Average Channel Width Research Articles

Long-term geomorphic effects of longitudinal training walls in the Grand River, Michigan (USA)

The Grand River is the longest river in Michigan, flowing from northwest Hillsdale County to Lake Michigan, and draining an area over 14,400 km2. Bathymetric surveys of a ~ 38 km reach of the river from Grand Rapids to the confluence with Bass River, performed in 1906, were uncovered in the Grand Rapids Community Archives and Research Center in 2014. These maps show depth recordings across the channel along cross sections spaced ~90 m apart. The maps also show the location of numerous training walls that were built in the river in the 1890's as an effort to maintain navigation. The 1906 maps were georeferenced, and the bathymetric data were digitized, converted to bed elevation, and interpolated into an elevation model of the channel bed. High-resolution multibeam echo sounding surveys were conducted in June 2019 and 2020 over the same reach and provided a means to assess over 100-years of geomorphic changes. The results from these analyses showed substantial changes to the average channel width and width variability, with some locations narrowing by up to 50 % (~90 m). Volumetric difference maps between 1906 and 2020 revealed a streamwise spatial variation in the net erosion and deposition, with upstream reaches being predominantly erosional and downstream reaches exhibiting net deposition, with the transition occurring close to the extent of backwater influence from Lake Michigan. The presence of the training walls also resulted in the development of many mid-channel islands and narrowing of the channel through floodplain accretion. Findings from this study have implications for river management projects that have been proposed for the Grand River, as well as other rivers where these structures might be implemented.

Reach scale channel planform dynamics of transboundary River Jaldhaka within Himalayan Foreland Basin

ABSTRACT The slopes of Himalayan piedmont and foothill plain are being modified by the Himalayan origin river systems. In this study, spatiotemporal dynamics of channel planform of braided River Jaldhaka have been estimated using United States Army Map (1956) and landsat satellite images (1980-MSS, 1990-TM, 2000-TM, 2010-ETM+ and 2022-OLI) for the delineation of banklines, channel length, sinuosity index, braiding index, channel widths, identification of partial channel avulsion sites and bankline migration using Digital Shoreline Assessment System (DSAS) toolbar. Linear Regression Rate, Net Bankline Movement and End Point Rate were also calculated. Results revealed that the lower reach is more sinuous (maximum average channel sinuosity 1.65) compared with reach-I (1.29) and II (1.11)). The maximum channel width was in the year 2022 (968.6 m) and minimum average channel width was in 1956 (239.87 m). The maximum BI value (3.55) has been calculated in the sub reach-2 (SR-2, reach-I). Similarly, DSAS output shows maximum average EPR values (6.43 m/year) in lower reach which was most erosion prone bank. Bank facies study showed that non-cohesive bank materials accelerate rapid rate of channel avulsion and bank erosion. The variation of discharge, velocity, presence of vegetation and anthropogenic interventions controls the nature of planform changes of Jaldhaka River.

Temporal change in channel form and hydraulic behaviour of a tropical river due to natural forcing and anthropogenic interventions

ABSTRACT Assessing the degradation of river channels is crucial in the Anthropocene era, particularly in the deltaic areas worldwide. The present study aims to investigate the degradation of the Mathabhanga-Churni River giving emphasis on the temporal change of channel morphology and hydraulic behaviour and comparing the current situation with the historical past based on planform morphology and meander geometry of 118 meander loops, and width, depth, cross-sectional area, and hydraulic behaviour (velocity, discharge, stream power) at 47 cross-sections. The absence of lateral dynamicity, the static character of channel sinuosity during the last century (1913–2018), and the constant meander morphology reflects the static meander geometry and degradation of the river. The reduction of average channel width, depth, and cross-sectional area supports the falling trend of channel forms. Findings on hydraulic behaviour indicate declining discharge (~50% reduction during 1915–2018) that induces the present-day downscaled velocity and lowered stream power. Neotectonics (eastward tilting of the Bengal delta) and anthropogenic stressors such as stream crossings, agriculture on river beds, brickfields, and urbanisation have a severe impact on the hydromorphology of the channel, turning the active river into a stagnant and polluted channel.

