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Analytical Methods and Approaches for Water Resources Project Planning 5 Engineering The Corps of Engineers played important roles throughout the twentieth century in developing and refining water resources engineering analytical approaches. There were major investments in research, both on a project level in Corps district offices and through programs of basic research at the Corps’ five major research centers, which in 1999 were joined under a common administrative structure and are now collectively known as the Engineer Research and Development Center (ERDC; see Box 5-1). The Corps is today known in the civil and environmental engineering profession for its development of a broad spectrum of analytical and modeling conventions. These contributions include the Corps’ Hydrologic Engineering Center (HEC) family of hydraulic engineering computer codes, standards for in situ measurement of soil engineering properties, dredging and dredged material management guidance (including beneficial reuse options), structural models of massive concrete monolith construction, and artificial intelligence computer applications to support construction project managers. As a rule, practicing engineers look to the Corps for technological leadership. The Corps has responded by summarizing its design approaches in engineering manuals that have become standard texts that are used in universities and professional practice around the world, which are now available electronically through the Corps’ Internet library. The focus of this report is on Corps analytical methods and project evaluation approaches. In contemporary engineering practice, analytical methods and project evaluation are embodied in mathematical modeling. Although there are many dimensions to Corps engineering practices—from civil design, to hydraulics, to ecosystem intervention, to construction, and even to large-scale physical models of river reaches and coastal works—mathematical models represent the contemporary embodiment of analytical methods and, thus, the nexus of this chapter’s discussions. The Corps’ traditional approach to engineering modeling—as, indeed, the practicing profession’s approach more generally—has been to
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Analytical Methods and Approaches for Water Resources Project Planning BOX 5-1 Engineer Research and Development Center The Corps operates five basic and applied research laboratories throughout the continental U.S. under the Engineer Research and Development Center. Each has a special mission, contributing to the breadth of science and technology needs demanded by water resources and military engineering projects. In order of size, these are the following: Waterways Experiment Station, WES (Vicksburg, MS). The WES comprises several individual laboratories focusing on environmental, structural and geotechnical, coastal and hydraulic engineering, and information technology. The WES is the oldest and largest major Corps research facility, established in response to the Mississippi River flood of 1927. Started as a hydraulic modeling laboratory for river works studies, principally on the Mississippi and its tributaries, WES today undertakes broad research on both civil works and military engineering. Construction Engineering Research Laboratory, CERL (Urbana, IL). Among the newer of the major Corps laboratories, CERL focuses on vertical construction applications, principally buildings and related facilities. The laboratory has been a leader in research on innovative materials for building construction, on construction technology and automation, and on advanced computer technology for construction and construction management. Cold Regions Research and Engineering Laboratory, COREL (Hanover, NH). COREL has the specialized mission, reflected in its name, of developing and testing engineering technology for civil works and military engineering in cold climates, including polar regions. COREL conducts research on material and operations in winter battlefields; cold effects on construction; impacts of human activity on the environment of cold regions; and on the physics of snow, ice, and frozen ground. isolate well-defined issues for analysis and to develop deterministic mathematical models or empirical design procedures by which to address them. Large factors of safety have been applied to calculated predictions of natural forces or to facility capacities in order to ensure exceptionally low likelihood that forces will exceed capacities and lead to failure. The result has been that hydraulic, structural, and similar facilities failures of Corps-designed works have indeed been rare. “Overdesign” of facilities, however, generally increases project costs.
