A new high-resolution historic substrate layer for the Laurentian Great Lakes

Session: Seeing Below the Surface: Quantifying the Underwater Environment with Image Analysis

Gust Annis, The Nature Conservancy, [email protected]
Matthew Herbert, The Nature Conservancy, [email protected]
Jared Ross, Michigan State University, [email protected]
Stephanie Hickel, The Nature Conservancy, [email protected]

Abstract

Detailed digital substrate data and maps are needed to help inform a variety of Great Lakes issues including the identification of potential spawning areas, sites for restoration, and a better understanding of erosional and depositional processes.  Currently available digital substrate layers for the Great Lakes are limited by their consistency, geographic extent, or resolution.  To help address these limitations, we extracted substrate information from historic navigational charts (circa 1853-1920) to produce a consistent substrate layer for the Great Lakes.  We used 83 historic charts to digitize 22,000 substrate point records which documented over 70 different substrate types.  We lumped similar types into 12 general classes and produced a continuous raster surface with a 100-meter cell size.  The resulting map provides a new 21^st century rendition of detailed survey data that was collected more than a century ago.  The map and data will help guide management and restoration efforts for aquatic species throughout the Great Lakes while at the same time providing a historic baseline to substrate composition in highly altered areas.  The substrate maps we produced provide a more consistent, detailed, and generally higher resolution digital geospatial data layer than has been available from other sources to date.