meandering streams
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2022 ◽  
Vol 14 (1) ◽  
pp. 234
Author(s):  
Mary C. Barlow ◽  
Xinxiang Zhu ◽  
Craig L. Glennie

Convolutional neural networks (CNNs) are becoming an increasingly popular approach for classification mapping of large complex regions where manual data collection is too time consuming. Stream boundaries in hyper-arid polar regions such as the McMurdo Dry Valleys (MDVs) in Antarctica are difficult to locate because they have little hydraulic flow throughout the short summer months. This paper utilizes a U-Net CNN to map stream boundaries from lidar derived rasters in Taylor Valley located within the MDVs, covering ∼770 km2. The training dataset consists of 217 (300 × 300 m2) well-distributed tiles of manually classified stream boundaries with diverse geometries (straight, sinuous, meandering, and braided) throughout the valley. The U-Net CNN is trained on elevation, slope, lidar intensity returns, and flow accumulation rasters. These features were used for detection of stream boundaries by providing potential topographic cues such as inflection points at stream boundaries and reflective properties of streams such as linear patterns of wetted soil, water, or ice. Various combinations of these features were analyzed based on performance. The test set performance revealed that elevation and slope had the highest performance of the feature combinations. The test set performance analysis revealed that the CNN model trained with elevation independently received a precision, recall, and F1 score of 0.94±0.05, 0.95±0.04, and 0.94±0.04 respectively, while slope received 0.96±0.03, 0.93±0.04, and 0.94±0.04, respectively. The performance of the test set revealed higher stream boundary prediction accuracies along the coast, while inland performance varied. Meandering streams had the highest stream boundary prediction performance on the test set compared to the other stream geometries tested here because meandering streams are further evolved and have more distinguishable breaks in slope, indicating stream boundaries. These methods provide a novel approach for mapping stream boundaries semi-automatically in complex regions such as hyper-arid environments over larger scales than is possible for current methods.


2021 ◽  
Vol 56 (3) ◽  
pp. 127-142
Author(s):  
Hosein Nezaratian ◽  
Javad Zahiri ◽  
Mohammad Fatehi Peykani ◽  
AmirHamzeh Haghiabi ◽  
Abbas Parsaie

Abstract Transverse mixing coefficient (TMC) is known as one of the most effective parameters in the two-dimensional simulation of water pollution, and increasing the accuracy of estimating this coefficient will improve the modeling process. In the present study, genetic algorithm (GA)-based support vector machine (SVM) was used to estimate TMC in streams. There are three principal parameters in SVM which need to be adjusted during the estimating procedure. GA helps SVM and optimizes these three parameters automatically in the best way. The accuracy of the SVM and GA-SVM algorithms along with previous models were discussed in TMC estimation by using a wide range of hydraulic and geometrical data from field and laboratory experiments. According to statistical analysis, the performance of the mentioned models in both straight and meandering streams was more accurate than the regression-based models. Sensitivity analysis showed that the accuracy of the GA-SVM algorithm in TMC estimation significantly correlated with the number of input parameters. Eliminating the uncorrelated parameters and reducing the number of input parameters will reduce the complexity of the problem and improve the TMC estimation by GA-SVM.


2021 ◽  
Vol 29 (2) ◽  
pp. 100-107
Author(s):  
Serdar Yedier ◽  
Derya Bostanci ◽  
Nazmi Polat

Abstract The aim of the current study was to determine the length-weight relationship (LWR) and length-length relationship (LLR) with condition factor (K) values for Oxynoemacheilus angorae from the Perşembe Plateau meandering streams in Ordu, Turkey. A total of 65 fish specimens, which were caught with electrofishing gear, were examined. Fish standard length (SL), fork length (FL), total length (TL), and body weight (W) were determined. There were no statistical differences between the measurements of male and female O. angorae specimens; therefore, the female and male specimens were evaluated together in the current study. The LWR equation and determination coefficient of O. angorae were W = 0.014 TL2.7359 (r2 = 0.9659). The 95% confidence interval of the b value for the O. angorae specimens from the Perşembe Plateau meandering streams was 2.7261 to 2.7435. In the present study, it was determined that O. angorae specimens showed negative allometric growth. Calculations of O. angorae TL-SL, TL-FL, and FL-SL relationship equations and determination coefficients were as follows: TL = 0.2091+1.1646 SL, (r2 = 0.986); TL = 0.1341+1.0301 FL (r2 = 0.9914); and FL = 0.0998+1.1261 SL, (r2 = 0.9868), respectively. A new maximum total length was recorded for O. angorae in this study. The average condition factor value of O. angorae was 0.9954. This value could have indicated that this species was encountering some problems in this habitat. The O. angorae parameters determined were the first data reported for the Perşembe Plateau meandering streams in Ordu, Turkey (Middle Black Sea Region).


Author(s):  
Cristopher Alexander Gamboa-Monge ◽  
Ana Maria Ferreira-da-Silva ◽  
Laura Segura-Serrano ◽  
Isabel Guzmán-Arias

This paper aims to be a contribution to the evaluation of the resistance factor of the alluvial meandering streams of natural origin. The well-known “divided resistance” approach, commonly adopted nowadays for straight streams with a bed covered by ripples and dunes is extended to include an additional term that considers the resistance due to the meandering of the stream. For the present analysis, 40 laboratory experiments and 285 field observations are evaluated, where it is found that the contribution of the meandering of the stream to its overall resistance may vary from negligible to very substantial, which depends on the stream geometric and flow conditions. In addition, it is determined that the most influential components for the resistance factor in meandering conditions depend on the relation between channel-averaged flow depth (hav) and the average grain size of the bed material (D50), the deflection angle of a meandering flow at the crossover Oi (θ0), and also the relation between flow width (B) and the channel-averaged flow depth (hav); these relations are used to develop a mathematical expression capable to predict the resistance to flow due to the meandering of the stream. It is shown that the equation introduced in this paper leads to considerably improved predictions of average flow velocity and conveyance capacity of meandering streams, which is of significance for an improved management of inland waterways.


2019 ◽  
Author(s):  
Aminreza Meghdadi ◽  
Morteza Eyvazi ◽  
Zohre Najatijahromi ◽  
Bahram Saghafian

Abstract. Riffle-pool sequences in the thalweg paths of meandering streams are of pivotal importance to the hyporheic exchange pattern in a fluvial network, but the complex hydrodynamic, morphological, and sedimentary features of riverbed sediments increase the difficulties associated with vertical hyporheic exchange (VHE) quantification. This study applied depth-dependent radon (222Rn) and diel temperature variations to quantify VHE and residence time (tr). The study was conducted in four different hyporheic areas with riffle-pool sequences in the third-order Ghezel-Ozan River, located in north-west Iran. The mean values of temperature-derived VHE (VHET) and radon-derived VHE (VHERn) were 0.67±0.32 m/day and 0.63±0.36 m/day, respectively. Due to effects of sediment bed heterogeneity on temperature variation and 222Rn activity at downwelling and upwelling points, there were discrepancies between radon-derived (trRn) and temperature-derived residence time (trT), with mean values of 2.11±1.17 days and 1.87±1.26 days, respectively. The value of trT was well within uncertainty boundaries at a 95 percent confidence interval (p<0.05) and was lower than trRn at the downwelling points. The analysis of vertical diel temperature, radon and electrical conductivity variations revealed subsurface water exchange to be greatly affected by larger scale regional flow. The comparison between VHET and VHERn with VHE obtained from PHAST model simulation (VHEPHAST) revealed a higher correlation between VHET and VHEPHAST (R2=0.96) than with VHERn (R2=0.76). Furthermore, vertical hydraulic conductivity (Kv) of the sediment-bed materials, calculated in situ by the permeameter test, indicated not only that Kv was up to 21 % higher in areas dominated by upward movement than at downwelling points, but also principle component analysis (PCA) demonstrated the dependence of Kv on porosity, VHE, and %sand of the stream-bed materials. This study provides evidence that vertical flux in the hyporheic zone is mainly affected by stream sinuosity and regional subsurface flow, and that the temperature method is more suitable than radon activity to quantify hyporheic exchange patterns.


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