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Appendix 3 - risk factors, evaluation parameters and decision criteria for evaluating the risk of proposed water crossings to fish and fish habitat

Appendix 3 table details the numerous risk factors, evaluation parameters and decision criteria that are intended to support Ministry of Natural Resources (MNR) staff in their evaluation of risk for proposed water crossings. Appendix 3 does not assign priority to any individual or combination of risk factors, and it is not assumed that one or more of the evaluation parameters that are within “medium” or “high” risk decision criteria will necessarily shift a project into a similar risk assessment category.

Appendix 3 table should be used in conjunction with Department of Fisheries and Oceans (DFO) Pathways of Effects (PoE) diagrams to better understand the type of cause-effect relationships that are known to exist and the mechanisms by which stressors ultimately lead to effects in the aquatic environment.

The ministry reviewers should utilize the contents of appendix 3 table as a collection of considerations, together with local knowledge, site conditions and fishery management objectives that help to inform the development of appropriate avoidance and mitigation measures to reduce or eliminate the potential effects of proposed projects.

Table - risk factors, evaluation parameters and decision criteria for evaluating the risk of proposed water crossings to fish and fish habitat

Risk factor: fish presence

Evaluation parameters	Low risk / decision criteria	Medium risk / decision criteria	High risk / decision criteria	Information source	Rationale
Channel type (permanent, intermittent, ephemeral)	Intermittent ephemeral	Permanent	Permanent	Topographic maps Aerial photographs Forest resource inventory maps	Permanent streams are accepted to support fish and thus have fish habitat associated with them.
Watershed area	Very small watersheds, no significant water surface area	Small watersheds	Large watersheds; significant water surface area	Topographic maps Aerial photographs Forest resource inventory maps	The probability of fish being present at a site is correlated with stream size. Watershed area and stream order are indicators of stream size. The threshold watershed size varies with the species, stream characteristics (slope, etc.) and geographic/physiographic area.
Watershed position (1:20,000) Stream order/	1^st order (unless flows directly to 3^rd order or higher or known fish-bearing water)	2^nd order (unless flows directly to 3^rd order or higher or known fish-bearing water)	3^rd order and greater	Topographic maps Aerial photographs Forest resource inventory maps	N/A
Barriers that would prevent fish passage	Physical - downstream	Physical -downstream; passable only in some years	None	Topographic maps Aerial photographs	Temporary natural (beaver dam) or man-made barriers should not be considered as indicators of the probability of fish being absent upstream.
Fish presence	Confirmed absent from similar/nearby watersheds	N/A	Confirmed present in similar/nearby watersheds	Lake surveys Research Investigations Public reports Direct observations	N/A
Fish community sensitivity	Generalist	N/A	Specialist	Lake surveys Research Investigations Public reports Direct observations Land Information Ontario (LIO)	Scientific literature Decision support tools Generalist/specialist can refer to habitat requirements or life history depending on context, and varies with life stage, e.g. brook trout and walleye are specialists, and bass are generalists.
Species at Risk	Absent	Potentially present	Present	LIO For the Species At Risk in Ontario (SARO) list please refer to the ministry website or Environment Canada’s website or DFO's species at risk maps	N/A
Habitat type: spawning, rearing, nursery, feeding, migration	Marginal	Important	Critical	LIO Aerial photographs Surveys Research Direct observations	Look at fish habitat at the proposed crossing site, downstream and upstream of the proposed crossing site.
Area impacted (total habitat impacted m²)	Small streams; narrow flood plains; relatively short structures (low fills)	N/A	Large streams; causeways; long structures (high fill, wide road)	Aerial photographs Direct observations	Depending on the type of structure, the area impacted may be reduced. For example, portable bridges would generally impact a smaller area than culverts.
Productive capacity	Bedrock/sand substrate, dystrophic waters, no cover	N/A	Aquatic macrophytes; silt/sand, cobble/ boulder substrate, instream or overhead cover	Aerial photographs Soils maps Direct observations	N/A
Substrate (habitat sensitivity)	Bedrock	N/A	Sand, gravel, cobble; groundwater discharge	Aerial photographs Soils maps Surficial geology Maps Direct observations	N/A
Habitat supply	High	Medium	Low	LIO Aerial photographs Surveys Research Direct observations	If habitat is in low supply, any impacts to that habitat by construction of the crossing elevate the risk to fish that use that habitat.
Cumulative impact	No other developments in area	Water crossings in area	Other developments in area or large numbers of crossings already in the watershed	LIO Sustainable forest licensee maps of roads and water crossings	This parameter relates to the density of development in the watershed.
Potential for fishery	Low probability	Possible	Existing	Ministry files Knowledge	N/A

