Collecting Background Information

Having identified the type of Hydrology Report and MTO approvals required, the drainage practitioner should complete the following tasks. These tasks will ensure that all necessary information is taken into account in making any decision and in developing the design criteria.

The MTO Regional Structural Section or Bridge Office may alter requirements presented in this document. The drainage practitioner must demonstrate that adverse drainage impacts to the highway right-of-way and upstream/downstream riparian landowners will not occur. The design of the crossing should be based on runoff conditions anticipated 20 years from the time of design, taking full account of present and probable future municipal controls over increases of runoff from new development.

Review Previous Drainage Studies


Previous drainage studies may have been done for the watershed, the watercourse or the specific water crossing being considered. The Hydrology Report should document all previously completed drainage studies relevant to the proposed water crossing site(s) and extract any relevant information.

Previous drainage studies include the following types of studies:

  • Watershed and Subwatershed Studies provide the goals, objectives and criteria for the management of resources in a watershed, subwatershed or area of specific interest. Additional information is provided in the discussion below.
  • MTO Environmental Study Reports documents the alternatives studied, methods used and recommended alternative, according to the requirements of the Environmental Assessment Act.
  • Preliminary Design Reports are typically submitted at the early stages of design and may include an outline of all potential drainage issues, propose design alternatives and recommend mitigative works for any impacts associated with the different alternatives. These reports may have been prepared many years in the past and if so, they will need to be revisited and verified. However, the information contained in these reports should be considered and incorporated in the final design report, with the necessary modifications.
  • Other Drainage Studies may have been prepared by the Conservation Authority, MNR, MOE and/or municipalities. These studies could include:
    • Flood Line Mapping Studies.
    • Flood Damage Reduction Program Studies (FDRP studies);
    • Erosion Control Studies; or
    • Flood Control Studies.

Watershed and Subwatershed Studies

Documentation Requirements

Where a previous drainage study is in existence and any objectives, goals, design criteria and other elements from that study are intended to be used in the proposed Hydrology Report, the report must clearly indicate if MTO formally endorsed the previous drainage study.

  • If MTO endorsed the previous drainage study, documentation of relevant objectives, goals, design criteria and other elements of the referenced study must be included (with clear references to its source). This may include:
    • Limits on regulatory flood flows and water levels;
    • Fish habitat restoration or protection objectives;
    • Identification of flood or erosion prone areas; or
    • The type of drainage system that is required.

    Adherence of the Hydrology Report to the referenced drainage study must also be clearly documented.

    When making submissions based on previously completed drainage studies, changes that have occurred to MTO drainage practice must be considered. Other agencies also undertake these types of updates. Contact the MTO Regional Structural Section, the Regional Planning and Design Section or the Highway Design Office (Drainage and Hydrology) to determine if changes have occurred to the MTO drainage practice since the previous drainage study was completed. If there have been changes, the proponent must demonstrate how the previously completed drainage study is in conformance with current MTO drainage practice.

  • If MTO did not endorse the previous drainage study, there may be two reasons. The Hydrology Report should document which of the following reasons apply.
    1. MTO may not have endorsed the previous drainage study since MTO was not on the circulation list and had not reviewed it. In this case, the previous drainage study should be reviewed by MTO for conformity to MTO drainage practice. Should the study be acceptable to MTO, an endorsement can be issued. Once complete, the proposed Hydrology Report can be reviewed on the basis of conformity to the previous drainage study.
    2. MTO may not have endorsed the previous drainage study because of a disagreement with certain objectives, goals, design criteria, methods or other elements of the previous drainage study. Determine the aspects of the previously completed drainage study that were not acceptable to MTO. Once this has been established there are two options available.
      • If the proposed Hydrology Report does not encompass any area of disagreement, MTO can review the Hydrology Report in isolation of the previously completed drainage study. The review would be based on conformity with current MTO drainage practice.
      • If the proposed Hydrology Report encompasses an area of disagreement, a meeting between all supporting regulatory agencies is warranted to sort out those controversial aspects of the previously completed drainage study.

Previous Environmental Study Reports, Preliminary Design Reports and Detail Design Reports for Provincial Highways

When proposing to design a water crossing it will be necessary to obtain information that describes the watercourse being crossed. To obtain this information and data, it is prudent to contact the MTO Regional Structural, Planning and Design and Environmental Offices. Information may be available from environmental study reports, preliminary design reports and detail design reports.

