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Berms can be used to direct flow of water through permanent ponds, ephemeral pools and [[wetlands]], or on slopes with [[vegetated filter strips]].
Berms can be used to direct flow of water through permanent ponds, ephemeral pools and [[constructed wetlands]], or on slopes with [[vegetated filter strips]].
They may be utilised to divert water through the wetland, creating a longer flow path. This increases the efficiency of the system by increasing the hydraulic residence time. The top of the banks may be below or above water level. Flow diversion banks are usually submerged at nominal operating level.
They may be utilised to divert water through the wetland, creating a longer flow path. This increases the efficiency of the system by increasing the hydraulic residence time. The top of the banks may be below or above water level. Flow diversion banks are usually submerged at nominal operating level.
===Height===
===Height===
* Freeboards should be adequate to prevent over-topping during storm events and allow overflow of less frequent storm events through controlled and protected emergency overflow points. Berm freeboards should also consider berm soil consolidation and subsidence, and also that the wetland can gradually fill with vegetation and with sediments which increase flow resistance and decrease freeboard during wetland life.
* [[Freeboard]]s should be adequate to prevent over-topping during storm events and allow overflow of less frequent storm events through controlled and protected emergency overflow points. Berm freeboards should also consider berm soil consolidation and subsidence, and also that the wetland can gradually fill with vegetation and with sediments which increase flow resistance and decrease freeboard during wetland life.
* Controlled overflow points that are riprapped dips in the surface or concrete weirs should be incorporated into the top of the berm of each wetland cell so that if the wetland is overtopped the flow exiting the wetland does not cut channels into the top of the berm that could compromise the integrity of the berm.
* Controlled [[overflow]] points that are rip-rapped dips in the surface or concrete [[weirs]] should be incorporated into the top of the berm of each [[wetland]] cell so that if the wetland is overtopped the flow exiting the wetland does not cut channels into the top of the berm that could compromise the integrity of the berm.
===Top width===
===Top width===
===Slope===
===Slope===
Berm slope is dictated by geotechnical considerations and slope-stability analysis.
Berm [[slope]] is dictated by geotechnical considerations and slope-stability analysis.
*Maximum berm slopes typically used are 2:1 (horizontal: vertical).
*Maximum berm slopes typically used are 2:1 (horizontal: vertical).
* However, it is better to keep slopes at 3.5:1 or lower angle to minimize sloughing of the slopes into the wetlands while maximizing wetted area in the wetlands.
* However, it is better to keep slopes at 3.5:1 or lower angle to minimize sloughing of the slopes into the wetlands while maximizing wetted area in the wetlands.
* Slopes up to 10:1 or 20:1 are used when a shallow littoral shelf is desired to create vegetation and habitat diversity. The side slopes may be rip-rapped with stone to reduce the potential for erosion or rodent burrowing.
* Slopes up to 10:1 or 20:1 are used when a shallow littoral shelf is desired to create vegetation and habitat diversity. The side slopes may be rip-rapped with stone to reduce the potential for erosion or rodent burrowing.
<ref>CH2MHill. (2014). Wetland Design Guidelines City of Saskatoon. Retrieved from https://www.saskatoon.ca/sites/default/files/documents/transportation-utilities/construction-design/new-neighbourhood-design/wetlands_design_guidelines.pdf</ref>
<ref>CH2MHill. (2014). Wetland Design Guidelines City of Saskatoon. Retrieved from https://www.saskatoon.ca/sites/default/files/documents/transportation-utilities/construction-design/new-neighbourhood-design/wetlands_design_guidelines.pdf</ref>
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