Modeling Biochemical Oxygen Demand Through the Middle and Lower Savannah River1

Abstract: In order to improve modeling accuracy and general understanding of lotic biochemical oxygen demand (BOD), this study characterized river metabolism with the current Georgia Environmental Protection Division method for the middle and lower Savannah River basin (MLSRB) and several alternative methods developed with 120‐day, long‐term biochemical oxygen demand (LTBOD) data from the MLSRB. The data were a subset of a larger two‐year LTBOD study to characterize and understand BOD in the MLSRB, located approximately between Augusta, Georgia, and Savannah, Georgia, along the border of Georgia and South Carolina. The LTBOD data included total oxygen loss and nitrogen speciation for separately quantifying nitrification. Results support the following insights and opportunities for modeling methods: (1) it is important to modeling accuracy that residuals be checked for even dispersion to avoid areas of over‐ and underprediction; (2) modeling with bounded, yet unfixed, rates is a sufficiently simple alternative to fixed‐rate modeling that can eliminate the need for manual adjustments and provide additional system understanding to inform regulation; (3) if fixed rates modeling is desired, model quality for this system might be improved through revising the current low rate (along with the associated f‐ratio updates) from 0.02/day rate to 0.006/day and potentially adding a new rate at 1.0/day in some cases; and (4) the current 57/43 ratio of slow/fast BOD is reasonable based on the 52/45/3 slow/fast/faster BOD proportions of this study.     

Synthetic endocrine disruptors in the environment and water remediation by advanced oxidation processes

The present study is an overview of the literature on classes and types of compounds described as "endocrine disruptors" and their treatability in water by advanced oxidation processes, which generate hydroxyl radicals in water. The review is limited to details of the destruction of three classes of endocrine disruptors, namely bisphenols, alkylphenols and phthalates, which are among the most highly suspected endocrine disrupting compounds that interfere with the hormonal system of wildlife. It was found that photocatalysis with titanium dioxide was the most frequently tested advanced oxidation method most likely due its potential to render complete mineralization. There is sufficient research also with direct and indirect photolysis and ozonation, which were less effective for the overall mineralization but more representative of the conditions existing in real water treatment plants.     

Modeling patterns of breakdown (or archetypes) of human and organizational processes in accidents using system dynamics

Systems approaches to safety have received growing attention in modern accident investigation techniques (e.g., STAMP, Accimap) with the emphasis shifted to the organizational dynamics (or archetypes) that may lead to an erosion of defenses and a drift out of the safety margins. Although the literature contains many applications of archetypes and system dynamics to safety, this richness comes at a cost of learning. It has become very difficult for safety practitioners to integrate the diverse studies of system dynamics with their diverging models. To provide a practical tool of system dynamics in accident investigation, this article reviews earlier studies and integrates them as a classification of patterns of breakdown (or archetypes) of both human and organizational processes on the basis of two control models, that is, the Extended Control Model (ECOM) and the Viable System Model (VSM). In this article, archetypes are represented as variants of two generic templates of performance which exploit many elements of complexity theory and system control. Apart from providing a practical tool to safety practitioners to access the literature on archetypes, the generic templates of ECOM and VSM can be used in building simulators of individual and organizational processes for risk analysis.     

Analysis of Spatial and Temporal Evolution of Vegetation Cover in the Spanish Central Pyrenees: Role of Human Management

A vegetation cover increase has been identified at global scales using satellite images and vegetation indices. This fact is usually explained by global climatic change processes such as CO₂ and temperature increases. Nevertheless, although these causes can be important, the role of socioeconomic transformations must be considered in some places, since in several areas of Northern Hemisphere an important change in management practices has been detected. Rural depopulation and land abandonment have reactivated the natural vegetation regeneration processes. This work analyses the vegetation evolution in the central Spanish Pyrenees from 1982 to 2000. The analysis has been done by using calibrated-NDVI temporal series from NOAA-AVHRR images. A positive and significant trend in NDVI data has been identified from 1982 to 2000 coinciding with a temperature increase in the study area. However, the spatial differences in magnitude and the sign of NDVI trends are significant. The role of land management changes in the 20th century is considered as a hypothesis to explain the spatial differences in NDVI trends. The role of land-cover and human land-uses on this process has been analyzed. The highest increment of NDVI is detected in lands affected by abandonment and human extensification. The importance of management changes in vegetation growth is discussed, and we indicate that although climate has great importance in vegetal evolution, land-management changes can not be neglected in our study area.     

