DIGITAL MAPPING AND CHARACTERIZATION OF INTERTIDAL HABITATS IN WELLFLEET HARBOR, NAUSET MARSH, AND HATCHES HARBOR, CAPE COD NATIONAL SEASHORE

Mike Bradley Chuck LaBash Peter August

Regional Technical Support Center for GIS Environmental Data Center University of Rhode Island Department of Natural Resources Science Kingston, RI Introduction and Purpose

During the summer of 2002, the National Park Service expressed the need for intertidal habitat maps that could be used for coastal zone mapping and for the identification of environmentally sensitive areas within Cape Cod National Seashore. Part of the data needs included more detailed information on non-vegetated intertidal areas. As result, a georeferenced digital map of intertidal estuarine habitats was developed based on hydrology, soils, and vegetation that may be used for coastal zone management applications within Wellfleet and Hatches Harbors, and Nauset Marsh.

Aerial Photography

Delineations of intertidal habitats were based on 1:20,000 true-color 9 x 9 inch aerial photography taken June 20, 2000 (James W. Sewall Co, Old Town, ME) as ordered by the Massachusetts Department of Environmental Protection for an eelgrass mapping project (contact: Charles Costello, http://www.state.ma.us/mgis/eelgrass.htm). Contact prints were ordered through the Earth Science Information Office at the University of Massachusetts (contact: Dennis Swartout, http://www.umass.edu/tei/esio). All photographs were taken at or near low tide as per project guidelines (http://www.state.ma.us/mgis/eelgrass.htm).

Methodology

GIS Theme Development Delineations were carried out with the assistance of a mirror stereoscope, hardcopy aerial contact print stereo pairs, and using vertical exaggeration to aid in the discrimination of intertidal areas. Delineations were made on acetate overlays. Delineations were ‘heads-up’ digitized using MassGIS 1:5000 orthophotography by matching the scale of orthophotography to the overlay (1:20,000) and sketching the delineations. More detailed digitizing was done (at smaller scales) using the sketches and features (i.e. houses, tidal creeks, vegetation, ect) common in both data sets (orthos and stereo pairs) and as guides. All digitization was done in ArcGIS 8.3 and using the geodatabase data format. Polygon topology was created by converting the geodatabase to an ArcInfo coverage format. An attempt was made to delineate intertidal habitats to mean-lower-low water (mllw). To accomplish this, site visits were conducted during spring low tides and in Wellfleet Harbor, low tide lines were walked with Trimble GeoXT 1-3 meter GPS unit. These lines and field notes were used as guides during the digitizing process.

Field and Lab Work Field visits were timed to correspond spring tides of the month. During these visits, map delineations were ground-truthed, low tide lines were GPS’d, georeferenced digital photographs of map units taken, and soil samples were collected and described for unvegetated map units. For each un-vegetated map unit, at least two samples were collected and for variable map units, more samples were collected. Sample locations were chosen arbitrarily and at random. At each sample point, field data such as soil texture (Figure 1), color, amount of shells and gravel and cobble was noted for each horizon designated. Soil samples were collected and returned to the lab for drying. In the lab, samples were analyzed for particle size and organic matter following Natural Resource Conservation Service guidelines (Soil Survey Staff, 1992). Once dried, samples were weighed and sieved through a 2mm sieve to remove coarse fragments (gravel, cobble, and shells). Approximately 10-g of sieved sample was removed for analysis of amount of sand, silt, and clay. Each 10-g sample was placed in a 250 ml plastic bottle with 10-ml calgon, filled with de-ionized water, and placed on a mechanical shaker overnight. Samples with high amounts of organic matter were pre-treated with

H2O2 prior to shaking to alleviate the cementing effect of organic matter. After shaking, samples were wet-sieved through a 0.05 mm sieve to separate the sand fraction. The clay and silt fractions were captured in a sedimentation column and the clay fraction removed by pipette. The sand fractions were dried and weighed, and dry sieved through a nest of sieves to determine individual sand fraction percents (i.e. percent of coarse and fine sand). Percent organic matter was determined by percent weight loss on ignition (500o C).

