River Pattern Classification System

River mould Classification SystemAbstractA new empirical river phase classification clay is established establish on the generalization of the renowned Darcy-Weisbach equation. A parameter for representing river shape is derived and defined as the river ensample discriminant criteria. aft(prenominal) transformation, the discriminant brinks are expressed as dimensionless form relating the enemy factor to the telling roughness factor of the street, which reflect the guide ramp, sediment size, bank position and maneuver geometry integrated. Adopting the most promising discriminant mode that combines both politics supposition and running(a) constancy theory, a threshold function is used to branch single-thread channels (including straight and weave) from multi-thread channels, and a nonher one is employed to distinguish immutable and unstable multi-thread channels (i.e., anabranching and braid) in this paper. A novel bank strength impact factor () is proposed her ein and turns out to be instead representative. just about channel purposes are redefined using this order and proved to be fair(a) enough. Analysis of various data arrays reveals that riparian vegetation condition is a sensitive part of this classification dust of rules, in particular for single-thread channels, but not braided channels, because overlarge width-depth ratio(W/d) would have strongly weaken this impact. Moreover, we support that fleeting anabranching or braiding creationion could also occur in single-thread typical zone following external disturbance, but would eventually go behind dynamic equilibrium state. Despite some construction mechanism shortcomings, our discriminant manner acting is supported by the selected existing data sets and could effectively distinguish trinity distinct types of channels by just a few hydrodynamic parameters.Keywords river pattern Darcy-Weisbach equation river shape bank strength1 incomingRiver pattern reveals the phys ical geometry and dynamic behavioral process of a river system (Schumm, 1985 Nanson and Knighton, 1996). It is well up understood that an alluvial channel could adjust itself to the ever-changing water supply hunt and sediment conditions. Thus river patterns could exhibit a series of unceasing variations, described as straight, meandering and braided patterns in tradition (Leopold and Wolman, 1957). It is delightful necessary to distinguish several distinct types of channels for better soul the consistent changing progresses of river channels in different environment conditions. many classification schemes using discriminant functions have been proposed, based on a set of typical properties, such as discharge, channel slope, width-depth ratio, sediment corpuscle size, etcetera Noteworthy is that the still least well-known multi-thread river pattern, anabranching pattern, has been attracting considerable attention (e.g., Schumm, 1981, 1985 Nanson and Knighton, 1996 Wende and Nanson, 1998 Tooth and Nanson, 1999 Burge, 2006 Eaton et al., 2010 Kleinhans and forefront den Berg, 2011). It makes great contribution to the diversity of river systems (Wende and Nanson, 1998). Then based on tradition, following the popular discriminant mode and collapseing a novel river pattern discriminant method comprise the focus of this paper, and lead to the capture of different channel patterns, including single-thread, anabranching and braided.Many early empirical attempts used Leopold and Wolman (1957)s method as base model, to improve understanding quantitative process of rive pattern transformation. Most of them focused on the hypercritical discharge to construct discriminant function, afterwards also included critical channel slope and bed grain size (Henderson, 1963 Millar, 2000). For a given bankfull discharge, braided usually corresponds to increased slope, composition which in turn usually result in stronger sand commit rate, increased bank erosion and coarse r bed surface sediment (Eaton et al., 2010). ascribable to billetful impediment that almost all channel properties have been varying desultorystrickly or methodically with flow progression down bombard, some newly threshold schemes successively appear on related research hotspot topics, of which critical specific stream power(Nanson and Croke, 1992 new wave den Berg, 1995 Lewin and Brewer, 2001 Petit et al., 2005) is outstanding. It can be viewed as a potential status with maximum flow energy and minimum sinuosity condition (Van den Berg, 1995). The classification between braided and meandering channels with high sinuosity in unconfined alluvial floodplains is well acceptable. But the argument about it also exists all the while. Lewin and Brewer (2001) argued that the summary of potential bankfull stream power and grain size by Van den Berg (1995) is virtually ineffective the classification of river pattern should not be limited to obtain an all-sided discriminant method, but t he thresholds integrated with patterning process domain. Petit et al. (2005) conducted experiments on different sized rivers and concluded that critical specific stream power is the smallest for the largest river, while turns to the higher value in intermediate