NWI+ Data Layers

Several data layers may be available for each project area: NWI - Common Types, LLWW Types (NWI+ Landscape, NWI+ Landform, and NWI+ WaterFlowPath), eleven Functions, Restoration Types (NWI+ Restoration Type1, NWI+ Restoration Type 2), NWI+ P-WetAreas, and layers for accessing more information (e.g., Wetland Codes). These layers are described in detail below. The date of the imagery used for each project is listed in the project name, e.g., Delaware Wetlands 2007 or Connecticut 2010. If you are a first-time user, be sure to read “Intro to the Mapper.” For questions, contact Ralph Tiner, Regional Wetland Coordinator, U.S. Fish and Wildlife Service (FWS) at:  .

NWI – Common Types – this layer displays wetlands and deepwater habitats mapped by the U.S. Fish and Wildlife Service National Wetlands Inventory Program and classified by the Service’s official wetland classification system (Cowardin et al. 1979). For display purposes wetlands have been separated into a number of groups typically by ecological system (Marine, Estuarine, Palustrine, Lacustrine, and Riverine) and/or vegetation type (aquatic bed, marsh, shrub swamp, forest, etc.). To view the legend for these types, open the “Show Legend Tool” and click on symbol before the layer name “NWI – Common Types.” For specific NWI nomenclature, simply click on the “Wetland Codes” box and a series of dots (points) will appear on the wetlands.  Click on a dot and a search box will appear showing the applicable NWI and LLWW codes for that area and the acreage of the NWI polygon. A link to the Cowardin et al. document can be found under the main topic – “National Wetlands Inventory (NWI).”

LLWW Types – these layers (“NWI+ Landscape”, “NWI+ Landform”, and “NWI+ WaterFlowPath”) display NWI wetlands and deepwater habitats by hydrogeomorphic-types according to Tiner (2003, 2011, or more recent versions): landscape position, landform, and water flow path (see “LLWW” page for a description of these types and a link to the classification document – dichotomous keys and mapping codes). For this classification, ponds have been separated from other wetlands for more detailed classification. Like was done for NWI Types, to view the LLWW code for a wetland and waterbody check the box “Wetland Codes” and dots will appear on the wetlands. Click on a dot and a search box will appear displaying the NWI code, LLWW Code, and acreage of the NWI polygon (see the dichotomous keys/mapping codes document for a key to coding and the actual project report for additional information on the application of the classification for the specific project area).  To view the legend, use the “Show Legend Tool.”  Some of the more frequently used codes are: for wetland landscape position = ES – Estuarine, MA – Marine, LS – Lotic Stream, LR – Lotic River, LE – Lentic, and TE – Terrene; for landform = BA – Basin, FL - Flat, FP - Floodplain, FR - Fringe, IS – Island, and SL – Slope; for water flow path = TH – Throughflow, OU – Outflow, IS – Isolated, IN – Inflow, and BI – Bidirectional-nontidal, and BT – Bidirectional-tidal. For additional codes, see the LLWW page and the link to the dichotomous keys publication (the link is also on the NWI+ Web Mapper).

Function – these layers display wetlands identified as potentially significant for each of eleven functions: surface water detention (SWD), streamflow maintenance (SM), coastal storm surge detention (CSS), nutrient transformation (NT), sediment and other particulate retention (SR), carbon sequestration (CAR), bank and shoreline stabilization (BSS), provision of fish and aquatic invertebrate habitat (FAIH), provision of waterfowl and waterbird habitat (WBIRD), provision of other wildlife habitat (OWH), and provision of habitat for unique, uncommon, or highly diverse plant communities (UWPC). Descriptions of these functions and the wetlands that provide those functions are found in a 2003 correlation report and tables that update the relationships; a link to these documents can be found on the LLWW page. To view the functions for a particular wetland of interest just check the applicable function box. You can only view one function at a time. If interested in the NWI or LLWW classification for the wetlands simply check the "Wetland Codes” box. As with the other layers, if you want to see the legend, use the “Show Legend Tool.”

