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

2. 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.

3. 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.

4. 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)

5. 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)

6. 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)

7. 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.

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

9. 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…