Map Tools & Spatial Data

Map Tools

BMP Targeting Maps

BMP Targeting Maps have been created using CAST delivery factors and 2022 Progress loads to communicate which land-river segments in the watershed would be most effective for BMP targeting. Delivery factors represent the fate and transport of nutrients and sediment from the land to the water. So, the higher the delivery factor, the higher the amount of nutrients and sediment are likely to run off from that area. There are six bivariate targeting maps, one for each nutrient and sector. The legend on each map has a box with 9 colors, representing the variation of loads and delivery factors in each land-river segment, from low to high. The lightest, bottom square in the legend correlates to the land-river segments on the map that have the lowest loads, and the lowest delivery factors. The square at the top of the legend, which has the darkest coloring, shows the areas that have the highest loads, and the highest delivery factors. These are the areas that would be most effective for BMP targeting. The Explaining Changes in Nitrogen and Phosphorus Loads Using Land Management Practice Data and How These Data Can Indicate Where Practices Could be Targeted in the Future presentation explains how these data can be used. The button below will take you to the maps.

BMP Targeting Maps

CAST Phase 6 Public Reports - Compare Map

Use the Compare Map tool available in Public Reports (logged off of CAST account) and Results (logged into CAST account) on the navigation bar to compare nitrogen, phosphorus, and sediment loads at either the edge-of-stream (EOS) or edge-of-tide (EOT) between the publicly-shared scenarios available in CAST. The publicly-shared scenarios include annual progress, no action, Everything by Everyone, Everywhere (E3) and the Phase 2 Watershed Implementation Plans (WIP2).

The Chesapeake Bay Watershed Model Phase 6 Map Viewer provides basic mapping functionality for a subset of Public Reports for Load Scenarios available from the CAST Tool. It also contains map layers for several commonly requested data layers associated with the Chesapeake Bay suite of models.

In 2017, the EPA's Healthy Watersheds Program published the results of their Preliminary Healthy Watersheds Assessments (PHWA), a project that brought together nationally consistent data to assess watershed health and vulnerability. In order to visualize the results, the Chesapeake Healthy Watersheds Assessment Tool was developed to facilitate exploration of the data. The readily available online, geospatial tool supports and informs management related to watershed health and vulnerability at the catchment scale.

The Environmental Justice and Equity Dashboard provides access to a variety of spatial data layers pertinent to addressing environmental issues in areas with underrepresented populations, which include communities of color, low income, and linguistically isolated communities. These data reflect demographics of underrepresented populations, environmental justice and public health issues, quality of life concerns, and other data important for additional Outcomes of the Chesapeake Bay Watershed Agreement of 2014.


Spatial Data for Download

Shapefiles are available for download as GIS layers and KMZ files. The GIS layers were simplified to produce the KMZ files. The KMZ layers are suitable for web mapping, but not for area or boundary calculations. Boundaries could be shifted by up to 10 meters with the simplification to remove polygon vertices. For most accurate layers, download the shapefiles.

  • Segmentation GIS  KMZ
    • This dataset includes Phase 6 Land-River Segments. Phase 6 Land-River Segments represent the union of land segments, which are primarily based on county boundaries, and river segments, which are based on small watershed boundaries.  The segmentation is designed so that each land-river segment drains to only one of the 92 tidal water segments.
    • If you are working at a scale of Maryland 8-digit watershed, use these images and spreadsheet to map to a CAST modeling segment.
  • Hydrologic Unit Codes (HUCs)
    • HUCs spatial data are available for download through this USGS website.
  • Hydrogeomorphic Regions GIS
    • This dataset includes the boundaries of the 11 hydrogeomorhpic regions in the Chesapeake Bay watershed.
  • Combined Sewer Overflow GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program. The CBP collected these data in 2017 directly from state regulatory agencies, counties, and municipal organizations.
  • Municipal Separate Storm Sewer System (MS4) GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program. The CBP collected these data in 2017 directly from state regulatory agencies, counties, and municipal organizations.
  • Federal Lands GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program for use by the Federal Facilities Workgroup.  The dataset used information and resources related to the water quality improvement efforts of federal facilities within the Chesapeake Bay Watershed. Data is compiled from various authoritative data sources including the Protected Areas Database V. 1.4, Federal Agencies, and in some cases States and other jurisdictions.
  • Maryland Regulated Area GIS  KMZ
    • This dataset includes MS4 areas provided by the Maryland Department of the Environment. MD_SHA is under the jurisdiction of the Maryland State Highways Administration. MD_STATE is under the jurisdiction of other state agencies.
  • Direct Loads GIS  KMZ 
    • Direct Loads Include Wastewater, Rapid Infiltration Basins, Large Monitored Septic Systems, and Developed Land Spray Irrigation
  • Stream Layer GIS KMZ
    • This dataset includes the stream layer that is used by the Chesapeake Bay Program. This layer is for visual purposes only. Please note that the stream layer is not used in any CAST calculations (i.e., loads).