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.

Width‐Based Discharge Partitioning in Distributary Networks: How Right We Are

AbstractRiver deltas are home to large populations and can be composed of complex channel networks which convey flows of matter to the shoreline. Knowledge of flow within individual channels is needed to quantify the distribution of discharge across the delta, and thus its sustainability over time. Due to a lack of field measurements at the local channel scale, researchers leverage remote sensing data to estimate the partitioning of flow. We compare data from 15 river deltas to discharge partitioning estimates based on channel network graphs derived from remote sensing imagery. We quantify errors in the common width‐based method and test alternative partitioning techniques to find that width‐based discharge partitioning is universally applicable, suggesting that absent any site‐specific information, discharge partitioning by average channel width is an appropriate approach. We also provide networks, streamflow measurements, and flux partitioning estimates for 28 delta networks as the Discharge In Distributary NeTworks (DIDNT) dataset.

Numerical simulation and experimental analysis of ice crystal growth and freezing-centrifugal desalination for seawater with different compositions

In this study, numerical and experimental studies of ice directional crystallization for the NaCl, Na2SO4, MgCl2, and MgSO4 solutions were investigated. The comparison of energy consumption between freezing-centrifugal desalination and the conventional method was discussed. The phase-field method was employed to simulate the ice directional crystallization process. A microscope experimental setup was established to observe the morphology of dendrites and verify the theoretical model in the directional crystallization process. The absolute deviations of the average width of the brine channel between numerical and experimental results are less than 15%, which indicates that the phase-field method can present the performance of ice directional crystallization well. The results also showed that in the directional crystallization process, the solutions with SO42- (Na2SO4 and MgSO4 solutions, and their mixtures) form narrower brine channels than that of NaCl and MgCl2 solutions due to their low diffusion coefficient. Moreover, the impacts of ions and brine channel on the freezing-centrifugal desalination were investigated by the experiments. When the rotation speed and centrifugal time were set at 5000 rpm and 2.0 min, respectively, the salt removal efficiency of NaCl and MgCl2 was higher than 96%, while they were less than 13% for the Na2SO4 and MgSO4 solutions. Hence, the SO42- ion plays a significant role in preventing sea ice desalination due to narrower brine channels.

All Logjams Are Not Created Equal

AbstractLogjams create diverse physical and ecological effects in stream channels, including at least temporary storage of water, sediment, and particulate organic matter. We hypothesize that logjams that span the entire bankfull channel width in channels ≤25 m wide are more effective in storing these materials than non‐channel spanning logjams. We test this hypothesis by systematically comparing characteristics of 183 logjams from 17 stream reaches in the Southern Rocky Mountains. Our data set is novel in that it evaluates naturally occurring logjams in unaltered streams in a single study area specifically based on whether they span the stream channel. We find that channel‐spanning logjams have a significantly larger number of wood pieces, longer & wider pieces, more ramp and bridge pieces, and greater logjam height and volume, both as raw data and when standardized by average channel width. Channel‐spanning logjams also have significantly greater backwater pool volume and volume of particulate organic matter stored in backwater pools and in logjams. Restoration employing engineered logjams in relatively small channels currently focuses on non‐spanning logjams, but could be expanded to include spanning logjams.

Transmission loss estimation for ephemeral sand rivers in Southern Africa

Ephemeral sand rivers represent an important water resource in Southern Africa. These rivers only flow for a few days in a year. However, much of this water infiltrates the underlying river bed sediments where it is protected from evaporation and utilized by farmers throughout the dry season. Despite their importance, little is known about how much recoverable water is annually stored within the sand. A particular difficulty concerns obtaining reliable estimates of transmission losses (the amount of water that infiltrates the river bed). The objective of this article was to develop an improved methodology for quantifying transmission loss from ephemeral sand rivers by calibrating a lumped rainfall-runoff model to observed river flow data. Fifteen years of daily river flow data were obtained from four sand rivers in Botswana, namely, Shahshe, Ntshe, Tati and Metsimotlhabe. These data were supplemented with meteorological data from AgMERRA (Ruane et al., 2015) and precipitation data from CHIRPS (Funk et al., 2015). Our simplified rainfall runoff model had four unknown parameters including a river bed infiltration factor, a surface storage capacity, a river bed storage capacity and an average river channel width. Posteriori parameter distributions were derived using a GLUE (Beven and Binley, 1992) methodology. Our study confirms that upper and lower bounds for transmission loss can be obtained by calibrating a lumped rainfall runoff model to a single set of river flow gauging data. Transmission loss was found to represent between 55% and 85% of the total surface runoff at these locations.

