Changes

<h3>Post-Development Hydrologic Changes</h3>

<h3>Post-Development Hydrologic Changes</h3>

'''Water Quantity Changes'''

'''Water Quantity Changes'''

While rainfall intensity, soil and vegetation characteristics, slope length and steepness all play a role in the timing and rate of runoff generation, the creation of impervious surfaces – including rooftops, driveways, roads and parking lots – disrupts rainfall’s ability to penetrate the soil surface and infiltrate.  In heavily urbanized, well-drained areas, the time of concentration is significantly reduced due to the relative smoothness of impervious surfaces, and the dense network of stormwater conveyance infrastructure including gutters, catch basins and subsurface pipes.  

While rainfall intensity, soil and vegetation characteristics, slope length and steepness all play a role in the timing and rate of runoff generation, the creation of impervious surfaces – including rooftops, driveways, roads and parking lots – disrupts rainfall’s ability to penetrate the soil surface and infiltrate.  In heavily urbanized, well-drained areas, the time of concentration is significantly reduced due to the relative smoothness of impervious surfaces, and the dense network of stormwater conveyance infrastructure including gutters, catch basins and subsurface pipes.  

'''Climate-Related Impacts'''

'''Climate-Related Impacts'''

Since 1995, Ontario has had a weather-related state of emergency almost every single year (Swiss Re, 2010). The City of Windsor saw extreme events that caused severe flooding in 2007, 2010, 2016 and 2017 (City of Windsor, 2012). The Ottawa region experienced one extreme event every year for five years, and in the Greater Toronto Area (GTA), there have been four extreme rainfall events in the past ten years (Environment Canada, 2014). Such high intensity events produce heavy rainfall in relatively short periods of time. While it is reasonable to expect runoff to be produced under such conditions – particularly when rain falls which exceeds a soil’s hydraulic conductivity - the production of stormwater is exacerbated in urban areas where the overwhelming majority of surfaces are impervious. The problems associated with managing stormwater volumes are exacerbated when dense stormsewer networks efficiently convey stormwater runoff volumes from a large contributing upland area to a single outlet location, such as a stormsewer outfall in a river or stream.

Since 1995, Ontario has had a weather-related state of emergency almost every single year (Swiss Re, 2010). The City of Windsor saw extreme events that caused severe flooding in 2007, 2010, 2016 and 2017 (City of Windsor, 2012). The Ottawa region experienced one extreme event every year for five years, and in the Greater Toronto Area (GTA), there have been four extreme rainfall events in the past ten years (Environment Canada, 2014). Such high intensity events produce heavy rainfall in relatively short periods of time. While it is reasonable to expect runoff to be produced under such conditions – particularly when rain falls which exceeds a soil’s hydraulic conductivity - the production of stormwater is exacerbated in urban areas where the overwhelming majority of surfaces are impervious. The problems associated with managing stormwater volumes are exacerbated when dense stormsewer networks efficiently convey stormwater runoff volumes from a large contributing upland area to a single outlet location, such as a stormsewer outfall in a river or stream.

'''Alleviating Pressures Using Low Impact Approaches to Development'''

'''Alleviating Pressures Using Low Impact Approaches to Development'''

There are many reasons that make LID the smart choice when it comes to stormwater management. The creation of well-designed permeable landscapes provides an opportunity to capture, retain and infiltrate stormwater runoff close to its source.  Rather than treat stormwater as a waste product to be discarded, LID recognizes stormwater for what it is – a resource to be safeguarded and harnessed for the benefit of both the built and natural environment.

There are many reasons that make LID the smart choice when it comes to stormwater management. The creation of well-designed permeable landscapes provides an opportunity to capture, retain and infiltrate stormwater runoff close to its source.  Rather than treat stormwater as a waste product to be discarded, LID recognizes stormwater for what it is – a resource to be safeguarded and harnessed for the benefit of both the built and natural environment.