Visualizing Willapa Bay Habitats Using ArcGIS

Recently this semester in ENVS 330 my class has been studying Willapa Bay in Washington as a way to continue practicing research.  In preparation for the research proposals we are about to write, we have been discussing Willapa Bay in class in a variety of forms, such as presenting news articles, creating concept maps connecting the actors involved in aquaculture in this region.  Most recently, we did a brief project in class using ArcGIS to visualize the different types of habitats in the area and practice interpreting Metadata.  We downloaded zip files provided to the class that came from National Oceanic and Atmospheric Administration, Department of Commerce to create our GIS map. This data was collected in field surveys.  Photographs were interpreted and mapped and the digitized into GIS format (shapefiles.  The researchers followed the parameters of the Coastal Change Analysis Program and used comparative data from the Marine Resources Consultants and the University of Washington.  They then classified the habitats using SCHEME (System for Classification in Estuarine and Marine Environments.  This involves 7 main classes  of habitat, which are unconsolidated sediments (mud) submersed aquatic vegetation, corals/hardbottom, tidal Marsh, tidal Swamp, land, and unknown benthic habitat. All of this information was found in their metadata at this link.

 

My outcome can be seen in Figure 1 below.  I chose not to merge the layers so that viewers could clearly see them, however, this means that overlap between the different habitats can not be shown.  Labels showing square mileage, but only for the habitats that covered a significant area.

 

Fig. 1

This map shows the different habitats at Willapa Bay using SCHEME codes. Color coded areas are shown without the layers being merged or transformed, therefore overlap between habitats is not shown.

As shown in the legend in Figure 1, each primary SCHEME Code number relates to a specific habitat. All habitat types can be seen at Willapa bay except reefs/hardbottom (code 3) and tidal swamps (code 3).  Because Reefs and tidal swamps do not appear at Willapa Bay, these habitats do not appear in the data set.

 

After creating the map, I downloaded the data to create a chart using google sheets.  I created a simple bar graph to show the different in area in square miles for each of the 5 habitats at Willapa Bay, which can be seen in figure 2. The X axis is labeled by Scheme code, not habitat.  To understand this graph, know that 4 is tidal marsh, 6 is land, 7 is unknown benthic habitat, 11 is unconsolidated sediments (mud), 212 is discontinuous submersed aquatic vegetation (SAV), and 211 is continuous submersed aquatic vegetation.  Each habitat is described in metadata.  Unconsolidated sediments are defined by having less then 10% SAV or coral. Submersed aquatic vegetation (SAV) is defined by covering 10-100% of a surface, and discontinuous is when there is a break in cover rather than continuous beds.  SAV includes rooted plants and microalgae.  Tidal marshes are described as vegetated areas “along low-wave energy intertidal areas and river mouths,” and land refers to areas above the tide lines.

Figure 2

I found the square mileage of each habitat area in the attributes table in ArcGIS.  The habitat with the largest area in Willapa Bay is discontinuous submersed aquatic vegetation, which spans 59.91 miles.  Unconsolidated sediments voer the second largest area, which is 33.01 square miles.  Tidal marshes cover 9.58 square miles, land covers 7.47 square miles. continuous SAV covers 1.45 square miles, and unknown benthic habitat is only .82 miles of Willapa bay.

The most beneficial aspect of this activity was being able to try to draw connections to what our class has been discussing by visualizing the data, both through the GIS map and the bar graph.  In class we have been learning about how burrowing shrimp soften the sediment at the bottom of the bay as they travel, which probably correlates to the high amount of unconsolidated sediments in this region.  This has been a concern for aquaculture farmers at Willapa Bay because oysters suffocate in mud, so those areas are not suitable for oyster farming.  The Submersed Aquatic Vegetation that makes up most of the region most likely consists of a lot of seagrass, which we have learned promotes biodiversity and provides habitats for a variety of species, but also interferes with oyster aquaculture.  To test this hypothesis about the burrowing shrimp and seagrass I would need to further analyze the data and do more research.  If I chose to do this in the future for further research on this topic, I could use the same data to find out what type of vegetation was in these areas by looking at subclass, but I would have to find data and do research from other sources to learn more about the effect of the burrowing shrimp.

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