Changes

==Strategies==

==Strategies==

===Disconnect impervious areas===  

===Disconnect impervious areas===  

Impervious areas have varying degrees of hydrologic impact depending on their connection to the receiving waterbody.  For example, impervious areas such as parking lots that drain directly to a concrete gutter and storm sewer will have a much greater impact than parking lots graded to drain to densely vegetated pervious areas.  Roof leaders or downspouts, parking lots, driveways, sidewalks, and patios should be disconnected from the storm sewer and directed towards stabilized pervious areas where possible (see [[downspout disconnection]] and [[vegetated filter strips]] for further design guidance).  Opportunities for directing impervious surface runoff to pervious areas are first considered during the site layout stage. Sheet flow should be encouraged from all impervious surfaces draining to pervious areas. In cases of concentrated flow, the flow can be broken up with level spreaders or flow dissipating riprap. Use the following guidance for the pervious runoff receiving areas:

Impervious areas have varying degrees of hydrologic impact depending on their connection to the receiving waterbody.  For example, impervious areas such as parking lots that drain directly to a concrete gutter and storm sewer will have a much greater impact than parking lots graded to drain to densely vegetated pervious areas.  Roof leaders or downspouts, parking lots, driveways, sidewalks, and patios should be disconnected from the storm sewer and directed towards stabilized pervious areas where possible (see [[downspout disconnection]] and [[vegetated filter strips]] for further design guidance).   

 

Opportunities for directing impervious surface runoff to pervious areas are first considered during the site layout stage. Sheet flow should be encouraged from all impervious surfaces draining to pervious areas. In cases of concentrated flow, the flow can be broken up with level spreaders or flow dissipating riprap. Use the following guidance for the pervious runoff receiving areas:

*Undisturbed densely vegetated areas and buffers – A hydrologist and/or ecologist should be consulted before designing a site to drain to sensitive natural heritage features like pocket wetlands.

*Undisturbed densely vegetated areas and buffers – A hydrologist and/or ecologist should be consulted before designing a site to drain to sensitive natural heritage features like pocket wetlands.

*Landscaped and disturbed areas – With the proper treatment, the landscaped areas of the site can accept runoff from impervious areas. Deep tilling or soil aeration is recommended for topsoil that has been replaced or compacted by construction equipment. Former agricultural lands tend to develop a “hardpan” or compacted layer 0.5-1 meter below the soil surface from repeated plowings and farm equipment. Breaking up the hardpan may improve infiltration rates. [[Soil amendments]] can be applied to hydrologic soil group (HSG) C and D soils to encourage runoff absorption. See Figure 3.2.5 for guidance. Use deep rooting vegetation in landscaped areas when possible which will maintain and possibly improve the infiltration rates over time.

*Landscaped and disturbed areas – With the proper treatment, the landscaped areas of the site can accept runoff from impervious areas. Deep tilling or soil aeration is recommended for topsoil that has been replaced or compacted by construction equipment. Former agricultural lands tend to develop a “hardpan” or compacted layer 0.5-1 meter below the soil surface from repeated plowings and farm equipment. Breaking up the hardpan may improve infiltration rates. [[Soil amendments]] can be applied to hydrologic soil group (HSG) C and D soils to encourage runoff absorption. See Figure 3.2.5 for guidance. Use deep rooting vegetation in landscaped areas when possible which will maintain and possibly improve the infiltration rates over time.