Efficient microfluidic enrichment of nano-/submicroparticle in viscoelastic fluid.

The enrichment and focusing of the nano-/submicroparticle (e.g., 150-1000nm microvesicle shed from the plasma membrane) in the viscoelastic fluid has great potentials in the biomedical and clinical applications such as the disease diagnosis and the prognostic test for liquid biopsy. However, due to the small size and the resulting weak hydrodynamic force, the efficient manipulation of the nano-/submicroparticle by the passive viscoelastic microfluidic technology remains a major challenge. For instance, a typically long channel length is often required to achieve the focusing or the separation of the nano-/submicroparticle, which makes it difficult to be integrated in small chip area. In this work, a microchannel with gradually contracted cross-section and high aspect ratio (the ratio of the height to the average width of channel) is utilized to enhance the hydrodynamic force and change the force direction, eventually leading to the efficient enrichment of nano-/submicroparticles (500 and 860nm) in a short channel length (2cm). The influence of the flow rate, the particle size, the solid concentration, and the channel geometry on the enrichment of the nano-/submicroparticles are investigated. With simple structure, small footprint, easy operation, and good performance, the present device would be a promising platform for various lab-chip microvesicle-related biomedical research and disease diagnosis.

Estimation of natural streams longitudinal dispersion coefficient using hybrid evolutionary machine learning model

Among several indicators for river engineering sustainability, the longitudinal dispersion coefficient () is the main parameter that defines the transport of pollutants in natural streams. Accurate estimation of has been challenging for hydrologists due to the high stochasticity and non-linearity of this hydraulic-environmental parameter. This study presents a new hybrid machine learning (ML) model integrating a Gaussian Process Regression (GPR) and an evolutionary feature selection (FS) approach (i.e. Covariance Matrix Adaptation Evolution Strategy (CMAES)) to estimate in natural streams. The dataset consists of geometric and hydraulic river system parameters from 29 streams in the United States. The modeling results showed that the proposed model outperformed other models in the literature, producing more stable and accurate estimations. The FS approach evidenced the significance of the cross-sectional average flow velocity (U), channel width (B), and channel sinuosity σ to estimate the dispersion coefficient. In quantitative terms, the integrated GPR model with feature selection approach attained the minimum root mean square error () and maximum coefficient of determination (). The proposed hybrid evolutionary ML model arises as robust, flexible and reliable alternative computer aid technology for predicting the longitudinal dispersion coefficient in natural streams.

The roles of flood magnitude and duration in controlling channel width and complexity on the Green River in Canyonlands, Utah, USA

