The Flow of Development in Allegheny County
2020 - 2023 Development and Stormwater Control Measures
Developed landscapes have more impervious cover than undeveloped natural areas. During storms, water draining from development can cause excess polluted stormwater runoff.
If not properly addressed, polluted runoff causes degradation to streams, rivers, and lakes.
Current best practices for stormwater management require developed land to be drained to stormwater control measures, such as rain gardens, infiltration basins or vegetated swales. These practices filter, cool, and absorb runoff and release clean runoff to streams.
Regulating Soil and Water
Allegheny County Conservation District (ACCD) maintains a delegation agreement with the PA Department of Environmental Protection (DEP) to administer the Chapter 102 Erosion Control regulatory program in Allegheny County. These statewide regulations require:
- Erosion control measures during construction to minimize downstream sedimentation.
- Stormwater control measures after development to treat stormwater.
Across Allegheny County, hundreds of stormwater control measures currently treat runoff.
Applications for Development
ACCD receives applications for earth disturbance and development, including National Pollution Discharge Elimination System (NPDES) Construction Stormwater Permits, required for earth disturbances over one acre for most activities.
Applications for Development in Allegheny County
2020 - 2023 This map shows approved applications for proposed development submitted to ACCD for review between 2020 and 2023.
Types of applications include:
- NPDES Permits for developments over an acre
- Erosion Control Plans for sites disturbing less than 1 acre, timber harvests, oil and gas activities, and projects near streams and wetlands
Explore the Map
ACCD mapped site boundaries of all approved applications received in this time period. This data can be used to study development trends in Allegheny County between 2020 and 2023.
Use the +/- buttons to zoom in/out of the map. Click and drag to pan to a different location. Clicking on a mapped feature will pop-up information about that site. If more than one feature is selected, use the arrows in the popup box to toggle between them.
Development by Municipality
Map of Allegheny County development trends between 2020 and 2023
Zoom into the map to see the individual development sites within each municipality.
About the Data:
To compare trends across municipalities of varying sizes, the data was normalized by calculating total cumulative acres of applications per square mile within each municipality. Using a unit of application acres per square mile ensures that larger and smaller municipalities are evenly represented.
Development by Watershed
Water from stormwater management controls flows downstream through the watersheds of the county.
This map shows development trends within each of Allegheny County's 40 watersheds.
Zoom into the map to see the individual development sites within each watershed.
About the Data:
The data was normalized by calculating the cumulative acres of applications per square mile so that watersheds of varying sizes can be proportionately compared.
Stormwater Control
Stormwater control measures (SCMs), also known as Best Management Practices (BMPs), are designed to manage stormwater runoff and mitigate the effects of development on local water quality. These measures aim to reduce pollution, prevent erosion, manage flow rates and promote the natural infiltration of rainwater. Different SCMs are employed to address specific aspects of stormwater management. SCM implementation is often a required component of permit applications. SCMs remain in place in perpetuity and are required to be maintained regularly to manage the excess stormwater resulting from developed areas.
Stormwater Control Measures in Allegheny County
2020-2023
This map shows Implemented SCMs within Allegheny County. These structures were inspected by ACCD staff and are confirmed to have been built. The SCMs included in this data set are associated with NPDES and Erosion and Sediment Control General Permits (ESCGP) that were terminated by ACCD between 2020 and 2023.
About the Data:
When a development permit is issued by ACCD, all associated SCMs are assigned a Planned status. Depending on funding, economic climate, etc., sometimes an approved development site and its associated SCMs are never constructed.
After construction of a development site is complete, ACCD receives a Notice of Termination (NOT) submission and performs a final comprehensive inspection. If the site is stabilized, constructed per the approved plan, and all SCMs are properly installed and functioning, the NOT is issued and the SCM status changes from Planned to Implemented. Implemented SCMs have been inspected by ACCD and are confirmed to have been constructed.
While ACCD maps both Planned and Implemented SCMs, only Implemented SCMs are included in the shared data set. This is because a certain number of Planned SCMs will either not be built or the permit may be amended, leading to modifications in SCM size, type, or capacity.
Explore the Map
Use the +/- buttons to zoom in/out of the map. Click and drag to pan to a different location. Clicking on a mapped feature will pop-up information about that SCM. If more than one feature is selected, use the arrows in the popup box to toggle between them.
Stormwater Control Measures by Municipality
Allegheny County stormwater management trends between 2020 and 2023
Zoom into the map to see the individual SCMs within each municipality.
About the Data:
To compare trends across municipalities of varying sizes, the data was normalized by calculating the number of SCMs per square mile within each municipality. Using a unit of SCMs per square mile ensures that larger and smaller municipalities are evenly represented.
Stormwater Control Measures by Watershed
Water from stormwater management controls flows downstream through the watersheds of the county.
This map shows stormwater management trends within each of Allegheny County's 40 watersheds.
Zoom into the map to see the individual SCMs within each watershed.
About the Data:
The data was normalized by calculating the number of SCMs per square mile so that watersheds of varying sizes can be proportionately compared.
Download Data
The data is hosted on the Western Pennsylvania Regional Data Center’s open data portal. Visit the portal to download shapefiles, CSV data attribute tables, and data dictionary files
