Abstract:

This coverage contains polygons and lines representing NWI digital data which are records of wetland location and classification as defined by the U.S. Fish & Wildlife Service. Wetland features were photo interpreted from color-infrared aerial photos from the National High Altitude Program (NHAP) taken in 1983 and 1984. No ground truth information was gathered or applied to this data.

Purpose:

This digital, geographically referenced data set was developed by the Iowa Department of Natural Resources to carry out agency responsibilities related to management, protection, and development of Iowa's natural resources.

Address:

109 Trowbridge Hall

Horizontal_Positional_Accuracy_Report:

Attribute Accuracy Report: Attribute accuracy is tested by manual comparison of the source with hard copy printouts and/or symbolized display of the digital wetlands data on an interactive computer graphic system. In addition, WAMS software (USFWS-NWI) tests the attributes against a master set of valid wetland attributes.

Logical Consistency Report: Polygons intersecting the neatline are closed along the border. Segments making up the outer and inner boundaries of a polygon tie end-to-end completely enclose the area. Line segments are a set of sequentially numbered coordinate pairs. No duplicate features exist nor duplicate points in a data string. Intersecting lines are separated into individual line segments at the point of intersection. Point data are represented by two sets of coordinate pairs, each with the same coordinate values. All nodes are represented by a single coordinate pair which indicates the begining or end of a line segment. The neatline is generated by connecting the four corners of the digital file, as estabished during initialization of the digital file. All data crossing the neatline are clipped to the neatline and data within a specified tolerance of the neatline are snapped to the neatline. Tests for logical consistency are performed by WAMS verification software (USFWS-NWI).

Completeness Report: All photo-interpretable wetlands are mapped. In the treeless prairies, 1/4 acre wetlands are mapped. In forested areas, small open water and emergent wetlands are mapped. In general, the minimum mapping unit is from 1 to 3 acres depending on the wetland type and the scale and emulsion of the source aerial photography. In regions of the country where evergreen forested wetlands predominate, wetlands smaller than 3 acres may not be mapped. Thus, a detailed of the ground and historical analysis of a single site may result in a revision of the wetland boundaries established through photographic interpretation. In addition, some small wetlands and those obscured by dense forest cover may not be included in this dataset.

Spatial Accuracy Report: The spatial accuracy of this coverage is unknown. It is estimated that the line work has an accuracy of 15 to 50 meters based on use of USGS topo maps as a base and the variable water levels that wetlands may have at different times.

Process_Description:

1. Digital wetlands data are either manually digitized or scanned from stable-base copies of the 1:24,000 scale wetlands overlays registered to the standard U.S. Geological Survey (USGS) 7.5 minute quadrangles into topologically correct data files using Wetlands Analytical Mapping Systems (WAMS) software. Files contain ground plainmetric coordinates and wetland attributes. The quadrangles were referenced to the North American Datum of 1927 (NAD27) horizontal datum. The scanning process captured the digital data at a scanning resolution of 0.001 inches; the resulting raster data were vectorized and then attributed on an interactive editing station. Manual digitizing used a digitizing table to capture the digital data at a resolution of at least 0.005 inches; attribution was performed as the data were digitized. The determination of scanning versus manual digitizing production method was based on feature density, source map quality, feature symbology, and availablitiy of production systems. The data were checked for position by comparing plots of the digital data to the source material.

2. The NWI dlgs obtained from the Fish and Wildlife Service were converted using AMLS into ARC/INFO polygon coverages. These AMLS were modified to retain both attribute description formats (parsed and unparsed currently called DESC1 and DESC2).

3. Once the DLG's were converted to ARC/INFO format, they were mapjoined into 250 quadrangles coverages.

4. Obtained county files in UNIX format from the EPA Region 7. Converted to singular precision coordinate, cleaned and reprojected to UTM zone 15.

5. Added acreage field. The size of the polygon in acres was then calculated and added to the attribute ACREAGE.

Entity_and_Attribute_Overview:

Area: Area of poly/region in square meters

Perimeter:Perimeter of poly/region in meters

Nwi22_: Internal polygon identifier

Nwi22_id: User-assigned feature number

Major1:Attribute creating during the conversion process to join the PAT INFO table to the PCODE data table.

Desc1:Unparsed Wetland and Deepwater Habitats Classification.

Desc2:Parsed Wetland and Deepwater Habitats Classification.