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Analytical Methods and Approaches for Water Resources Project Planning Topographic Engineering Center, TEC (Fort Belvoir, VA). Unlike the other Corps laboratories, TEC has a predominantly military mission, developing and testing new technologies of mapping, spatial information sensing and processing, and battlefield information systems, and over the years has been closely related to the mission of the National Imaging and Mapping Agency (NIMA; formerly the Defense Mapping Agency). The TEC contributes to the Corps’ civil works mission through its geographic information system technology and applications of remote sensing technology to terrain analysis. Hydraulic Engineering Center, HEC (Davis, CA). HEC is a small research center dedicated to the development of hydraulic and hydrological engineering analysis methods and associated computer applications. Over the past four decades, HEC has developed computer applications for flood frequency forecasting, flood routing, sedimentation transport, flood hazard risk analysis, and other engineering problems, that have become industry standards in Corps projects and in the private sector. The ERDC has been useful in many ways, offering specialized technical expertise not only to the Corps, but also to the academic and professional communities associated with various Corps activities. ERDC’s engineering and design manuals have been internationally accepted and widely referenced for project guidance (e.g., ERDC’s Shore Protection Manual, now being replaced by the Coastal Engineering Manual, is the internationally accepted design reference for coastal and navigation projects). Historically, the Corps has had a close association with research institutions around the world and with the university research community, and has been known for its rational-analytical approach to engineering problems. Corps personnel have been active participants in professional societies such as the American Society of Civil Engineers, and its engineering methods have been widely aired at national conferences and in peer-reviewed archival journals. Historically, this has been in sharp con-
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Analytical Methods and Approaches for Water Resources Project Planning trast with the more empirical approach favored by much of the U.S. civil engineering profession (see Shallat, 1994), although the development of Corps technology, especially in earlier decades, has not been without its critics. Although traditional engineering models and approaches applied to planning generally produce reasonable results, efforts in improving algorithms, approaches, or enhanced applications should not be abandoned. The primary role of engineering in decision making is in developing technical analyses and evaluations that are based largely on assumptions that aid in the eventual development of project alternatives. Engineering assumptions usually govern the project cost portion of benefit-cost analysis, which lends itself to close scrutiny, especially on controversial Corps projects. Although Corps design manuals have been an asset to the agency (and the engineering community in general), in some instances they can also act as limiting factors that discourage creative thinking by the Corps’ project team (and project manager), thereby “boxing” them in to preset policy and procedural aspects. This has particularly been a problem in decision-making analysis, especially as technologies evolve and numerical techniques advance, with some Corps personnel still applying “old” techniques and technology. Although it can be argued that ERDC possesses state-of-the-art models, not all Corps districts have access to, or use those models. The Corps will have to make some adjustments in this realm if it is to possess high-quality technical expertise on engineering project analysis. METHODS AND TECHNIQUES Engineering models employed by the Corps on major projects can, as a first approximation, be categorized into four sets: (1) hydraulics and hydrology (H&H), (2) hydrodynamics and sediment transport, (3) geology and geotechnical, and (4) structural models. Other types of engineering models are used on civil works projects—for example, terrain models or environmental models of contaminant fate and transport—but these either are closely related to one or more of the four main categories or are of lesser importance in major project planning decisions. Hydraulics and Hydrology Hydraulic and hydrologic models treat the flow of water in natural
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Analytical Methods and Approaches for Water Resources Project Planning and man-made channels or coastal regions, and the water cycle of rainfall, runoff, and groundwater. Hydraulic and hydrologic methods of analysis are used to make forecasts of flood frequencies (i.e., the probabilities that flood discharges of certain magnitude will be exceeded within given periods of time—for example, annually) or water heights at specific stream reaches with flood flows of known discharge values. The Corps has played an important historical role in developing these H&H methods. In order to support Corps planning in the future, it will be essential to develop models more fully, or perhaps develop model suites, linked to a common data base that more fully evaluate groundwater and surface water interactions, and that are capable of simulating a system for an extended period of time, rather than for a single rainfall event. Hydrodynamics and Sediment Transport Hydrodynamic models address the various intricacies of the coastal zone, including wave generation, development, propagation, and resulting processes. Sediment transport models are typically used hand-in-hand with hydrodynamic models to predict sedimentation patterns, littoral transport, beach stability, or near- and offshore sediment dynamics. The Corps has long been a leader in the development of scientific and engineering tools in this area, as well as in developing manuals. The recent publication in this series is the Coastal Engineering Manual (CEM), which will replace the Shore Protection Manual (SPM), also developed by the Corps, which has historically been used for the design and analysis of coastal and navigation engineering projects. Geology and Geotechnical Engineering These models treat the engineering properties and behavior of naturally occurring or treated geological materials—soil, rock masses, and groundwater—and the geological processes that affect those materials and structures constructed on or in them. Examples of such geological processes are earthquakes, regional subsidence, and swelling soils. Geotechnical models are used to develop forecasts of the strength of dam and levee embankments to the forces of water impounded behind them, the intensity of seismic ground shaking that the foundation of a structure can withstand without liquefying, settlement processes of nearshore and upland fills, or the spatial extent of contamination caused by groundwater
