The role of shear strength and bank stability in determining long-term channel morphology is addressed as part of a larger study by the US Geological Survey to quantify channel adjustments over time and space. It is well documented that following a disturbance such as dredging or straightening, degradation migrates headward along alluvial streams. Loess-derived sediments are particularly susceptible to mass failure following bed-level lowering. All stream systems studied drain to the Mississippi River from the Obion, Forked Deer, Wolf, and Hatchie River basins. The relative stability of a slope or channel bank is a function of the forces that resist mass movement versus the gravitational forces that tend to drive that slope towards failure. Trials at successively higher normal pressures produce a series of points on the Mohr-Coulomb line which, by linear regression, are used to calculate effective cohesion (c') and the effective friction angle.

Since about 1900, widespread changes in hydrology across the Mississippi River Basin have occurred, resulting in important changes in the delivery of water and sediment to the Lower Mississippi River (LMR).This is due to a combination of natural and anthropogenic factors.There have been increases in annual precipitation and 1-to 7-day totals over large parts of the basin.Changes in seasonal distributions were also identified, as were increases in hurricane-related rainfall.Streamflow to the LMR has increased significantly over the past 100 years.Median water yields have increased across most of the mid-continent and decreased in the western-most parts of the Missouri and Arkansas River basins.Suspended-sediment loads to the LMR have dramatically declined.The Lower Mississippi River is receiving about 500 million tonnes per year less suspended sediment today than in the 1940s (616 Mt/y to 98 Mt/y).Human impacts on hydrology and sediment transport throughout the basin are important.In the mid-continent, water yield per unit precipitation showed increases, but markedly decreased in the western parts of the basin.Decreases can be attributed to the construction of thousands of dams, associated flow regulation, withdrawals for agriculture, and to a lesser extent, the increased evaporation behind impoundments.

Large wood (LW) is an important element in riparian and mountain ecosystems and influences geomorphic controls, particularly in torrents and mountain rivers. Despite several advantages, LW can also exacerbate flood damage near infrastructure due to logjams or backwater rise and is often treated as a potential hazard. In an attempt to reduce such problems, channel slopes and banks are often clear cut in practice. This leads to a debate between the opinions of different scientists as well as stream and forest managers, where it is difficult to find a compromise between optimizing risk mitigation and eco-morphological functionality. Regarding risk mitigation due to LW, situations where the positive effects of vegetation succumb to negative effects should be identified to distinguish if shrubs or small trees (DBH < 10 cm) are more suitable to maintain streambank and hillslope stability. However, drastically removing vegetation can severely influence the ecosystem which should be avoided. In the case where large trees (DBH > 10 cm) have the potential to reduce the magnitude and frequency of recruitment processes, practices for forest management need to be optimized. Based on literature research, this article summarizes state of the art knowledge of vegetation effects on LW recruitment processes. In doing so, it focuses on three main recruitment processes: hydraulic bank erosion, geotechnical bank erosion and hillslope failure. Hydraulic bank erosion is responsible for delivering high volumes of sediment as well as LW in mountain catchments by removing streambank material through excess shear stress. The positive effects of vegetation can be quantified and implemented in modeling approaches through the adjustment of discharge-specific resistance coefficients or by using stochastic approaches. Geotechnical bank erosion and hillslope failure contribute to LW recruitment through failure. Root reinforcement is predominately the most important effect on how vegetation stabilizes streambanks and hillslopes. Based on the information mentioned above, a flow chart was formulated that uses specific criteria to define conditions in which forest management should be performed to mitigate potential LW recruitment without drastically removing all trees.

