College of Environmental Design
LANDSCAPE ARCHITECTURE AND ENVIRONMENTAL PLANNING
University of California, Berkeley
202 Wurster Hall #2000
Berkeley, California 94720-2000
30 June 2014
Dwayne Johnson Regulatory Branch,
U.S. Army Corps of Engineers
P.O. Box 1229
Galveston, Texas 77553-1229
Re: file number SWG-2012-01007
Dear Mr. Johnson,
I have reviewed the Harris County Flood Control District’s (HCFCD) permit application for its proposal to “restore” over a mile of Buffalo Bayou in the “Memorial Park Demonstration Project”, and I offer the following comments.
First, some words about my background. I am a fluvial geomorphologist and hydrologist. I received my BA in geology (cum laude) from Princeton University, my MS in Earth Sciences from University of California Santa Cruz, and my PhD in Geography and Environmental Engineering from the Johns Hopkins University. My book Tools in Fluvial Geomorphology (published by John Wiley & Sons, 2003) is the reference work for methods in the field, and the second edition of the book is about to go to the publisher for an early 2015 release. I have also published well over 100 articles in international journals and chapters in books on topics related to fluvial geomorphology and its applications to river management. As a professor at UC Berkeley, I have taught the graduate-level courses Hydrology for Planners (originally taught by my predecessor at Berkeley, Luna Leopold, starting in the early 1970s) since 1990 and Restoration of Rivers and Streams since 1992. I served on the Environmental Advisory Board to the chief of the US Army Corps of Engineers from 2002-2007, as the Clarke Scholar at the Institute for Water Resources of the US Army Corps in Washington, DC, in 2011, on two National Academy of Science panels, and on the Independent Science Board for the Calfed Ecosystem Restoration Program in California. I have provided expert testimony on fluvial geomorphic issues before the California legislature and Water Resources Control Board, the US Congress, and the International Court of Justice in the Hague.
In my opinion, the proposed project would be misguided and not a wise investment of public funds.
First, it is notable that many projects constructed using the techniques proposed have failed by washing out within a few years or months of construction. Examples include Deep Run, Maryland (Smith and Prestegaard 2005), and Cuneo and Uvas Creeks, California (Kondolf 2006). However, even if these projects do not wash out, there is a fundamental problem in that they seek to stabilize stream channels by hardening the banks with root wads and/or boulders, preventing the natural migration of stream channels that is demonstrated to provide the best habitat values in natural rivers (Beechie et al 2010, Florsheim et al 2008, Stanford et al. 2005). This is why there is increasing interest in setting aside corridors in which rivers can migrate, flood, erode and deposit, creating high-quality aquatic and riparian habitat, without running into conflict with human infrastructure (Piegay et al 2005, Smith 2008, Rapp and Abbe 2003, Kondolf 2011). As typical of such projects, the proposed Buffalo Bayou project would take a sinuous but irregular channel and turn it into a series of symmetrical meander bends. There is no scientific justification for this in terms of river quality, but such treatments evidently have a strong appeal to many, perhaps related to deep-seated cultural preferences (Kondolf 2006). Unfortunately, in order to create the desired “ideal channel”, much of the existing riparian forest must be destroyed. The proposed project promises to replant the disturbed areas, but the loss of high-quality riparian forest for what is at best a questionable goal should be a cause of concern. At Deep Run, stripping the riparian forest to build the ideal channel form reduced the hydraulic roughness of the floodplain, resulting in higher velocity flows across the floodplain, which cut a new channel that ignored the channel constructed in the “restoration” project (Smith and Prestegaard 2005).
The HCFCD proposal does not justify the need for the proposed intervention, with its multiple impacts. For example, on p. 37 (of 658) the permit application states “Overall geomorphic assessment comment(s): The stream is recovering; the restoration project will decrease the time needed for natural recovery and allow protection of surrounding property.”
The permit application does not specify what the stream is recovering from, how it is recovering, and how the disturbance created by the proposed project would “decrease the time needed for natural recovery.” Just the opposite would seem to be the case, assuming the stream is in fact recovering from something. A nuanced reading of the statement suggests that the real goal is “protection of surrounding property”, i.e., preventing the banks from moving.
The permit application characterizes ongoing bank erosion as “severe”, but does not establish that it is in any way pathological. Recent geomorphic and ecological research demonstrates that actively migrating meandering rivers have high ecological value and biodiversity (Stanford et al. 2005, Florsheim et al 2008). This fact, combined with the high quality of the existing riparian habitat, should raise red flags about a proposal to remove this riparian forest and fix the river banks in place.