Predictions of river channel adjustment to changes in streamflow regime based on relations between mean channel characteristics and mean flood magnitude can be useful to evaluate average channel response. However, because these relations assume equilibrium sediment transport, their applicability to cases where streamflow and sediment transport are decoupled may be limited. These general relations also lack the specificity that is required to connect specific characteristics of the streamflow and sediment regime with the dynamics of channel morphological change that create channel complexity, which is often of ecological interest. We integrate historical records of channel change, observations of scour and fill during a snowmelt flood, measurements of sediment transport, and predictions from a two-dimensional streamflow model to describe how annual peak flow magnitude and peak-flow duration interact with the upstream sediment supply to control channel form for a 15-km study reach on the regulated Green River in Canyonlands National Park, Utah. Two major decadal-scale episodes of channel narrowing have occurred within the study area. For each of these episodes, the reduction in average channel width was consistent with the change predicted by hydraulic geometry relations as a function of average flood magnitude. However, channel narrowing occurred during periods of exceptionally low annual floods. The most recent episode of channel narrowing occurred between 1988 and 2009, during low-flow cycles when the 5-yr mean peak flow was less than 60% of the long-term (1959–2016) mean peak flow. These findings, together with findings from previous studies, demonstrate that decreases in peak-flow magnitude caused by streamflow regulation, climate change, or a combination of those factors have driven episodes of channel narrowing on the Green River. Observations of streamflow, sediment-transport, and morphologic change coupled with predictions from a two-dimensional streamflow model indicate that peak flow magnitudes of at least 75% of the long-term mean peak flow are required to transport bed-material sand in suspension in all regions of the multi-thread channel and that the ~2-month duration of the snowmelt flood played an important role in creating conditions necessary to maintain channel conveyance. These results indicate that detailed characterizations of channel response such as these are needed to predict how river channels will respond to changes in streamflow regime that affect annual peak flow magnitude and duration.

Geomorphic changes in the Jhelum River due to an extreme flood event: a case study

The unprecedented extreme flood occurred in Jhelum basin, India in the first week of September, 2014 due to continuous spell of high intensity antecedent rainfall. The rainstorm observed over the basin during the event was unprecedented in terms of accumulated rainfall. In this study, Operational Land Imager (OLI) Landsat images taken before and after flood were employed to assess the morphologic and geomorphic effects of the flood along both the sides of the Jhelum River. The total erosion and sedimentation for the study reach due to flooding were 278 and 2.7 ha respectively. The flow length and the average channel width were decreased by 500 m and 25 m respectively. The study reach was divided into meander loops (M), straight stretches (S), and island bars (B) based on sinuosity and braiding. The maximum erosion in the meander loops was observed in M5 section, B4 section in island bars, and S7 section in straight stretches of the river. The maximum erosion was observed in the riparian cover due to this flood. However, damage to the built-up cover was practically very limited to the selected river reaches due to the reinforced channel banks. It is evident from the findings of the erosion on different sections of the meander loops and straight reaches that as the sinuosity increases, the erosion also increases for a relatively significant areal extend of each land cover. This result gives insight to the incompetent management measures of riparian cover, which is a principal reason for the huge economic losses during flood.

UAV-based remote sensing of immediate changes in geomorphology following a glacial lake outburst flood at the Zackenberg river, northeast Greenland

ABSTRACT Two detailed geomorphological maps (1:2000) depicting landscape changes as a result of a glacial lake outburst flood were produced for the 2.1-km-long section of the Zackenberg river, NE Greenland. The maps document the riverscape before the flood (5 August 2017) and immediately after the flood (8 August 2017), illustrating changes to the riverbanks and morphology of the channel. A series of additional maps (1:800) represent case studies of different types of riverbank responses, emphasising the importance of the lateral thermo-erosion and bank collapsing as significant immediate effects of the flood. The average channel width increased from 40.75 m pre-flood to 44.59 m post-flood, whereas the length of active riverbanks decreased from 1729 to 1657 m. The new deposits related to 2017 flood covered 93,702 m2. The developed maps demonstrated the applicability of small Unmanned Aerial Vehicles (UAVs) for investigating the direct effects of floods, even in the harsh Arctic environment.

Flood inundation mapping and monitoring using SAR data and its impact on Ramganga River in Ganga basin.

