Sewershed RH-018 · NYC DEP Combined Sewer Overflow Tributary Area
RH-018 - Cobble Hill, Brooklyn
Properties in this area share the RH-018 combined sewer — during moderate-to-heavy rain, runoff can exceed pipe capacity faster than it drains, which is what drives sewer backup exposure block by block. Here’s what that looks like for Cobble Hill, Brooklyn specifically.
RH-018 is a combined sewer area covering 242 properties in Cobble Hill, Brooklyn. Flood Form rates 33% of them Moderate or High for stormwater exposure, and 74% for groundwater. 57% of lots have yard area that legally qualifies for on-site infiltration. Ground elevation is typically 15 ft. The median building dates to 1931. 70% of parcels sit over a historic stream or pond.
242
Properties in sewershed
56.6%
Legally eligible for on-site infiltration
33%
Stormwater exposure: Moderate or High
74%
Groundwater exposure: Moderate or High
What sets RH-018 apart
15 ft
Median ground elevation
80%
Average impervious cover per lot
1931
Median year built
70%
Properties over a historic stream or pond
Stats computed from Flood Form’s NYC parcel data as of October 9, 2026
Common solutions for Cobble Hill properties
Downspout Diversion
Redirects roof runoff away from the combined sewer and into landscaped or permeable areas on the lot.
Infiltration System
Drywells or infiltration chambers that let stormwater soak into the ground on-site instead of entering the sewer.
Detention System
Holds stormwater temporarily and releases it slowly, reducing peak flow into the combined sewer during a storm.
Drain Improvement
Upgrades yard, area, or foundation drains so water is carried away from the building instead of pooling.
Foundation Waterproofing
Protects the foundation from groundwater intrusion, relevant where groundwater exposure runs high.
Nearby sewersheds
- RH-016Cobble Hill2,042 properties · 18% with Moderate or High stormwater exposure
- RH-019Cobble Hill352 properties · 25% with Moderate or High stormwater exposure
- RH-014Brooklyn Heights753 properties · 21% with Moderate or High stormwater exposure
- RH-035Carroll Gardens815 properties · 23% with Moderate or High stormwater exposure
- RH-031Carroll Gardens324 properties · 35% with Moderate or High stormwater exposure
- RH-030Carroll Gardens482 properties · 40% with Moderate or High stormwater exposure
Want to see where your specific property stands?
Get Your Property’s Flood Form