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Created page with "Gravel diaphragms are simply gravel filled trenches which act as inlet structures by redistributing concentrated flow to sheet flow: reducing the erosive power of the water an..."
Gravel diaphragms are simply gravel filled trenches which act as inlet structures by redistributing concentrated flow to sheet flow: reducing the erosive power of the water and promoting infiltration. They also act as a pretreatment by settling out sediment particles before they reach any downstream structure or practice.
{{TextBox|1=Gravel diaphragms are ideal for distributing flow and providing pretreatment for
*[[Bioretention cells]]
*[[Bioswales]]
*[[Enhanced grass swales]]
*[[Vegetated filter strips]]}}
===Planning considerations===
*Diaphragms can be designed along curves as readily as straight lines,
*As they are not a conveyance practice, they should be designed along a single contour line, promoting the level spreading function,
*Flow should be directed into the device laterally,
===Design===
*Where flow comes off an impervious surface, a drop of 75 mm or more to the surface level of the diaphragm is recommended,
*Typical dimensions for the trench excavation are 300 mm deep and 600 mm wide. The trench may be any length,
*The trench should be lined with before filling with gravel,
*River rock or decorative aggregate may be included in a layer at the top of the gravel fill, for aesthetic value.
===Materials===
<h4>Geotextile</h4>
{{:geotextiles}}
<h4>Gravel</h4>
{{:Pea gravel}}
===References===
[http://vwrrc.vt.edu/swc/april_22_2010_update/DCR_BMP_Spec_No_2_SHEET_FLOW_Final_Draft_v1-8_04132010.htm|VIRGINIA DCR STORMWATER DESIGN SPECIFICATION No. 2]
{{:Feedback}}
{{TextBox|1=Gravel diaphragms are ideal for distributing flow and providing pretreatment for
*[[Bioretention cells]]
*[[Bioswales]]
*[[Enhanced grass swales]]
*[[Vegetated filter strips]]}}
===Planning considerations===
*Diaphragms can be designed along curves as readily as straight lines,
*As they are not a conveyance practice, they should be designed along a single contour line, promoting the level spreading function,
*Flow should be directed into the device laterally,
===Design===
*Where flow comes off an impervious surface, a drop of 75 mm or more to the surface level of the diaphragm is recommended,
*Typical dimensions for the trench excavation are 300 mm deep and 600 mm wide. The trench may be any length,
*The trench should be lined with before filling with gravel,
*River rock or decorative aggregate may be included in a layer at the top of the gravel fill, for aesthetic value.
===Materials===
<h4>Geotextile</h4>
{{:geotextiles}}
<h4>Gravel</h4>
{{:Pea gravel}}
===References===
[http://vwrrc.vt.edu/swc/april_22_2010_update/DCR_BMP_Spec_No_2_SHEET_FLOW_Final_Draft_v1-8_04132010.htm|VIRGINIA DCR STORMWATER DESIGN SPECIFICATION No. 2]
{{:Feedback}}