Documentation Requirements

The Hydrology Report should provide documentation on the relevant objectives, goals, design criteria and other elements of the previous studies (with clear references to the source of the information), such as:

  • Magnitude of extreme flood flows and water levels;
  • Water quality objectives;
  • Fish habitat restoration or protection objectives;
  • Identification of flood or erosion prone areas; and
  • Restrictions on the drainage system in the vicinity of the proposed water crossing locations.

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Identify Data Needs and Availability


The process of completing the hydraulic design of a water crossing requires the collection of a significant amount of data. The type of data required and the availability of this data will vary from site to site. Once previous drainage studies have been reviewed it will be easier to determine which information is available and which information must still be collected. It may also become clearer what information is not available.

Depending on the type of data available, the method of analysis may vary. For example, in locations where stream flow data is not available, using data from an adjacent, hydrologically similar, watercourse may be necessary. In other cases, hydrologic analysis methods using precipitation and watershed characteristics may be the only means to determine the design flow rates. It is usually necessary to use more than one method of flow rate analysis to verify the stream flow estimates.

Documentation Requirements

The following are the types of data that are commonly required to complete the design and assessment of a water crossing alternative. The availability or lack of this data should be documented in the Hydrology Report. The resolution to the issue of missing data should be documented. If alternative methods of analysis are to be used due to the lack of data, the rationale and justification for this decision should be presented. The following are some of the data types. This data can be documented in appendices and/or within the body of the report:

  • Precipitation and Other Climatic Data - Environment Canada collects precipitation data for a number of rainfall gauging stations in Ontario. This data is more abundant than stream flow data and is therefore, available for more potential crossing sites. The data is provided either as a continuous record over a long period of time, as Intensity-Duration-Frequency curves (I.D.F. curves), or as a mathematical representation of the rainfall distribution. The Hydrology Report should provide the following information as a minimum
    • Rainfall station name, number and location. A clear map should be included that shows this information.
    • Type of precipitation data collected (I.D.F. curves, single event, continuous record or regulatory storm).
      • In the case of continuous precipitation records, the data should be analysed to ensure the quality of the data is suitable for use in the hydrologic analysis. A description of this assessment, the quality of the data and any analysis required to prepare the data for the hydrologic analysis should be included.
      • Design Storm Events
        • Type and duration.
        • Rainfall discretization.

  • Topographic Data - These are usually obtained from the Ontario Base Maps (OBMs) topographic layer, the National Topographic Series or municipal engineering departments. Missing information can be gathered from field surveys.
  • Ground Cover Data - This data can be obtained from the OBMs, photo mosaics, site visit and municipal sources.
  • Air Photos - These are available from the Regional Remote Sensing Units of MTO, Conservation Authorities, MNR, and other sources. The data to be documented should include the findings on topography, land use, soil and vegetative cover, layout of bridges, culverts and roadside ditched, types of paved roadway, buildings and other ground features.
  • Soil Data - This data will include:
    • Soil data for the watershed, which is to be used in the hydrologic analysis. This information will be provided from a number of sources including: soil survey map, watershed studies and/or subwatershed studies; and
    • Soil data for the watercourse, which will be used for stream stability analysis, scour analysis, design of erosion protection measures. This information is obtained from soil investigations that are usually submitted under a separate geotechnical report. Further discussion of soil data within the watercourse is covered in the section "Identify Characteristics of the Watercourse".
    A more comprehensive list of soil data sources is presented in the Chapter 7, table 7A.2 (4 of 5) of the DMM.
  • Watercourse cross-sections - This data can be obtained from field surveys and from Conservation Authorities, if flood profile models have been prepared for the watercourse.
  • Precipitation and Other Climatic Data - This data is available from Environment Canada, Conservation Authorities and Municipalities. Intensity-Duration-Frequency (I.D.F.) curves for MTO districts are also available in the MTO Drainage Management Manual (1997).
  • Water Levels at Lakes, Harbours and Controlled Structures - This data is available from Water Survey of Canada, dam operators, waterway authorities, conservation authorities and hydroelectric agencies such as Ontario Power Generation (OPG).
  • Fish, Wildlife and Terrestrial Data - This data is available from the Ontario Ministry of Natural Resources and Conservation Authorities.
  • Field surveys - These will be done to complement and verify other sources of data. In some cases, such as when collecting watercourse cross-section profiles, this may be the main source of the data.