Remote sensing-based flood inundation mapping and monitoring is very crucial input before, during, and after floods. Ganga-Ramganga doab is one of the prolonged flood-affected area in middle Ganga plain due to seasonal monsoon which leads to rise in water levels of Ganga and Ramganga rivers. The focus of the present study is to map severe flood condition captured through synthetic aperture radar (SAR) data during August-September 2018, and to explain the impact on Ramganga river morphology. SAR data is preferred for flood mapping and real-time monitoring in all weather conditions. In this study, dual-polarized (VV and VH) Sentinel-1 SAR images coupled with hydrological data (river water level) were used to produce flood inundation maps. Thresholding technique has been applied to determine the flood mapping through Sentinel-1 data. VH and VV polarisation methods have been applied for a comparison of their respective accuracies in delineating surface water. Results have been validated against a Sentinel-2 optical image, and both polarisations produced a total accuracy of more than 93%. VV polarisation has high accuracies than VH polarisation as similar results are observed in previous studies as well. The finding reveals that severe bank erosion took place in the Ramganga channel which significantly affected the channel morphology, mainly the massive mobilisation of channel sediments. The results show that the average channel width increased from 46 to 336 m. The proposed approach demonstrates that the microwave remote sensing data along with GIS can be used efficiently for flood inundation mapping, monitoring, and analysing its effect on channel morphology. Therefore, the results of this study will help to take the initiative to reduce the flood hazard impact in the doab area and increase the flexibility in the process of flood management.

A modern analog for meandering rivers of the Mina del Carmen Formation (Albian) at Cañadón Seco oilfield, Golfo San Jorge Basin, Patagonia

Fluvial sandstone reservoirs within the Mina del Carmen Formation (Albian) currently produce up to 10% of the liquid hydrocarbons of the Golfo San Jorge Basin, mainly from isolated channel belts encased in a fine-grained, pyroclastic-rich floodplain. In spite of their economic importance, no modern analogs for the subsurface fluvial reservoirs have been proposed yet, mainly due to the reduced thickness of the channels in relation to the vertical resolution of available 3-D seismic surveys. At Cañadón Seco oilfield (South Flank of the Golfo San Jorge Basin), the planform of a meandering channel belt in Upper Mina del Carmen Formation has been imaged in a 3-D seismic dataset using seismic attributes. The meandering channel belt is up to 13 m thick and 3200 m width, with a sinuosity of 3.61 and has an average channel width of 192 m. Using the measured parameters obtained from the seismic dataset, we tested the applicability of empirical relations developed for modern rivers; the results of the statistical equations showed a close correspondence with seismic measurements and allowed us to estimate data of formative river discharge and upstream catchment area for the subsurface example. Both values were then parallel with a database of river discharge and area of up to 1018 hydrometeorological stations in drainage catchments around the world. Nine rivers of the database show discharge-area values comparable to those obtained using empirical equations. After a review of satellite imagery of the nine areas, a modern analog for the subsurface example was found in the Middle Ebro River (Spain). The analog consists of a meandering fluvial depositional system in a foreland basin setting, with seasonal discharge variability. The approach followed in the research can be of use to any fluvial basin, but considering that fluvial systems are highly variable in scale, geometry, pattern and composition, the extrapolation of results to other regions or even to other strata within the Mina del Carmen Formation, should be done with caution.

A variable parameter bidirectional stage routing model for tidal rivers with lateral inflow

Water stage variations are complicated in tidal rivers due to the combination of upstream flood and downstream tide. This study proposed a bidirectional stage routing model (BSR) for tidal rivers by considering the stage hydrograph as the overlay of bidirectional propagation of upstream flood wave and downstream tidal wave. The basic stage routing equations derived from the storage equation and water balance equation are used to calculate the upstream flood wave routing and the downstream tidal wave propagation, respectively. The lateral inflow can be directly specified as an additive term in the basic equation of BSR model or indirectly estimated by a lateral flow rate reflecting the proportion of lateral inflow to the upstream water. Parts of the model parameters are time-variable to account for the effect of water surface slope on water stage. The model inputs include stage hydrographs at the upstream and downstream boundaries. The channel geometric characteristics data are not required when the average channel width is estimated as a parameter. The case study results in the tidal reaches of the Caoe River and Qiantang River in China demonstrate that the BSR model performs well in water stage simulation. With relatively simple structure, modest data requirement and stable performance, the physically-based BSR model has the potential for water stage routing in tidal rivers when channel geometry data are not available.

