Difference between revisions of "Wetlands"
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==Planning considerations== | ==Planning considerations== | ||
==Design== | ==Design== | ||
{| class="wikitable" | |||
!Element | |||
!Design Objective | |||
!Criteria | |||
|- | |||
|Drainage Area | |||
|Sustaining vegetation, volumetric turnover | |||
|5 Ha (≥10 Ha preferred) | |||
|- | |||
|Treatment Volume | |||
|Provision of appropriate level of protection (Table 3.2) | |||
|See Table 3.2 | |||
|- | |||
|Active Storage | |||
|Detention | |||
|Suspended solids settling 24 hrs (12 hrs if in conflict with min. orifice size) | |||
|- | |||
|Forebay | |||
|Pre-treatment | |||
|Minimum depth: 1 m; ii) Sized to ensure non-erosive velocities leaving forebay; iii) Maximum area: 20 % of total permanent pool | |||
|- | |||
|Length-to-Width Ratio | |||
|Maximize flow path and minimize short-circuiting potential | |||
|i) Overall: minimum 3:1; ii) Forebay: minimum 2:1 | |||
|- | |||
|Permanent Pool Depth | |||
|Vegetation requirements, rapid settling | |||
|The average permanent pool depth should range from 150 mm to 300 mm | |||
|- | |||
|Active Storage Depth | |||
|Storage/flow control, sustaining vegetation | |||
|Maximum 1.0m for storms < 10 year event | |||
|- | |||
|Side Slopes | |||
|Safety | |||
|i) 5:1 For 3 m above and below permanent pool (ii) Maximum 3:1 elsewhere | |||
|- | |||
|Inlet | |||
|Avoid clogging/freezing | |||
|i) Minimum 450 mm; ii) Preferred pipe slope: >1%; iii) If submerged, obvert 150 mm below expected maximum ice depth | |||
|- | |||
|Outlet | |||
|Avoid clogging/freezing | |||
|i) Minimum: 450mm outlet pipe; ii) Preferred pipe slope: >1%; iii) If orifice control used, 75mm diameter minimum; (iv) Minimum 100mm orifice preferable | |||
|- | |||
|Maintenance Access | |||
|Access for backhoes or dredging equipment | |||
|(i) Provided to approval of Municipality; (ii) Provision of maintenance drawdown pipe preferred | |||
|- | |||
|Buffer | |||
|Safety | |||
|Minimum 7.5 m above maximum water quality/erosion control water level | |||
|} | |||
==Performance== | ==Performance== | ||
STEP (under previous name SWAMP) conducted their own research into the performance of stormwater wetlands, the project page and report can be viewed [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/conventional-stormwater-management/constructed-wetlands/performance-assessment-of-an-open-and-covered-stormwater-wetland-system-aurora-ontario/ here]. | STEP (under previous name SWAMP) conducted their own research into the performance of stormwater wetlands, the project page and report can be viewed [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/conventional-stormwater-management/constructed-wetlands/performance-assessment-of-an-open-and-covered-stormwater-wetland-system-aurora-ontario/ here]. |
Revision as of 01:07, 29 September 2018
Overview[edit]
Wetlands are an ideal technology for:
- Text A
- Text B
Type A | Type B | Type C |
---|---|---|
Surface water | Minimal Any surface flow can be slowed with check dams |
Ponding is encouraged with check dams |
Soil | Filter media required | Amendment preferable when possible |
Underdrain | Common | Uncommon |
Maintenance | Medium to high | Low |
Stormwater benefit | High | Moderate |
Biodiversity benefit | Increased with native planting | Typically lower |
Planning considerations[edit]
Design[edit]
Element | Design Objective | Criteria |
---|---|---|
Drainage Area | Sustaining vegetation, volumetric turnover | 5 Ha (≥10 Ha preferred) |
Treatment Volume | Provision of appropriate level of protection (Table 3.2) | See Table 3.2 |
Active Storage | Detention | Suspended solids settling 24 hrs (12 hrs if in conflict with min. orifice size) |
Forebay | Pre-treatment | Minimum depth: 1 m; ii) Sized to ensure non-erosive velocities leaving forebay; iii) Maximum area: 20 % of total permanent pool |
Length-to-Width Ratio | Maximize flow path and minimize short-circuiting potential | i) Overall: minimum 3:1; ii) Forebay: minimum 2:1 |
Permanent Pool Depth | Vegetation requirements, rapid settling | The average permanent pool depth should range from 150 mm to 300 mm |
Active Storage Depth | Storage/flow control, sustaining vegetation | Maximum 1.0m for storms < 10 year event |
Side Slopes | Safety | i) 5:1 For 3 m above and below permanent pool (ii) Maximum 3:1 elsewhere |
Inlet | Avoid clogging/freezing | i) Minimum 450 mm; ii) Preferred pipe slope: >1%; iii) If submerged, obvert 150 mm below expected maximum ice depth |
Outlet | Avoid clogging/freezing | i) Minimum: 450mm outlet pipe; ii) Preferred pipe slope: >1%; iii) If orifice control used, 75mm diameter minimum; (iv) Minimum 100mm orifice preferable |
Maintenance Access | Access for backhoes or dredging equipment | (i) Provided to approval of Municipality; (ii) Provision of maintenance drawdown pipe preferred |
Buffer | Safety | Minimum 7.5 m above maximum water quality/erosion control water level |
Performance[edit]
STEP (under previous name SWAMP) conducted their own research into the performance of stormwater wetlands, the project page and report can be viewed here.
Gallery[edit]
Emergent wetland vegetation supported by stormwater runoff at Kino Environmental Restoration Project. Photo by Matthew Grabau, US Fish and Wildlife Service
Azalea Park, Charlottesville VA - "This side of the park, formerly located along a runoff channel that led into Moore's Creek, has been converted into a wetland which supports a surprising amount of insect and amphibian life." -Credit and Photo: Scott Clark (certhia on Flickr).