(1991). Applied Linear Regression Models. Journal of Quality Technology: Vol. 23, No. 1, pp. 76-77.

Applied Linear Regression Models

Foreword 1. Introduction 2. Runoff, erosion and delivery to the coastal ocean 3. Temporal variations 4. Human impacts Appendices. Global River Database: Appendix A: North and Central America Appendix B: South America Appendix C: Europe Appendix D: Africa Appendix E: Eurasia Appendix F: Asia Appendix G: Oceania References Index.

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River Discharge to the Coastal Ocean: A Global Synthesis

More than a hundred hydropower dams have already been built in the Amazon basin and numerous proposals for further dam constructions are under consideration. The accumulated negative environmental effects of existing dams and proposed dams, if constructed, will trigger massive hydrophysical and biotic disturbances that will affect the Amazon basin's floodplains, estuary and sediment plume. We introduce a Dam Environmental Vulnerability Index to quantify the current and potential impacts of dams in the basin. The scale of foreseeable environmental degradation indicates the need for collective action among nations and states to avoid cumulative, far-reaching impacts. We suggest institutional innovations to assess and avoid the likely impoverishment of Amazon rivers.

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Damming the rivers of the Amazon basin

Previous geologic research on Holocene Mississippi River deltaic deposits has verified that the present delta plain and associated nearshore barrier islands and submarine shoals are either direct or indirect products of cyclic delta-building events that have operated on a variety of temporal and spatial scales. A major depositional element of the modern delta plain is the delta complex, of which there are six: (1) Maringouin, (2) Teche, (3) St. Bernard, (4) Lafourche, (5) Balize, and (6) Atchafalaya. Major delta-building events have occurred at a frequency of one every 1- 2 kyr. Deposits associated with the six major delta complexes are fundamental constructional units of the delta plain, which collectively covers an area of - 30,000 km2. Sedimentary deposits associated with these delta-building events range in thickness from about 10 to 100 m. Their construction is modulated by stream capture, which develops a new delta complex by way of a new river course. Delta complexes may be comprised of one or more delta lobes. As a product of this delta switching, the depositional architecture of the delta plain consists of laterally offset and stacked delta lobes. Within delta lobes are subdeltas and even smaller crevasse splays. These smaller scale deltas sedimentologically and geomorphically mimic their larger delta lobe counterparts, but they are considerably thinner, cover less area, and have a shorter period of development an d abandonment. Subdeltas are usually < 10 m thick and may fill shallow bays that cover over 300 km2. They build and deteriorate on time-scales of 150-200 years. Crevasse-splays or overbank splays are < 5 m thick, cover only a few square kilometers, and are abandoned after several decades of active growth. Each delta evolves through a rapid regressional phase as water and sediment are capture d from an antecedent river course. If highstand conditions persist long enough, deltas may prograde to the outer shelf to form wedges of deltaic sediment much thicker than their inner shelf counterparts. The delta-building process starts with the filling of interior lakes (lacustrine deltas), which is followed by bayhead delta-building at the coast, and finally by progradation across the marine shelf (shelf delta). Delta complexes and delta lobes, as well as their smaller counterparts, experience three phases of growth and abandonment: (1) rapid growth with increasing-to-stable discharge, (2) relative stability during initial stages of waning discharge, when sediment input balances the collective effects of subsidence, and (3) abandonment, followed by rapid subsidence-driven subaerial delta deterioration. In the rapid growth stage, formerly eroding-subsiding coastal environments experience delta plain accretion and coastal progradation from renewed sediment input. On the abandonment side of the cycle, marine processes overwhelm fluvial processes and rework the delta perimeter. Forced by the combined processes of subsidence, the delta surface undergoes progressive submergence. Transgressive sand bodies created by wave reworking of the delta evolve from headland beaches and spits, to barrier islands, and finally to submarine shoals as the abandonment phase is completed.

Dynamic Changes of the Holocene Mississippi River Delta Plain: The Delta Cycle

Sedimentation and turbidity are significant contributors to declines in populations of North American aquatic organisms. Impacts to lotic fauna may be expressed through pervasive alterations in local food chains beginning at the primary trophic level. Decreases in primary production are associated with increases in sedimentation and turbidity and produce negative cascading effects through depleted food availability to zooplankton, insects, freshwater mollusks, and fish. Direct effects at each trophic level are mortality, reduced physiological function, and avoidance; however, decreases in available food at trophic levels also result in depressed rates of growth, reproduction, and recruitment. Impacts of turbidity to aquatic organisms often seem inconsistent among watersheds and experiments, but this apparent difference is actually due to the lack of correlation between suspended sediment concentrations (mg/L) and units of measure (Nephelometric Turbidity Units, NTU). The use of NTU as a surrogate measurem...

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Effects of sedimentation and turbidity on lotic food webs: a concise review for natural resource managers

The decline in freshwater mussel populations in many river basins throughout North America has been attributed, in part, to land-use modifications that cause changes in sediment regimes However, t

Sediment, Land Use, and Freshwater Mussels: Prospects and Problems

Sediment dynamics in the lowermost Mississippi River

Reconciling economic growth and energy supply with the reduction of greenhouse gas emissions and other goals for environmental protection is a major challenge for emerging economies such as Brazil. Establishing energy security standards consistent with realistic economic growth projections while considering climate change requires complex calculations and relies upon risky assumptions. Yet, such calculations and decisions must be made to avoid future energy shortages and economic crises. This paper discusses the current dilemma concerning planning and decision-making for the Brazilian electric sector considering the construction of hydroelectric power plants in the Amazon region, energy security requirements, projected economic growth and climate change feedbacks.

How much is enough? An integrated examination of energy security, economic growth and climate change related to hydropower expansion in Brazil

The roles of various mechanisms that supply sediments from major sources, including rivers and nearshore shelf, to coastal Louisiana are not well understood or quantified, temporally or spatially. Recent studies reveal that an important association between riverine sediment input and the cyclic passage of winter storms results in a periodic supply of suspended sediments to coastal marshlands. The fact that these two mechanisms coincide in winter and early spring maximizes the availability of particulate matter for counteracting coastal land loss by enhancing substrate accretion and plant productivity. Identification of these optimum periods of suspended sediment activity, when overbank sedimentation, riverine concentrations, flood processes, and cold front passages are synergistic, can maximize the performance of wetland restoration efforts, because mineral matter and nutrients are critical for marsh vitality. When mitigation of coastal land loss is planned, it would be advantageous for weekend restoration to consider this timing when both sediment availability and constructive processes of sediment transport are optimal.

Joann Mossa

Papers

Sediment, Land Use, and Freshwater Mussels: Prospects and Problems

Sediment dynamics in the lowermost Mississippi River

How much is enough? An integrated examination of energy security, economic growth and climate change related to hydropower expansion in Brazil

Synergism of riverine and winter storm-related sediment transport processes in Louisiana's coastal wetlands

Channel planform and land cover changes on a mined river floodplain