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Analytical Methods and Approaches for Water Resources Project Planning seepage through a contaminated industrial site. The Geotechnical Engineering Laboratory at the Corps Waterway Experiment Station in Vicksburg, Mississippi, was an early and distinguished center for geotechnical research and has developed numerous design manuals and models for such applications. Structural Structural models treat the strength of structural systems, such as buildings, dams, breakwaters, bulkheads, jetties, and other constructed works, to withstand the loads—both natural and human-induced—to which they are subjected. Structural engineering is a broad and ancient practice, yet the Corps’ unique purview of large water retaining and conducting facilities, as well as coastal protection structures, implies that the application areas it addresses are distinct from much of structural engineering practice associated with facilities such as buildings, roads, and bridges. Structural methods of analysis are used, for example, to evaluate the strength of large concrete dams, test the ability of a constructed breakwater to withstand extreme wave impacts, or test the dynamic responses of lock gates to varying loads of towboats. The Corps has developed several engineering manuals and design software of specific application for structural design, especially in the realm of coastal and navigational uses. Systems Approaches and Perspectives Water resources projects have become ever more complex and interconnected. For example, navigation, flood control, and ecosystem restoration projects on the Upper Mississippi River merge into one another geographically and create engineering, economic, and environmental impacts that cannot be separated from one another. Regional-scale projects, such as the Everglades Restoration, Coastal Louisiana, and CalFed, are becoming more common and involve complex interactions among impacts that have heretofore been primarily analyzed in isolation. These growing complexities necessitate a systems engineering approach to project planning. A systems engineering approach to water resources planning involves a holistic view spatially, temporally, and across disciplines, which fundamentally changes the dynamics of planning. The systems approach
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Analytical Methods and Approaches for Water Resources Project Planning has been driven in part by changes in technology, increasing pressure to lower costs and shorten project completion times, higher performance requirements, increasing complexity, and the increasing importance of information technology and real-time control in large civil works and environmental projects. This approach has also been driven by a growing awareness of long-range, distant-time, and interdisciplinary consequences of large projects that were not anticipated at the time of planning. On the methods side, growing awareness of systems thinking in large water resource projects presents challenges to engineers and planners. These challenges include: (1) a growing awareness of a need to interrelate modular components of technology across disciplines in systems integrations; (2) a growing importance of teams of experts from different disciplines working together on complex projects, along with the associated problems of communication, interpretation, and documentation; (3) a centralization of information-dominated systems, which exploit commercial software and telecommunications technologies and derive information from a wide array of sources; and (4) a growth in volume of numerically intensive, multidimensional, heterogeneous, spatially distributed data that have to be accessed jointly by engineering, economic, and scientific planners. These systems engineering issues are not unique to the Corps or even to water resources projects, and they arise in all aspects of large government and private sector projects. Given the Corps’ traditional engineering and planning strengths and its national prominence, it is in position to aggressively pursue the development of systems engineering and economic planning methods that could benefit planning activities in natural resources management in the Corps and the federal government. Risk and Uncertainty Analysis The historical approach to coping with uncertainty in water resources engineering has been to design on the basis of a best-estimate of some extreme loading or stress (e.g., an extreme flood, extreme coastal storm, or extreme drought), and then augment that design by a fixed safety factor. The factor of safety is some multiple of the extreme event loading, for example, 50 or 100 percent more, or some other increment. This is an engineering tradition that is only now beginning to change in European and U.S. codes (Aashto, 1998; Cen, 1993). The Corps has been in the forefront of a transition from deterministic methods of analysis to
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Analytical Methods and Approaches for Water Resources Project Planning risk-based methods that explicitly account for uncertainty (Box 5-2). This is an important transition because, as concluded by previous National Research Council committees (NRC, 1995, 1996, 2000) and detailed in Corps reports (USACE, 1992), risk and uncertainty-based methods lead to projects better tailored to local conditions and available data than those that are based on deterministic analyses. In particular, earlier deterministic approaches to project planning may not provide consistent levels of safety, consistent benefit-cost ratios, or consistent interpretations of environmental impacts across the nation. Such variations across projects and locales can, to a better degree, be captured by risk-based BOX 5-2 Risk and Uncertainty in Flood Damage Reduction Studies Many flood damage reduction projects involve the construction of levees. The historical approach to coping with hydraulic and hydrologic uncertainties of large floods was to base levee design on a best-estimate of the height required to retain a flood with an annual probability p = 0.01 of being exceeded (the so-called one hundred-year flood), and then augment that height by a standard levee “freeboard” of 3 feet. This became an engineering tradition across the nation. Challenges to the concept of a standard increment of freeboard emerged in the early 1990s when it was noted that the standard 3 feet did not account for geographic or hydrologic differences at different locations, and thus afforded different levels of flood protection to different localities. This also drew into question the standard procedures for calculating the economic benefits conferred by levee freeboard. The Corps’ Hydraulic Engineering Center developed an innovative risk analysis approach to flood damage reduction analysis that holds great promise for rationalizing the way uncertainties are accounted for in project planning. This approach uses probabilistic methods, combined with statistical analysis of historical streamflows and stages and geographic information systems, to quantify the uncertainties associated with estimates of water heights and resulting property damage. The risk analysis approach has now become part of the National Flood Insurance Program levee certification procedure jointly conducted by the Corps and the Federal Emergency Management Agency. SOURCE: NRC (2000).
