A Framework for Identifying and Verifying Bankfull in Diverse Landscapes and Watershed Conditions
Will Harman, PG
Stream Mechanics
Raleigh, NC
Bankfull discharge and dimensions are used in numerous assessment and design methodologies. Over the last twenty years, bankfull regional curves have been developed throughout the country to support these assessment and design methods. These bankfull regional curves are published in peer-reviewed journals, government documents, conference proceedings, and more. In almost all cases, the manuscripts simply state that the bankfull regional curves can be used as an aid in identifying bankfull stage in un-gaged watersheds and assist with designing the riffle dimension (area, width, and depth). These manuscripts typically do not provide a detailed method for how to identify and then verify the bankfull feature, especially when multiple features are present or the watershed is highly regulated. This ambiguity has led to frustration and erroneous bankfull field calls, a problem that is exacerbated by the fact that inexperienced professionals are often the ones making these field calls.
This presentation lays out a framework to methodically identify the bankfull feature and separate it from the inner berm and terrace features if they are present. The framework has been applied in diverse landscapes ranging from sub-arctic Alaska, the Rocky Mountains, the Appalachian Mountains, and the Coastal Plain of North Carolina. The framework can also be applied in regulated watersheds, such as those found in Colorado and Wyoming. The benefit of using this framework is an improvement in making repeatable bankfull calls by different practitioners, even those with minimal experience. This in term improves the repeatability of the assessment methods being used.
About Will Harman, PG
Will Harman is a founder of Stream Mechanics and Ecosystem Planning and Restoration. In the course of his 32-year career, he has participated in hundreds of stream restoration projects, representing a wide variety of landscape settings and techniques. Examples include steep gradient, step-pool designs in Alaska to low gradient meandering streams in North Carolina, and urban solutions in San Antonio, Texas.
He has authored numerous peer-reviewed journal articles and proceeding papers on stream assessment and restoration methods and was the principal author of two design manuals. He developed the Stream Functions Pyramid Framework and co-developed the Stream Quantification Tool, which is being used by many state and federal agencies to quantify the functional uplift from stream restoration practices.
Prior to working in the private sector, Will was on the faculty at NC State University where he co-founded the NC Stream Restoration Program. He is a licensed geologist in North Carolina.