rivers, then becomes the highest in head water streams. The reasons are down to the bedforms larger resistance that consumes energy for bedload rape. Recently, Kleinhans (2010) emphasized that channel pattern is directly bound up with the presence of bars. Then, Kleinhans and van den Berg (2011) combined the empirical stream power-based discrimination method and a physics-based bar pattern prediction method to undertake bold exploration about the underlying reasons of different river channel patterns. It was found that the range of specific potential stream power is rather narrow in gravel-bed meandering channel collectible to nonlinearity of sediment transport anabranching channel is ir applicable to stream power but subje ct to surplus factors such as bank strength, lateral confinement, avulsion, and vertical morphodynamics change river pattern can actually be defined by bar pattern, channel division number, and bifurcation condition.The features common in empirical methods are that more is based on statistical correlation derivation, less to clearly expound innate processes for discriminating river pattern. These models may really be questioned about application to broader scope, due to archetype data restrictions. Considering the shortcomings, many researchers have been contributing to develop physically based theories, and explore the relationship variables controlling river evolution process and pattern. atomic number 82 theories are government theory and linear stability models. Rational governance model is developed for predicting reach-averaged channel pattern response to the controlled environment variables in equilibrium, such as width-depth ratio, relative roughness and channel slope (Eaton et al., 2004). This concept employs optimization theory to achieve relative stability of the fluvial system by assessing the resistance and energy expenditure, meanwhile adjusting channel geometry to given flow conditions (Valentine et al., 2001 Huang et al., 2004). It has been proved much more successful than statistical empirical equations in predicting the variation of width and slope along downstream area and service of process understanding the influence of bank stability on channel geometry (Chew and Ashmore, 2001 Millar and Eaton, 2011). While, linear stability models are used for discriminating river pattern which based on physically morphodynamic equations. This theory explains that meandering is formed along with bend instability from planimetric perturbation (van Dijk et al., 2012). As perturbation propagates downstream, pattern transition towards braided occurs associated with quaternary bars. In addition, this theoretical method could predict the threshold tha t bifurcation occurs by width-depth ratio (W/d) (Parsons et al., 2007 Crosato and Mosselman, 2009). A significant disadvantage in this theory is that we cannot establish a typical relationship about channel geometries, such as slope with discharge and sediment size, only if the channel dimensions have been obtained (Eaton et al., 2010). However, when combining regime theory with linear stability models, means that morphodynamic condition and fluvial system stability are together considered to describe pattern transition progress, has belatedly been given particular attention, represented by Eaton (Eaton and Church, 2004 Eaton, 2006 Eaton et al., 2004, 2010).In this paper, we attempt to develop a physical based classification system combining regime theory and linear stability theory, just like Eaton et al. (2010). A threshold could be used to distinguish single-thread and stable multi-thread channels, and other one could be used to distinguish stable and unstable multi-thread chan nels, from a stability perspective. However, when rereading the original work by Eaton et al. (2010), some limitations of subjectivity becomes clear that a threshold value of W/d =50 originally recommended for discriminating braided channels was employed to derive bifurcation criteria, and the number of channel divisions exceeding cardinal was subjectively fictitious as the beginning of system instability. We hold that this handling should be regarded warily due to lack of absolute objective stability or instability criterion in fact.We turn in another new way. The famous Darcy-Weisbach equation (Weisbach, 1848 Darcy, 1857) is generalized from artificial rectangular channel case to natural alluvial channel cases and expressed as functions of assumed river shape parameter, resistance factor and relative roughness factor. A relevant scatter diagram reveals that several typical channel patterns correspond to differentiable distribution mode. Based on strictly fitting, river shape par ameter is contumacious and defined as river pattern discrimination criterion. After transformation, we develop a new dimensionless style threshold for distinguishing different river patterns. Then the classification system based on two dimensionless threshold equations is established. However, it is also, by necessary, practically dependant to certain subjectivity, especially the judgment of system instability. Considering the data fitting dependency, this method may be better treated as an empirical method.