I have been asked to participate in a workshop to discuss my agency's policy regarding compliance with Executive Order (EO) 11990: Protection of Wetlands and the process for identifying wetlands. At present the agency policy is that funding recipients are to comply with the agency EO process if wetlands (jurisdictional or non-jurisdictional) are identified using the 1987 Manual, yet pending receipt of information to indicate that wetlands may have been identified using the 1987 Manual the only source they should consult is the NWI map. As expected this creates a problem when the NWI map says there are no wetlands, yet the funding application contains a Clean Water Act permit for the purpose of filling a wetland; however, the higher level staff refuses to address the problem as they are convinced that NWI maps are reliable indicators of the presence or absence of wetlands and the “occasional” omission of wetlands from the inventory is a fluke. Does someone out there have a good list of references regarding the reliability or unreliability of NWI maps?

Thanks,

Regarding the reliability of NWI maps, Len said:

"...this creates a problem when the NWI map says there are no wetlands, yet the funding application contains a Clean Water Act permit for the purpose of filling a wetland; however, the higher level staff refuses to address the problem as they are convinced that NWI maps are reliable indicators of the presence or absence of wetlands and the “occasional” omission of wetlands from the inventory is a fluke..."

Dear Len,
If the funding application contains a CWA permit then other parties such as consultants and regulatory personnel could receive funding for their services, and this may be the purpose of the funding (saving jobs).

Often, NWI maps are used in situations when there is not sufficient resources to conduct field work on all projects, especially in remote locations. Any wetlands that are not-shown on the NWI map may be marginal, or the color-infrared aerial photograph that was used to prepare the NWI may have been taken when the weather was dry, or the wetlands may have resulted from hydrology modifications that occurred after the date of this photograph, or the wetlands may in fact be uplands. This is why NWI maps are only a tool and are not precise indicators of wetland boundaries.

This message has been edited. Last edited by: Johnny Stevens,

I am not aware of any published references that deal with this problem, It would be interesting to see if NWI data from other areas is as spotty as it is here.

You might want to put a map of NWI wetlands vs wetlands mapped on the ground to show the workshop attendees the problems with the data.

The 2009 SWS meetings had this abstract:
Symposium 6.1 Tiner, R.; U.S. Fish & Wildlife Service, 300
Westgate Center Drive, Hadley, MA 01035;
ralph_tiner@fws.gov

THE NATIONAL WETLANDS INVENTORY - WHERE
WE'VE BEEN AND WHERE WE CAN GO
The National Wetlands Inventory (NWI) Program recently
celebrated its 30th anniversary. The U.S. Fish and Wildlife
Service created the NWI to produce information on the
distribution, extent, shape, size, and type of wetlands found
across the country. This information was needed to provide
critical information to resource planners and decision-makers to
aid in conserving America's wetlands. The NWI began making
wetland maps in the mid-1970s using conventional
photointerpretation and cartographic techniques. With the advent
of the computer age, geographic information technology became
available for using wetland map information for computer
analysis. Concurrently, changes in aerial imagery helped the
NWI get more detail, thereby improving on its original data.
Today, digital imagery is available for mapping yielding a
tremendous cost savings. Many collateral data sources are in
digital form and can more readily be used to improve the NWI
product. Also wetlands can be further classified to provide
information needed for better characterizing wetlands and for
predicting wetland functions on a large-scale (e.g., watersheds,
states, and regions). In the past 15 years, the NWI has suffered
from budget cuts and program redirection that has limited its
ability to provide timely data for resource management. Many
options are available to advance the program or to change the
direction of the program; these will be presented.