Quality Assessment: Physical: Forest Canopy
Remote sensing is the tool most often used to examine canopy cover over large areas. Remote sensing ranges from satellite images that differentiate among soil, water and vegetation by the type of light reflected, to pictures taken from airplanes. High-level aerial photographs like the one below can show distinct landforms such as forests, pastures, and tilled lands, in addition to highways and waterways. Photo: Aerial photograph of the upper Wheeling Creek watershed. Photo courtesy of Dr. Ben Stout.
Canopy cover can also be estimated more economically by standing in the center of the sample area and looking at the sky directly overhead. Scientists estimate the percentage of their field of vision that appears to be covered by vegetation. This percentage is the canopy cover. A similar method entails taking a picture from this position and measuring the percentage of the picture covered with vegetation using image analysis software.
The percentage of a stream covered by canopy decreases naturally with increasing stream order. This is a function of stream width. However, canopy cover can also be diminished by human activities such as logging, farming and construction. For this reason, measurements of canopy cover can be useful in detecting certain polluters--either present or past.
and Catchment Area / Stream Order /
Forest Canopy / Width, Depth, and Velocity
/ Rock Size / Turbidity
/ Total Solids / Temperature
Some images © 2004 www.clipart.com
Center for Educational Technologies, Circuit Board/Apple graphic logo, and COTF Classroom of the Future logo are registered trademarks of Wheeling Jesuit University.