Quick Reference Guide

This document identifies the procedure for completing a hydrotechnical design report, commonly referred to as a "Hydrology Report". It provides the detailed documentation requirements for Hydrology Reports prepared for MTO and the rationale for requiring this information. MTO documentation requirements are grouped into six groups of tasks to reflect the different steps that are to be taken in the planning and design of water crossings. Each grouping is comprised of a number of tasks that the drainage practitioner may need to undertake. Task Summary (Figure 1) illustrated the task groups and the related task in each group. The six task groups are as follows:

This document is suitable for application throughout Ontario for the design of MTO bridges and culverts over waterways or where MTO approval is required. The level of detail of the analysis presented in a Hydrology Report may vary depending on the size and level of impact of a particular crossing. Review the section "Level of Detail of Analysis" for more information. However, all the information requirements identified in this document should be provided unless it is not relevant to the site-specific conditions.

Where a water crossing design alternative is being considered, any potential impacts to the waterway, the highway or surrounding lands and buildings must be examined.

Along with the six task groups outlined above, additional information is provided for two activities that are part of the process of developing a hydrology report, namely:

Note: This information is provided to clarify technical and policy terminology, as defined by MTO. It also provides the necessary linkages between this document and the MTO Drainage Management Manual (DMM) and MTO policies. The information presented in these two sections should not be used as a substitute for the DMM or any of the policy documents. The designer must refer to the original documents for the planning and design of the water crossing structure.

Summary of Tasks

A brief explanation of the document structure is provided below and is also shown on Summary of Tasks (Figure 1).

The task group "MTO Approvals" describes the task to identify when a Hydrology Report is required and the level of detail of the report at the different structural planning stages. It also identifies the approvals required from MTO under different conditions. The tasks in this grouping and the rationale for requiring this information are identified in Identifying the Need and Type of Hydrology Report (Table 1) and they include:

The grouping "Collecting Background Information", describes the tasks that provide the necessary background information, which is the basis of all analysis. The tasks in this grouping and the rationale for requiring this information are identified in Collecting Background Information (Table 2) and they include:

The task group "Identifying Drainage Issues" describes the tasks required to identify potential impacts of the proposed crossing alternatives on the surrounding environment. Some technical analysis may be required in the resolution of the issues (see below). The tasks in this grouping and the rationale for requiring this information are identified in Identifying Drainage Issues (Table 3) and they include:

The task group "Performing the Hydraulic Design" describes the tasks required to complete the hydrologic and hydraulic analysis associated with the design of the structure. A technical analysis is generally required to complete these tasks (see below). The tasks in this grouping and the rationale for requiring this information are identified in Performing the Hydraulic Design (Table 4) and they include:

The task group "Mitigating Impacts to the Drainage System" describes the possible mitigative works that should be considered to address impacts to the surrounding environment, including the highway drainage system and how they can be resolved. The tasks in this grouping and the rationale for requiring this information are identified in Mitigating Impacts to the Drainage System (Table 5) and they include:

The task group "Finalizing Design and Construction Issues" identifies additional design and documentation requirements that need to be completed, in addition to the design of the water crossing structure. The tasks in this grouping and the rationale for requiring this information are identified in Finalizing Design and Construction Issues (Table 6) and they include:

The task group "Selecting Computational Methods" defines the various computational methods referred to in the document. This grouping provides brief descriptions on the following analyses with reference to the related sections in the MTO Drainage Management Manual:

The grouping MTO Drainage Policy, contains references to the applicable MTO drainage policy. This grouping provides a brief description of:

Identifying the Need and Type of Hydrology Report (Table 1)

Task Issue Relevance to MTO
MTO Approvals Determine the Requirements for a Hydrology Report.
  • Identifying why a Hydrology Report is prepared.
  • The Structural Planning Guideline identifies three levels of planning. The Hydrology Report should be in line with the process identified in the Guideline.
  • If other reports have been prepared earlier they should be identified and their content summarized to ensure continuity.
Acquire MTO Approvals.
  • There are formalized approvals processes in MTO that should be followed to eliminate any unnecessary delays in the progress of the Hydrotechnical Study and preparation of the Hydrology Report.

