Changes

New York City – “New York City has created a Green Infrastructure Plan and is committed to goals that include the construction of enough green infrastructure throughout the city to manage 10% of the runoff from impervious surfaces by 2030.”  cited in Mellilo et al 2014

New York City – “New York City has created a Green Infrastructure Plan and is committed to goals that include the construction of enough green infrastructure throughout the city to manage 10% of the runoff from impervious surfaces by 2030.”  cited in Mellilo et al 2014

Zahmatkhesh et al 2015 – NYC modelling study of LID vs no LID scenarios. Based on the model results, it was observed that future runoff volumes increased in comparison to historical runoff volumes due to expected increase in rainfall. The monthly runoff volumes decreased when looking at the with-LID scenarios. Runoff increases by 44% under a projected scenario without LIDs, while runoff decreases by 17% for with-LIDs scenario.  “Although the effect of LID implementation on projected runoff based on the maximum scenario was not considerable, future runoff corresponding to a 25-year return period for the mean P scenario will correspond to a 50-year event, and runoff corresponding to 5-year return period for minimum scenario will correspond to a 25-year event, for the same scenarios after using LIDs. The de- crease in runoff reduction was more for climate scenarios that had less precipitation for the future time period. Among the implemented LID types, porous pavement was noted to have the greatest effect on peak flow reduction. In summary, faced with uncertain future weather conditions considering the adverse impacts of cli- mate change, LIDs can provide mitigation benefits.”

Zahmatkhesh et al 2015 – NYC modelling study of LID vs no LID scenarios. Based on the model results, it was observed that future runoff volumes increased in comparison to historical runoff volumes due to expected increase in rainfall. The monthly runoff volumes decreased when looking at the with-LID scenarios. Runoff increases by 44% under a projected scenario without LIDs, while runoff decreases by 17% for with-LIDs scenario.  “Although the effect of LID implementation on projected runoff based on the maximum scenario was not considerable, future runoff corresponding to a 25-year return period for the mean P scenario will correspond to a 50-year event, and runoff corresponding to 5-year return period for minimum scenario will correspond to a 25-year event, for the same scenarios after using LIDs. The de- crease in runoff reduction was more for climate scenarios that had less precipitation for the future time period. Among the implemented LID types, porous pavement was noted to have the greatest effect on peak flow reduction. In summary, faced with uncertain future weather conditions considering the adverse impacts of cli- mate change, LIDs can provide mitigation benefits.”

“New York City is adopting this new stormwater rule to reduce the adverse impacts on City sewers from runoff during rainstorms that are more severe than combined sewers are designed to handle and, to the greatest extent possible, maximize the capacity of these systems. Sewer overflows, floods, and sewer backups can occur when excessive stormwater from impervious surfaces enters too quickly into the combined sewer system. The new Stormwater Rule will allow the City to more effectively manage stormwater runoff from new developments and alterations in combined sewer areas by reinforcing, specifying and prescribing the methods and standards for the application, permitting, construction and inspection of sewer connections to the City sewer system. DEP expects the rule to: ● slow the flow of stormwater from sites, ● mitigate flooding and sewer backups, ● protect the sewer system, and, ● mitigate combined sewer overflows.” The new rule is: “For a new development, the Stormwater Release Rate will be the greater of 0.25 cubic feet per second (cfs) or 10% of the Allowable Flow, unless the Allowable Flow is less than 0.25 cfs, in which case the Stormwater Release Rate shall be the Allowable Flow. (Allowable Flow means the stormwater flow from a development that can be released into an existing storm or combined sewer based on existing sewer design criteria.)”  The City Record, January 4, 2012, NYC (mode detail on this new rule is found in this document). More info found in http://www.sprlaw.com/new-york-city-adopts-new-stormwater-performance-standards-for-development-projects/

“New York City is adopting this new stormwater rule to reduce the adverse impacts on City sewers from runoff during rainstorms that are more severe than combined sewers are designed to handle and, to the greatest extent possible, maximize the capacity of these systems. Sewer overflows, floods, and sewer backups can occur when excessive stormwater from impervious surfaces enters too quickly into the combined sewer system. The new Stormwater Rule will allow the City to more effectively manage stormwater runoff from new developments and alterations in combined sewer areas by reinforcing, specifying and prescribing the methods and standards for the application, permitting, construction and inspection of sewer connections to the City sewer system. DEP expects the rule to:  

*slow the flow of stormwater from sites,  

*mitigate flooding and sewer backups,  

*protect the sewer system, and,  

*mitigate combined sewer overflows.”  

The new rule is: “For a new development, the Stormwater Release Rate will be the greater of 0.25 cubic feet per second (cfs) or 10 % of the Allowable Flow, unless the Allowable Flow is less than 0.25 cfs, in which case the Stormwater Release Rate shall be the Allowable Flow. (Allowable Flow means the stormwater flow from a development that can be released into an existing storm or combined sewer based on existing sewer design criteria.)” <ref>The City Record, January 4, 2012, NYC http://www.sprlaw.com/new-york-city-adopts-new-stormwater-performance-standards-for-development-projects/ </ref>

 

===Philadelphia===

===Philadelphia===

City of Philadelphia Green Streets Design Manual 2014 – “As we witness the effects of climate change causing storms of greater frequency and severity, the green infrastructure we build on our streets is an added safeguard that can help mitigate flash flooding during such events.”

City of Philadelphia Green Streets Design Manual 2014 – “As we witness the effects of climate change causing storms of greater frequency and severity, the green infrastructure we build on our streets is an added safeguard that can help mitigate flash flooding during such events.”