Educational Module 2 Benthic Terrain Classification Larkin 2001

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

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% Slope Angle (Degree) Rise • Degree Slope = the measure of the slope angle Run

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 Harbor • Slope Analysis • BPI • Benthic Zone Classification

Error Correction- • Note: On Page 12, Step 1 should read: – Add ppg 5 m 84_neg. In the Spatial Analyst… – Step 1 a—Make sure the ppg 5 m 84_neg grid is showing…