The authors thank Dr. Rosgen for his lengthy discussion as it presents an opportunity for us to clarify and expand on some of the criticisms that are presented in the original manuscript as well as to differentiate between what the Discussion presents as ‘‘facts’’ and what he terms the ‘‘opinions’’, and ‘‘untrue...and inaccurate statements’’ made by Simon et al. (2007). Prior to publication Simon et al. (2007) went through an intensive 14-month peer-review process by three anonymous reviewers and an Associate Editor. It is unlikely that we and the reviewers were so ‘‘incorrect’’ about so many things. Certainly, we want to assure readers of this journal that this material was not an opinion piece, but was substantiated and fully supported by peer-reviewed, documented findings. These types of exchanges in the peer-reviewed literature are, however, welcome and are critical for the testing, validation, and advancement of science. The same cannot be said of manuscripts published in proceedings of meetings or by certain private publishers where no technical review is required. Yet quotes and citations from these sources are often given equal weight and can be particularly misleading.

JAWRA Journal of the American Water Resources AssociationVolume 44, Issue 3 p. 793-802 Reply to Discussion1by Dave Rosgen2 “Critical Evaluation of How the Rosgen Classification and Associated ‘Natural Channel Design’ Methods Fail to Integrate and Quantify Fluvial Processes and Channel Responses”3 A. Simon, A. Simon Respectively, Research Geologist, USDA-ARS, National Sedimentation Laboratory, Oxford, Mississippi 38655Search for more papers by this authorM. Doyle, M. Doyle Associate Professor, Department of Geography, University of North Carolina, Chapel Hill, North Carolina 27599Search for more papers by this authorM. Kondolf, M. Kondolf Associate Professor, Department of Landscape Architecture and Environmental Planning, University of California at Berkeley, Berkeley, California 94720Search for more papers by this authorF.D. Shields Jr., F.D. Shields Jr. Research Hydraulic Engineer, USDA-ARS National Sedimentation Laboratory, Oxford, Mississippi 38655Search for more papers by this authorB. Rhoads, B. Rhoads Professor, Department of Geography, University of Illinois, Urbana-Champaign, Illinois 61801Search for more papers by this authorM. McPhillips, M. McPhillips Principal Scientist, Intuition and Logic, Inc., Amelia Island, Florida.Search for more papers by this author A. Simon, A. Simon Respectively, Research Geologist, USDA-ARS, National Sedimentation Laboratory, Oxford, Mississippi 38655Search for more papers by this authorM. Doyle, M. Doyle Associate Professor, Department of Geography, University of North Carolina, Chapel Hill, North Carolina 27599Search for more papers by this authorM. Kondolf, M. Kondolf Associate Professor, Department of Landscape Architecture and Environmental Planning, University of California at Berkeley, Berkeley, California 94720Search for more papers by this authorF.D. Shields Jr., F.D. Shields Jr. Research Hydraulic Engineer, USDA-ARS National Sedimentation Laboratory, Oxford, Mississippi 38655Search for more papers by this authorB. Rhoads, B. Rhoads Professor, Department of Geography, University of Illinois, Urbana-Champaign, Illinois 61801Search for more papers by this authorM. McPhillips, M. McPhillips Principal Scientist, Intuition and Logic, Inc., Amelia Island, Florida.Search for more papers by this author First published: 16 May 2008 https://doi.org/10.1111/j.1752-1688.2008.00213.xCitations: 13 (E-Mail/Simon:asimon@ars.usda.gov) 1 Reply to Discussion No. JAWRA-08-0022-Y of the Journal of the American Water Resources Association 44(3):793-802 (Copyright © 2008). 2 Discussion No. J07-0148 of the Journal of the American Water Resources Association 44(3):782-792 (Copyright © 2008). 3 Paper No. J05-210 of the Journal of the American Water Resources Association 43(5):1117-1131. Discussions are open until December 1, 2008. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume44, Issue3June 2008Pages 793-802 RelatedInformation