Interestingly, the bank erosion is estimated in the permit application (p.10 of 658) to have an annual volume of 359 tons per year. Yet the projected cut and fill volumes (p.12 of 658) show a net “cut” of 1078 tons, or nearly three times the claimed current bank erosion rate. In reading the permit application, I did not see where this excess material would be disposed, but if it is to be washed away by the river, that means the amount of sediment produced by project construction would exceed the ongoing erosion rate. It is not clear that an ongoing erosion rate of 359 tons per year for this reach would really be problematic, but if it were, it seems that the proposed project would create nearly three times this amount from its cutting and filling.
The geomorphic justification for the project is weak at best. On p.37 (of 658), the permit application states, “The major cause of bank erosion are [sic] tight radius meander bend curves and tight pool-to-pool spacing.” To a geomorphologist, this would require some explanation at the least, and even then the justification is unlikely to be convincing. Elsewhere on the same page, the permit application acknowledges, “Watershed contains a high degree of impervious cover. Full urbanized watershed. No impervious cover changes.” If bank erosion is increased over natural rates, the urbanization of the watershed would seem a more likely cause than an inferred “tight” spacing of pools.
Clearly, the process of ripping out the existing riparian forest and channel and imposition of the new “ideal” form on this reach of Buffalo Bayou would create disturbances, and the permit application fails to demonstrate that these disturbances would not contribute to significant degradation of waters of the United States.
In summary, the project as proposed by HCFCD for Buffalo Bayou is not justified on geomorphic or ecological grounds. It appears to be aimed at stabilizing the river, at a considerable ecological cost, as well as a substantial financial cost to the citizens of Houston. If such sums are to be spent to improve rivers in Houston, an alternative approach of purchasing land and/or easements to increase the width of the river corridor at key points should be considered, as a more robust approach that allows the river to heal itself (Smith 2008, Piegay et al 2005), and one that would avoid the environmental damage that would occur with the proposed project.
If you have any questions regarding my comments, please contact me at the email address below.
Thank you for the opportunity to submit comments on this matter.
G. Mathias Kondolf, PhD
Professor of Environmental Planning
Department of Landscape Architecture and Environmental Planning
Beechie TJ, Sear DA, Olden JD, Pess GR, Buffington JM, Moir H, Roni P, and Pollock MM. 2010. Process-based principles for restoring river ecosystems. BioScience 60: 209-222.
Florsheim JL, Mount JF, Chin A. 2008. Bank erosion as a desirable attribute of rivers. Bioscience 58(6): 519-529.
Habersack HM, Piégay H. 2008. River restoration in the Alps and their surroundings: past experience and future challenges. Gravel-Bed Rivers VI: From Process Understanding to River Restoration. H. Habersack, H. Piégay, M. Rinaldi (eds). Elsevier B.V., Amsterdam; 703-735. Kondolf GM. 2006. River restoration and meanders. Ecology and Society. [online] URL: http://www.ecologyandsociety.org/vol11/iss2/art42/
Kondolf GM. Setting goals in river restoration: When and where can the river ‘heal itself’? Stream Restoration in Dynamic Fluvial Systems: Scientific Approaches, Analyses, and Tools. in Simon A et al. (eds) Geophysical Monograph Series Vol.194 pp.29-43. American Geophysical Union, Washington DC. DOI: 10.1029/2010GM001020.
Piégay H, Darby SE, Mosselman E, Surian N. 2005. The erodible corridor concept: applicability and limitations for river management. River Research and Applications 21: 773-789.
Rapp CF, Abbe TE. 2003. A framework for delineating channel migration zones. Ecology Publication #0306-027, Washington State Departments of Ecology and Transportation, Olympia, Washington.
Smith, MP, R Schiff, A Olivero, and J MacBroom. 2008. The Active River Area: A Conservation Framework for Protecting Rivers and Streams. The Nature Conservancy, Boston MA
Smith, SM, and KL Prestegaard. 2005. Hydraulic performance of a morphology-based stream channel design, Water Resour. Res., 41, W11413, doi:10.1029/2004WR003926.
Stanford JA, Lorang MS, Hauer FR. 2005. The shifting habitat mosaic of river ecosystems, Verhandlungen des Internationalen Verein Limnologie 29: 123-136.