Sewershed HP-021 · NYC DEP Combined Sewer Overflow Tributary Area
HP-021 - Throgs Neck, Bronx
Properties in this area share the HP-021 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 Throgs Neck, Bronx specifically.
HP-021 is a combined sewer area covering 155 properties in Throgs Neck, Bronx. Flood Form rates 27% of them Moderate or High for stormwater exposure, and 11% for groundwater. 68% of lots have yard area that legally qualifies for on-site infiltration. Ground elevation is typically 8 ft. The median building dates to 1935. 1% of parcels sit over a historic stream or pond.
155
Properties in sewershed
67.7%
Legally eligible for on-site infiltration
27%
Stormwater exposure: Moderate or High
11%
Groundwater exposure: Moderate or High
What sets HP-021 apart
8 ft
Median ground elevation
68%
Average impervious cover per lot
1935
Median year built
1%
Properties over a historic stream or pond
Stats computed from Flood Form’s NYC parcel data as of October 9, 2026
Common solutions for Throgs Neck 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
- HP-022Throgs Neck481 properties · 46% with Moderate or High stormwater exposure
- HP-020Schuylerville551 properties · 37% with Moderate or High stormwater exposure
- HP-019Schuylerville948 properties · 35% with Moderate or High stormwater exposure
- HP-018Schuylerville247 properties · 45% with Moderate or High stormwater exposure
- HP-017Schuylerville333 properties · 44% with Moderate or High stormwater exposure
- TI-004Whitestone480 properties · 16% with Moderate or High stormwater exposure
Want to see where your specific property stands?
Get Your Property’s Flood Form