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The Real Value of the Reference Reach

Grant Ginn, PE
Stantec Consulting
Asheville, NC

Reference Reaches have been a staple of the stream restoration industry for several decades, but the concept and the data that come from them are not without their drawbacks. Many practitioners comment on the difficulty in finding true reference streams that are appropriate for design applications, the difficulty in translating measurements of reference streams to the constraints imposed by new construction, and the restraint on design that can come from regulatory interpretation of the data. The academic community has pointed out the potential for data that can be plagued with bias, some which are apparent and related to collection methods. However, there are more obscure elements related to observer preferences and cognitive bias that are difficult, if not impossible, to quantify or separate from the data.

As a discipline we have generally ignored these concerns and continued to use reference reach data as a bases for design, albeit with some degree of contempt. Two decades ago, it was standard practice to collect reference reach data for each project. As the industry has matured it has become more common practice to reuse previously collected data for similar projects. Another shift that has taken place is that, in the past, reference reach data collection was usually led by the project designer with the crew often using rudimentary survey methods, such as, laser levels and taped sections. Over time the trend has been to rely more on technicians or junior staff using more sophisticated GPS survey methods. While this adds a level of improved efficiency it doesn’t come without some sacrifices that include potential loss of quality of data collected, disconnection of the data from the designer, and lost opportunities for teaching and mentoring.  

An alternative approach that shifts the focus from data collection to observation training can restore the reference reach to its proper and best role in the design of natural rivers. By using a ‘direct measurement’ approach, instead of a ‘survey’ approach, practitioners can learn to shift their focus from data acquisition to studying the forms and processes of the river. This can be done without sacrificing the quality of the data. By developing better observational skills it helps to ensure that over time more meaningful data is actually collected and incorporated into the decision-making process of the design. By shifting the focus to observation training, the true value of the reference reach survey can be realized, which is the transfer of knowledge and skills that develop the next generation of river designers.