Changes

===Water quality impacts===

===Water quality impacts===

The surface runoff generated in urban areas frequently carries with it a cocktail of pollutants.  Although it is variable in nature, runoff pollutants are typically derived from a combination of fine sediments from atmospheric deposition, oil, grease and [[heavy metals]] (including Cd, Cu, Fe, Ni, Pb, Zn, etc.) from vehicular traffic and industrial activities, nutrients derived from lawn fertilizers and pet waste, and – in seasonally cold climates – road salts from [[winter]] maintenance activities <ref>Aryal, R. Vigneswaran, S. Kandasamy, J.; Naidu, R. 2010. Urban Stormwater Quality and Treatment. Korean Journal of Chemical Engineering, 27(5):1343-1359</ref> <ref> Trenouth, W.R. Gharabaghi, B., Perera, N. 2015. Road salt application planning tool for winter de-icing operations. Journal of Hydrology. 524:401-410</ref>. These pollutants accumulate on the road surface during the antecedent dry period between consecutive rainfall events, and are washed off at the onset of rainfall. The majority of particles are washed off with the first flush of stormwater runoff, typically considered to be accounted for with the first 25 mm, or one inch or runoff <ref>Stenstrom, M.K. Kayhanian, M. 2005. First flush phenomenon characterization. Prepared for California Department of Transportation, Division of Environmental Analysis. Available at URL: http://www.dot.ca.gov/hq/env/stormwater/pdf/CTSW-RT-05-073-02-6_First_Flush_Final_9-30-05.pdf</ref>.

The surface runoff generated in urban areas frequently carries with it a cocktail of pollutants.  Although it is variable in nature, runoff pollutants are typically derived from a combination of fine sediments from atmospheric deposition, oil, grease and [[heavy metals]] (including Cd, Cu, Fe, Ni, Pb, Zn, etc.) from vehicular traffic and industrial activities, nutrients derived from lawn fertilizers and pet waste, and – in seasonally cold climates – road [[salt]] from winter maintenance activities <ref>Aryal, R. Vigneswaran, S. Kandasamy, J.; Naidu, R. 2010. Urban Stormwater Quality and Treatment. Korean Journal of Chemical Engineering, 27(5):1343-1359</ref> <ref> Trenouth, W.R. Gharabaghi, B., Perera, N. 2015. Road salt application planning tool for winter de-icing operations. Journal of Hydrology. 524:401-410</ref>. These pollutants accumulate on the road surface during the antecedent dry period between consecutive rainfall events, and are washed off at the onset of rainfall. The majority of particles are washed off with the first flush of stormwater runoff, typically considered to be accounted for with the first 25 mm, or one inch or runoff <ref>Stenstrom, M.K. Kayhanian, M. 2005. First flush phenomenon characterization. Prepared for California Department of Transportation, Division of Environmental Analysis. Available at URL: http://www.dot.ca.gov/hq/env/stormwater/pdf/CTSW-RT-05-073-02-6_First_Flush_Final_9-30-05.pdf</ref>.

==Alleviating pressures using LID==

==Alleviating pressures using LID==