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Analytical Methods and Approaches for Water Resources Project Planning methods. Even in common and traditional areas of project planning (such as construction cost estimation), the need for improved methods of capturing uncertainty is demonstrated by history (Shallat, 2002). Although the Corps has been aggressive in developing risk-based methods of analysis for flood damage reduction studies and certain studies of navigation projects, methodological developments are needed (1) to strengthen the capability to employ risk-based methods on the broad range of engineering economic analyses used in project planning; (2) to extend risk-based methods to ecosystem restoration projects that involve large magnitudes of uncertainty; (3) to continue to expand the use of risk-based methods in traditional engineering disciplines such as structural, geotechnical, and coastal engineering; and (4) to enhance the development of uncertainty distributions about numerous other parameters. Risk and uncertainty analysis can be a powerful tool if properly developed and constrained. The Corps should adopt a long-term focus toward enhancing and expanding the use of this analysis. The Corps, along with the U.S. Bureau of Reclamation, has taken a lead among engineering agencies in incorporating quantified expert judgment in risk-based methods of analysis (e.g., Klosterman and Sanders, 2000). This line of investigation should be continued, given the importance of engineering and scientific judgment to so many of the analyses used to evaluate water resource project plans. Engineering Methods for Ecosystem Restoration Hydraulics and hydrology and geotechnical methods of analysis are of central importance to the Corps’ ecosystem restoration mission. Although ecosystems are biological, they depend ultimately on physical aspects of the natural environment, such as flow regimes, sedimentation patterns, and contaminant transport. Yet analytical methods that the Corps has traditionally used for hydraulic, hydrologic and geotechnical modeling were not developed with this use in mind and are in many ways inadequate to the needs of ecosystem restoration planning. For example, such methods are validated for making forecasts of relevance to a levee’s required height to retain flood flows, but they are not (or at least not yet) validated for making forecasts related to, detention times in riparian wetlands. The latter may be critical to ecosystem restoration project planning. Corps planners and engineers lack agency-sanctioned manuals that provide technical guidance and support for the design of engineered as-
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Analytical Methods and Approaches for Water Resources Project Planning pects of ecological restoration. Such manuals would be the equivalent of those now used for river hydraulic design, geotechnical site characterization, and structural analyses. They would refer to issues associated with the design, installation, and maintenance of systems that make use of natural materials; to the size and strength of a structure used within the restored area; to engineering adaptations affecting fluvial geomorphology; and to other engineering methods that lend themselves to treatment in a technical manual. Corps designs are generally influenced by a tradition of protecting people and property, where the consequences of failure are costly to human health and safety; in contrast, in restored areas the consequences of failure may be less dramatic. In part, the lack of manuals may result in a lack of willingness by more cautious designers to apply engineering techniques of ecosystem restoration or may lead to “overdesign” and increased costs. COMMENTARY Three aspects of the Corps’ engineering analysis and methods bear close attention in the years ahead. The importance of these relates to the changing paradigms of U.S. water resources management and to the changing needs of Corps projects and activities. These are (1) systems engineering aspects of water resource planning, (2) impacts of risk and uncertainty on planning, and (3) integrating engineering methods of analysis with ecosystem restoration planning. Another important consideration in Corps planning studies, and of the engineering methods therein, is the value of occasional independent review. Corps planning studies would also benefit by including a summary of the key assumptions used in engineering design, models, and methods of analysis. These dimensions of a planning study are often extremely complicated and technical and are difficult for the layperson to understand. Furthermore, they often tend to be located at various places in a planning study, making it difficult to grasp the key issues and approaches quickly. Equally important to ensuring the use of credible methods and techniques is having the resources to apply and implement them. Although the Corps may have some ability to stay abreast of engineering and technical advances, it suffers from a limited ability to recruit and retain talented personnel. The Volcker Report looked carefully at the issue of personnel within the federal government. Its observations parallel some of this report’s observations regarding Corps personnel issues (NCPS, 2003):
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Analytical Methods and Approaches for Water Resources Project Planning Far too many talented public servants are abandoning the middle levels of government, and too many of the best recruits are rethinking their commitment, either because they are fed up with the constraints of outmoded personnel systems and unmet expectations for advancement or simply lured away by the substantial difference between public and private sector salaries in many areas. Support from the administration and Congress for the Corps to recruit and retain well-qualified staff, to be able to hire staff from outside the agency, and to create realistic and rewarding career advancement paths, will all be important to the Corps as it addresses twenty-first century engineering and planning challenges.
Representative terms from entire chapter: