Academic literature on the topic 'Braided River Morphology'

Climate has been proposed conventionally as the primary factor that determines periglacial river activity (aggradation) and pattern (braided). This concept does not explain the rich diversity in river patterns and morphological processes in both the present and past periglacial environments: besides braided rivers and sandur, meandering, anabranching, transitional and deltaic rivers also occur. A first attempt is made to combine past and present periglacial river types with regard to their morphology, processes and environments. The processes that control river energy and morphology are discussed especially for periglacial conditions. This approach permits an assessment of the responses of periglacial rivers to climatic conditions and the modulation of the responses due to changes in the basin properties. Examples drawn from palaeo- and present-day periglacial rivers and environments demonstrate that there is no unique type of periglacial river but rather an azonal fluvial system with a number of periglacial variants.

Abstract. The abundance of global, remotely sensed surface water observations has accelerated efforts toward characterizing and modeling how water moves across the Earth's surface through complex channel networks. In particular, deltas and braided river channel networks may contain thousands of links that route water, sediment, and nutrients across landscapes. In order to model flows through channel networks and characterize network structure, the direction of flow for each link within the network must be known. In this work, we propose a rapid, automatic, and objective method to identify flow directions for all links of a channel network using only remotely sensed imagery and knowledge of the network's inlet and outlet locations. We designed a suite of direction-predicting algorithms (DPAs), each of which exploits a particular morphologic characteristic of the channel network to provide a prediction of a link's flow direction. DPAs were chained together to create “recipes”, or algorithms that set all the flow directions of a channel network. Separate recipes were built for deltas and braided rivers and applied to seven delta and two braided river channel networks. Across all nine channel networks, the recipe-predicted flow directions agreed with expert judgement for 97 % of all tested links, and most disagreements were attributed to unusual channel network topologies that can easily be accounted for by pre-seeding critical links with known flow directions. Our results highlight the (non)universality of process–form relationships across deltas and braided rivers.

The paper represents the geographical analysis of braided river channels development and distribution for the first time in Russian Scientific Literature. On asmall-scale map of Russia we display the distribution of braided channels on small and middle mountain, semi-mountain and plain rivers, in free and limited conditions of channel changes development (on rivers with wide floodplain and incised channel), which are determined by geologic-geomorphologic structure of the territory. On the large and largest rivers we distinguish braided reaches of different morphological types according to the MSU classification (single, conjugated, one-sided and alternate one-sided, sub-parallel branches, etc) and also bifurcations as aconsequence of meander cut-off which complicate the morphology of straight and meandering channels. Separately we display bifurcations on the other structural levels of channel processes development point mid-channel bifurcations on mountain reaches of large rivers, split channels and deltaic braided reaches. The causes of different types of braided channels development in different natural conditions are described.

AbstractSystematic lithofacies, palaeocurrent, palaeomorphological and palaeohydrological analyses have provided detailed information about a hitherto unstudied river system of the Siwalik foreland basin of the Himalaya. Three distinct lithofacies associations, each representing a specific depositional setting, have been identified and named as ‘Facies Association A’, ‘Facies Association B’ and ‘Facies Association C’. The ‘Facies Association A’ comprises pebbly sandstone, cross-bedded sandstone, ripple-laminated sandy siltstone and bioturbated mudstone lithofacies and represents deposits of a braided channel. The ‘Facies Association B’ comprises cross-bedded sandstone, bioturbated mudstone, fine sandstone–mudstone alternation and lensoid to prismatic sandstone lithofacies and represents deposits of a channel, natural levee, crevasse-splay and flood plain of a meandering stream. The ‘Facies Association C’ comprises mottled siltstone–mudstone heterolith and fine sandstone lithofacies and represents deposits of the upland interfluve region. The braided stream had a maximum depth of 4.15 m, maximum width of 305 m and maximum discharge of 7045 cumec, whereas the meandering stream had a sinuosity of 1.26, maximum depth of 3.71 m, maximum width of 180 m and maximum discharge of 4070 cumec. The area had a regional radial outward flow pattern, but dominantly towards the SSW. However, the braided river had a bimodal flow pattern due to an active basement-high-induced bend along its course. A comparison of the sediment characters and morphological and hydrological parameters of these streams with those of the modern rivers of the Ganga (Gangetic) basin has enabled us to infer that this river system was located in the medial-distal megafan-interfan setting of the basin.