Downstream channel changes and the likely impacts of flow augmentation by a hydropower project in River Dikrong, India

ABSTRACTThe Dikrong River, a tributary of the Brahmaputra River Basin in India, has been receiving additional water from an adjacent river since 2002 under the operation of the 405 MW Ranganadi hydel project. Flow duration curves and indicators of hydrological alteration analyses reveal that the downstream river flow has been significantly altered post-2002. Examination of the channel pattern in a Geographic Information System environment using satellite images from 1973 to 2014 displays that the channel planform has also changed over time, wherein it has become wider, less meandering and more braided. Sinuosity decreased from 1.9 in 1987 to 1.66 in 2002 and has stabilized since then. Simultaneously, braiding increased from 1.55 (1987) to 1.81 (2014). The average bankfull channel width from 1973 to 2014 varied between 378 and 573 m. The river also displays erratic and unevenly distributed bank migration and erosion patterns. However, channel changes could be observed even prior to the hydel project’s influence through flow addition. Thus, this study analyses the temporal and spatial changes in downstream channel morphology of the Dikrong River and examines whether they have been influenced by the hydrological alterations caused by the hydel project.

Dynamic characterization of meandering channels planform

Meandering channels develop different geometry patterns along the floodplain during its evolution. These natural processes lead to developing lateral and longitudinal migration, describing a sort of swept that affect the human activities. As the equilibrium geometry of natural channels depends on: the flow and sediment discharge, geological conditions of valley, soil properties, and vegetation among others, the preliminary characterization is not easy. Due to this, several engineering and scientific problems require an appropriate description of morphological processes. The dynamic characterization like the quantification of wavelength, amplitude, sinuosity, and curvature using Medium Temporal Scheme (MTS) is using widely. Unlike the traditional scheme that only uses short or long-term schemes, MTS includes relevant morphological events (e.g., cutoff). In addition this, the satellite images has increased and achieves a high spatial resolution, even more when studying large basins. This paper presents and validates a MATLAB®-based toolbox called Meander Statistics Toolbox (MStaT) to perform the dynamic characterization of several meandering channels using the MTS. To run MStaT only need the centerline (CL), and the average width of channel as input parameters. To maximize the toolbox, MStaT incorporates the Wavelet Analysis (WA) to decompose the signal (CL) and obtains the power spectrum. Finally, two studies cases (synthetic and natural channels) will be presented to validate MStaT.

Effects of an extreme flood on river morphology (case study: Karoon River, Iran)

An extreme flood occurred on 14 April 2016 in the Karoon River, Iran. The occurred flood discharge was the highest discharge recorded over the last 60years in the Karoon River. Using the OLI Landsat images taken on 8 April 2016 (before the flood) and 24 April 2016 (after the flood) the geomorphic effects were detected in different land cover types within the 155-km-long study reach. The results show that the flood significantly affected the channel width and the main effect was high mobilization of channel sediments and severe bank erosion in the meandering reaches. According to field surveys, the flood occupied the channel corridor and even the floodplain parts. However, the channel pattern was not significantly altered, although the results show that the average channel width increased from 192 to 256m. Statistical results indicate a significant change for active channel width and sinuosity index at 99% confidence level for both indexes. The flood-induced morphological changes varied significantly for different land cover types along the Karoon River. Specifically, the channel has widened less in residential areas than in other land cover types because of the occurrence of bank protection structures. However, the value of bank retreat in residential and protected sides of the Karoon River is more than what we expected during the study of extreme flood.

Effects of urbanization on river morphology of the Talar River, Mazandarn Province, Iran

In the present study, we investigate the effects of urbanization growth on river morphology in the downstream part of Talar River, east of Mazandaran Province, Iran. Morphological and morphometric parameters in 10 equal sub-reaches were defined along a 11.5 km reach of the Talar River after land cover maps were produced for 1955, 1968, 1994, 2005 and 2013. Land cover types changed extremely during the study period. Residential lands were found to have increased in area by about 1631%, while forest land and riparian vegetation decreased in by approximately 99.9 and 96.2%, respectively. The results of morphometric and morphological factors showed that average channel width (W) for all 11.5 km of the study river decreased by 84% during the study period, while the flow length increased by about 2.14%.