Risk factor: fish passage

Risk factor	Evaluation parameters	Low risk / decision criteria	Medium risk / decision criteria	High risk / decision criteria	Information source	Rationale
Structure installation	Slope of channel at structure location	<0.5%	0.5-2.0%	>2.0%	Topographic maps Digital terrain model Aerial photographs Decision support tools (OFAT	The risk associated with a specific slope varies with stream size and substrate characteristics. As slope increases, it is more likely that a culvert cannot be properly embedded due to coarser substrates. A culvert installed where the channel is sloped will have higher water velocity during high flows; low water depth during low flows and is less likely to have natural channel substrates inside the structure.
Structure installation	Channel substrate	Sand and gravel	Cobble	Boulders and bedrock	Direct observation Aerial photographs Surficial geology Maps	The risk associated with a specific slope varies with stream size and substrate characteristics. As slope increases, it is more likely that a culvert cannot be properly embedded due to coarser substrates. A culvert installed where the channel is sloped will have higher water velocity during high flows; low water depth during low flows and is less likely to have natural channel substrates inside the structure.
Structure sizing	Design flow	25 year or greater	10 year	5 year	Supplied by sustainable forest licensee	Structures with lower design flows, or which constrict flows (prevent access to floodplain), will have higher water velocity
Structure sizing	Structure width relative to channel or flood plain width	>1.0%	0.5 – 1.0%	<0.5%	Direct observation Aerial photographs	N/A
Structure sizing	Changes to water velocity	Little change or low velocities	Some change or moderate velocities	Substantial change or high velocities	Installation practices at crossing provided by sustainable forest licensee Published literature on fish swimming abilities (DFO's SPOT tool	High water velocities can act as barriers to fish passage. The influence of water velocity is different for each species.
Base flow depth	Water depth in structure	>20cm (depth adequate for most migrating fish, sturgeon may be an exception)	10 cm	<5 cm	Digital terrain model Topographic maps	Beaver dams should not be considered barriers to fish movement because they are a natural influence on most watercourses. Beaver dams are generally temporary in nature. DFO's Interim code of practice: beaver dam removal should also be followed.
Fish present	Barriers	Other barrier to fish movement immediately downstream	N/A	No barriers	Aerial photographs Direct observation	N/A

Risk factor: erosion/sedimentation

Risk factor	Evaluation parameters	Low risk / decision criteria	Medium risk / decision criteria	High risk / decision criteria	Information source	Rationale
Erosion and sedimentation from on land activities	Slope of approaches	1 – 4% 0-15% (0-8°)	5 – 8% 16-30% (9-17°)	9 – 12% 31-45% (18-24°) Extreme >12% > 46% (>25°)	Digital terrain model Slopes provided by Regional Engineering Unit.	Stream valley cross-section describes the slope of the approaches and potential for erosion.
Erosion and sedimentation from on land activities	Length of approaches to top of bank	0 to 10 metres	10 to 50 metres	> 50 metres	Information supplied by sustainable forest licensee	Approaches sloping to water crossings are sources of sediment through runoff which is exacerbated through improper grading.
Short-term sediment and direct impacts to fish	Timing (species occurrence or thermal regime)	Construction outside the timing window	N/A	Construction inside the timing window	Information supplied by sustainable forest licensee	N/A
Short-term sediment and direct impacts to fish	Installation method	Isolated from flowing water	N/A	In stream	Information supplied by sustainable forest licensee	N/A
Short-term sediment and direct impacts to fish	Planning and practitioner proficiency	All of listed items	1 or 2 of listed items	None of listed items	Information supplied by sustainable forest licensee ministry training records Compliance records	Proficiency list: sustainable forest licensee procedures sound practical experience water crossing Installation training training in use of guidelines
Long-term (change to natural channel processes) Long-term (change to natural channel processes) C	Soils on banks	Bedrock, stony	Loam, clay	Sand, silt	Surficial geology maps	Type of soil influences erodibility
Long-term (change to natural channel processes) Long-term (change to natural channel processes) C	Stream type (Rosgen 1996)	Bedrock dominated, entrenched, step, pool Aa+, A, B,	Meandering but not entrenched, stable banks, riffle/pool C, D, E	Entrenched and actively meandering, unstable (braided channel) – relocate crossing F, G	Rosgen, 1996	The influence of stream type must be considered within the context of channel slope (see Structure installation) and the type of structure proposed for installation at the site.
Long-term (change to natural channel processes) Long-term (change to natural channel processes) C	Changes to water velocity	Little change or low velocities	Some change or moderate velocities	Substantial change or high velocities	Installation practices at crossing provided by sustainable forest licensee	Changing the water velocity and alignment of the flow can cause downstream erosion.
Long-term (change to natural channel processes)	Fill height	1 – 1.5 metres	1.6 -3.9	4.0 + metres	Information supplied by sustainable forest licensee	Higher fill heights mean there is greater surface area for water to impact, even if graded to a stable angle of repose. Stabilization of fill slopes would lower risk. Fill acts as a dam and the greater the fill height, the more head and risk of ‘piping’ through the fill.
Long-term (change to natural channel processes)	Fill material	Rock, cobble	Pit run gravel	Sand, silt, clay	Information supplied by sustainable forest licensee	N/A
Crossing failure	Design flow	25 year or greater	10 year	5 year	Information supplied by sustainable forest licensee	The risk of catastrophic failure
Crossing failure	Fill type	Rock, pit run gravel	Loam, clay	Sand, silt	Information supplied by sustainable forest licensee	Fill type influences erodibility and hence the likelihood of failure.
Downstream fish habitat occurrence	Downstream habitat type	Marginal	Important	Critical	LIO Aerial photographs Surveys Research Direct observations	If a chronic or catastrophic sedimentation event occurs, downstream habitat may be directly or indirectly impacted. Distance downstream at which an impact will occur is dependent upon flow, velocity and type of material being transported. Professional judgment is used to identify how far downstream habitat may be impacted.

Updated: August 07, 2024

Published: June 16, 2021