NWI+ Restoration Type1 – this layer identifies former wetlands (now nonwetlands) that are in a land use where wetland restoration may be possible. Type 1 restoration sites should be former wetlands that were converted to either potentially “developable land” by drainage and/or filling or deepwater habitats by impoundment (diking) or excavation (dredging). Most of the former sites should be agricultural land that involved wetland drainage or barren land that may represent drained wetlands or filled wetlands. The latter sites are deepwater habitats created from wetlands by impoundment (e.g., L1UBHh in NWI code) or by dredging (e.g., E1UBLx in NWI code). All of the designated sites were mostly likely wetlands based on soil mapping; these sites should not include deepwater habitats created by flooding dryland in river valleys. The referenced sites should have potential for restoration.  Whether or not they are viable sites depends on site-specific characteristics, landowner interest, agency funding/priorities, and other factors. For the name of the soil type mapped at a particular site, click the “NWI+ P_RestType 1 SoilCodes” layer.  If the site is agricultural land or barren land, restoration will typically require action to bring back the hydrology and may involve removal of fill. For an inundated sites (now deepwater habitats), full or partial removal of the dike or dam would be needed to restore more natural hydrologic regimes, while excavated sites would require restoration of wetland elevations by bringing in suitable fill material.

NWI+ Restoration Type 2 – this layer shows existing wetlands that have been impaired to a degree that affects their ability to function like an undisturbed natural wetland. Click on the “Wetland Codes” box for access to NWI and LLWW codes as described above.  In the coastal zone, most of these type 2 restoration sites are either partly drained wetlands (with “d” modifier in the NWI code) or tidally restricted wetland. The former are extensively ditched (e.g., E2EM1Pd in NWI code) while the latter are separated by other tidal wetlands by roads and/or railroads (look for “td” – tidally restricted/road or “tr” – tidally restricted/railroad in the LLWW code). For inland wetlands, these sites also include partly drained wetlands (“d” modifier), impounded wetlands (“h” modifier; often ponds – PUBHh – built on hydric soils), excavated wetlands (“x” modifier, typically ponds – PUBHx – dug out from a wetland), and farmed wetlands (NWI code = Pf or PSSf). Sites designated have impairments that may be restorable through various means including plugging drainage ditches, destroying tile drains, removing tide gates, installing self-regulating tide gates, increasing culvert sizes, breaching impoundments, for example.

NWI+ P-WetAreas – this layer identifies “areas that may support wetlands based on soil mapping.” These are areas that did not exhibit a recognizable wetland photo-signature on the aerial imagery used for NWI mapping, but were mapped as hydric soils by USDA soil surveys. They are portions of hydric soil map units from the USDA Natural Resources Conservation Service (NRCS) soil survey geographic database (SSURGO database) that were not farmland, roads, residential houses and lawns, or commercial, industrial or “other” development on the imagery used for NWI mapping (see applicable report). Since they were designated as hydric soil map units, they have a high probability of containing at least some wetland despite not possessing a readily identifiable wetland signature on the aerial imagery used by the NWI. It is a well-known fact that NWI methods cannot detect all wetlands (especially drier-end wetlands – seasonally saturated types) due to limitations of remote sensing techniques and the difficulty of identifying some types even in the field. Many of these hydric soil areas are adjacent to mapped wetlands and may therefore represent the drier portion or upper limit of the wetland while other areas may be upland inclusions within a hydric soil mapping unit. When you click on "NWI+ P-WetArea Codes” box, a series of dots (or points) will appear on the polygons.  Click on these dots to see the hydric soil type (“MUSYM” – the soil map unit symbol used by NRCS, and “muname” – soil map unit name - predominant soil series). Inclusion of these data make the NWI+ database more complete in terms of locating areas of photointerpretable wetlands and other areas with a high probability for wetland occurrence based on soil mapping.




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