River research in New Zealand is strongly conditioned by management requirements defined by environmental legislation. Principal areas of investigation at present include information on river morphology, habitat and instream flows required for management of fluvial ecosystems; erosion, sediment transport and sediment yield; and gravel-bedded and braided river processes. Research in these areas has tended to have a strong orientation towards field observations as a basis for developing quantitative (commonly statistical) models, and ultimately the provision of guidance material and decision support systems for resource managers. A fourth area of particular emphasis has been channel networks and hydraulic geometry. Again, the work generally has been field-intensive, but has been directed towards testing models such as the optimal channel network concept. Current research directions are focusing particularly on gravel-bed river mechanics, climatic and tectonic controls on landscape evolution, and instream habitat hydraulics and ecosystems.

Recent research on braided river morphology shows that the intensity (number of anabranches) of braiding channels increases with dimensionless discharge and (or) stream power. This variation in intensity reflects the adjustment of total sinuosity of the river to imposed gradient at a given discharge and grain size. Only a subset of channels is active at a given time and this active braiding intensity reflects the limited number of channels that can sustain bed load transport as the flow is divided. This is governed mechanistically by the dynamics of bifurcations and avulsions. Braided channel networks also have a characteristic length scale (or scales) related to the wavelength of the bars from which braiding develops and to the scale of the bars and confluence–bifurcation units within the braided network. The range of scales is limited by the size (and, therefore, number) of the active channels within the network and the width of the entire river.

Abstract. Most Alpine rivers have undergone significant alterations in flow and sediment regimes. These alterations have notable effects on river morphology and ecology. One option to mitigate such effects is flow regime management, specifically through the reintroduction of channel-forming discharges. The aim of this work is to assess the morphological changes induced in the Piave River (Italy) by two distinct controlled-flood strategies, the first characterized by a single artificial flood per year and the second by higher-magnitude but less frequent floods. This work involved applying a two-dimensional reduced-complexity morphodynamic model (CAESAR-LISFLOOD) to a 7 km long reach, characterized by a braided pattern and highly regulated discharges. Numerical modelling allowed the assessment of morphological changes for four long-term scenarios (2009–2034). The scenarios were defined considering the current flow regime and the natural regime, which was estimated by a stochastic physically based hydrologic model. Changes in channel morphology were assessed by measuring active-channel width and braiding intensity. A comparison of controlled-flood scenarios to a baseline scenario (i.e. no controlled floods) showed that artificial floods had little effect on channel morphology. More channel widening (13.5 %) resulted from the high-magnitude flood strategy than from the application of the other strategy (8.6 %). Negligible change was observed in terms of braiding intensity. The results indicate that controlled floods do not represent an effective solution for morphological recovery in braided rivers with strongly impacted flow and sediment regimes.

Abstract. The Bayanbulak Grassland, Tianshan, China is located in an intramountane sedimentary basin where meandering and braided gravel-bed streams coexist under the same climatic and geological settings. We report on measurements of their discharge, width, depth, slope and grain size. Based on this data set, we compare the morphology of individual threads from braided and meandering streams. Both types of threads share statistically indistinguishable regime relations. Their depths and slopes compare well with the threshold theory, but they are wider than predicted by this theory. These findings are reminiscent of previous observations from similar gravel-bed streams. Using the scaling laws of the threshold theory, we detrend our data with respect to discharge to produce a homogeneous statistical ensemble of width, depth and slope measurements. The statistical distributions of these dimensionless quantities are similar for braided and meandering streams. This suggests that a braided river is a collection of intertwined channels, which individually resemble isolated streams. Given the environmental conditions in Bayanbulak, we furthermore hypothesize that bedload transport causes the channels to be wider than predicted by the threshold theory.

Abstract. For extending the applications of structure-from-motion (SfM) photogrammetry in river flumes, we present the main challenges and methods used to collect a large dataset (>1000 digital elevation models, DEMs) of high-quality topographic data using close-range SfM photogrammetry with a resulting vertical precision of ∼1 mm. Automatic target detection, batch processing, and considerations for image quality were fundamental to the successful implementation of the SfM technique on such a large dataset, which was used primarily for capturing details of gravel-bed braided river morphodynamics and sedimentology. While the applications of close-range SfM photogrammetry are numerous, we include sample results from DEM differencing, which was used to quantify morphology change and provide estimates of water depth in braided rivers, as well as image analysis for mapping bed surface texture. These methods and results contribute to the growing field of SfM applications in geomorphology and close-range experimental settings in general.

Les rivières en tresses constituent des plaines alluviales complexes constituées d'une mosaïque d'unités correspondant à des échelles spatio-temporelles différentes. L'objectif de cette thèse a été d'utiliser des données de LiDAR aéroporté pour améliorer la connaissance des réponses morphologiques des lits en tresses à différentes échelles spatio-temporelles. Dans un premier temps, 2 levés LiDAR séquentiels ont permis de détecter les changements morphologiques d’une tresse de 7 km survenus suite à une crue de période de retour 14 ans. Ces travaux ont été réalisés sur le site du Bès, un affluent de la Bléone. Les résultats ont mis en évidence l’importance des différentes étapes de traitement de l’information dans le calcul du bilan sédimentaire (réalignement des nuages de points séquentiels, évaluation de la bathymétrie, variabilité spatiale de l’incertitude altimétrique). L’exploitation des résultats a de plus montré un profond remaniement des chenaux tressés, du fait de l’occurrence de nombreuses avulsions. Dans un deuxième temps, les données LiDAR ont été utilisées pour caractériser la signature morphologique des lits en tresses à l’échelle plurikilométrique. L’analyse a porté sur un linéaire de plus de 25 km réparti sur 9 sites, dans les bassins versants de la Drôme, du Drac et de la Bléone. Premièrement, ces données mettent clairement en évidence l’effet du confinement de la tresse sur ses propriétés morphologiques avec entre autres un élargissement de la bande active à l'amont de ces zones. Deuxièmement, deux périodes caractéristiques ont été mises en évidence : autour de 3-4 et de 9-10 fois la largeur de la bande active. La période à 3-4 serait liée à la dynamique des macroformes. La période à 10 pourrait être liée à la dynamique de transfert à long terme des sédiments et pourrait correspondre aux successions longitudinales des mégaformes sédimentaires. Finalement, les données de LIDAR aérien ont été couplées à une étude diachronique de photographies aériennes pour reconstruire l'historique de formation des différentes unités spatiales composant la plaine d'inondation et relier cette structure avec les caractéristiques des unités de végétation. 3 rivières en tresses ont été étudiées dans les Alpes françaises avec un degré croissant d'activité : le Bouinenc, la Drôme et le Bès. Cette méthodologie a permis de reconstruire les différentes phases d'incision du lit avec deux périodes majeurs : avant 1948 et seconde partie du 20ème siècle. Il a aussi été montré l'impact des crues sur l'incision et l'élargissement de la bande active en lien avec le régime sédimentaire. Ces changements à long terme jouent un rôle significatif pour expliquer la mosaïque de la végétation de la plaine d'inondation avec une végétation bien développée et composée majoritairement d'unité matures dans le cas d'une rétraction et d'une incision sur le long terme. Les rivières plus actives présentent une diversité d'unité de végétation plus équilibrée. Enfin, la présence de lande arbustive semble être un bon indicateur des périodes d'incision
Braided rivers form complex floodplains composed of sedimentary deposits mosaics, which differ in term of spatial and time scales, in function of hydrologic forcing and sediment supply. The goal of this thesis is to use airborne LiDAR to improve our understanding of braided channel morphological responses at different spatial and time scales.In a first time, two sequential airborne LiDAR surveys were used to reconstruct morphological changes of a 7-km-long braided river channel following a 14-year return period flood. This was done on the Bès River, a tributary of the Bléone River in southeastern France. Results highlighted the importance of different data processing steps in sediment budget computation (surface matching, bathymetry assessment, spatially distributed propagation of uncertainty). Analysis of these data also shows that the braided channel pattern was highly disturbed by the flood owing to the occurrence of several channel avulsions.In a second time, LiDAR data were used to look at longitudinal signatures of cross-sectional morphology at the scale of several kilometers. This study was done on 9 study reaches distributed on five braided rivers in Drôme, Drac and Bléone catchments. These data highlighted the effect of braided river confinement/obstruction on morphologic signature with upstream widening pattern. Secondly, two characteristic wavelengths have been identified from these signals: 3-4 and 10 times the active channel width. The first could be link to the dynamics of macroforms. The second could be associated to the dynamics of megaforms and long term sediment transfer.Finally, airborne LiDAR data were associated with archived aerial photos to reconstruct floodplain formation and relate this geomorphic organisation with vegetation patch characters. This is achieved on 3 different braided rivers in French Alps with an increasing degree of activity: the Bouinenc Torrent, the Drôme River and the Bès River. This methodology allowed us to establish the timing of channel incision with the identification of two major periods: before 1948 and second part of 20th century. Impacts of flood history on channel incision and widening pattern were also highlighted. These long term changes are playing a significant role to explain vegetation mosaics with a well-developed vegetated floodplain mainly composed of mature units following long term narrowing and incision. Rivers with higher activity show an equi-diversity of floodplain vegetation units. Finally, presence of shrubland patches seems to be good indicator of incision periods

The recent emergence of Structure-from-Motion Photogrammetry (SfM) has created a cost-effective alternative to conventional laser scanning for the production of high-resolution topographic datasets. There has been an explosion of applications of SfM within the geomorphological community in recent years, however, the focus of these has largely been small-scale (102 - 103 m2), building on innovations in low altitude Unmanned Aircraft Systems (UAS). This thesis examines the potential to extend the scope of SfM photogrammetry in order to quantify of landscape scale processes. This is examined through repeat surveys of a ~35 km2 reach of the Dart River, New Zealand. An initial SfM survey of this reach was conducted in April 2014, following a large landslide at the Slipstream debris fan. Validation of the resulting digital elevation models using Independent Control Point's (ICPs) suggested encouraging results, however benchmarking the survey against a long-range laser scanned surface indicated the presence of significant systematic errors associated with inaccurate estimation of the SfM bundle adjustment. Using a combination of scaled laboratory field experiments, this research aimed to develop and test photogrammetric data collection and modelling strategies to enhance modelling of 3D scene structure using limited constraints. A repeat survey in 2015 provided an opportunity to evaluate a new survey strategy, incorporating a convergent camera network and a priori measurement of camera pose. This resulted in halving of mean checkpoint residuals and a reduction in systematic error. The models produced for both 2014 and 2015 were compared using a DEM differencing (DoD) methodology to assess the applicability of wide-area SfM models for the analysis of geomorphic change detection. The systematic errors within the 2014 model confound reliable change detection, although strategies to correlate the two surveys and measure the residual change show promise. The future use of SfM over broad landscape scales has significant potential, however, this will require robust data collection and modelling strategies and improved error modelling to increase user confidence.

Thesis (M.S.) University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 27, 2007) Includes bibliographical references.

Braided rivers are complex, fascinating fluvial pattern, which represent the natural state of many gravel and sand bed rivers. Both natural and human causes may force a change in the boundary conditions, and consequently impact the river functionality. Detailed knowledge on the consequent morphological response is important in order to define management strategies which combine different needs, from protection of human activities and infrastructures to preservation of the ecological and biological richness. During the last decades, research has made significant advance to the description of this complex system, thanks to flume investigations, development of new survey techniques and, to a lesser extent, numerical and analytical solutions of mathematical models (e.g. Ashmore, 2013). Despite that, many relevant questions, concerning the braided morphodynamics at different spatial and temporal scales (from the unit process scale, to the reach scale, and eventually to the catchment scale) remain unanswered. For example, quantitative analysis of the morphological response to varying external controls still requires investigation and needs the definition of suitable, stage-independent braiding indicators. In addition, the morphodynamics of the fundamental processes, such as bifurcations, also needs further analysis of the driving mechanisms. General aim of the present study is to develop new methods to exploit, in an integrated way, the potential of the new possibilities offered by advanced monitoring techniques, laboratory models, numerical schemes and analytical solutions. The final goal is to fill some gaps in the present knowledge, which could ultimately provide scientific support to river management policies. We adopted analytical perturbation approaches to solve the two-dimensional shallow water model; we performed laboratory simulations on a large, mobilebed flume; we analysed existing topographic measurements from LiDAR and Terrestrial Laser scanning Devices; and we simulated numerically the river hydrodynamics. Within each of the six, independent, research chapters, we interconnected results from the different approaches and methodologies, in order to take advantage of their potential. Summarising, the more relevant and novel outcomes of the present work can be listed as follows:(i) We explored the morphological changes during a sequence of flood events in a natural braided river (Rees River, NZ) and we proposed a morphological method to assess the sediment transport rate. In particular we propose a semi-automatic method for estimating the particles path-length (Ashmore and Church, 1998) on the basis of the size of the deposition patches, which can be identified on the basis of DEM of differences. Comparison with results of numerical simulation confirmed that such an approach can reproduce the response of the bedload rate to floods of different duration and magnitude. (ii) We developed a new indicator of the reach-scale morphology and, on the basis of existing laboratory experiments, we explored its dependence, under regime conditions, to the controlling factors: slope, discharge, confinement width, grain size. In spite of its synthetic nature, this simple indicator embeds the information needed to estimate the variability of the Shield stress throughout the braided network, and consequently enables to assess the transport-rate and its variation with the driving discharge. (iii) We investigated, through flume experiments, the effect of the flow unsteadiness on the sediment transport in a braided river. This is possible only by following a statistical approach based on multiple repetitions of the same flow hydrograph. Results revealed that for confined network an hysteresis of the bedload response occurs, which leads to higher sediment transport during increasing flow, whereas relatively unconfined networks always show quasi-equilibrium transport rates. (iv) A second set of laboratory experiments provided information on the morphodynamics of a braided network subject to variations of the sediment supply. We proposed a simple diffusive model to quantify the evolution of the one-dimensional bed elevation profile. Such simple approach, albeit having a limited range of practical applications, represents the first attempt to quantify this process and enables to study the relevant temporal and spatial scales of the phenomenon. (v) We solved analytically the two-dimensional morphodynamic model for a gravel-bed river bifurcation. This furnishes a rigorous proof to the idea proposed by Bertoldi and Tubino (2007) to interpret the morphological response of bifurcation in light of the theory of the morphodynamic influence. The analytical approach enables to investigate the fundamental mechanics which leads to balance, and unbalance, configurations and, from a more practical point of view, allows for a better prediction of the instability point than the existing 1D models (e.g. Bolla Pittaluga et al., 2003).

