Alluvial Channels Research Articles

Historical development of the Regime Geometry Equations, Part-I

The present study intended to review the historical development of the regime geometry equations proposed by many researchers since 1895. Kennedy started the search for the attributes of stable channels on the Upper Bari Doab Canal of Punjab in 1980-1984. The regime concept was presented by Lindley (1919) that later on Lacey (1930) modified to a set of most widely used regime relations. Later on, Blench (1941-1957), and Simons and Albertson (1960) presented their equations. This period is called ‘canal regime period’ because most of the research focused on canal design. The concept of regime was extended to river systems by Leopold and Maddock in 1953. In 1963, Henderson proposed some regime equations that can be applied for predicting canal and river geometry. This period was the transition from canal regime period to river regime period and from an empirical approach to analytical approach and is called as ‘Transitional Period’. Many other researchers written the information based on analytical approach, or a combination between analytical and empirical approaches, and more focused to river regime especially gravel bed river regime. This period is, called ‘River regime period’. Flow discharge, sediment size, and bed-load sediment are the three main factors that influence the geometry of alluvial channels. The hydraulic geometry relationships indicate that sediment size and bed-load sediment strongly influence the channel slope, moderately influence the flow velocity, and slightly influence the channel depth and the channel width. This study also shows that in terms of Shields parameter, the exponents of discharge, sediment size, and sediment transport are dependent on the relative submergence (D/d50).

التحكم بفيضان مروحة رانية الفيضية شمال العراق وفقاً لنموذج فيلمان (دراسة جيومورفولوجية)

The research dealt with the study of the flow on the surface of the Rania flood fan located in the north of Iraq within the Sulaymaniyah Governorate by applying the (Filmman) model for the purpose of identifying the dangerous areas and finding solutions to those areas from the risk of flooding. After studying the morphometric analysis of the waterways of the fan, the role of the natural factors represented by tectonic, geological, climate and hydrology was highlighted in the occurrence of torrents, which are among the most severe, The geomorphological hazards affected by urban facilities, agricultural lands and road networks on the surface of flood fans. The total number of waterways reached (948) streams ،And the total lengths of the waterways amounted to (446689) m. Three channels of waterways appeared on the surface of the Rani flood fan, which are the bed rocks channel pattern, the semi-dominant channel pattern, and the alluvial channel pattern. The research found that the flow risk values fall within the first category of the final classification table for the equations of the (Filmman) model with the risk value (High), which represented the dangerous flood areas, where it appeared that the expenditures at the points (q1, q2, q3) fall within the high-risk drainage According to the final classification of the Felman equations Where their expenses

Evolution of tributary junctions and their capacity for rearing juvenile Chinook salmon (Oncorhynchus tshawytscha) on a regulated river

AbstractThe Trinity River in northern California was adjusting to unregulated flood and mining impacts when it was dammed and flow regulation began in 1960. We examine the subsequent evolution of the river's alluvial channel through 60 years of increases in regulated mainstem flow regimes in an unconfined and confined valley where Rush and Indian creeks respectively join the river 6.9 and 26.7 river kilometres from Lewiston Dam. The resulting capacity of the tributary junctions for rearing Chinook salmon fry in the current flow regime is evaluated with an empirical model developed for the Trinity River. Results indicate that morphologic changes at Indian Creek were relatively minor after damming because mainstem flows were restricted to a narrow channel in comparison to the channel at Rush Creek. Conversely, active channel and bar areas significantly declined at Rush Creek because the mainstem sediment supply was more severely reduced by flow regulation that enabled riparian vegetation to colonize the expansive alluvial surfaces that were present. These changes reduced instream habitat, suggesting salmon populations in large valleys may be at higher risk below dams than in smaller valleys where the reduced flow is confined to an already narrow channel. However, the relatively wide and unconfined valley responded more positively to increases in flow and sediment through the regulatory periods to yield significantly higher capacities for rearing Chinook fry. Therefore, while unconfined reaches may be particularly susceptible to change when a river is dammed, they may also provide the greatest opportunity for restoration of salmon populations.

A Natural GMS Laboratory (Granulometry-Morphometry-Situmetry): Geomorphological-Sedimentological-Mineralogical Terrain Analysis Linked to Coarse-Grained Siliciclastic Sediments at the Basement-Foreland Boundary (SE Germany)

The “natural GMS laboratory” (granulometry-morphometry-situmetry) is located within the Variscan Basement in SE Germany (Fichtelgebirge Mts.), which is uplifted relative to its Permo-Mesozoic foreland along a deep-seated lineamentary fault zone. This transitional study area is crossed by straight to low drainage systems in the basement, turning meandering channel systems into high sinuosity when entering the foreland. Due to its good geological coverage, the entire region is subjected to an advanced-level terrain analysis and completed with a sedimentological study focusing on the GMS tool. Unlike many applications in the past, the three components of the GMS tool that are of almost equal value ought to be used in combination and not as stand-alone procedures so as to be integrated into other near-surface geoscientific methods, e.g., sediment petrography. The strong points of granulometry of coarse-grained/gravel-sized sediments are its extension into the smaller sand and clay grain size intervals using the sorting, mean and/or median values for an environmental analysis. Morphometry can be linked to the compositional geosciences, e.g., mineralogy and geochemistry. The grain shape is intimately connected with the lithology, providing options from triaxial measuring of the lithoclast to the digital image analysis. It is a favorable tool to supplement the provenance of lithoclasts. Situmetry is the key element of hydrodynamic research and directly builds upon its sister methods. Its applications and numerical approaches are useful for the identification and quantification of physical land-forming processes. It is the fan sharpness and the orientation of lithoclasts relative to the direction of the talweg and in relation cross-sectional valley features that integrate the GMS tool into geological and geomorphological mapping, both of which result in a digital terrain model. Horizontal rose diagrams are useful for the upper reaches of drainage systems, be they of alluvial or non-alluvial types, and vertical ones for alluvial channels in the distal and proximal foreland where stacked patterns of depositional terraces are of widespread occurrence. In general, the GMS tool can be applied to sedimentological, geomorphological, petrographic and tectonic objects in basements and foreland basins; in applied geosciences, it is suitable for the identification of mineral resources and of areas vulnerable to geohazards, and in genetic geosciences for the discrimination of supergene chemical and physical depositional and land-forming processes.

Urban stream syndrome: Quantifying topographic variation along an urban-rural gradient.

Topographic variation within fluvial systems is essential for providing a mosaic of physical habitats and supporting the dynamic hydraulic, geochemical, and biological processes that determine both aquatic and riparian ecosystem function. In highly-modified rivers through both urban and rural settings, the physical heterogeneity of alluvial channels has been diminished by anthropogenic activities. As riparian areas are increasingly under pressure from agricultural and urban development, identifying the geomorphic controls on physical heterogeneity through these environments is critical. In this study, we use the bed coefficient of variation (CV) extracted from a high-resolution bathymetric LiDAR survey as a dimensionless metric for topographic variation and physical heterogeneity over 100km of the Boise River corridor that spans an urban-rural gradient. Our CV results for both the streambed and channel demonstrate that the average topographic variation of reaches in urban areas is 22-25% lower than reaches located in rural areas along the same river. While these results initially support the application of the urban stream syndrome hypothesis, CV values had similar magnitudes in both urban and rural reaches suggesting there is a dominant control on topographic variation that was not directly related to urban land use. Analysis of CV values relative to normalized levee width indicates that the causative driver of morphologic simplification in the channel was lateral constraints from levees. In the Boise River, topographic variation increased linearly with normalized levee widths that ranged between 50% and >300% of the average channel width. Further, topographic variation was maximized in reaches where flow expansion during high discharge inundated between 1 and 2 times the average channel width (approximately 65-70% of the available floodplain). Our simple and objective watershed-scale approach leverages high-resolution topography data to identify reaches of high physical heterogeneity for river conservation, as well as help guide environmental flow releases in managed rivers.

A Large Bridge Pier in an Alluvial Channel: Local Scour versus Morphological Effects and the Role of Physical Models

A Large Bridge Pier in an Alluvial Channel: Local Scour versus Morphological Effects and the Role of Physical Models

Effects of initial and boundary conditions on gravel-bed river morphology

Assuming that the equilibrium geometry of river channels does not depend on their initial state but solely on boundary conditions, several formulas have been derived that relate the channel depth and width to the river bankfull discharge and bed material. However, due to the existence of a threshold for sediment motion and the strong non-linearity between sediment transport and flow rate, this assumption might not be generally valid for gravel-bed rivers. This research clarifies the role of the initial conditions, more specifically the initial channel width, on the geometry of gravel-bed rivers considering a variety of boundary conditions. The approach includes laboratory experiments and two-dimensional modeling, reproducing the evolution of alluvial channels with different starting widths, discharge regimes and sediment input rates. The experiments represent the Arc River (France). Thus, the characteristics of this river were used in the numerical model to obtain a realistic virtual case complementing the experiments. Different boundary and starting conditions resulted in either braided or single-thread channels. We found that the initial width strongly influences the evolution process and leaves a footprint on the river braid-belt extension. The active width of braided systems and the width of single-thread channels do not depend on the starting condition. They depend on sediment input rather than on discharge variability. Different initial widths result in different final bed levels. This indicates that the initial channel width may affect the degree of channel incision or aggradation. The results of this study justify the use of equilibrium formulas for single-thread rivers.

Impacts of Vegetation on Dryland River Morphology: Insights From Spring‐Fed Channel Reaches, Henry Mountains, Utah

AbstractA better understanding of how vegetation influences alluvial channels could improve (a) assessments of channel stability and flood risks, (b) applications of vegetation as a river management tool, and (c) predictions of channel responses to climate change and other human impacts. We take advantage of a natural field experiment in the semi‐arid to arid Henry Mountains, Utah, USA: large spatial differences in bed and bank vegetation are found along some alluvial channels due to localized perennial springs caused by aquicludes in the underlying bedrock. Airborne LiDAR topography and flood modeling are used to constrain channel morphology, vegetation density, and flow velocity at different flood discharges for three spring‐fed reaches along intermittently flowing streams. The spatial distribution of vegetation quantitatively influences both the magnitude and direction of channel adjustment. Reaches with abundant bed vegetation are significantly wider (by an average of ≈50%), with shallower flows and lower velocities, than reaches with little bed vegetation. Reaches with dense channel bank vegetation are ≈25% narrower and ≈25% deeper than sparsely vegetated reaches. We interpret that sediment grain size influences the spatial distribution of vegetation within spring reaches, but that bank vegetation may be more important than grain size for “threshold” width adjustments. Widths, depths, and velocities are fairly insensitive to whether local hydraulic roughness is parameterized in terms of local vegetation density or is assumed spatially constant, suggesting that the underlying “bare earth” topography of the channel bed and banks exerts more control on local flow than does local vegetation density in this landscape.

Assessment of dam-induced changes in ecogeomorphological behaviour and fluvial functionality in the Damodar River, West Bengal, India

Abstract Anthropogenic interventions in the form of dams and barrages often alter the fluvial functionality and eco-geomorphological (geomorphology, hydrology, and ecology) behaviour of river systems. The present work examines the environmental flow, channel metamorphosis, and fluvial functionality of the Damodar River in the context of Damodar Valley Corporation (DVC) dams and development. Structural (dams, barrages, weirs, etc.) and non-structural (urban–industrial and agricultural disposal with effluents, sand mining, etc.) interventions hinder the ecological functionality of the river. This study portrays that the eco-geomorphological behaviour and fluvial functionality of the river have changed due to flow alteration and diversion by dams and barrages and due to rapid urban–industrial and agricultural growth in the basin area. These changes have affected riverine ecological integrity. The ecological functionality level of this study area ranges from 85 to 181, i.e. from poor to good–fair. The ecological functionality level in the sample channel sections (i.e., the immediate upstream and downstream of the Durgapur Barrage) is poor, and the value ranges from 61 to 100 due to the hydrological impact of the barrage and the Durgapur urban–industrial belt. This assessment work will help to restore the fluvial environment for humans as well as riverine biota. HIGHLIGHTS Dams and barrages have altered the hydrological flow regimes, affecting the eco-geomorphological behaviour of alluvial channels. Dam-induced fluvial metamorphosis is evident in the channel morphological parameters and channel classification. The fluvial functionality index has been applied to evaluate the ecological functionality level for the restoration of the riverine environment.

A random displacement model of sediment transport in ice-covered alluvial channel flows.

There is a need for developing efficient models to simulate the sediment transport phenomenon in ice-covered alluvial channel flows, which is essential in enriching the theory of riverbed evolution. This study establishes a random displacement model parameterized with the time-averaged streamwise velocity U(z), the sediment settling velocity ωs(z), and the turbulent diffusion coefficient Dz(z) to calculate the suspended sediment concentration and the longitudinal dispersion coefficient for ice-covered alluvial channels. The proposed model is first validated to determine if it could be used to predict the sediment concentration profiles by comparing to limited experiments published in the literature. Results show that the simulations agree well with the measurements except for the underestimated concentration near the ice cover boundary. Once validated, the random displacement model is applied to explore the variation law of the suspended sediment concentration and the longitudinal dispersion with different sediment particle release modes. The sediment concentration and the stable value of the longitudinal dispersion coefficient for a given flow condition in the dynamic equilibrium state are not affected by the change of the particle release mode. The Fickian time required for the longitudinal dispersion coefficient converging to a constant, however, has a close relationship with the particle release mode and increases as the water depth increases.

Holocene deposits at the lower shoreface and inner shelf of the Dutch coast

To further detail insights into the composition and distribution of Holocene and late Pleistocene deposits at the surface and in the shallow subsurface of the lower shoreface of the Dutch coast, vibrocores were collected in three coastal sections. The study areas Noordwijk, Terschelling and Ameland Inlet represent contrasting settings: closed Holland coast vs. segmented Wadden coast (Noordwijk – Terschelling) and lower shoreface of a barrier island vs. lower shoreface of an ebb-tidal delta (Terschelling – Ameland Inlet).Six different depositional environments were distinguished: 1. the active layer, 2. seabed deposits, 3. lower-shoreface deposits, 4. ebb-delta channel deposits, 5. tidal channel deposits, and 6. alluvial (river) channel deposits. The several dm-thick active layer forms the mobile top of the seabed-, lower-shoreface- and ebb-delta channel deposits. Ebb-delta channel deposits (probably grading into terminal-lobe deposits) are restricted to the Terschelling and Ameland Inlet areas, fluvial deposits to the Noordwijk site. The front of the Ameland Inlet ebb-tidal delta is steep and consists of material supplied by the main ebb channel. These ebb-delta channel deposits are reworked by waves and currents, they grade seawards into seabed deposits. The low-gradient shoreface of the Terschelling site consists of a thin active layer on top of ebb-delta channel deposits. At the Noordwijk site fluvial deposits with incised bodies of tidal channel sand underlie a steep shoreface and a ridge-swale topography farther offshore.The ebb-delta channel deposits at the shoreface of Terschelling are similar to those at the front of the ebb-tidal delta of Ameland Inlet. Moreover, the tidal channel deposits that are common in the Noordwijk area, occur in only one core at Terschelling. This indicates that the deposits underlying the shoreface of Terschelling were formed in the ebb-tidal delta of a precursor of Ameland Inlet and not in the transgressive setting of a retreating barrier island. These deposits were possibly formed as part of the ebb delta of the Middelzee, a large medieval predecessor of the Ameland tidal basin, this needs to be confirmed by dating.Reworking of the shoreface of the prograded Subboreal beach barriers at Noordwijk at water depths of 12.5–13.5 m produced a 1.1-m-thick series of fining-upwards storm beds, including the active layer. At the shoreface of Terschelling storm beds are missing at these depths and only an active layer 0.2 m thick occurs. This suggests that the largest part of reworked sediment at Terschelling is carried off, which implies large-scale erosion of the shoreface. This needs further investigation.

Local Scour at Triangular Labyrinth Side Weirs Located on an Alluvial Channel

The studies on labyrinth side weirs have received considerable attention in existing literature. A mobile bed, which causes significant morphological bed changes, can be induced by the side overflow weir. In this study, the local scour depths that occur near a triangular labyrinth side weir at a 90° angle in a straight channel with an alluvial bed were experimentally examined under steady flow conditions with free overflow of the weir. Based on a dimensional analysis applied according to the parameters of the study, it was determined that dimensionless equilibrium scour depth is dependent on the approach flow intensity, dimensionless side weir crest height, dimensionless median grain size, dimensionless side weir opening, and dimensionless volumetric amount of upstream sediment feed under live-bed scour conditions. For different combinations of weir opening length and weir height, data for a set of 81 runs were obtained. The results show that an increase in weir crest height results in a decrease in dimensionless maximum scour depth. In the clear-water scour experiments, sediment deposits were observed downstream of the weir. In the live-bed scour experiments, the dimensions of the scours and sediment deposits that occurred upstream and downstream of the weir exhibited periodic changes. Good consistency was attained in the developed empirical equations between the calculated and measured values of the equilibrium scour depth.

Bank re‐erosion action to promote sediment supply and channel diversification: Feedback from a restoration test on the Rhine

AbstractRiver regulation alters hydrological and sediment regimes and consequently affects habitat complexity and dynamics, biodiversity and ecosystem services. Although channel bank erosion is a key geomorphological process supplying alluvial channels with coarse sediments and diversifying aquatic and riparian habitats, banks have often been stabilized to limit erosion risk to human activities and facilities. The objective of this paper is to assess the effects, and their sustainability, of bank protection removal on a 300‐m long reach of the Old Rhine (France/Germany) to promote sediment supply, channel diversification and a rehabilitation of fluvial morpho‐sedimentary processes. This action was combined with the construction of two island groynes to locally increase bank erosion processes. Yearly detailed monitoring was implemented over 6 years, including classical bathymetric surveys, airborne topo‐bathymetric and terrestrial LiDAR, and bed grain‐size and bedload tracking. Following a Q15 flood, the restoration induced a weak sediment supply. The restoration diversified habitats due to the implementation of the two island groynes, inducing bank scouring and the creation of new macroforms, as well as local bed grain‐size diversification and fining. The cross‐sectional diversity of the restored water channel was close to the regularization engineering phase. Channel bedform diversification persisted 6 years due to the persistence of the two island groynes. The action induced the rehabilitation of fluvial forms, in a static manner, rather than the rehabilitation of fluvial morpho‐sedimentary processes, which raises questions about the sustainability of the benefits of such management actions in terms of fluvial functionality and naturality.

Covariation in width and depth in bedrock rivers

AbstractThe width and depth of rivers are generally inversely related. For a given discharge, wider rivers tend to be shallower than narrower rivers, which are correspondingly deeper. This is particularly true in bedrock and mixed bedrock–alluvial channels, where deep pools occur downstream of lateral constrictions, downstream of which the channel becomes wider and shallower. However, covariation of width and depth in bedrock and mixed bedrock–alluvial rivers has never been explored due to the lack of field measurements. Here we present a 375 km survey of width and depth measurements in the Fraser Canyon, British Columbia, which alternates irregularly among alluvial (no bedrock exposed on either bank), bedrock‐constrained (bedrock exposed on one bank), and bedrock‐bound (bedrock exposed on both banks) sections. We find that bedrock‐bound reaches have the deepest and narrowest sections, followed by bedrock‐constrained reaches and alluvial reaches, which feature the shallowest and widest sections of channel. There is an inverse relation between width and depth for all the channels, with alluvial channels having the highest correlation between these two variables, and thus the greatest covariance. We further explore the relation between width and depth and the downstream hydraulic geometry of 42 individual bedrock‐bound canyons. There is an inverse relation between canyon width and depth, with substantial variation within individual canyons. The downstream hydraulic geometry for these bedrock‐bound canyons does not follow that typical of alluvial channels; depth is the only variable that adjusts substantially as a response to increasing discharge and upstream basin area.

Thermal Spring System Plumbing across a Major Normal Fault: Pah Tempe, Utah, USA

Abstract Faults, including their cores and associated fracture zones, can play an important role in controlling the flow of ground water. Pah Tempe Hot Springs at Timpoweap Canyon in southwestern Utah provides excellent exposures of the damage zone of a major normal fault and associated groundwater discharge. This includes numerous point discharges of ~40°C Na-Cl water into the Virgin River along a ~500 m stretch of the footwall damage zone of the Hurricane fault, part of the greater Wasatch-Hurricane fault system. An impermeable fault core and fine-grained rocks in the hanging wall impede cross-fault flow and force thermal waters to rise to the surface. The spectacular canyon-wall exposures permit an investigation of a fractured bedrock vadose zone as an analogue to subjacent aquifers. Photogrammetry (visual and infrared) enabled the mapping of discrete inflow locations, as well as permeable discontinuities in the canyon walls. Geochemistry, including reaction-path models, defined plausible chemical evolution pathways of thermal waters, whereas high-resolution geophysical surveys provided information on subsurface disruption and the depth to bedrock beneath Virgin River channel alluvium. The synthesis of these approaches indicates that permeable pathways in fractured carbonate rocks exhibit heterogeneous patterns. Some rock volumes contain abundant permeable fractures, bedding-plane partings, and solution cavities. Yet, within such volumes, one fracture may be permeable, whereas another only a few cm away may not. On a large scale (tens of meters), entire volumes of bedrock may be impermeable. Geophysical studies can shed light on gross fracture patterns in the bedrock aquifer but are incapable of showing which features accommodate flow. Patterns of permeability in the thick vadose zone may be the best predictor of subjacent flow paths in the aquifer. Thermal waters represent the leakage of deep brines or the mixing of Virgin River underflow with deep brines. Carbonate rocks exhibit self-organization where stochastic distribution of fracture apertures channel flow into wider features that channel additional flow. In turn, these features self-widen through solution weathering. By contrast, siliciclastic and basement rocks are not nearly as prone to dissolution. Thus, fluxes are partitioned into north-south fractures that will tend to have aperture in this east-west extending region. The results of this study help improve the conceptualization of flow systems near fault zones, and the methods employed may be a template applicable to the study of other systems.

River floodplain abandonment and channel deepening coincide with the onset of clear‐cut logging in a coastal California redwood forest

AbstractChanges in both land use and climate can alter the balance of transport capacity and sediment supply in rivers. Hence, the primary driver of recent incision or aggradation in alluvial channels is often unclear. The San Lorenzo River on the central coast of California is one location where both climate and land use—specifically, clear‐cut forestry of coastal redwoods—could explain recent vertical incision and floodplain abandonment. At our field site on the San Lorenzo, we estimate the magnitude of recent incision using both the ratio of bankfull to critical Shields numbers ( ) and the geomorphically effective discharge, calculated from historical gauge data. The Shields number ratio suggests that the normalized bankfull stress of the San Lorenzo River is in the upper 1–2% of West Coast rivers, and the effective discharge corresponds to flow depths ~2–4 m below current bankfull conditions. Radiocarbon ages from detrital charcoal in floodplain sediment reveal active floodplain deposition during the 1600s and possibly into the 1800s, constraining the timing of incision to the last few centuries. Multiple hanging tributaries above the mainstem San Lorenzo River, along with patterns in vegetation on terrace surfaces, corroborate our estimates of the magnitude and timing of incision. Taken together, our findings suggest that floodplain abandonment in this reach was mainly due to methods employed during logging that increased shear stress on the channel bed and reduced sediment storage capacity. We suggest that direct channel modifications in rivers can counterbalance increases in sediment delivery due to clear‐cutting, resulting in channel incision rather than aggradation. Today, a young, lower surface appears to be forming adjacent to the San Lorenzo River, which we interpret as an incipient floodplain that is in equilibrium with modern sediment supply and transport capacity.

Establishing Stage–Discharge Rating Curves in Developing Countries: Lake Tana Basin, Ethiopia

A significant constraint in water resource development in developing countries is the lack of accurate river discharge data. Stage–discharge measurements are infrequent, and rating curves are not updated after major storms. Therefore, the objective is to develop accurate stage–discharge rating curves with limited measurements. The Lake Tana basin in the upper reaches of the Blue Nile in the Ethiopian Highlands is typical for the lack of reliable streamflow data in Africa. On average, one stage–discharge measurement per year is available for the 21 gaging stations over 60 years or less. To obtain accurate and unique stage–discharge curves, the discharge was expressed as a function of the water level and a time-dependent offset from zero. The offset was expressed as polynomial functions of time (up to order 4). The rating curve constants and the coefficients for the polynomial were found by minimizing the errors between observed and predicted fluxes for the available stage–discharge data. It resulted in unique rating curves with R2 > 0.85 for the four main rivers. One of the river bottoms of the alluvial channels increased in height by up to 3 m in 60 years. In the upland channels, most offsets changed by less than 50 cm. The unique rating curves that account for temporal riverbed changes can aid civil engineers in the design of reservoirs, water managers in improving reservoir management, programmers in calibration and validation of hydrology models and scientists in ecological research.

Overcoming equifinality: time-varying analysis of sensitivity and identifiability of SWAT runoff and sediment parameters in an arid and semiarid watershed.

The phenomenon of "equifinality for different parameters" limits the link between parameters and catchment characteristics; however, solving the equifinality problem is a major challenge in the development, generalization, and application of a model. This study focused on the Yanhe River Watershed to investigate the time-varying characteristics of sensitivity and identifiability of SWAT (Soil and Water Assessment Tool) runoff and sediment parameters based on the Sobol' and generalized likelihood uncertainty estimation methods. The results indicate that (i) the nondominated sorting genetic algorithm-II has good adaptability and reliability in parameter calibration of the SWAT model in the Yanhe River Watershed. The evaluation indicators (Nash-Sutcliffe efficiency, R2, and percent bias) of monthly runoff and sediment in the Ganguyi hydrological station were all satisfactory per the SWAT model during the calibration and validation periods. (ii) The interaction between runoff and sediment parameters is a crucial reason for parameter sensitivity, which has obvious time-varying characteristics and is largely dependent on precipitation in the Yanhe River Watershed. Temporal and spatial variability of precipitation should be considered in the detailed analysis of parameter identifiability, and watershed managers should not ignore changes in the runoff process when regulating sediment. (iii) Only a relatively small number of parameters can be identified in the runoff and sediment simulation process of the Yanhe River Watershed, such as CN2 (initial soil conservation service runoff curve number for moisture condition II), CH_K2 (effective hydraulic conductivity in main channel alluvium), ALPHA_BF (baseflow alpha factor), USLE_C (cover and management factor), USLE_P (support practice factor), and USLE_K (soil erodibility factor), due to high surface runoff, reduced lag time, reduced low flows, increased peak flows, and channel erosion, respectively. More importantly, there is a strong positive correlation between parameter identifiability and parameter sensitivity. Both are effective methods of parameter diagnosis, but the identifiability of parameters is not equivalent to its sensitivity. Our results strongly suggest that a detailed parameter sensitivity and identifiability analysis is a critical step in improving hydrological model performance to reduce the risk of "equifinality for different parameters" while articulating all relevant hydrological processes.

Quantification of turbulent flow anisotropy in an alluvial channel mining pit

In this paper, turbulence anisotropy over a mining pit is studied. Laboratory experiment is performed in a flume with non-cohesive sand under steady flow condition. Two different geometric shaped mining pits, namely trapezoidal pit and irregular pit were excavated and instantaneous velocity data along the flow depth are taken at upstream, downstream and inside the mining pit. Turbulent anisotropy at various locations of the pit are compared. Stream-wise turbulence anisotropy is more in the upstream flow and nearly constant over the flow depth as compared to the other sections. For near bed flow in the pit, span-wise and vertical anisotropic contribution is more prominent as compared to the other components. Anisotropic invariant map (AIM) explains presence of two dimensional anisotropy near the bed for all the sections. It further illustrates the occurrence of two dimensional anisotropy in the outer flow zone in the pit. Mostly cigar shaped turbulence is observed in the upstream of the pit that changes to pancake shaped for near bed flow in the pit. At downstream of the pit, two dimensional anisotropy occurs near the bed and further it inclines to the three dimensional isotropy in the upper flow region.

Siting, disassaying and exfilling of the Mamão Dam in Ecuador/RN

Over four decades, there has been silting process of the riverbed that flows into the Mamão Dam, which supplies the water needs of the city of Ecuador-RN. This process has been taking place, caused largely by the receipt of mining tailings upstream of the reservoir. Thus, it became necessary the dredging consisting of removing the debris build-up and the bed debris and the riverbanks, offering a free flow to the waters that are intended for, and the excavation of the waste particles and accumulated sediment in the bed reservoir. For this, it was necessary; there were the necessary techniques for the conservation and proper maintenance so that did not occur obstruction of alluvial channel this spring. The work consisted of advice to the Municipality of the City of Ecuador, state of Rio Grande do Norte, where it made a technical feasibility study to recover the amount of previously existing water in the weir, were recovered to meet the population's consumption demand city and county. The study was conducted in 2013 and thus met the revitalization process and also the awareness of miners and miners, as the appropriate place for deposit of tailings stemmed these activities.