to benefit from the water flowing through the watercourse in its natural state;
    • obligations to receive it even if it becomes a nuisance due to flooding, erosion or other reasons;
    • the owner has no legal ground to complaint if upstream riparian owners reasonable use the watercourse as an outlet, even though the result could be an increase in the amount of water; and
    • person's not riparian owners who obtain an outlet to the stream are liable to a downstream riparian owner whose land is damaged by the increased amount of water.
  • Use of Water: a riparian owner has the right to have the water flow in its natural state with regard to both quantity and quality, subject to certain qualifications, and may put the water from the natural watercourse to any reasonable use. Reasonable use of a stream has been defined as a use up to the capacity of the banks of the stream.
  • Interference with Natural Watercourses: anyone who interferes with a natural watercourse, must ensure that the works are adequate to carry the flow of water, even that resulting from an extraordinary rainfall.

Surface or Sheet Flow

An owner who paves the surface of their land and thereby increases the rate of surface runoff is not normally liable under common law, even though his/her action may aggravate previously existing flooding problems.

Such lack of liability does not absolve the owner from assessing the environmental implications of increasing the runoff.

If a ditch, pipe or curb and gutter is constructed to collect surface water, it is then necessary to provide a sufficient outlet for the collected water.

An owner does not have the right to collect surface water in this fashion and discharge it onto the lands of other riparian landowners.

Subsurface Flow

Subterranean flowing streams that have definite courses may be treated for all practical purposes, as natural watercourses on the surface.

An owner is entitled to put an underground stream to any reasonable use.

Top of page   Top of page

Common Law and The MTO

The Ministry of Transportation (MTO), as a landowner, has common law rights that other landowners (i.e. developers) must recognize. MTO must also recognize the rights of other landowners upstream and downstream.

Common Law

Common law is a body of principles based on long standing usages and customs, and on court decisions recognizing, affirming and enforcing such usages and customs. Common law, therefore, is largely a matter of precedent; the precedents can be modified as customs change and new practices arise. Common law principles:

  • always apply unless enlarged, modified or superseded by statute law;
  • give regard to current societal standards (i.e. what is deemed to be reasonable conduct in a given set of circumstances as well as reasonable expectations concerning what should or should not be foreseeable to a prudent person), and therefore are evolving; and
  • are based on judgements rendered by the courts.

When reviewing common law principles, the type of water flow involved in any problem must be identified. Following this logic, common law, as it relates to highway drainage management, can be divided into the following subsections.

  • Natural Watercourses:
    • Riparian Rights and Obligation;
    • Use of Water;
    • Interference with Natural Watercourses;
    • Diversions; and
    • Watercourse Crossings.
  • Surface Flow:
    • Obstruction of Surface Flow;
    • Increase of Surface Flow;
    • Collection of Surface Flow; and
    • Surface Flow and the MTO.
  • Subsurface Flow:
    • Underground Water in a Defined Channel; and
    • Underground Water not in a Defined Channel.

Most applicable to this document are the rights and obligations associated with natural watercourses. These include the following:


  • Riparian owners have the following rights with regard to natural watercourses across their lands:
    • To drain catchment area lands to the watercourse as long as flows do not exceed the capacity of the lower channel in its natural state;
    • To discharge collected water via drains or ditches to the watercourse as long as flows do not exceed the capacity of the lower channel in its natural state;
    • To make extraordinary use of water (e.g. operation of a mill) as long as the quantity and quality are not diminished;
    • To have water flow to him/her in its natural state via the watercourse; and
    • To use the stream water for domestic or natural purposes.
  • Higher lands can drain onto lower lands.
  • A lower land owner does not have to receive water from higher lands as long as the lower land owner does not injure an adjacent land owner when exercising the right not to receive surface water.
  • A land owner :
    • Can collect and drain surface water but must have a sufficient outlet.
    • Can dig a pond to retain water;
    • Can build a dyke as long as the dyke does not collect or concentrate flow; and
    • Can raise the level of the lower land above the higher land.
    • Cannot direct high land water to lands that did not have water before.


  • Riparian owners:
    • May not bring waters that have not fallen within the natural catchment to the stream.
    • May not sell or assign the right to drain into a watercourse.
    • Must ensure a sufficient outlet where there is interference with a natural watercourse.
    • Must obtain a water taking permit from MOEE for withdrawals greater than 50,000 L/day.
    • Must accept increased flows as long as it results from reasonable use.

Top of page   Top of page

Statutory Mandates of the Regulatory Agencies

The statutes governing water management are presented below. Refer to the following sections in Chapter 2 of the "Drainage Management Manual" (MTO 1997) for additional information on:

Appendix 2C - Statute Law;
Appendix 2D - Agency Mandates; and
Appendix 2E - Documents Supporting Statutory Mandates.

Federal Statutes

  • The Federal Fisheries Act (DFO).
  • The Canada Water Act (DOE).
  • Navigable Waters Protection Act (TC).
  • Canadian Environmental Assessment Act (DOE).