Braided rivers are complex, fascinating fluvial pattern, which represent the natural state of many gravel and sand bed rivers. Both natural and human causes may force a change in the boundary conditions, and consequently impact the river functionality. Detailed knowledge on the consequent morphological response is important in order to define management strategies which combine different needs, from protection of human activities and infrastructures to preservation of the ecological and biological richness. During the last decades, research has made significant advance to the description of this complex system, thanks to flume investigations, development of new survey techniques and, to a lesser extent, numerical and analytical solutions of mathematical models (e.g. Ashmore_2013). Despite that, many relevant questions, concerning the braided morphodynamics at different spatial and temporal scales (from the unit process scale, to the reach scale, and eventually to the catchment scale) remain unanswered. For example, quantitative analysis of the morphological response to varying external controls still requires investigation and needs the definition of suitable, stage-independent braiding indicators. In addition, the morphodynamics of the fundamental processes, such as bifurcations, also needs further analysis of the driving mechanisms. General aim of the present study is to develop new methods to exploit, in an integrated way, the potential of the new possibilities offered by advanced monitoring techniques, laboratory models, numerical schemes and analytical solutions. The final goal is to fill some gaps in the present knowledge, which could ultimately provide scientific support to river management policies. We adopted analytical perturbation approaches to solve the two-dimensional shallow water model; we performed laboratory simulations on a large, mobile-bed flume; we analysed existing topographic measurements from LiDAR and Terrestrial Laser scanning Devices; and we simulated numerically the river hydrodynamics. Within each of the six, independent, research chapters, we interconnected results from the different approaches and methodologies, in order to take advantage of their potential. Summarising, the more relevant and novel outcomes of the present work can be listed as follows: 1) We explored the morphological changes during a sequence of flood events in a natural braided river (Rees River, NZ)and we proposed a morphological method to assess the sediment transport rate. In particular we propose a semi-automatic method for estimating the particles path-length (Ashmore and Church, 1998) on the basis of the size of the deposition patches, which can be identified on the basis of DEM of differences. Comparison with results of numerical simulation confirmed that such an approach can reproduce the response of the bedload rate to floods of different duration and magnitude. 2) We developed a new indicator of the reach-scale morphology and, on the basis of existing laboratory experiments, we explored its dependence, under regime conditions, to the controlling factors: slope, discharge, confinement width, grain size. In spite of its synthetic nature, this simple indicator embeds the information needed to estimate the variability of the Shield stress throughout the braided network, and consequently enables to assess the transport-rate and its variation with the driving discharge. 3) We investigated, through flume experiments, the effect of the flow unsteadiness on the sediment transport in a braided river. This is possible only by following a statistical approach based on multiple repetitions of the same flow hydrograph. Results revealed that for confined network an hysteresis of the bedload response occurs, which leads to higher sediment transport during increasing flow, whereas relatively unconfined networks always show quasi-equilibrium transport rates. 4) A second set of laboratory experiments provided information on the morphodynamics of a braided network subject to variations of the sediment supply. We proposed a simple diffusive model to quantify the evolution of the one-dimensional bed elevation profile. Such simple approach, albeit having a limited range of practical applications, represents the first attempt to quantify this process and enables to study the relevant temporal and spatial scales of the phenomenon. 5) We solved analytically the two-dimensional morphodynamic model for a gravel-bed river bifurcation. This furnishes a rigorous proof to the idea proposed by Bertoldi and Tubino (2007) to interpret the morphological response of bifurcation in light of the theory of the morphodynamic influence. The analytical approach enables to investigate the fundamental mechanics which leads to balance, and unbalance, configurations and, from a more practical point of view, allows for a better prediction of the instability point than the existing 1D models (e.g. Bolla Pittaluga et al., 2003).