Refer to Chapter 7 of the MTO Drainage Management Manual for a more detailed description of the different types of data, their sources and data collection on site.

The documentation requirements for collected data are described in the following sections of this documents:

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Identify Characteristics of the Watercourse


An essential task required to develop a water crossing is to collect information and data that describe the watercourse being crossed. This data serves as input to all aspect of planning, development and design of the water crossing alternatives.

Documentation Requirements

This section outlines the information required to describe the watercourse being crossed. This data should be documented in the Hydrology Report either in appendices, computer input/output summaries or in the main body of the report. The stream characteristics to be obtained and documented include:

  • Cross-sections upstream and downstream of the crossing. Since this data will most likely be used as input to a water surface profile analysis software, the documentation of this data can be done through the presentation of the input data to the analysis methods or design software. Refer to the Web document "Evaluation of Drainage Management Software: Detailed Evaluations" for further details. Each detailed evalutation includes a link to "Minimum Requirements for inclusion in report " specifically addressing this issue.
  • Watercourse bed slope. Using the cross-section data and field surveys it will be possible to determine the bed slope of the watercourse. This data should be documented in schematic diagrams, tables and/or text. The implications of this information on the characteristics of the flow (critical, subcritical or supercritical), analysis techniques and design options should be identified.
  • Meander pattern of the river reach, and the meander at the location of the crossing. This information will identify if the stream is straight or on a bend, having single or multi-channel configuration. The implications of the meander patterns on stream stability and design considerations should be included in the discussion associated with this data.
  • Channel bank condition: weathered, vegetated, eroding, and slumping. These characteristics may be determined based on the study of aerial photographs, photo mosaics, contour maps, and field surveys. These aspects are required to predict the watercourse stability, especially during floods and over an extended period of time. This determination is essential to ensure a proper design of the bridge or culvert structure and related stream stabilization works. Refer to the section "Investigate Stability of the Watercourse" for more details on assessing the stability of the stream based on the data gathered.
  • Stream Flow Data - Water Survey of Canada, in co-operation with Conservation Authorities provide stream flow data for a number of stream gauging stations in Ontario. The Hydrology Report should document the gauging station used and an assessment of the quality of the data should be completed and summarised. If transposing of the data from distant gauging stations was done, it should be identified and the methods used described. Flow or water level controls upstream and downstream of the proposed water crossing should be identified and their impact on the usability of the data should be confirmed. In cases where stream gauges in the vicinity of the crossing cannot be found, this should be clearly stated and the implications on the design methods and analysis should be described.
  • Soil Data - Soil data within the watercourse are obtained from soil investigations that are usually submitted under a separate geotechnical report. The information to be documented in the hydrotechnical analysis includes:
    • borehole data, defining the various soil layers with borehole locations plotted on Plan and Elevation views:
    • recommendations for the bed and side slopes, excavation, backfilling,
    • differential settlement and
    • slope instability problems.

    Soil information related to anticipated abutment and pier foundation design can be quite extensive. Therefore, only a brief summary of the conclusions/findings should be included in the Hydrology Report. Data that will be used in scour, stream stability and erosion control analysis should be provided in detail. The Soils Report should be clearly referenced wherever the data from the report is used in the analysis.

  • Water Levels at Lakes, Harbours and Controlled Structures - This data is available from Water Survey of Canada and/or the authority that controls these facilities such as, the Waterway Authorities, Conservation Authorities or Hydro-electric Agencies such as Ontario Power Generation (OPG). The documentation should identify if such controls will affect the hydraulic performance of the proposed structure. A summary of water level records should be provided showing the critical water levels. Water level control curves should also be included in the report, if applicable.
  • The History of Flooding - includes historical records, high water marks, if available, residence reports, dates of flooding events, extent of flooding and damages.
  • The History of Debris Carrying Flows or Ice Jamming - The possibility and extent of debris and ice jamming problem needs to be identified. This information should include: date of historic events, locations and elevation of marks associated with high ice, extent of damage that occurred, identification of the sources of the data and the characteristic of the watershed and the watercourse that are associated with debris and ice jamming problems.
  • Fish, Wildlife and Terrestrial Data - DFO, MNR and the Conservation Authority (if one exists) would provide this information as well as the requirements for protection for fish habitat. Refer to the sections "Identify Requirements of Other Agencies" for further information.