Provincial Statutes

  • Ontario Water Resources Act (MOE)
  • Environmental Protection Act (MOE)
  • Environmental Assessment Act (MOE)
  • Conservation Authorities Act (MNR)
  • Lakes and Rivers Improvements Act (MNR)
  • Drainage Act (OMAF)
  • Planning Act (MMAH)
  • Municipal Act (MMAH)

Top of page   Top of page

Statutory Mandate of MTO

The regulatory water management role of the Ministry of Transportation is mandated by the Public Transportation and Highway Improvement Act (PTHIA). Water management approvals are issued through Encroachment Permits or Building and Land Use Permits.

The water management mandate of MTO is defined by the following.

  • MTO Drainage Directives.
  • "Drainage Management Manual" (MTO 1997).

MTO, as an agent of the Crown, will not issue an approval that will contravene another regulatory agency's statutory mandate. For this purpose, and prior to issuing any approvals, MTO requires confirmation that the necessary approvals from other regulatory agencies have been granted, approvals in principle have been provided or no approvals are required. MTO permit approval may be given conditional on such an approval being granted.

MTO will interact with other regulatory agencies to confirm their positions and resolve any legislative conflicts if they arise.

Top of page   Top of page

Design Criteria for Highway Drainage Works

Highway drainage system design criteria are outlined in PHY Directive B100, or the "Drainage Management Manual" (MTO 1997). Refer to these documents for complete details. For convenience, these documents have been included (with noted references) in the following sections. Contact the MTO Regional Highway Planning and Design Office for more details.

  • Conveyance of the regulatory storm is discussed in PHY Directive B100. Where highway drainage works will increase flooding of buildings or developable land during a regulatory flood, it shall be designed to the regional flood criteria, unless otherwise approved. The highway major system will accommodate the regulatory storm flow that exceeds the capacity of the highway storm sewer system.
  • The Level of control must be selected to completely mitigate drainage impacts to the receiving drainage system. Refer to Collecting Background Information for more details.
  • The major system should be checked as it provides a continuous overland route for the portion of the flow that cannot be conveyed by the minor system. Hazards to the travelling public and damage to property adjacent to the highway must be prevented. The highway must also be checked against major flows to ensure that it can remain accessible to emergency vehicles during major storm events unless such access is not required. For further details refer to page 56 in Chapter 3 of the "Drainage Management Manual" (MTO 1997).
  • Flow along highways should be kept within reasonable limits during major storms, to permit the passage of emergency vehicles and for safety considerations. Suggested guidelines are as follows:
    • crown of freeway to remain unsubmerged;
    • depth of flow at crown of arterial road should not exceed 0.15m; and
    • depth of flow at gutters should not exceed 0.4m.

  • Freeboard requirements for highway roadside ditches: as a guide use 0.3m.
  • Freeboard requirements for highway bridges and culverts are discussed in the Canadian Highway Bridge Design Code (CHBDC, 2001) which states that, when geometric and other considerations permit, the approach grade elevation shall be 1.0 m for freeways, arterial and collector roads, and 0.3 m for other roads. If consideration of a regulatory flood is required and relief flow is permitted, the grade shall be set to optimise relief flow. Refer to MTO Directive B-100 to identify when accommodation of the regulatory flood is required. Freeboard for pedestrian or bicycle access paths passing through multi-use water crossings shall be at least 1.0 m from the normal water level for spans of more than 6.0 m; and 0.5 m from the normal water level for spans of 6.0 m or less. For further details refer to page 27 in Chapter 3 of the "Drainage Management Manual" (MTO 1997).
  • Relief flow may be permitted over the highway during regulatory storm events at bridge or culvert crossings to accommodate flood flows (refer to PHY Directive B100). For further details refer to page 28 in Chapter 3 of the "Drainage Management Manual" (MTO 1997).
  • The design flow criteria may be modified in exceptional cases, such as for unusually large structures, unusually low traffic volumes, or for vital routes which must remain useable during regional flood conditions. Use of regional flood criteria in the latter case shall be justified by a cost-benefit analysis.
  • Other design criteria are presented in the "Drainage Management Manual" (MTO 1997).
    • In Chapter 3: pages 39 to 42 (bridges), 44 to 49 (culverts), page 58 (storm sewers), 60 (roadside ditches), 62 (highway major system), and pages 75 to 86 (stormwater management detention facilities).
    • In Chapter 4: ditch cross section and lining (page 12), profile invert and crest elevations (page 12), roadside safety (page 13), porous soil (page 13), limited availability of right-of-way (page 13), aesthetic considerations (page 14), sewer materials (page 39), sewer elevations (page 40), hydraulic conditions in the sewer (page 40), sewer outlet conditions (page 40), exfiltration to the road subgrade (page 41), safety to people and vehicles (page 41), sewer accessories (page 41), curbs and gutters (page 51), gutter inlets (page 52), longitudinal grades (page 52), cross fall (page 52), hydroplaning (page56), median barriers (page 56), shoulder gutters (page 56), external tributary areas (page 56), gutter flow calculation (page 56), inlet spacing (page 57), and stormwater management detention facilities (79 to 82).
    • In Chapter 5: detailed hydraulic design (page 4), flow conveyance and backwater (page 9), scour (page 43), river ice (page 78) and debris flow (page 93).

Top of page   Top of page

Back to Top