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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| Line 38: | Line 38: | ||
|Drainage Area | |Drainage Area | ||
|Sustaining vegetation, volumetric turnover | |Sustaining vegetation, volumetric turnover | ||
| − | |5 Ha (≥10 Ha preferred) | + | |style="text-align: left|5 Ha (≥10 Ha preferred) |
|- | |- | ||
|Treatment Volume | |Treatment Volume | ||
|Provision of appropriate level of protection (Table 3.2) | |Provision of appropriate level of protection (Table 3.2) | ||
| − | |See Table 3.2 | + | |style="text-align: left|See Table 3.2 |
|- | |- | ||
|Active Storage | |Active Storage | ||
|Detention | |Detention | ||
| − | |Suspended solids settling 24 hrs (12 hrs if in conflict with min. orifice size) | + | |style="text-align: left|Suspended solids settling 24 hrs (12 hrs if in conflict with min. orifice size) |
|- | |- | ||
|Forebay | |Forebay | ||
|Pre-treatment | |Pre-treatment | ||
| − | | | + | |style="text-align: left| |
#Minimum depth: 1 m; | #Minimum depth: 1 m; | ||
#Sized to ensure non-erosive velocities leaving forebay; | #Sized to ensure non-erosive velocities leaving forebay; | ||
| Line 63: | Line 63: | ||
|Permanent Pool Depth | |Permanent Pool Depth | ||
|Vegetation requirements, rapid settling | |Vegetation requirements, rapid settling | ||
| − | |The average permanent pool depth should range from 150 mm to 300 mm | + | |style="text-align: left|The average permanent pool depth should range from 150 mm to 300 mm |
|- | |- | ||
|Active Storage Depth | |Active Storage Depth | ||
|Storage/flow control, sustaining vegetation | |Storage/flow control, sustaining vegetation | ||
| − | |Maximum 1.0m for storms < 10 year event | + | |style="text-align: left|Maximum 1.0m for storms < 10 year event |
|- | |- | ||
|Side Slopes | |Side Slopes | ||
|Safety | |Safety | ||
| − | | | + | |style="text-align: left| |
#5:1 For 3 m above and below permanent pool; | #5:1 For 3 m above and below permanent pool; | ||
#Maximum 3:1 elsewhere | #Maximum 3:1 elsewhere | ||
| Line 77: | Line 77: | ||
|Inlet | |Inlet | ||
|Avoid clogging/freezing | |Avoid clogging/freezing | ||
| − | | | + | |style="text-align: left| |
#Minimum 450 mm; | #Minimum 450 mm; | ||
#Preferred pipe slope: >1%; | #Preferred pipe slope: >1%; | ||
| Line 84: | Line 84: | ||
|Outlet | |Outlet | ||
|Avoid clogging/freezing | |Avoid clogging/freezing | ||
| − | | | + | |style="text-align: left| |
#Minimum: 450mm outlet pipe; | #Minimum: 450mm outlet pipe; | ||
#Preferred pipe slope: >1%; | #Preferred pipe slope: >1%; | ||
| Line 92: | Line 92: | ||
|Maintenance Access | |Maintenance Access | ||
|Access for backhoes or dredging equipment | |Access for backhoes or dredging equipment | ||
| − | | | + | |style="text-align: left| |
#Provided to approval of Municipality; | #Provided to approval of Municipality; | ||
#Provision of maintenance drawdown pipe preferred | #Provision of maintenance drawdown pipe preferred | ||
| Line 98: | Line 98: | ||
|Buffer | |Buffer | ||
|Safety | |Safety | ||
| − | |Minimum 7.5 m above maximum water quality/erosion control water level | + | |style="text-align: left|Minimum 7.5 m above maximum water quality/erosion control water level |
|} | |} | ||
Revision as of 01:13, 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
