• Despite statements to the contrary, the commercial navigation and ecosystem restoration components of the study have proceeded essentially on separate tracks. There is little evidence that prominent and important trade-offs and interactions between these two sectors and other users on the UMR-IWW were carefully considered.

  • There has been more attention devoted to considering nonstructural measures in the April 2004 draft feasibility study than in previous versions. The study still lacks adequate analysis in this realm, however, and some promising nonstructural approaches for managing waterway traffic appear not to have been considered at all. The failure to fully consider nonstructural measures precludes any statement about the desirability of structural measures.

  • The approach to estimating the benefits of lock extensions, using scenarios and upper and lower bounds on benefit estimates, is a reasonable way to deal with the uncertainties that attend the long lifetimes of inland waterway infrastructure, but the scenarios of future waterway traffic levels remain problematic. On further consideration, the largest concerns focus on the single forecast of non-grain commodities, and the scenarios reflect a bias in the direction of future increases in exports.

  • The Tow Cost Model used to estimate benefits of lock extensions can provide no more than an approximate upper bound on benefits. In an attempt to deal with the TCM’s shortcomings, the Corps developed the “ESSENCE” model. This model incorporates a hypothetical demand curve to estimate benefits of proposed lock extensions, but the curve has no empirical foundation. The ESSENCE model is therefore incapable of producing any credible estimate of a lower bound of the benefits of lock extensions. Economic feasibility has therefore not been demonstrated for any of the navigation alternatives.

  • Substantial effort has been devoted to designing an ecological restoration program, and the proposed restoration measures represent an impressive range and number of candidate actions. The assembly of these measures into restoration alternatives, however, is not adequately grounded in principles and theories of large river floodplain science and restoration. For example, evaluation of the candidate alternatives relies, in part, on metrics (e.g., “area affected”) that are poorly correlated with ecological outcomes. The ranking of alternatives is therefore unpersuasive.

  • The Corps’ Preferred Plan, if carried out as described, provides for a program of incremental implementation, an excellent framework for comprehensive adaptive management. If the Corps is provided the resources—and if it commits to the needed data collection, improved modeling techniques, and evaluation—many of the flaws and omissions in its study can be corrected in the course of implementation by application of adaptive management principles.

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement