A simple channel complexity metric for analyzing river ecosystem responses
O'Neill, Brian J.; Thorp, James H.
River complexity has become an important aspect of river science, especially in light of the anthropogenic disturbances and regulation which have simplified many rivers and led to negative consequences for ecosystem structure and function. Current metrics for analyzing channel complexity, which were primarily designed for fluvial geomorphologists, overlook many types of channel structures that are vital for ecological processes. These earlier metrics tend to be overly complex, expensive, and time consuming for ecological studies where the main goal is not focused on geomorphic complexity as the end product, but rather on elucidating the ecological effects of that complexity. To better understand impacts of hydrogeomorphic fluctuations on river ecosystems, we developed the River Channel Complexity Ratio (RCCR), a simple method for estimating channel complexity of riverscapes. This was developed initially for braided prairie rivers, but it can be employed to measure many types of channel features and structures in other river types. The RCCR is a ratio between the total shoreline length within a river and the shoreline length of a single channel. The ratio can be analyzed over time in reference to various abiotic variables (e.g., discharge and space) and employed to explain changes in ecological variables, such as system metabolism and community structure.