The SWI is a screening tool to help identify approximate locations of wetlands and waterways.
The SWI consists of wetland inventories and other natural resource mapping that identify approximate locations of wetlands and waters (streams, ponds, etc.), listed below. The SWI web map gives users the ability to review all the maps together. This reduces the probability of the SWI lacking a wetland or water that is present on the ground, sometimes called “giving a false negative result." The SWI is updated on a regular basis as new mapping becomes available. This web map is still in development and is missing some mapping – read on for more information.
Included Layers: Each mapping type, or “layer," has accuracy limitations. For greater detail see the Disclaimer and Layer descriptions and limitations. Actual field conditions determine the presence or absence of wetlands.
- US Fish and Wildlife Service (USFWS) National Wetlands Inventory (NWI) – wetlands and waters
- DSL-Approved Local Wetlands Inventories (LWI) – wetlands and waters
- The current web map does not include the LWI mapping, which will be added soon. The web map does show the outlines of LWI study areas and the LWI names. If the area of interest is within an LWI study area then do not use this tool at this time (see * below), but instead go to the LWI web page to view the LWI maps and reports in PDF. LWI mapping is more accurate than NWI and NHD mapping within an LWI study area.
*See guidance below for using the SWI and LWIs.
- US Geological Survey (USGS) National Hydrography Dataset (NHD) – waters
- US Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey
- Soil mapping is included to show areas where the soil is more likely to be wetter longer, increasing the potential for wetland presence. This does not mean that wetlands are present but does show where there is a higher probability for wetland presence. Use caution in these areas. See information below to request additional information from DSL. Wetlands may occur outside of these mapped soil areas, for example in low areas where water may collect.
Other mapping that is part of the SWI
The following portions of the SWI are not available in digital GIS format but may be added to the web map in the future:
- DSL-approved Wetland Delineations
- DSL-approved compensatory mitigation sites
At this time DSL cannot display tax lot information. It is hoped that agreements may be gained so the SWI may display tax lot mapping and enable search functions with tax map and lot numbers in the future.
How to read the SWI
When first opening the SWI map ALL the layers are turned on, but don't display until the user zooms in closer. Make sure all the layers are displaying for site screening. If a wetland, water, or soil feature is mapped, then wetlands or waters may be present. See information below to request additional information from DSL. On-site investigation may be needed to verify if wetlands and waters exist on a given property. The SWI does not replace field verification.
Until the LWI mapping is added, if the area of interest is within an LWI study area then do not use this tool yet, but instead go to the LWI web page to view the LWI maps and reports in PDF (see * below).
* (from above) Considerations for using the SWI with LWIs: LWIs developed earlier than 2002 did not map wetlands smaller than one-half acre. This may have resulted in small unmapped wetlands. LWIs developed after 2009 have a higher accuracy requirement than earlier LWIs. The more time since an LWI was approved, the more opportunity for natural and human-caused changes since the mapping was created. This may have resulted in changes to the presence and extent of wetlands and waters on the ground. Consider using the SWI together with the LWI mapping for wetlands and waters screening.
For greater detail see the How to/Next steps and the Disclaimer and Layer descriptions and limitations
Request more information from DSL
For greater detail see the How to/Next steps document.
For Local Government Planning – The SWI (or LWI) is used by local governments to check if a project area is near mapped wetlands, waters or certain soils. If it is, and the project includes ground-disturbing activities, the local government will send a wetland land use notice (WLUN) to DSL. The DSL response describes next steps that may be needed to proceed with the project, if any. For local governments needing more information, click “back" to the Wetland Planning and Conservation page and find the “Wetland land use notice" section including the online submittal form and WLUN statutes.
For general information – Everyone else may use the SWI to learn more about a location. Anyone may request a free, off-site wetland and waters determination request which is an in-office analysis of the presence, if any, of wetlands and waters on a particular property. When making a determination request include details about the planned project to help DSL jurisdictional coordinators provide more detailed responses about possible next steps.
To learn more or if you have questions regarding a particular property or project, please see “Assistance for landowners" or contact a DSL aquatic resource or jurisdictional coordinator for that county. Find contact information on the DSL Staff Directory.