Full document / COSOC-W-86-002 - the National Sea Grant Library

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To test this procedure, a simple grid sampling technique was used to quantify habitat types
for 16 previously digitized 124,000 scale NWI maps. For the purposes ol these
preliminary tests, the numerous habitat types designated on the NWI maps were
aggregated Into six general categories: 1) sail marsh; 2) fresh marsh; 3) tidal Hats; 4)
swamp; 5) open water; and 6) uplands. Alter some testing, a 45 acre grid cell size with
approximately 900 sampling points per map was determined to be bolh efficient and
accurate for estimating these six habitat types at this scale. Each map was sampled
separately by mounting the grid over the map and systematically recordingthe habitat
type at each sampling point. This Information was recordedon data sheets and entered
into a computer mapping and statistics program. Based on the results (Table 1), It
appeared thai grid sampling could provide a time and cost-elleclive technique for
compiling a reasonably accurate coastal wetlands data base.
Table 1. Grid sampling results fortwo test areas in coastal Louisiana and Texas.
TOTAL ACREAGE FOR TWO TEST AREAS
(Coastal Louisianaand Texas)
Habitat Digital Grid % Difference
1. Upland 109.227 108.443 -0.72
2. Open Water 434.898 431.959 -0.68
3. Salt Marsh 97.642 97217 -0.44
4. Fresh Marsh 17,584 17/385 +1.71
5. Tidal Flat 8.013 7.885 -1.97
6. Swamp 138S lOfli -iaa
TOTAL 668,587 664,420 -0.62
Coastal Wetlands Workshop
On April 29.1986. SAB and NMFS held a workshop bringing together Individuals with
experience in wetlands mapping and management to discuss NOAA's efforts to compile a
national coastal wetlands data base. Sixteen professionals from six Federal organizations
participated: U.S. Environmental Protection Agency (EPA), U.S. Army Corps ol Engineers
(COE), USGS, FWS, NMFS, and NOS. Specific objectives were to: 1) review current
informationon Ihe distribution and extent of coastal wetlands; 2) outline the requirements
tor Improving this data base; and 3) develop recommendations for NOAA to proceed
further with this work.
In general, workshop participants endorsed NOAA's proposal to grid sample NWI maps
(Strategic Assessment Branch, 1986). Itwas suggested however, that the technique be
modified to Improve the quality and usefulness of the data being developed. Two key
recommendations were proposed:
1) Expand the habitat categories sampled from six to the fifteen listed below:
a. high salt marsh J. estuarine forested-scrub/shrub
b. low salt marsh k. tidal fresh forested-scrub/shrub
c. brackish marsh L non-tidal fresh forested-scrub/shrub
d. unclassified non-fresh marsh ra unclassified fresh forested-scrub/shrub
e. tidal fresh marsh n. upland
I. non-tidal fresh marsh o. openwater-fresh
g. unclassified Iresh marsh p. openwater-non-fresh
h. tidal flats
2) Conduct a more complete statistical evaluation of the grid sampling procedure.
These recommendations were examined by NOAA and incorporated into the operational
phase ol the project