The resistance surface that formed the basis of our coastal marten connectivity model is comprised of several data layers that represent forested and non-forested land cover, waterbodies, rivers, roads, and serpentine soils.

This dataset contains the bays and estuaries data used in the resistance surface.

In areas where larger rivers entered estuaries near the ocean, we created a bay/estuary data layer and assigned each pixel a resistance value of 20. This layer was created because the GNN (Gradient Nearest Neighbor forest model; see report and LEMMA 2014a for details), our primary land cover dataset, terminated at the coastline and explicitly excluded estuaries as null values. As many estuaries (especially in Oregon) are narrow, sinuous, and traverse inland for substantial distances, it was necessary to fill in these null values with supplemental resistance values that would need to be crossed in addition to the resistance of our single pixel river stream lines. The cumulative resistance of the river and the estuary pixels represented significant barriers to modeled movement by martens.

Development Process

To represent bay and estuary features on our resistance surface, we needed to develop dataset that perfectly integrated with the forested and non-forested land cover datasets that were derived from the GNN Structure forest model, as many estuaries are represented in the GNN footprint as null values. To ensure that no null values would remain within the modeling extent, we first converted the GNN raster footprint of non-null values into a single polygon. We then manually created a set of 'filler' polygons along the Pacific Coast wherever these 'null-value estuaries' existed. The GNN polygon and filler polygons were then converted to a binary raster. Finally, we used Raster Calculator to produce a raster of bays and estuaries by comparing our 'filled' raster to the original GNN raster footprint:

IF a GNN pixel is null and the filled raster is not null, then retain the pixel as a bay/estuary pixel.

Con(IsNull("GNNRaster")&("FilledRaster"==1),99))

ResistanceData_BaysEstuaries is the resulting raster.

Additional context and information on the development of the resistance surface can be found by reviewing the resistance surface data and accompanying metadata, as well as the corresponding spreadsheet of resistance surface data sources and resistance values. For additional information on our broader connectivity analysis, please see the report developed for this project, especially the sections titled Data Layers and Mapping Landscape Resistance to Movement, which describe the process and logic used in developing these data layers, compiling them into a resistance surface, and determining resistance values.