Classification system used for mapping ESTUARINE I Subtidal a. Channel II Intertidal a. Unvegetated i. Irregularly exposed to regularly flooded: - Mud flat - Fine sand flat - Sand Flat - Marsh Creek - Shellfish bed - Panne ii. Irregularly flooded: - Beach b. Vegetated: - Spartina alternaflora - Salt meadow - Cattails - Phragmites MARINE I Subtidal II Intertidal a. Unvegetated i. Irregularly exposed to regularly flooded: - Sand flat ii. Irregularly flooded - Beach UPLAND I Dune top II Upland islands

Map Unit Descriptions:

Subtidal – estuarine: Permanently flooded areas in an estuarine setting. These areas generally do not conduct tidal currents and are not shaped like a channel (polygon’s length to width ratio ~1). Subtidal – marine: Permanently flooded areas in an estuarine setting. These areas generally do not conduct tidal currents and are not shaped like a channel (polygon’s length to width ratio ~1). Channel: Permanently flooded areas in an estuarine setting that actively conducts tidal currents. Marsh Creek: Intertidal creeks that conduct tidal currents and are bounded by salt marsh vegetation. Substrates are highly variable, ranging from silt to sand sized particles Panne: Usually permanently flooded pools (but can be intertidal) generally found in the high marsh. Sand flat – marine: Irregularly exposed to regularly flooded habitats consisting mostly of coarse sand (sand grains are mostly 1- 0.5 mm in size) and no organic matter. Surface gravel and cobble maybe common as well. These habitats are found in a marine setting; that is, areas that are exposed to relatively high wind and wave energies and include the swash zone. Sand flat – estuarine: Irregularly exposed to regularly flooded habitats consisting mostly of coarse sand (sand grains are mostly 1- 0.5 mm in size) and no organic matter. Surface gravel, cobble, and shells maybe common as well. These habitats are found in an estuarine setting; that is, areas which are not exposed to high wind and wave energies. Ocean beach: Irregularly flooded habitats consisting mostly of coarse sand (sand grains are mostly 1- 0.5 mm in size) and no organic matter. Surface gravel and shell fragments maybe common as well. These habitats are found in a marine setting; that is, areas which are exposed to relatively high wind and wave energies. Beach – estuarine: Irregularly flooded habitats consisting mostly of medium sand sized particles (sand grains are mostly 0.5 – 0.25 mm in size) and no organic matter. Surface gravel and shell fragments maybe common as well. These habitats are found in an estuarine setting; that is, areas which are not exposed to high wind and wave energies. Fine sand flat: Irregularly exposed to regularly flooded habitats consisting, on average, of loamy sand textured substrates (Figure 1). These habitats typically consist of a surface (0-10 cm) finer textured layer (sandy loam to fine sand) over a coarser one (sand). These habitats are traversable at low tide and have measurable amounts of organic matter (2% on average). Shellfish beds and intertidal eelgrass beds may also be found within this map unit. Typically, these habitats are located adjacent to mud flats going out toward more open water and estuarine sand flats. Mud flat: Irregularly exposed to regularly flooded habitats consisting relatively fine grained material (loam) with relatively high amounts of organic carbon (3.4% on average). These habitats are generally not traversable at low tide and are located immediately adjacent to the salt marsh. Shellfish bed: Irregularly exposed to regularly flooded habitats consisting mostly of shellfish. All of these map units were either ground verified or incorporated from prior datasets. Spartina alternaflora: Emergent tidal wetland consisting mostly of Spartina alternaflora, but can have mixtures of S. patens, Distichlis spicata, Salicornia, and Limonium. Salt meadow: Emergent tidal wetland consisting mostly of Spartina patens, but can include significant cover of Juncus gerardii especially in Hatches Harbor. Phragmites: Emergent tidal wetland consisting mostly of Phragmites australis. Cattail: Emergent tidal wetland consisting mostly of Typha latifolia. Upland (dune top): upland dune areas comprised of typical dune vegetation. Upland: Forested upland islands.

Figure 1. The Natural Resources Conservation Service texture triangle. (from: Keys to soil taxonomy, 8th ed, USDA-NRCS printing office). Final Products Final products for this project are on a single cd. These products include the habitat coverage, and four shapefiles of GPS data, photo locations, and sampling locations. GIS data is provided in both Mass SPM Nad83 and UTM Zone 19 Nad83. Additionally, a final report, lab data, digital photos and an ArcMap project (photos.mxd) will also be found on the cd. The ArcMap project contains the habitat data and a shapefile of photo locations hyperlinked to digital photographs. Federal Geographic Data Committee-compliant metadata was produced using ArcCatalog and then parsed to produce four metadata files: inter_hab.xml, inter_hab.html, inter_hab.txt, and inter_hab. sgml

References

Soil Survey Staff. 1992. Soil survey laboratory methods manual. Soil Survey Investigations Report No. 42, USDA-SCS, Washington, D.C. APPENDIX – LAB DATA

Coarse Depth Field Coarse Field Shell v. coarse Coarse Med. sand Fine sand v. fine silt clay USDA Texture Sample ID MapUnit Horizon Field Texture Munsell Color Munsell Name Fragments sand (%) OM % (cm) Fragments (%) Fragments (%) sand (%)* sand (%) (%) (%) sand (%) (%) (%) class (%)