This paper overviews the field investigations and numerical modelling of bank erosion rates in two regulated rivers in south east Australia. The first case study was the assessment of the rates of bank erosion under natural and regulated flows in the upper Murray River system downstream of Khancoban Dam to Jingellic. The field investigations and numerical modelling of flows and bank erosion are overviewed. It is concluded that: (i) regulation has caused important changes in the hydrologic regime of the Swampy Plain and Upper Murray Rivers in the reaches closest to Khancoban Dam and (ii) regulation has led to changes in bank ‐ erosion rates with increases in the reaches closest to the dam and decreases in the reaches farthest downstream, the former related to greater flow durations that exceed erosion thresholds. The second case study is the assessment of the rates of bank erosion under different and alternative flow releases along the Mitta Mitta River and the development of metrics to limit erosion downstream from Dartmouth Dam. The field investigations and numerical modelling of flows and bank erosion are overviewed. The magnitude and duration of flows above erosion thresholds exert strong influences on bank erosion rates and these were used to develop metrics for operational guidance to limit erosion. It is concluded that: (i) erosion rates modelled with BSTEM ‐ Dynamic ranged from 0.9 to 9.8 m 3 /m of channel length between 2006 and 2016 (ii) erosion thresholds ranged from about 5,200 ML/d to almost 13,000ML/d and (iii) bulk ‐ water transfers have the greatest potential to cause significant bank erosion because of high flow rates and durations above erosion thresholds.

Large woody debris (LWD) exacerbates flood damages near civil structures and in urbanized areas and the awareness of LWD as a risk is becoming more and more relevant. The recruitment of "fresh" large woody debris has been documented to play a significant role of the total amount of wood transported during flood events in mountain catchments. Predominately, LWD recruitment due to hydraulic and geotechnical bank erosion and shallow landslides contribute to high volumes of wood during floods. Quantifying the effects of vegetation on channel and slope processes is extremely complex. This manuscript therefore presents the concepts that are being implemented in a new modelling framework that aims to improve the quantification of vegetation effects on LWD recruitment processes. One of the focuses of the model framework is the implementation of the effect of spatio-temporal distribution of root reinforcement in recruitment processes such as bank erosion and shallow landslides in mountain catchments. Further, spatio-temporal precipitation patterns will be considered using a probabilistic approach to account for the spatio-temporal precipitation variability to estimate a LWD recruitment correction coefficient. Preliminary results are herein presented and discussed in form of a case study in the Swiss Prealps.

Vegetation can have an important role in controlling channel planform, through its effects on channel roughness, and root-reinforcement of bank and bar materials. Along the Platte River in central Nebraska, USA, The Platte River Recovery Implementation Program (PRRIP) has been tasked with managing the planform of the river to benefit endangered species. To investigate the potential use of planned short duration high flow (SDHF) events to manage bar vegetation, this study combined several approaches to determine whether flows of up to 227 m(3)s(-1) through the central Platte River, could remove cottonwood, Phragmites and reed canarygrass stands of various ages and densities from in-channel bars. First, fieldwork was carried out to measure the uprooting resistance, and resistance to bending for each species. Second, a set of flume experiments was carried out to measure the forces exerted on the three species of interest under different flow conditions. Finally, a numerical study comparing drag forces (driving) measured in the flume study, with uprooting forces (resisting) measured in the field, was carried out for each species to determine the likelihood of plant removal by SDHF events. Results showed that plants with more than a year of root growth, likely cannot be removed through drag and local scour alone, even at the 100-year recurrence interval discharge. At most, a few cottonwood seedlings could be removed from bars through drag, scour and undercutting, where rooting depths are still small. The results presented here help us further understand the positive feedbacks that lead to the creation of permanent, vegetated bars rather than mobile braided channels. As such, the findings could help inform management decisions for other braided rivers, and the combined field, flume and modeling techniques used in this study could be applied to other fluvial systems where vegetation and planform dynamics are of interest. Copyright (C) 2016 John Wiley & Sons, Ltd.

