Abstract: Session D 10:30 am (Back to Session D)
Getting It Right in the Coastal Plain: Challenges and Constraints Associated with Restoring Stream Channels in the Western Coastal Plain of Maryland
Anne Arundel County, DPW,
Watershed Protection and Restoration Program
Most stream restoration efforts in Maryland have been focused in urban Piedmont areas due to stormwater runoff impacts from large population centers and mitigation needs for public projects in those regions. As a result, stream restoration design approaches have largely been developed for, and tested in, Piedmont areas. The same stream restoration design approaches were then applied to other physiographic provinces. However, questions remain concerning whether these approaches are entirely appropriate for other physiographic provinces.
The Anne Arundel County Watershed Protection and Restoration Program implements stream restoration projects for our county, which is located entirely in the Western Coastal Plain. Anne Arundel County is planning to install over 25 miles of stream restoration over the next few years. As we move forward with these designs, some fundamental geomorphic questions have been discussed, including: What should a natural Coastal Plain stream look like? Do Coastal Plain streams evolve differently from Piedmont streams? Do Coastal Plain streams have the same pre-history as Piedmont streams, and do they respond to land use changes in the same way?
Differences in geology, soils, and hydrology result in different boundary conditions for Coastal Plain streams. Geology alone presents significant challenges for stream restoration in Anne Arundel County, including acidic soils and unstable native sediments. Many of the smaller watersheds in central Anne Arundel County are sand-bed streams with no natural gravel source. In these settings, grain size is less important to channel roughness than bed form, vegetation, woody debris and other geomorphic influences. Streams in the depositional Coastal Plain landscape are subject to different sediment processes than transport-dominated Piedmont reaches, and Coastal Plain streams may have evolved from different pre-disturbance conditions. For example, many headwater channel gullies in Anne Arundel County were originally dry valleys and some floodplain areas were open water that filled in with sediment. These settings often require different design approaches and construction methods.
This presentation will provide a background on the unique features of working in the Coastal Plain setting and different methodologies we’ve used to address these challenges as we attempt to answer the questions above.