Difference between revisions of "Wetlands"
Jump to navigation
Jump to search
Jenny Hill (talk | contribs) m (→Design) |
Jenny Hill (talk | contribs) m (→Design) |
||
| Line 57: | Line 57: | ||
|Length-to-Width Ratio | |Length-to-Width Ratio | ||
|Maximize flow path and minimize short-circuiting potential | |Maximize flow path and minimize short-circuiting potential | ||
| − | | | + | | |
| + | #Overall: minimum 3:1; | ||
| + | #Forebay: minimum 2:1 | ||
|- | |- | ||
|Permanent Pool Depth | |Permanent Pool Depth | ||
| Line 69: | Line 71: | ||
|Side Slopes | |Side Slopes | ||
|Safety | |Safety | ||
| − | | | + | | |
| + | #5:1 For 3 m above and below permanent pool; | ||
| + | #Maximum 3:1 elsewhere | ||
|- | |- | ||
|Inlet | |Inlet | ||
|Avoid clogging/freezing | |Avoid clogging/freezing | ||
| − | | | + | | |
| + | #Minimum 450 mm; | ||
| + | #Preferred pipe slope: >1%; | ||
| + | #If submerged, obvert 150 mm below expected maximum ice depth | ||
|- | |- | ||
|Outlet | |Outlet | ||
|Avoid clogging/freezing | |Avoid clogging/freezing | ||
| − | | | + | | |
| + | #Minimum: 450mm outlet pipe; | ||
| + | #Preferred pipe slope: >1%; | ||
| + | #If orifice control used, 75mm diameter minimum; | ||
| + | #Minimum 100mm orifice preferable | ||
|- | |- | ||
|Maintenance Access | |Maintenance Access | ||
|Access for backhoes or dredging equipment | |Access for backhoes or dredging equipment | ||
| − | | | + | | |
| + | #Provided to approval of Municipality; | ||
| + | #Provision of maintenance drawdown pipe preferred | ||
|- | |- | ||
|Buffer | |Buffer | ||
Revision as of 01:10, 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 |
|
| 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 |
|
| Inlet | Avoid clogging/freezing |
|
| Outlet | Avoid clogging/freezing |
|
| Maintenance Access | Access for backhoes or dredging equipment |
|
| 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]
Wetlands on the Rouge River, Toronto ON. Photo credit: Vlad Litvinov (flickr)
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).
Walberswick Mill sluice, part of the water level control and coastal defence infrastructure within the marshes, UK