Le complément constitue un élément majeur de l’immunité innée. La protéine du complément C4 appartient à la voie classique. Déficits en protéines de cette voie, héréditaires ou acquis sont associés à des maladies à dépôts de complexes immuns et prédisposent aux infections à germes encapsulés. Si les déficits partiels en C4 sont fréquents dans la population générale et pas forcément associés au développement de maladies auto-immunes, le déficit complet en C4 est exceptionnel et s’associe dans le 75–87 % des cas à un lupus discoïde. Un patient de 44 ans est adressé dans notre service en raison de l’apparition d’une lymphadénopathie généralisée, fatigue, perte de poids et sudations nocturnes. Le patient ne présente pas d’antécédents ou de comorbidités. L’anamnèse familiale est négative pour toute pathologie inflammatoire ou tumorale. L’examen physique met en évidence des multiples adénopathies non douloureuses à niveau des aires ganglionnaires cervicales et inguinales ; le reste de l’examen est normal. Le bilan biologique est normal. Les sérologies virales HIV, HAV, HBV, HCV, EBV, CMV, parvovirus B19 sont négatives. L’électrophorèse des protéines sanguines est normale ainsi que le dosage pondéral des immunoglobulines et de sous-classes des IgG. La recherche d’anticorps anti-nucléaires (ACAN) et anti-cytoplasme des polynucléaires (ANCA) est négative. En revanche, l’activité du complément hémolytique total (CH50) est dramatiquement abaissée (1 % ; range 70–130 %), associée à une activité du C1 inhibiteur (78 % ; range (67–150 %) et des taux de C3 (1,20 g/L ; range 0,66–1,35 g/L) normaux, mais avec un déficit profond en C4 (< 0,02 g/L ; range 0,08–0,34 g/L). Il n’y pas de cryoglobulinémie ; un test de mélange montre une augmentation des taux de C4 suggérant l’absence d’un facteur neutralisant. Les taux d’anticorps contre diphtérie, tétanos, rougeole, varicelle et les pathogènes encapsulées streptococcus pneumoniae (serotypes 9 N, 11A, 14, 17F, 19, 23F), haemophilus influenzae type B et Neisseria meningitidis sont normaux. L’analyse par cytométrie en flux montre la présence d’une population monoclonale de cellules B CD5–/CD10–, suggérant un lymphome à grandes cellules B de bas grade. Un PET–CT montre plusieurs adénomégalies hypermétaboliques cervicales et thoraco-abdominale, ainsi qu’une fixation inhomogène du 18-FDG à niveau huméral et fémoral. Une biopsie exérèse thoracoscopique d’un ganglion paratrachéale droit montre une infiltration lymphomateuse de cellules B. L’immunophénotypage révèle une population monoclonale B CD19+/CD20++/CD5–/CD10/CD38/CD11c+/CD103/CD25/Ki67+/CD44+/BCL6dim/BCL2–/IRF4+. La ponction-biopsie de la moelle montre une infiltration nodulaire et interstitielle par des cellules lymphomateuses B lambda+, CD20+, CD19+, CD38–, CD5–. Nous retenons un diagnostic de lymphome B diffus à grandes cellules avec un phénotype de cellules B activées de stade IV selon classification de Hans et al, [1] avec un international prognostic index (IPI) score de 2. Après 6 cycles de chimiothérapie par R-CHOP (rituximab, cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, prednisone), le patient est en rémission complète. Quatre semaines après la dernière cure de chimiothérapie la CH50 ainsi que le taux de C4 se sont quasi-normalisée (69 % et 0,06 g/L respectivement). Nous décrivons ici, le cas d’un patient n’ayant aucun passé immunologique et qui développe un lymphome non-hodgkinien associé à un déficit complet en C4, qui se normalise après traitement du lymphome. L’association d’une hypocomplémentémie C4 à un lymphome n’est décrite qu’au cours de l’association à un syndrome de Sjögren préexistant [2]. La protéine C4 du complément est impliquée dans la sélection négative des cellules B auto-réactives. Son déficit s’associe donc à la survie prolongée des cellules B avec un risque accru de développer des mutations défavorables pouvant finalement aboutir au développement tumoral [3]. Chez notre patient, le rôle promoteur du déficit en C4 dans l’apparition du lymphome est central, faisant de lui un « coupable direct ». L’exploration routinière du complément chez les patients porteurs de lymphomes pourrait corroborer cette hypothèse.

Waves generated by high-speed recreational boats can play a significant role in bank erosion and failure along riverbanks. Frequent passes of these boats in confined channels increase suspended-sediment concentration and turbidity at relatively shallow water depths, and increase the erosion rate by wave breaking and long-shore currents. In the current study, boat-generated waves and turbidity were measured in the Connecticut River along a reach between Vernon Dam, Vernon, VT and French King Bridge, Miller Falls, MA. Two-meter-long self-powered, self-logging wave staffs were used to measure the water level and waves at three sites. Based on these uninterrupted measurements, boat-generated wave-characteristics were obtained for a period of four months between May 2015 and September 2015. As part of this study, turbidity and wave measurements at these three sites were carried out during a series of in situ experiments with a 5.7 m long tri-hull motorboat. The experiments included a total of 36 controlled passes parallel to the shoreline at speeds ranging from 8 km/h up to 55 km/h. Boat speed and path was measured with a GPS logger and the turbidity level near the bank was measured using two optical backscatter sensors. Relations between the wave height, wave period and turbidity level were investigated. This paper presents the results of these additional measurements and discusses relations between turbidity levels and boat-generated waves.

Chapter 11 Channel form and adjustment: characterization, measurement, interpretation and analysis Andrew Simon, Andrew Simon Cardno ENTRIX, Oxford, MS, USASearch for more papers by this authorJanine Castro, Janine Castro US Fish and Wildlife Service, Portland, OR, USASearch for more papers by this authorMassimo Rinaldi, Massimo Rinaldi Università degli Studi di Firenze, Florence, ItalySearch for more papers by this author Andrew Simon, Andrew Simon Cardno ENTRIX, Oxford, MS, USASearch for more papers by this authorJanine Castro, Janine Castro US Fish and Wildlife Service, Portland, OR, USASearch for more papers by this authorMassimo Rinaldi, Massimo Rinaldi Università degli Studi di Firenze, Florence, ItalySearch for more papers by this author Book Editor(s):G. Mathias Kondolf, G. Mathias Kondolf University of California, Berkeley, USASearch for more papers by this authorHervé Piégay, Hervé Piégay CNRS, University of Lyon, FranceSearch for more papers by this author First published: 06 April 2016 https://doi.org/10.1002/9781118648551.ch11Citations: 4 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary Channel form has long been recognized as a diagnostic tool in evaluating fluvial landforms. This chapter presents an overview of available techniques, methods and parameters for characterizing and measuring channel forms and analysing and interpreting changes over time. Synthetic review of analysis of channel changes, including measurement of some of the parameters that aid in quantifying channel processes responsible for morphological changes. The term longitudinal profile refers to a graphical 2D representation of bed morphology, where bed elevation is plotted against longitudinal distances downstream along the channel. Alluvial rivers display a wide spectrum of channel forms and morphological units on a variety of landforms, such as alluvial fans, confined alluvial valleys and wide alluvial valleys that can be identified and classified during stream reconnaissance. Some of the reasons offered for the lack of adequate analyses include lack of data, lack of time, budget constraints or personnel limitation. Citing Literature Tools in Fluvial Geomorphology RelatedInformation

Many parts of the Mississippi River Basin are experiencing vastly different hydrologic conditions than they did 100 years ago as a result of changes in the magnitude of hydrologic inputs and withdrawals. These changes can be attributed to factors such as altered amounts and timing (seasonality) of precipitation, changes in rainfall-runoff relations due to altered land use, and anthropogenic disturbances to streams and river systems. Data from thousands of NOAA precipitation gages and USGS flow stations in the basin were used. This study uses HUC4 basin boundaries within the major river systems (i.e., Missouri, Ohio, etc.) draining to the Mississippi River to spatially subdivide the approximately 100-year data set. Results show that in general, although most of the Mississippi River Basin is receiving more rainfall than it did 100 years ago that there are vast areas where water yields have decreased significantly, particularly in the western part of the basin and particularly in spring. Parts of the western basin are experiencing 25 to more than 50% less discharge per unit area than they did 100 years ago. Precipitation has also shifted temporally such that winter precipitation has significantly decreased in many areas while spring and autumn precipitation has generally increased. The anthropogenic influence on water yield, appears to be large over vast areas, with values of water yield per unit precipitation also decreasing between 25 to more than 50% throughout much of this area. Not all areas of the basin, however, are experiencing decreases in water yield.

Physical models of the Big Sioux River, SD, were constructed to assess the impact on flow, drag, and bed erosion and deposition in response to the installation of two different types of engineered log jams (ELJs). A fixed-bed model focused on flow velocity and forces acting on an instrumented ELJ, and a movable-bed model focused on channel morphodynamics. The results show that: (1) downstream flow velocity, as expected, can be markedly affected by the presence of the ELJs, (2) both ELJ types afforded relatively large regions of bank protection, and (3) the relatively larger ELJ had a higher drag coefficient, relatively larger areas of bed deformation, and greater impact on the opposite stream bank as compared to the relatively smaller ELJ. These modeling results show that the style and size of ELJs can have a significant impact on flow resistance, bank protection, and stream channel responses, which should facilitate practitioners in the effective design of ELJs for natural rivers.

