Difference between revisions of "Wetlands"
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Jenny Hill (talk | contribs) m (→Design) |
Jenny Hill (talk | contribs) m (→Design) |
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|Forebay | |Forebay | ||
|Pre-treatment | |Pre-treatment | ||
|Minimum depth: 1 m; | | | ||
#Minimum depth: 1 m; | |||
#Sized to ensure non-erosive velocities leaving forebay; | |||
#Maximum area: 20 % of total permanent pool | |||
|- | |- | ||
|Length-to-Width Ratio | |Length-to-Width Ratio |
Revision as of 01:08, 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 |
|
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).