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How many homes are in the Waquoit Bay watershed? A count from the Cape Cod Commission’s parcel data

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The short version

The Cape Cod Commission’s Watershed MVP is a planning tool the Cape’s towns use to estimate nitrogen from every property. Behind it is a map layer with one point for each parcel, tagged with its watershed, town, land use and type of wastewater treatment. We counted the parcels it places in the Waquoit Bay watershed on November 13, 2026. There are 9,097 of them, and 7,210 are single-family homes. All but about 245 are on standard septic systems.

What we did

  • We queried the Commission’s public map service for the Watershed MVP (the “SubembaymentsParcelCentroids” layer) for every parcel tagged to the Waquoit Bay embayment.
  • We counted the parcels by the layer’s own land-use, town and wastewater categories. We did not change or reclassify any of them. The PDF below records each query and the service’s results.
  • The service doesn’t say when its parcel data was last updated, so this is a count of the data as it stood on the day we pulled it.

What we found

  • More than 7,000 homes. Of the 9,097 parcels, 7,210 are single-family homes, 137 are multi-family homes and 15 are condominiums or apartments. A multi-family parcel holds more than one home, so the number of homes is higher than the number of home parcels.
  • Room for more. Another 777 parcels are vacant land that could be developed, and 210 are vacant land that can’t be. The rest are other developed land (624), commercial (66), industrial (19), other undeveloped land (5) and 34 parcels with no category.
  • Three towns. Mashpee has 3,806 of the parcels, Falmouth 3,654 and Sandwich 1,637.
  • Almost all on septic. 8,852 parcels are on standard septic systems and 207 have nitrogen-reducing (innovative/alternative) septic systems. Three use a treatment plant that discharges to groundwater, one is sewered and 34 have no wastewater category.

What it means for Waquoit Bay today

Septic systems are the biggest controllable source of the bay’s nitrogen, so the number of homes on septic is the scale of the job. The Commission’s 2015 watershed summary counted 7,171 parcels in all, about 80% of them residential (see our summary of the Commission’s four-page watershed summary). Today’s data has about 1,900 more parcels. Some of that may be new building, but the data doesn’t say how much, and changes in how parcels are mapped could account for some of it. Treat the two counts as two snapshots, not a measured growth rate.

Map of the Waquoit Bay watershed, a tall narrow area, dotted with every parcel: rust-red dots for the 7,362 home parcels, which cover most of the southern half and patches in the north, and grey dots for 1,735 other parcels.
Every parcel in the Waquoit Bay watershed. Rust: home parcels (single-family, multi-family, condominiums and apartments). Grey: everything else. CPWB map from Cape Cod Commission Watershed MVP parcel data, accessed November 13, 2026.

See the data

Cape Cod Commission. (n.d.). WatershedMVP [Parcel data from the Watershed MVP map service, layer “SubembaymentsParcelCentroids”]. Retrieved November 13, 2026, from https://www.capecodcommission.org/our-work/watershedmvp/

License: The Commission’s map service states no license. The PDF below is CPWB’s record of our queries and the service’s counts, which are facts rather than a copy of the Commission’s data. The card image is a map CPWB made from the parcel points.

Parcel counts from the Watershed MVP data, retrieved November 13, 2026Download
See the data →

To explore the data yourself, see the Cape Cod Commission’s WatershedMVP page.

Drafted with AI assistance from the linked source.