MODELING THE EFFECTS OF VARIABLE ANNUAL FLOW ON RIVER CHANNEL MEANDER MIGRATION PATTERNS,SACRAMENTO RIVER,CALIFORNIA, USA1

ABSTRACT: Flow regulation impacts the ecology of major rivers in various ways, including altering river channel migration patterns. Many current meander migration models employ a constant annual flow or dominant discharge value. To assess how flow regulation alters river function, variable annual flows ‐ based on an empirical relationship between bank erosion rates and cumulative effective stream power ‐ were added into an existing migration model. This enhanced model was used to evaluate the potential geomorphic and ecological consequences of four regulated flow scenarios (i.e., different hydrographs) currently being proposed on the Sacramento River in California. The observed rate of land reworked correlated significantly with observed cumulative effective stream power during seven time increments from 1956 to 1975 (r²= 0.74, p = 0.02). The river was observed to rework 3.0 ha/yr of land (a mean channel migration rate of 7.7 m/yr) with rates ranging from 0.8 ha/yr to 5.1 ha/yr (2.0 to 13.3 m/yr), during the analyzed time periods. Modeled rates of land reworked correlated significantly with observed rates of land reworked for the variable flow model (r²= 0.78, p = 0.009). The meander migration scenario modeling predicted a difference of 1 to 8 percent between the four flow management scenarios and the base scenario.     

Critical Evaluation of How the Rosgen Classification and Associated “Natural Channel Design” Methods Fail to Integrate and Quantify Fluvial Processes and Channel Response1

Abstract: 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.     

A Critical Appraisal of Field Evidence From A Regional Survey for Acid Deposition Effects On Scottish Moorland Podzols

Samples have been collected from major horizons of 34 podzol profiles distributed throughout Scotland, all developed from granite or granitic tills and under Calluna moorland. the pH in water and calcium chloride pastes, exchangeable cations and cation exchange capacity, and extractable aluminium of the soils collected have been measured, and the results studied in relation to reported atmospheric deposition of H⁺, non-marine sulphur and nitrate. for all horizons, significant positive correlations were found between soil pH and rainfall mean pH, as might be expected when the critical load of H⁺ deposition is exceeded. Acidifying pollutant deposition also apparently increased soil extractable aluminium concentrations in the B and C horizons. However, exchangeable base cation concentrations tended to increase, rather than decrease, with increasing precipitation acidity. This effect was attributed to increases in biogeochemical cycling of base cations, increases in leaching inputs of base cations from overlying A/E horizon soils, and increases in the inputs of base cations leached from upslope. the results suggest that the simple steady state mass approach to the quantification of critical loads, as often applied, may be an oversimplification.     

A planning and decision-making framework for ecological restoration

A broad and objective perspective of ecological and socioenomic knowledge is required to underlie a scientific approach to the problems of terrestrial restoration ecology. Uncertainty associated with limited scientific knowledge highlights the crucial importance of the interaction between science and policy in weighing ecological restoration alternatives in relation to other management options. In this paper, we provide a pragmatic definition for restoration ecology that is suitable for extensive terrestrial applications and present a decision framework to help organize and clarify different phases of the decision process as it is related to ecological restoration. We argue that restoration planning should include a wider spectrum of participants and decisions than have traditionally been employed.     

ENHANCEMENT OF RIPARIAN ECOSYSTEMS WITH CHANNEL STRUCTURES1

ABSTRACT: Naturally occurring and man-made structures can be used for enhancing the development of riparian zones. Naturally occurring structures are cienagas, beaver dams, and log steps. Man-made structures include large and small channel structures and bank protection devices. All these structures affect streamflow hydraulics and sedimentation and can create a more favorable environment for riparian zone establishment. However, when they are used improperly, they can be destructive to existing riparian zones. Since stream processes are generally slow, long-time spans may pass before the effects of management action, good or bad, become visible. Also, the effects of large dam installations may appear a long distance downstream from the dam. Therefore, investigations must be of a wide scope. Interactions between riparian site, channel, and streamflow may be so complex that an interdisciplinary approach is required.