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Collecting Background Information (Table 2)

Task Issue Relevance to MTO
Review
Previous
Drainage
Studies
Conformance to a previous drainage study (e.g. watershed, subwatershed or master drainage plan, etc.).
  • Need to identify any past design criteria that are relevant to this submission and how they have been addressed.
  • Need to identify if previous drainage studies were endorsed by MTO.
  • Identify if the design objectives, goals, design criteria and other elements as promoted by the study acceptable to MTO
  • There may be cost savings if data and information are already available.
Conformance to previous highway studies (e.g. preliminary design reports).
  • MTO will not approve works that will conflict with existing or future highway works.
Identify
Data Needs
and
Availability
Identify the data required, the data that is readily available and the limitation in acquiring any additional data.
  • The use of appropriate data will determine the quality of the analysis. Such information will ensure all analysis are based on adequate data.
  • Data collection is a time consuming and costly activity in a study. Data needs should be identified at the earliest possible time to take advantage of cost saving opportunities.
  • The availability of data may determine the requirement to use different hydrologic and hydraulic analysis methods and software.
  • Additional data may be required to apply other analysis.
Identify
Characteristics
of the
Watercourse
Identify the physical characteristics of the watercourse.
  • Accurate hydrologic and hydraulic analysis can not be done without proper description of the watercourse.
Identify the History of Flooding.
  • Information on the historic conditions in the watercourse can be very useful in ascertaining the accuracy and validity of hydrologic and hydraulic analysis.
Identify
On-Site
Conditions
Visit the proposed water crossing site(s) and collect field data.
  • Many drainage problems can be identified by a site visit
  • Interviewing residents can be invaluable in identifying historical information on flooding, erosion, ice, debris and extreme event.
  • Photographs can be helpful in documenting details from the site for reference in the office or in the future.
Identify Site Constraints./td>
  • Identification of the physical constraints associated with the alternatives being considered can be easily determined on site.
Identify
Requirements
of Other
Agencies
Identify regulatory fish habitat requirements.
  • Do the streams being crossed sustain a fish community
  • Have the MOE, MNR, DFO, or the conservation authority issued requirements for fish habitat protection measures that are to be addressed in the Hydrology Report?
  • MTO will not proceed with proposals that contravene the authority or mandate of these agencies.
Identify regulatory flood line requirements.
  • MTO is required to maintain the regulatory flood lines for water crossings in accordance with the Flood Hazard Policy Statement, under the Planning Act and in agreement with the local Conservation Authority.
Identify necessary approvals of other agencies.
  • Identifying the required approval to determine what potential requirement may be set by other agencies.
  • Allow for the time required to obtain approvals.

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Identifying Drainage Issues (Table 3)

Task Issue Relevance to MTO
Identify
Existing
Drainage
Problems
Identify existing drainage problems on upstream or downstream riparian property.
  • It is important to identify existing problems of upstream or downstream property to ensure that any liabilities assumed by MTO are clear and that opportunities for corrective measures are addressed early in the design process.
  • Identifying the extent of the floodplain and the flood lines are necessary to assess the predevelopment condition.
  • Existing stream channel erosion may be an indication of stream instability and should be accounted for in the development of design options.
  • Identifying lands and structures that are susceptible to flooding prior to the construction of the crossing will establish the predevelopment conditions in the vicinity of the site.
Identify special problems.
  • Depending on the location of the proposed crossing, issues such as: crossing of inland lakes, consideration of wave action, navigability and physical modelling of bridge problems have to be identified and resolutions determined.
Identify
Issues
with other
Structures
Upstream
and
Downstream
Identify if there are bridge or culvert structures upstream or downstream.
  • All existing structures should be identified so that their impacts on the design and construction of the new crossing can be identified.
  • MTO does not want to be liable for any conditions that may arise in the future which may be attributed to the construction of the new structure.
Identify existing drainage problems of other bridge structures upstream or downstream.
  • The condition of other structures that may be impacted by the proposed structure should be documented to ensure that they do not become attributed to the new structure.
  • There may be design solutions in the new structure that can alleviate the problems associated with the other structures.
Identify the impact of the other structures on the design criteria for the crossing being considered.
  • Limitation on the design criteria may be imposed by the conditions of other structures. This limitation needs to be identified to ensure that they are taken into account in the design.
  • The rationale for setting the design criteria based on the limitation of other structures must be clear and well documented to minimize MTO's liabilities in case of future problems.
  • Cumulative impacts of multiple structures may result in unacceptable conditions.
  • Cost implication may result from the existence of other structures.
Investigate
Stability of
the
Watercourse
Identify the geomorphic condition of the watercourse.
  • Careful consideration of the location of the proposed structure has to be taken into account.
  • The risk of long-term changes of the stream channel and viability of the structure should be minimized throughout its expected life.
Develop the design criteria that would account for the conditions of the watercourse being crossed.
  • The design criteria need to be established to ensure the long term viability of the structure.
  • Approvals may be needed for additional works associated with some of the proposed design alternatives
Identify
Criteria
that Regulate the
Watercourse
Identify dams or weirs that control the water surface elevation in the watercourse.
  • Water levels may not be based on the natural flow in the stream but are regulated using water level curves.
  • Accurate knowledge of the water levels in the watercourse being crossed are essential for design.
Identify flow rate controls (e.g. Power generating station outlets).
  • Accurate knowledge of flow rates from all available sources is essential for proper design.
  • The existence of outlets in the vicinity of the crossing will require additional design consideration to protect these outlets.
Identify
Design
Alternatives
Outline the different alternatives for crossing the watercourse.
  • Consideration of a number of alternatives provides the opportunity of selecting an alternative that would most suit the project objectives.

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Performing the Hydraulic Design (Table 4)

Task Issue Relevance to MTO
Develop the
Design
Criteria
Develop the design criteria for the proposed structure based on collected data and MTO standards, policies, guidelines and manuals.
  • Establish design criteria that meet MTO policies, standards and accepted practices, and the CHBDC .
  • If requirements and standards cannot be met, documentation of the causes and considerations taken may be required for future reference to demonstrate due diligence in the establishment of design criteria.
Acquire approval for the proposed design criteria.
  • Ensure concurrence of all parties with the established design criteria.
Conduct the
Hydrologic
Analysis
Perform the hydrologic analysis, if required, to determine the design, check and regulatory flow rates that will be used to design the structure and associated erosion and scour mitigation measures.
  • Proper design requires the accurate determination of the flow rates that will be used to design the bridge or culvert opening and scour mitigation measures.
  • The methods used must be in conformance with the analysis methods and principles outlined in the MTO Drainage Management Manual.
Design
the Bridge
or Culvert
Opening
Perform the hydraulic analysis to size the bridge or culvert opening and assess the associated backwater.
  • Conformance with MTO drainage practice.
  • Conformance with the CHBDC and associated MTO Directives.
  • Conformance with the drainage practices of other regulatory agencies.
  • The CHBDC sets specific requirements for minimum freeboard at the approach and clearance to the soffit. These requirements should be met. Special approvals may be required for deviations from this requirement.
Analyse
Scour and
Determine
the Depth
of
Footings
Perform the analysis to ensure the level of scour will not jeopardise the structural integrity of the bridge or culvert crossing.
  • Conformance with MTO drainage practice.
  • Conformance with the CHBDC and associated MTO Directives.
  • Conformance with MTO drainage practice.
  • Conformance with the drainage practices of the regulatory agencies.
  • Identify if mitigative measures are required.
Design for
Ice and
Debris
Determine the requirement for conveying ice and debris flow and avoiding ice and log jams.
  • Ice and debris can exert large horizontal and vertical force on water crossing structures and cause substantial damage.
  • Ice and log jams can cause excessive flooding up stream due to backwater effect.
  • The sudden release of an ice or debris obstruction can cause excessive damage downstream.
Design to
Convey
the Regulatory Storm
Identify the high-water level, the flood- plain and path of the extreme event flow.
  • The high-water level, the flood plain and flow path for the regulatory flood should be determined.
  • The design of the structure may be changed to accommodate the regulatory flood.
  • There is a short and long term cost advantage to overtopping the approach rather than the structure. This should be considered without compromising the safety or the structural integrity of the crossing.
Determine the depth of flow at
  • the approach, and
  • over the structure.
  • The depth of flow should be acceptable. A determination of whether or not to allow for the passage of emergency vehicles should be made.
Impact on surrounding lands and structures.
  • Increased flooding of developable lands and structures should be assessed to ensure that the design requirements set by Directive B-100 are met.

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Mitigating Impacts to the Drainage System (Table 5)

Task Issue Relevance to MTO
Designing
Erosion
Protection
Measures
Provide scour and erosion control measures.
  • Channel training works required to protect the watercourse due to the introduction of the crossing should be properly designed.
  • Changes to the scope of the project may be associated with these requirements.
Design
Fish
Habitat
Protection
Measures
Design fish habitat protection measures.
  • Ensure the fish habitat requirements of DFO or MNR are identified with the option of compensation considered.
  • Ensure the flow velocities during migration periods do not exceed allowable flow velocities for migration of fish.
  • Confirm that the design of the fish habitat protection measures is structurally sound, functionally adequate and their hydraulic impacts are assessed and accounted for.
Address
Impacts
on Lands
and
Structures
Address impacts on lands and structures.
  • Account for the impact of extreme flow events on surrounding lands.
  • Address the issue of potential cost due to compensation for affected landowners.

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Finalizing Design and Construction Issues (Table 6)

Task Issue Relevance to MTO
Design
Bridge Deck
Drainage
Design bridge deck drainage.
  • Ensure conformance with the MTO Drainage Management Manual design standards and with the CHBDC requirements.
Complete the
Requirements
for Erosion
and Sediment
Control During
Construction
Complete the requirements for erosion and sediment control during construction.
  • Ensure MTO standards are met. Ensure no adverse impacts to the watercourse or downstream riparian land owners.
Recommending
the Best
Alternative
Recommending the best alternative.
  • Summarize all alternatives and clarify the differences after the completion of the design process.
  • Identify the recommendation of the designer. Provide the rationale for this recommendation.

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