the Bull Trout
Proper fish passage is essential to meet Department
of Fisheries and Oceans requirements in the Foothills
Natural Region, and it may take an engineered culvert
to do the job.
BY KAREN HALWAS
Senior Aquatic Ecologist
As land development in Alberta continues, new transportation
corridors are being built to allow access to formerly remote
areas. Where access roads dissect slopes, streams are encountered
and vehicle-crossing structures required.
Among other areas in Alberta, the Foothills Natural Region,
which extends north from Turner Valley along the eastern edge
of the Rocky Mountains, is affected by land development projects.
This article focuses on access road construction in the Foothills
Natural Region. It's also an appeal for ideas to help resolve
a culvert dilemma, which comes out of the region's special
circumstances and the warranted need to protect a sensitive
The Foothills are characterized by rolling topography. The
Upper Foothills Sub-region has a mean annual precipitation
of about 540 millimetres, which ranks this region among the
wettest in the province.
As a result, streams that drain the slopes are small and
frequent. These small streams, typically located in the headwater
areas of drainage systems, often do not possess preferred
fish habitat and, therefore, are unlikely to support fish.
Land developers often choose round, metal culverts to cross
such streams because culverts are relatively easy to obtain
and install and, therefore, are economical. In addition, culverts
are assumed to be a viable option under the circumstances
described since no specific regulation states they are not.
The Trouble With Culverts
Much of the Foothills Natural Region falls within the portion
of the province known as the Green Area. The Public Lands
Act of Alberta regulates culverts less than or equal to 1.5
metres in diameter in the Green Area. Under this legislation,
these culverts may be installed without the input of a professional
The Department of Fisheries and Oceans Habitat Management
Division also does not explicitly require engineered culvert
designs. However, an engineered design may help satisfy DFO's
policy of "no net loss of productive capacity of fish
habitat" by ensuring fish passage requirements are met.
Improperly designed and installed culverts can create fish
migration barriers as a result of five common conditions:
- excess drop at culvert outlet.
- high velocity within culvert barrel.
- inadequate depth within culvert barrel.
- turbulence within the culvert.
- debris accumulation at culvert inlet.
Migration barriers may render suitable habitat inaccessible
to fish. For example, the upper watershed may be unreachable
by downstream fish populations or fish above the barrier may
Enter the Bull Trout
Coincident with a large portion of the Foothills Natural
Region is the range for bull trout (Salvelinus confluentus).
In Alberta this species is distributed along the Continental
Divide. Compared to its relatives, the bull trout has the
most extensive natural range in Alberta and is considered
by many to be uniquely Albertan.
Bull trout have suffered population fragmentation and decline
throughout their range as a result of over harvest, displacement
by introduced species, and habitat degradation. Bull trout
is a "sensitive" species, which means that it is
not at risk of extinction or extirpation, but it may require
special attention or protection to prevent it from becoming
For these reasons, provincial and federal resource managers
intend to protect bull trout from further decline and are
taking steps to ensure its population recovery. These steps
may include the prevention and removal of migration barriers.
Given the risks to fish habitat associated with culverts
and the status of bull trout, resource managers are hesitant
to authorize the installation of new culverts in regions frequented
by this species, regardless of site conditions such as stream
size and habitat quality. Clear-span structures are the favoured
watercourse crossing structures from an environmental point
While industry generally supports the use of clear-span structures
to maintain aquatic habitat quality, it is becoming increasingly
concerned that an unconditional no-culverts policy is being
Clearly, concern for bull trout and other valued species
is warranted. However, the requirement for clear-span structures
across every hillside trickle may undermine the growing respect
between land developers and regulators.
A Practical Solution?
Clearly, round, metal culverts are not the preferred crossing
structure for streams with high quality habitat and the ability
to support bull trout. On the other hand, culverts are the
preferred crossing structure for drainages that lack fish
habitat and act as conduits for surface runoff only.
Central to the culvert dilemma are streams that have little
to no potential to support fish but are located in areas with
sensitive environmental issues. If land developers build culverts
for small streams in sensitive areas that will pass fish,
even if fish presence seems highly unlikely, will regulators
be more willing to approve culverts? This question remains
to be answered.
Without legislation to ensure culverts equal or less than
1.5 m in diameter to be installed in the Green Area are designed
by a professional engineer, it's unlikely industry will have
small culvert designs stamped by an engineer. Therefore, how
can fish passage be ensured and the concerns of regulators
Can a round, metal culvert be installed using a generic design
(one that does not require a site-specific design and the
stamp of a professional engineer) to minimize cost and maximize
fish passage potential in streams that are not likely to support
While the answer may lie in the large body of literature concerned
with culverts and fish passage (see Moore et al 1999), a more
practical and cost-effective solution likely will be required.
If you have a possible solution, please contact me at email@example.com.