Vegetated buffer strips are widely advocated and applied as a Best Management Practice in riparian environments. This chapter presents data on the mechanical properties of riparian species commonly found or planted in riparian environments and assesses their impact on streambank stability for a number of typical scenarios using the ARS Bank Stability Model. The ARS Bank Stability Model is used to assess the relative contributions made by the new and old species tested on bank stability in several scenarios, and to explore the consequences of root growth rates and mobilization. Vegetation affects streambank stability through mechanical and hydrologic processes, and the effects are both beneficial and detrimental. The chapter also evaluates the effects of plant age on root reinforcement and estimates the difference between potential and actual root strength contributions to soil strength and streambank stability.

Engineered log jams (ELJs) have become attractive alternatives for river restoration and bank stabilization programs. Yet the effects of ELJs on turbulent flow and the fluid forces acting on the ELJs are not well known, and such information could inform design criteria. In this study, a fixed-bed physical model was constructed to assess the introduction of ELJs along the Big Sioux River, SD. Two ELJ types were examined, referred to as ELJ-1 and ELJ-2. Both types were deflector jams, where ELJ-1 was rectangular and ELJ-2 was triangular, and oriented with one side attached to the channel bank. They were deployed either as single structures or in groups of two or three on the same side of the channel and at different separation distances. Results show that (1) time–mean and turbulent velocities and bed shear stresses were measurably altered near the ELJ, but spatially averaged flow just upstream and downstream of the structure was unaffected; (2) streamwise drag forces measured for the ELJs were significantly larger than the transverse forces, and the derived drag coefficients for the single structures were 2.72±0.19 for ELJ-1 and 1.60±0.37 for ELJ-2; and (3) the presence of an upstream structure created a near-bank wake region that extended a distance of more than 30 flow depths downstream, which greatly reduced drag forces and drag coefficients observed for the downstream structure by as much as 80%. These observations are further evidence of the efficacy of ELJs in providing near-structure scour pool development and bank protection downstream, and they can be used to inform and assess the design of ELJs for use in river restoration and bank stabilization projects.

A simple, compact, high-performance absorbing load (absorber) for narrow-band THz spectroscopy is described. Current commercially available THz absorbers offering more than 20 dB return loss are bulky, made of proprietary materials, and intrinsically broadband. This 240 GHz absorber consists of a precisely machined thin layer of PMMA (plexiglas) placed over a small volume of water. By diluting the water with glycerol, the effective refractive index of the back medium may be adjusted finely to maximize return loss. The resonant frequency of the absorber is tuned with the PMMA thickness. Reflectometry measurements of the absorber with a vector network analyzer (VNA)-based terahertz spectrometer show a peak return loss of over 47 dB at 240 GHz and an overall peak return loss between 230 and 250 GHz of over 60 dB. Preliminary calculations suggest that such absorbers can be designed to be effective over much of the sub-THz band. In addition, the absorber is highly sensitive to the refractive index of the back medium, suggesting this type of absorber can be used to track minute changes in the dielectric properties of aqueous solutions.

Streambank erosion can be an important form of channel change in unstable alluvial environments. It should be accounted for in geomorphic studies, river restoration, dam removal, and channel maintenance projects. Recently, one-dimensional and two-dimensional flows and mobile-bed numerical models have become useful tools for predicting morphological responses to stream modifications. Most, however, either ignore bank failure mechanisms or implement only simple ad hoc methods. In this study, a coupled model is developed that incorporates a process-based bank stability model within a recently developed two-dimensional mobile-bed model to predict bank retreat. A coupling procedure that emphasizes solution robustness as well as ease-of-use is developed and described. The coupled model is then verified and validated by applying it to multilayer cohesive bank retreat at a bend of Goodwin Creek, Mississippi. Comparisons are made between the predicted and measured data, as well as results of a previous modeling study. On one hand, the study demonstrates that the use of two-dimensional mobile-bed models leads to promising improvements over that of one-dimensional models. It therefore encourages the use of multidimensional models in bank erosion predictions. On the other hand, the study also identifies future research needs in order to improve numerical modeling of complex streams. The developed model is shown to be robust and easy to apply; it may be used as a practical tool to predict bank erosion caused by fluvial and geotechnical processes.