Ontario Stream Rehabilitation - Week 6

Barrier management: 1954 Hurricane Hazel

Massive flood for Ontario

After Hurricane Hazel we did what?

Conservation Authorities Created

Flood Protection Policies

The first dams were built by settlers (two reasons)

1.        Mill lumber and grind grain

2.         Create reservoirs for irrigation

Today, the Humber River (Toronto, ON)

>110 Anthropogenic obstructions (dams)

Post-1954, built dams to store floodwaters, where…

• Headwaters (minimize cumulative downstream impact)

• Dams interrupt the longitudinal gradient

• Form (shape), substrate, chemistry

• Although relatively short-lived, barriers are ”extreme cataclysmic

episodes” in the life cycle of a river (cataclysmic = destructive)

Impoundments - What happens?

• Nutrient and pollution traps

• Pollution: plants breakdown and release contaminants

• Nutrients can’t pass the dam, temperature heats up nutrients faster

Impoundments

Temp goes up and oxygen decreases

Eutrophication: water quality impact

The social problem?

Safety!

The social problem -safety

Older barriers risk failure

• A river will do whatever it can to be a river again.

The social problem? - Safety

• Natural heritage - fragmented population

• River Redhorse (Otonabee River, TSW) SAR

  • Atlantic salmon, Ganaraska River Migration

Sediment transport impacts…

Physical

Velocity Barriers

• Current too fast for fish

• Bad culvert design can create this hydrologic impact

Culverts are often preferred because?

Cheap and efficient at conveying water

Velocity Barriers

• Cheap and efficient at conveying water

• Perched = a new barrier

• Open bottom is best

• Slope of 0.5% and min. Depth of 25cm at low flow

Culvert Slope measurements

• Slope of 0.5% and min. Depth of 25cm at low flow

Concrete box culvert

It is too shallow and impedes fish passage

How do you eliminate these impacts? (Culverts)

-              Let the water out

-              Remove or partially remove an outlet conversion

-              top equals epiliminic flow, and the bottom equals hypoliliminc flow

Why do you want options for water depth?

-              This would tweak the temperature (hypo) and add oxygen and cool water.

So you are building a fishway? (Fish ladder)

Habitat: Quantity upstream and downstream = traffic motile species

-              Swimming capacities (burst speed and sustainability), the ladder won’t work if calculations are off.

Soil bioengineering

• Structural component for erosion protection

• Plant stems and roots

• Stronger and more effective as they age (H. Amirault)

• Terrestrial habitat too!

Soil bioengineering

• In Ontario what species?

• Willows, dogwoods, poplars

They are used because they grow fast and are tolerant to wet environments

 

• Collected when they are dormant

• No special storage if used within 12 hours

Cabled Log Jams  (Require tools to build)

-              Mimic natural log jams

-              Are anchored and accumulate and grow.

-              Cover for aquatic species

-              Old Christmas trees are used

-              Aircraft cable (stainless)

-              “T” bar posts

Stream rehabilitation techniques (Lecture)

Soil bioengineering and cabled log jams

Stream rehabilitation techniques:

1.        Barrier management

2.        Soil bioengineering 

3.        Habitat improvement

4.        Channel rehabilitation

Barrier Management definition

Barrier management evaluates environmental impacts of natural and artificial obstructions affecting river health.

Fishways

Fishways are structures designed to assist fishes in navigating around obstacles like dams and weirs during their migration and dispersal periods.

Soil bioengineering

A method for stabilizing and protecting eroded soils using plants and plant materials to reinforce soil integrity and prevent erosion. It utilizes living or dead vegetation, acting as both structural components and drainage mechanisms.

Cabled Log Jam

The cabled log-jam mimics natural log-jams, providing stability and functional habitat for aquatic life while maintaining river flow.