Over the past 10 years the Rosgen classification system and its associated methods of "natural channel design'' have become synonymous to some with the term "stream restoration'' and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely adopted by governmental agencies, particularly those funding restoration projects. The purposes of this article are to present a critical review, highlight inconsistencies and identify technical problems of Rosgen's "natural channel design'' approach to stream restoration. This paper's primary thesis is that alluvial streams are open systems that adjust to altered inputs of energy and materials, and that a form- based system largely ignores this critical component. Problems with the use of the classification are encountered with identifying bankfull dimensions, particularly in incising channels and with the mixing of bed and bank sediment into a single population. Its use for engineering design and restoration may be flawed by ignoring some processes governed by force and resistance, and the imbalance between sediment supply and transporting power in unstable systems. An example of how C5 channels composed of different bank sediments adjust differently and to different equilibrium morphologies in response to an identical disturbance is shown. This contradicts the fundamental underpinning of "natural channel design'' and the "reference- reach approach.'' The Rosgen classification is probably best applied as a communication tool to describe channel form but, in combination with "natural channel design'' techniques, are not diagnostic of how to mitigate channel instability or predict equilibrium morphologies. For this, physically based, mechanistic approaches that rely on quantifying the driving and resisting forces that control active processes and ultimate channel morphology are better suited as the physics of erosion, transport, and deposition are the same regardless of the hydro- physiographic province or stream type because of the uniformity of physical laws.

Over the past 10 years the Rosgen classification system and its associated methods of natural channel design have become synonymous (to many without prior knowledge of the field) with the term stream restoration and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely, and perhaps dominantly adopted by governmental agencies, particularly those funding restoration projects. For example, in a request for proposals for the restoration of Trout Creek in Montana, the Natural Resources Conservation Service required experience in the use and application of a stream classification system and its implementation. Similarly, classification systems have been used in evaluation guides for riparian areas and U.S. Forest Service management plans. Most notably, many highly trained geomorphologists and hydraulic engineers are often held suspect, or even thought incorrect, if their approach does not include reference to or application of a classification system. This, combined with the para-professional training provided by some involved in natural channel design empower individuals and groups with limited backgrounds in stream and watershed sciences to engineer wholesale re-patterning of stream reaches using 50-year old technology that was never intended for engineering design. At Level I, the Rosgen classification system consists of eight or nine major stream types, based on hydraulic-geometry relations and four other measures of channel shape to distinguish the dimensions of alluvial stream channels as a function of the bankfull stage. Six classes of the particle size of the boundary sediments are used to further sub-divide each of the major stream types, resulting in 48 or 54 stream types. Aside from the difficulty in identifying bankfull stage, particularly in incising channels, and the issue of sampling from two distinct populations (beds and banks) to classify the boundary sediments, the classification provides a consistent and reproducible means for practitioners to describe channel morphology although difficulties have been encountered in lower-gradient stream systems. Use of the scheme to communicate between users or as a conceptual model, however, has not justified its use for engineering design or for predicting river behavior; its use for designing mitigation projects, therefore, seems beyond its technical scope.

Classification systems provide one means for generalizing, organizing, and categorizing sets of diverse items into groups. Stream channels tend to fit into broad categories (e.g., braided, meandering, sinuous, and straight) that suggest the utility of having some type of stream classification system. Recently, "natural channel design" has been advocated as a goal for stream alterations and has become the heart of some stream classification systems. Similarly, "channel evolution" has been recommended as one means for gaining insight to dominant channel processes. Both approaches rely on observations and comparisons of channel condition and geomorphic form. However, the physical appearances of streams can be misleading, as they often represent only fleeting glimpses at conditions, usually transitory, that reflect many different states of anthropogenic disturbance. This poses a particular difficulty in terms of stream channel restoration efforts, as there are few or no "undisturbed" streams in many regions of the country against which to make reference in order to understand what types of restoration goals and potentials may be relevant. Nevertheless, several classification systems have been developed that are used to assist in or even to guide stream alteration activities, including stream restoration. This panel reviews the features of classification systems and considers their "pros and cons" for various applications, including stream restoration.