System:A complex of wetlands and deepwater habitats that share the influence of similar hydrologic, geomorphologic, chemical, or biological factors. This is the first letter in the NWI-CLASS code. The letters in parentheses are the system abbreviations used in the NWI-CODE. The five systems are:

L=Lacustrine

P=Palustrine

M=Marine

E=Estuarine

R=Riverine

Subsystem:Subdivided Systems into more specific categories. This applies to all systems except Palustrine. The Palustrine system does not have a SUBSYSTEM classification. SUBSYSTEM options vary for each SYSTEM. The full subsystem name has been included. The numbers in parentheses are the subsystem representations used in the NWI-CODE. They are as follows:

For the Lacustrine system:

Limnetic(1)

Littoral(2)

For the Marine system:

Subtidal(1)

Intertidal(2)

For the Estuarine system:

Subtidal(1)

Intertidal(2)

for the Riverine system:

Tidal(1)

Lower Perennial(2)

Upper Perennial(3)

Intermittent(4)

Unknown Perennial(5)

Class1:The highest taxonomic unit below the Subsystem level. They vary between the different SYSTEMS, and for Lacustine, Marine, and Estruarine they vary between SUBSYSTEMS. The letters in parentheses are the class abbreviations used in the NWI-CODE. They are as follows: for the Lacustrine system, Limnetic subsystem:

Rock Bottom(RB)

Unconsolidated Bottom(UB)

Aquatic Bed (AB)

Open Water(OW)

for the Lacustrine system, Littoral subsystem:

Rock Bottom(RB)

Unconsolidated Bottom(UB)

Aquatic Bed(AB)

Rocky Shore(RS)

Unconsolidated Shore(US)

Emergent(EM)

Open Water(OW)

for the Palustrine system:

Rock Bottom(RB)

Unconsolidated Bottom(UB)

Aquatic Bed(AB)

Unconsolidated Shore(US)

Moss Lichen(ML)

Emergent(EM)

Scrub Shrub(SS)

Forested(FO)

Open Water(OW)

for the Marine system, Subtidal subsystem:

Rock Bottom(RB)

Unconsolidated Bottom(UB)

Aquatic Bed(AB)

Reef(RF)

Open Water(OW)

for the Marine system, Intertidal subsystem:

Aquatic Bed(AB)

Reef(RF)

Rocky Shore(RS)

Unconsolidated Shore(US)

for the Estuarine system, Subtidal subsystem:

Rock Bottom(RB)

Unconsoidated Bottom(UB)

Aquatic Bed(AB)

Reef(RF)

Open Water(OW)

for the Estuarine system, Intertidal subsystem:

Aquatic Bed(AB)

Reef(RF)

Streambed(SB)

Rocky Shore(RS)

Unconsolidated Shore(US)

Emergent(EM)

Scrub Shrub(SS)

Forested(FO)

for the Riverine system, classes are the same for all subsystems:

Rock(RB)

Unconsolidated Bottom(UB)

Aquatic Bed(AB)

Streambed(SB)

Rocky Shore(RS)

Unconsolidated Shore(US)

Emergent(EM)

Open Water(OW)

Subclass1:This subdivides finer differences in life forms from CLASS levels.

Slash:Simple character " / " to divide different hierarchiacal levels.

Class2:Represents a mixture of CLASS levels.

Subclass2:Used when there is a mixture of SUBCLASS levels.

Water1:Water Regime modifers-Non-Tidal

Water2:Water Rigime modifers-Tidal

Chemistry:Water Chemistry modifers-Coastal Salinity, Inland Salinity, pH of Fresh Water

Soil:U.S. Soil modifier

n=Mineral soil: The depth of each horizon is measured from the top of the first horizon of mineral material.

g=Organic soil: The depth of each horizon is measured from the base of the aerial parts of the growing plants or, if there is no continuous plant cover from the surface of the layer of organic materials.

Special1: Special Modifier

Special2: Special Modifier

Special3: Special Modifier

x=Excavated: Lies within a basin or channel excavated by man.

h=Diked/Impounded: Created or modified by a man-made barrier or dike designed to obstruct the inflow of water. Created or modified by a barrier or dam which purposefully or unintentionally obstructs the outflow of water.

d=Partly Drained/Ditched: The water level has been artificially lowered, but the area is still classified as wetland because soil moisture is suficient to support hydrophytes. Drained areas are not considered wetland if they can no longer support hydrophytes.

f=Farmed: The soil surface has been mechanically or physically altered for production of crops, but hydrophytes will become reestablished if farming is discontinued.

r=Artifical: Refers to substrates classified as Rock Bottom, Unconsolidated Bottom, Rocky Shore, and Unconsolidated Shore that were replaced by man, using either natural materials such as dredge spoil or synthetic materials such as discarded automobiles, tires, or concrete.

b=Beaver: Created or modified by a beaver barrier to obstruct the inflow of water.

s=Spoil:

Many wetlands and deepwater habitiats are man-made, and natural ones have been modified to some degree by the activitives of man or beavers. Since the nature of these modifications often grealty influences the character of such habitiats special modifying terms have been included here to emphasize their importance. The following modifiers should be used or in combination wherever they apply to wetlands and deepwater habits.

Acres: Total acreage for each polygonNone

National Wetland Inventory for Allamakee, Clayton, and Winneshiek County, Iowa

Metadata: