Army Corps of Engineers

A framework is provided for scaling and scale issues in hydrology. The first section gives some basic definitions. This is important as researchers do not seem to have agreed on the meaning of concepts such as scale or upscaling. ‘Process scale’, ‘observation scale’ and ‘modelling (working) scale’ require different definitions. The second section discusses heterogeneity and variability in catchments and touches on the implications of randomness and organization for scaling. The third section addresses the linkages across scales from a modelling point of view. It is argued that upscaling typically consists of two steps: distributing and aggregating. Conversely, downscaling involves disaggregation and singling out. Different approaches are discussed for linking state variables, parameters, inputs and conceptualizations across scales. This section also deals with distributed parameter models, which are one way of linking conceptualizations across scales. The fourth section addresses the linkages across scales from a more holistic perspective dealing with dimensional analysis and similarity concepts. The main difference to the modelling point of view is that dimensional analysis and similarity concepts deal with complex processes in a much simpler fashion. Examples of dimensional analysis, similarity analysis and functional normalization in catchment hydrology are given. This section also briefly discusses fractals, which are a popular tool for quantifying variability across scales. The fifth section focuses on one particular aspect of this holistic view, discussing stream network analysis. The paper concludes with identifying key issues and gives some directions for future research.

/pdf/scale-issues-in-hydrological-modelling-a-review-1x61lpwqjr.pdf

Scale issues in hydrological modelling: A review

/ Although sedimentation is a naturally occurring phenomenon inrivers, land-use changes have resulted in an increase in anthropogenicallyinduced fine sediment deposition. Poorly managed agricultural practices,mineral extraction, and construction can result in an increase in suspendedsolids and sedimentation in rivers and streams, leading to a decline inhabitat quality. The nature and origins of fine sediments in the loticenvironment are reviewed in relation to channel and nonchannel sources andthe impact of human activity. Fine sediment transport and deposition areoutlined in relation to variations in streamflow and particle sizecharacteristics. A holistic approach to the problems associated with finesediment is outlined to aid in the identification of sediment sources,transport, and deposition processes in the river catchment. The multiplecauses and deleterious impacts associated with fine sediments on riverinehabitats, primary producers, macroinvertebrates, and fisheries are identifiedand reviewed to provide river managers with a guide to source material. Therestoration of rivers with fine sediment problems are discussed in relationto a holistic management framework to aid in the planning and undertaking ofmitigation measures within both the river channel and surrounding catchmentarea.KEY WORDS: Sedimentation; Fine sediment; Holistic approach; Ecologicalimpact; River restoration

http://deq.idaho.gov/media/525755-Biological_Effects_Fine_Sediment_lotic_Environment_Wood_Armitage_1997.pdf

Biological Effects of Fine Sediment in the Lotic Environment

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.

/pdf/river-discharge-to-the-coastal-ocean-a-global-synthesis-571z1g19ts.pdf

River Discharge to the Coastal Ocean: A Global Synthesis

Finite difference approximations for two-sided space-fractional partial differential equations

This text collects and collates the significant advances in analytical methods for alluvial channel design, river morphology, and mathematical simulation of river channel changes. It presents a complete analytical treatment of river morphology and its responses to environmental and human-made changes from the engineering point of view. For professionals in flood control, bridge design, irrigation and waterways, this book is a current, comprehensive refresher and reference. It is also a textbook in river sedimentation. Analytical and empirical methods are detailed for solving erosion and sedimentation problems, hydraulic design of channels, bridges, and related structures. From a sound physical foundation, mathematical techniques are presented for simulating river channel changes, and computer-aided analysis and design for river projects are illustrated by abundant examples.

Fluvial Processes in River Engineering

Minimum stream power and river channel patterns

[1] Although the Belanger-Boss theorem of critical flow has been widely applied in open channel hydraulics, it was derived from the laws governing ideal frictionless flow. This study explores a more general expression of this theorem and examines its applicability to flow with friction and sediment transport. It demonstrates that the theorem can be more generally presented as the principle of minimum energy (PME), with maximum efficiency of energy use and minimum friction or minimum energy dissipation as its equivalents. Critical flow depth under frictionless conditions, the best hydraulic section where friction is introduced, and the most efficient alluvial channel geometry where both friction and sediment transport apply are all shown to be the products of PME. Because PME in liquids characterizes the stationary state of motion in solid materials, flow tends to rapidly expend excess energy when more than minimally demanded energy is available. This leads to the formation of relatively stable but dynamic energy-consuming meandering and braided channel planforms and explains the existence of various extremal hypotheses.

/pdf/minimum-energy-as-the-general-form-of-critical-flow-and-4t5f4lefdo.pdf

Minimum energy as the general form of critical flow and maximum flow efficiency and for explaining variations in river channel pattern

A rational method has been developed to predict the regime geometry of straight active gravel streams. The analytical model is based upon a resistance equation, a bed load equation, and the condition of minimum stream power for gravel streams in equilibrium. The analytical channel geometry so obtained is in general agreement with previously established relations and observations. The analytical channel width is proportional to Q 0 . 4 7 , in which Q is the bank full discharge. Except for steep slopes, the width is essentially only a function of the discharge. The analytical depth increases with the discharge but decreases with the slope. On steep slopes, the width increases rapidly with the slope. This rapid increase in width accompanied by a decrease in depth indicates braiding tendency for steep gravel streams. As the bed load approaches zero at the lower boundary, this model for active streams reduces to the threshold theory.

Geometry of Gravel Streams

The hypothesis of minimum stream power for stable alluvial channels has been used to derive a condition for alluvial channels in equilibrium. A method incorporating this condition with a flow-resistance formula and a sediment-discharge formula has been developed to compute the width, depth, and slope of stable alluvial channels for a given set of water and sediment discharges. Applying this method yields a design chart that provides the stable width and depth of alluvial canals with trapezoidal shape for a given set of water discharge, channel slope, sediment size, and side slope. Comparing data from some regime canals and small experimental canals has shown good agreement between the observed data and analytical predictions.

Howard H. Chang

Papers

Fluvial Processes in River Engineering

Minimum stream power and river channel patterns

Minimum energy as the general form of critical flow and maximum flow efficiency and for explaining variations in river channel pattern

Geometry of Gravel Streams

Stable Alluvial Canal Design