WfOB-1 ocean beach C1 20 very coarse sand 10YR 6/4 light yellowish brown 35 5 34 41 54 5 0 0 100 <1 <1 0 coarse sand

HaOB-2 ocean beach C1 30 coarse sand 2.5Y 7/4 pale yellow 0 0 3 30 69 0 0 0 99 0 1 0 coarse sand

NaOB-3 ocean beach C1 30 medium sand 10YR 6/4 light yellowish brown 0 0 2 3 26 70 0 0 99 0 1 0 sand

WfEB-1 beach - estuarine C1 22 coarse sand 10YR 5/3 brown t 0 <1 3 33 58 6 0 100 0 <1 0.0 sand

HaSF(oc)-2 sand flat - marine C1 30 very coarse sand 2.5Y 6/4 light olive brown 35 0 44 76 23 0 0 0 99 <1 1 0 coarse sand

WfSF(oc)-1 sand flat - marine C1 25 coarse sand 5Y 3/1 very dark grey 0 0 1 3 20 62 14 0 99 <1 1 0 sand

WfSF(oc)-1 sand flat - marine C2 30 coarse sand 2.5Y 5/3 light olive brown 0 0 <1 0 4 59 36 0 99 <1 1 0 sand

NasSF(oc)-3 sand flat - marine C1 30 coarse sand 10YR 6/3 pale brown 0 0 2 4 25 69 2 0 100 0 <1 0 sand

HaSF-2 sand flat - estuarine C1 30 very coarse sand 2.5Y 5/4 light olive brown 10 0 16 56 40 1 1 1 99 0 1 0 coarse sand

NaSF-3 sand flat - estuarine C1 30 medium sand 10YR 6/4 light yellowish brown 0 0 <1 1 17 75 5 0 98 1 1 0 sand

WfSF-1 sand flat - estuarine C1 7 coarse sand 2.5Y 5/6 light olive brown 0 0 0 4 51 41 3 0 99 0 1 0 coarse sand

WfSF-1 sand flat - estuarine C2 20 coarse sand 5Y 5/1 gray 0 0 <1 3 54 35 7 0 99 <1 1 0 coarse sand

NaSF- 4 sand flat - estuarine C1 30 coarse sand 10YR 6/4 light yellowish brown 10 2 17 6 38 53 2 0 99 0 1 0 sand

WfSM-1 fine sand flat A1 5 sand 2.5Y 3/1 very dark gray 0 0 0 1 12 36 47 2 97 2 1 1 sand

WfSM-1 fine sand flat C1 20 coarse sand 5Y 4/1 very dark gray 0 0 0 1 12 33 49 3 98 1 1 1 sand

WfSM-2 fine sand flat A1 5 loamy sand 2.5Y 2/1 black 0 0 1 1 10 30 54 2 97 2 1 1 fine sand

WfSM-2 fine sand flat C1 20 sand 5Y 4/1 very dark gray 0 0 0 2 14 36 45 2 99 0 1 1 sand

WfSM-3 fine sand flat A1 2 silt loam 5Y 4/3 olive 0 0 2 6 25 22 12 7 72 15 13 7 sandy loam

WfSM-3 fine sand flat A2 10 sandy loam 2.5Y 2/1 black t t 3 14 39 31 9 2 95 3 2 1 sand

WfSM-3 fine sand flat C1 25 coarse sand 5Y 5/1 gray 1 0 2 14 44 36 5 0 98 1 1 0 sand

NaSM-4 fine sand flat A1 5 sandy loam N 2.5/ black 0 0 0 2 10 33 8 16 69 26 5 3 sandy loam

NaSM-4 fine sand flat C1 30 coarse sand 5Y 4/1 dark gray 0 0 1 3 16 55 14 6 94 1 3 1 sand

WfMF-1 mud flat C1 15 loam 5Y 2.5/1 black 0 t 1 3 10 15 19 20 67 20 13 5 fine sandy loam

NaMF-2 mud flat A1 8 silty clay loam 10Y 2.5/1 greenish black 0 0 0 0 1 5 2 12 20 65 15 4 silt loam

NaMF-2 mud flat C1 30 silt loam 10Y 2.5/1 greenish black 0 0 0 0 1 4 2 12 20 67 13 4 silt loam very fine sandy NaMF-3 mud flat A1 10 silt loam N 2.5/ black 0 0 0 0 0 4 12 40 56 38 6 2 loam very fine sandy NaMF-3 mud flat C1 30 fine sandy loam 10Y 2.5/1 greenish black 0 0 0 0 1 2 11 40 55 38 7 2 loam

* Very coarse sand refers to 1-2mm grain size, coarse sand = 1- 0.5mm, medium sand = 0.5- 0.25mm, fine sand = 0.25- 0.1 mm, very fine sand = 0.1 – 0.05 mm.