From headwaters to mouth, the physical variables within a river system present a continuous gradient of physical conditions. This gradient should elicit a series of responses within the constituent...

The River Continuum Concept

The Intergovernmental Panel on Climate Change (IPCC) Technical Paper Climate Change and Water draws together and evaluates the information in IPCC Assessment and Special Reports concerning the impacts of climate change on hydrological processes and regimes, and on freshwater resources – their availability, quality, use and management. It takes into account current and projected regional key vulnerabilities, prospects for adaptation, and the relationships between climate change mitigation and water. Its objectives are:

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Climate change and water.

Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies. Rivers provide a major pathway for ocean plastic waste, but effective mitigation is dependent on a quantification of active sources. Here, the authors present a global model of riverine plastic inputs, and estimate annual plastic waste of almost 2.5 million tonnes, with 86% sourced from Asia.

/pdf/river-plastic-emissions-to-the-world-s-oceans-2yzs8o2tlv.pdf

River plastic emissions to the world's oceans.

The relative importance in geomorphic processes of extreme or catastrophic events and more frequent events of smaller magnitude can be measured in terms of (1) the relative amounts of "work" done on the landscape and (2) in terms of the formation of specific features of the landscape. For many processes, above the level of competence, the rate of movement of material can be expressed as a power function of some stress, as for example, shear stress. Because the frequency distributions of the magnitudes of many natural events, such as floods, rainfall, and wind speeds, approximate log-normal distributions, the product of frequency and rate, a measure of the work performed by events having different frequencies and magnitudes will attain a maximum. The frequency at which this maximum occurs provides a measure of the level at which the largest portion of the total work is accomplished. Analysis of records of sediment transported by rivers indicates that the largest portion of the total load is carried by flow...

https://www.jstor.org/stable/info/30058255

Magnitude and Frequency of Forces in Geomorphic Processes

The longitudinal profiles of bedrock channels are a major component of the relief structure of mountainous drainage basins and therefore limit the elevation of peaks and ridges. Further, bedrock channels communicate tectonic and climatic signals across the landscape, thus dictating, to first order, the dynamic response of mountainous landscapes to external forcings. We review and explore the stream-power erosion model in an effort to (1) elucidate its consequences in terms of large-scale topographic (fluvial) relief and its sensitivity to tectonic and climatic forcing, (2) derive a relationship for system response time to tectonic perturbations, (3) determine the sensitivity of model behavior to various model parameters, and (4) integrate the above to suggest useful guidelines for further study of bedrock channel systems and for future refinement of the streampower erosion law. Dimensional analysis reveals that the dynamic behavior of the stream-power erosion model is governed by a single nondimensional group that we term the uplift-erosion number, greatly reducing the number of variables that need to be considered in the sensitivity analysis. The degree of nonlinearity in the relationship between stream incision rate and channel gradient (slope exponent n) emerges as a fundamental unknown. The physics of the active erosion processes directly influence this nonlinearity, which is shown to dictate the relationship between the uplift-erosion number, the equilibrium stream channel gradient, and the total fluvial relief of mountain ranges. Similarly, the predicted response time to changes in rock uplift rate is shown to depend on climate, rock strength, and the magnitude of tectonic perturbation, with the slope exponent n controlling the degree of dependence on these various factors. For typical drainage basin geometries the response time is relatively insensitive to the size of the system. Work on the physics of bedrock erosion processes, their sensitivity to extreme floods, their transient responses to sudden changes in climate or uplift rate, and the scaling of local rock erosion studies to reach-scale modeling studies are most sorely needed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JB900120

Dynamics of the stream‐power river incision model: Implications for height limits of mountain ranges, landscape response timescales, and research needs

Some hydraulic characteristics of stream channels — depth, width, velocity, and suspended load — are measured quantitatively and vary with discharge as simple power functions at a given river cross section. Similar variations in relation to discharge exist among the cross sections along the length of a river under the condition that discharge at all points is equal in frequency of occurrence. The functions derived for a given cross section and among various cross sections along the river differ only in numerical values of coefficients and exponents. These functions are:

/pdf/the-hydraulic-geometry-of-stream-channels-and-some-5x86vitggs.pdf

The hydraulic geometry of stream channels and some physiographic implications

The flood control controversy

The purpose of this book is to investigate the facts regarding flood control, a subject that has given rise to extreme controversy in the United States in recent years. The question of flood control is obviously a vital one not only to the United States but to many other countries. It is hoped that this book may lead to a far clearer understanding of the facts involved and so may prove a truly important influence in reconciling existing differences of opinion. Most of the material presented here has not previously been available to the general reader nor has it been easily accessible to professional people. Much of it, in fact, has been gathered by the authors from unpublished reports of government agencies and from discussions with technicians in the field. Part of the material, on the other hand, such as the sections on flood plain formation and the hydrologic effect of small dams, stems from original research by the authors. Additional publication details Publication type Book Publication Subtype Monograph Title The flood control controversy: Big dams, little dams, and land management Year Published 1954 Language English Publisher The Ronald Press Publisher location New York, NY Description xiii, 278 p. Public Comments Sponsored by The Conservation Foundation DOI Privacy Policy | Legal | Accessibility | Site Map | Contact USGS U.S. Department of the Interior | DOI Inspector General | White House | E-gov | No Fear Act | FOIA Although dams have been built in the world since times immemorial, large dam construction was earlier not possible though needed, because of lack of adequate design knowledge, construction equipment, new materials like cement and concrete and technology of construction. Also, economic conditions and institutional capacity existing in countries that needed large dams, did not enable them to take them up. Sustainable irrigated agriculture, drainage of rainfed crops and of irrigated land, and flood control and management Here's how you know Loading [MathJax]/extensions/tex2jax.js The flo d contr l co trov rsy: Big dams, little dams, and land management comprise the main action thrusts of the ICID. Loading [MathJax]/extensions/tex2jax.js

Thomas Maddock

Papers

The hydraulic geometry of stream channels and some physiographic implications

The flood control controversy

The flood control controversy: Big dams, little dams, and land management

Relation of suspended-sediment concentration to channel scour and fill

Flood control problems