Changes

IDF curves are developed from long-term rainfall records and models and are widely used to estimate design storms for stormwater management. IDF curves are crucial for [[Bioretention: Sizing|sizing LID]] BMPs because they:

IDF curves are developed from long-term rainfall records and models and are widely used to estimate design storms for stormwater management. IDF curves are crucial for [[Bioretention: Sizing|sizing LID]] BMPs because they:

# '''Define design storms:''' LIDs must be able to manage runoff from specific return-period events (e.g., 2-year or 10-year storms). IDF curves provide the rainfall intensity and depth to use for those design events.  

# '''Define design storms:''' LIDs must be able to manage runoff from specific return-period events (e.g., 2-year or 10-year storms). IDF curves provide the rainfall intensity and depth to use for those design events.  

# '''Determine [[Runoff volume control targets|runoff volumes]]:''' By applying rainfall depth (from IDF data) to a given catchment, engineers estimate the stormwater volume that LIDs need to capture, [[infiltration|infiltrate]], or detain (USDA, 2021)<ref>USDA. 2021. Estimating Runoff Volume and Peak Discharge. https://directives.nrcs.usda.gov/sites/default/files2/1712930818/31754.pdf</ref>.

# '''Determine [[Runoff volume control targets|runoff volumes]]:''' By applying rainfall depth (from IDF data) to a given catchment, the stormwater volume that LIDs need to capture, [[infiltration|infiltrate]], or detain can be estimated (USDA, 2021)<ref>USDA. 2021. Estimating Runoff Volume and Peak Discharge. https://directives.nrcs.usda.gov/sites/default/files2/1712930818/31754.pdf</ref>.

# '''Assess peak flows:''' LID facilities are often designed to reduce peak discharge. IDF curves help simulate storm hydrographs and assess how much peak flow reduction is required (City of Toronto, 2006) <ref>City of Toronto. 2006. Wet Weather Flow Management. https://www.toronto.ca/wp-content/uploads/2017/11/9191-wwfm-guidelines-2006-AODA.pdf</ref>.  

# '''Assess peak flows:''' LID facilities are often designed to reduce peak discharge. IDF curves help simulate storm hydrographs and assess how much peak flow reduction is required (City of Toronto, 2006) <ref>City of Toronto. 2006. Wet Weather Flow Management. https://www.toronto.ca/wp-content/uploads/2017/11/9191-wwfm-guidelines-2006-AODA.pdf</ref>.  

# '''Account for climate change:''' Historical data is no longer an accurate predictor of future extreme rainfall (CSA, 2025)<ref name = CSA2025>CSA, 2025. CSA 231:25 Developing and interpreting intensity-duration-frequency (IDF) information under a changing climate. https://www.csagroup.org/store/product/2431590/?srsltid=AfmBOopkRT3cosyCstZMacCmlthJxgfo6w6aFIXyuEExGmyBT8zw1vMs </ref>. Since IDF curves are based on historical data, climate change-scaled IDFs can be used to design LIDs that are resilient under future rainfall conditions (ECCC, 2025)<ref name = ECCC></ref>.

# '''Account for climate change:''' Historical data is no longer an accurate predictor of future extreme rainfall (CSA, 2025)<ref name = CSA2025>CSA, 2025. CSA 231:25 Developing and interpreting intensity-duration-frequency (IDF) information under a changing climate. https://www.csagroup.org/store/product/2431590/?srsltid=AfmBOopkRT3cosyCstZMacCmlthJxgfo6w6aFIXyuEExGmyBT8zw1vMs </ref>. Since IDF curves are based on historical data, climate change-scaled IDFs can be used to design LIDs that are resilient under future rainfall conditions (ECCC, 2025)<ref name = ECCC></ref>.