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Identify On-Site Conditions


For each water crossing site there are certain site conditions that will bear greatly on the design alternatives that can be considered. These conditions can be identified from a number of sources, as described in the previous section. However, a site visit is critical in identifying special conditions that are particular to each site. The site visit will also assist in determining the restrictions that these conditions place on the design criteria and on the complexity of the solutions that will be required to satisfy these criteria.

Documentation Requirements

The documentation of site conditions should include, but are not limited to the following:

  • Site information including the elevations of the top of bank, toe of bank and channel bed.
  • Bank traverse.
  • Utility/fence/property lines.
  • Overland slopes.
  • Restrictions on the approach slope and elevation and any other restrictions resulting in limitations on the clearance of the structure and freeboard at the approach, as identified by the CHBDC.
  • Stormsewer and channel outlets adjacent to the proposed crossing location, as well as other features that may require protection as part of the design of the crossing.
  • Special soil conditions and geological features that have to be avoided, accommodated or removed.
  • Other structures and features, upstream and downstream, that could have an impact on the proposed crossing or can be impacted by it. Refer to the section "Identify Issues with Other Structures Upstream and Downstream" for further details. table 7 provides additional details on the information that should be documented under this section.
  • Evidence of historical events. Historic high water surface elevations can be identified on-site from a number of indicators such as: marks on trees and structures and by interviewing long-term local residents along the watercourse. Such information should eventually be tied in with field surveys to a common datum. This data should related to known historic events, whenever possible.

Documentation Requirement for the Components of the Drainage System (Table 7)

Component Relevant Information to be Provided in Hydrology Report
Bridges Location, distance, structural characteristics (soffit elevation, span arrangement, pier details, abutments, and superstructure type)
Culverts Culvert type (e.g. elliptical, box, open footing, etc.), culvert configuration (e.g. single barrel, double barrel, etc.), diameter or span/rise, length, slope, material (e.g. CSP, concrete, etc.), and inlet/outlet configuration (e.g. head walls, wing walls, flared entrances, collars, etc.).
Erosion protection works Lining material/cover work, bank drainage, buffers strips, runoff diversions, drop structures, energy dissipaters, stilling basins, chutes, retaining walls and check dams.
Dams Size of reservoir, dam height, type, operational rule curve, spillway location, maintenance responsibilities, and ownership.
Other Water bodies, (e.g. ponds and drainage ditches) Name (if applicable), location, changes proposed and impacts on other system and performance, if any.

Site information is generally required to be tied-in with field surveys and plotted in Plan and Elevation views at appropriate scales. A bridge waterway opening would eventually be designed to fit in with or modify the site conditions. Therefore, these details would be used as a part of final design and drawings.

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Identify Requirements of Other Agencies


There are a number of agencies that are involved in the management and regulation of natural watercourses in Ontario. The mandate of these regulatory agencies may require that some restriction be placed on the design criteria and in some cases these may govern the design. Such agencies could include MNR, MOE, DFO, Transport Canada, Conservation Authorities and local municipalities.

In the case of crossing of municipal drains the local municipality and the Drainage Superintendent may place restrictions on the design.

Documentation Requirements

Any regulatory requirement and approval, which has to be considered as part of the design of a bridge or culvert structure, should be documented. These may include requirements under:

  • The Federal and Provincial fishery and wild life protection legislation.
  • The Environmental Assessment Act.
  • The Conservation Authority flood plain planning policy under the Planning Act.
  • The Federal Navigable Waters Protection Act.

These requirements may constrain certain design parameters such as location, type, size, span or clearance of the proposed structure. They may also add requirements for additional works for fish habitat protection, erosion control and channel training.

Document the requirements, if any, for the following:

  • Fish Habitat protection - Generally, in land development proposals, the MNR, DFO, or the local Conservation Authority will determine fish habitat requirements. Since fish habitat requirements are based on the sensitivity of the watercourse, requirements may be set before any impact assessment has been completed.
  • Regulatory flood line requirements - The local Conservation Authority, will in most cases have information on the flood lines that need to be maintained. It is always advisable to contact the Conservation Authority to identify and agree on their requirements before setting the design criteria for the proposed structure.
  • Navigable waters requirements - Transport Canada administers the Navigable Waters Act and accordingly, the clearance requirements may be determined based on consultation with Transport Canada.
  • Environmental Assessment requirements - If an Environmental Assessment was completed for the highway project, which the water crossing structure is part of, certain design requirements and constraints may have been set and will have to be adhered to.

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