Educational Module #2: Benthic Terrain Classification Emily M. Larkin and Dawn Wright Dept. of Geosciences, Oregon State University September, 2004 (Larkin 2001)

Objectives On completion of the project, you should be able to: – –Do a slope analysis. – –Use Raster Calculator to do simple analyses. – –Use Grid to process a short command sequence that is given to you. – –Define: Slope, Bathymetric Position Index, benthic, standard deviation and benthic zones.

Benthic Terrain Classification Benthic = of or pertaining to the seafloor. (e.g. A benthic animal lives on the seafloor.) Bathymetry can be classified into different zones based on what type of terrain it is.

Slope Slope is steepness of the landscape Percent Slope = Rise / Run * 100% Degree Slope = the measure of the slope angle Rise Run Slope Angle (Degree)

Bathymetric Position Index (BPI) BPI finds out where a pixel is in relationship to its neighbors. Raster calculator compares the position of a pixel to those around it. (after Weiss 2001)

Bathymetric Position Index BPI is calculated at a user-defined scale. – –The resolution of the grid * the outer radius in the BPI equation – –Fine-scale BPI—looks at small features (e.g small crests on a large slope) – –Broad-scale BPI—looks at large features (e.g. the large slope)

Benthic Zones Divide bathymetry into 4 zones: flats, slopes, crests and depressions Benthic zones have been linked to biodiversity (Karlson et al. 2004) Based on: – –Slope—greater or less than 5% – –Broad-scale BPI—less than or greater than 1 standard deviation from the mean WARNING—When you get to this part of the lesson, you must type everything correctly! Go slow and double-check.

Module #2 Bathymetry from Pago Pago Harbor Slope Analysis BPI Benthic Zone Classification

Error Correction-- Note: On Page 12, Step 1 should read: – –Add ppg5m84_neg. In the Spatial Analyst… – –Step 1a—Make sure the ppg5m84_neg grid is showing…