Les mécanismes complexes qui régissent la morphologie des rivières en tresses et l'interaction avec le tri granulométrique restent encore à approfondir. Cette thèse s'articule autour de trois thèmes : l'étude de la déstabilisation d'un système en tresses puis sa mise à l'équilibre, l'interaction de la morphologie avec le tri granulométrique et enfin la prédiction du transport solide. Pour cela, nous avons étudié 3 modélisations de différents systèmes alluviaux : des bancs alternés en granulométrie étendue (durée 100h), un système en tresses en granulométrie uniforme (durée 385h) et enfin un système en granulométrie étendue (durée 435h). Chaque modèle de tresses a subi plusieurs changements de conditions d'alimentation. Il ressort que seul un paramètre, la surface du lit situé au delà de la pente moyenne, pourrait être un bon candidat pour comparer l'état d'équilibre (érosion ou exhaussement) de différents systèmes. Pour une étude d'un site donnée, les paramètres classiques comme la pente ou le Bed Relief Index (BRI) sont tout aussi pertinents. Le tri granulométrique sur les systèmes divaguants se manifeste de plusieurs façons : il est à l'origine de la migration du chenal principal et participe activement à la formation de patchs sédimentaires, catalyseurs de l'émergence des bancs. Les lobes sédimentaires qui se retrouvent dans le modèle en granulométrie uniforme n'apparaissent que dans certains cas, laissant place à une mobilité des sédiments discontinue, généralement de proche en proche. La modélisation du transport solide dans ces systèmes à faciès complexes se heurte à la forte variabilité des conditions hyro-sédimentaires. L'abondance de confluences et des fronts de bancs modifie la relation de transport avec les conditions locales. L'influence de la morphologie est prépondérante dans la dynamique du transport solide
Complex mechanisms involved in braided rivers morphology and the interaction with the grain sorting are slightly studied. Throughout this thesis, we study the morphological signature of a system at equilibrium, and the interaction between the bed morphology and grain sorting. From our small-scale experiments, we studied the prediction of sediment transport. We studied three different small-scale streams, a alternate bars model with heterogeneous sediment (duration 100h), a braided stream model using uniform sand (duration 385h) and a braided stream model using sand and coarse sand mixture (duration 435h). Upstream conditions have been changed several times for each braided stream. It appears that the only one relevant index to compare sediments stages of different streams is the surface above the average slope. To study a single site's evolution, the traditional parameters such as slope or Bed Relief Index (BRI) are relevant enough. We observed different effects of grain sorting. First, grain sorting is responsible of selective depositions and led to active channel migration. The selective deposition leads to bar emergence. Sedimentary lobes that we observed on uniform sand model were rarely noticed on the sand and coarse sand mixture experiment. This results suggests that sediments motion is tiny linked to grain size range. Modeling of sediment transport in such varied morphology faces different problems. Plenty of confluences and fronts bars changes sediment transport and local conditions connections. The influence of morphology is predominant in the dynamic of sediment transport

The experience gained during the operation and maintenance stages of the Camisea pipeline transportation system (STD) in Peru, crossing from the Tropical jungle in the Cusco region to the coast, in Lima city, has enabled us to develop and apply techniques in construction and maintenance works focused on controlling of the vertical undermining of riverbeds and the erosion of margins at river crossings and creeks crossed by the pipeline carrying NG and NGL. According to the above, a technical assessment study was conducted of the crosses rivers and creeks that have high priority of the Camisea pipeline path, comprising — among other disciplines — hydraulic and undermining analysis, as well as an hydrologic and geo-morphological evaluation and other issues regarding general geology and geo-techniques at each crossing site. A work program was developed using the information obtained in the three sectors travelled by the (STD) in order to develop and complement works at the crossings of rivers and valleys aiming to protect the integrity of the pipeline from erosion produced by major and extraordinary floods in riverbeds and alluvial slides in narrow valleys, by means of confinement and sedimentation works. The jobs performed in rainforest, mountain and coastal terrain crossed by the pipeline considered different river morphology types — being the most common the straight, gravel braided and curved river travels — and regimes in both flow speed and width of the riverbed. From the topographic follow-up and monitoring stage on — before and after the rain season — at crossings beneath the riverbeds, it was determined that the deterioration process affecting the crossing stripe corresponds to erosion consisting in the alteration of the watercourse banks that affects the piping foundations. The works are completed considering the type of resources available at the site of the river crossing — i. e., the engineering is particular to each sector, and designing is performed upon available materials in the area. The most utilized works at river and creeks crossings on the Camisea piping system are as follows: i) protection of riverbeds and creeks slopes using gabion mesh and pads; ii) sedimentation systems on gabion mesh; iii) Energy dissipation devices at creeks crossings; iv) rip-rap–type armoring of riverbeds; v) confinement check dams; vi) marginal protection dikes; vii) marginal protection rock fill dams; viii) protection and sedimentation breakwaters, among others.