CAN GEOMORPHOLOGIC SCIENCE CONTRIBUTE TO MID-ATLANTIC STREAM RESTORATION PRACTICE?

Much of the geomorphic knowledge that is used to guide restoration design is out of date, oversimplified, or based on inadequate data. For example, meanders are often created as symmetrical sine-generated curves, when this model was rejected by geomorphologists 25 years ago. The concept of fluvial equilibrium and adjustment to a dominant discharge are common design tools, yet current ideas in fluvial geomorphology emphasize greater temporal variability and complexity in processes of erosion and deposition. Restoration goals often include reducing sediment production, yet monitoring data on sediment transport and sediment yields are virtually nonexistent in the mid-Atlantic region, and the available compilations suggest that sediment yield from stream channels has decreased during the last half of the 20th century. Inconsistencies between geomorphic science and restoration practice are not simply an indictment of restoration practice, however. Restoration is a branch of engineering, rather than a science, and its goals are different from those traditionally espoused by academic geomorphology. Furthermore, geomorphologists rarely create knowledge that can be directly applied to restoration practice. For example, we cannot specify the size and shape of a channel required to ensure the continuity of water and sediment supplied by a watershed. Ideally, geomorphologists should 1) help the restoration community better appreciate the complexity and temporal context of fluvial processes, and 2) develop geomorphic models that are quantifiable on the temporal and spatial scales relevant to stream restoration. As the restoration community needs to become better geomorphologists, so geomorphologists need to become better engineers.