EVOLUTION AND REVOLUTION IN COASTAL FLOODPLAIN RECONNECTION METHODS

In 2015, most stream restoration or rehabilitation projects are still being designed with techniques developed in the previous century. The two most common stream repair techniques, Natural Channel Design (NCD) and Regenerative Stream Channel Design (RSC), were developed in 1986 and 1997, respectively. The degraded reaches where many of these projects are being considered are "novel ecosystems" biologically and geologically - the current processes bearing little resemblance to historic geometries and processes.

But as practitioners continue to push the boundaries of where and to what ecological extent stream repair can be accomplished, new techniques must evolve to be responsive to unique site criteria, our evolved understanding of sediment and stream processes, and increasingly complex regulatory requirements. Currently, four new adaptations to NCD and RSC are under evaluation in Anne Arundel County, Maryland to achieve more project goals within a complex ecological and regulatory landscape surrounding the functional rehabilitation and repair of coastal plain streams, ditches, and gullies. All include increasing site stability and floodplain connectivity in a manner that attempts to mimic pre-colonial conditions and functions of coastal plain streams.

These four experimental methods include 1) NCD valley-wide controls, 2) In-situ grade control plugs, 3) In-situ valley-wide riffles, and 4) In-situ valley-wide log weirs. We will discuss the anticipated project benefits of these novel approaches, initial ecological responses, and benefits in cost and impact reduction vs. conventional RSC or NCD. Particular focus will be upon potential ecosystem benefits in floodplain reconnection and associated nutrient processing and sediment attenuation processes.