• Title/Summary/Keyword: mean river bed slope

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Development of an Estimation Method for Travel Time (도달시간 산정 방법의 개발)

  • Jeong, Jong-Ho;Keum, Jong-Ho;Yoon, Yong-Nam
    • Journal of Korea Water Resources Association
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    • v.35 no.6
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    • pp.715-727
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    • 2002
  • The travel time of a flood through a river reach can be estimated by dividing the river length by the mean velocity with which the flood passes downstream. It is closely related to storage constant for the watershed routing of a flood. There are so many empirical formulas available for the estimation of travel time but the results computed generally show great different depending on individual formulas. In the present study, the mean velocity data computed in the process of water surface profile computation for a probability flood through more than 100 different river reaches were collected along with the mean river bed slope of each river reach. And then, a regression analysis is made between the mean river bed slope and the mean velocity, which showed a wide scatter along the mean regression curve, which appears to be due to the different in the magnitude of probability rainfall and size of watershed area. Therefore, methods have been developed to remove the effect of these factors and generalized empirical equation is proposed to relate the mean velocity to mean river bed slope of a reach. Hence, if the mean river bed slope of a river reach is estimated from the longitudinal river profile, the mean velocity can be computed by the generalized equation along with the probability rainfall and watershed area of the river reach under consideration, which leads to the estimation of travel time through a river reach.

A Study on Selected Transverse Bed Slope Models in Channel Bend (유로만곡부의 횡방향 하상경사 산정 모형에 관한 연구)

  • Song, Jai Woo;Choi, In Ho;Kim, Ji Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.6
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    • pp.1395-1404
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    • 1994
  • Transverse bed slope in bend is a subject of scientific investigation since it provides the necessary information for channel design and protection of hydraulic structures (bank, bridge, etc), and study of river morphology. In this paper, selected models were examined and compared for the value of prediction of the transverse bed slope in curved alluvial channels(project area), by using field data, and fitting model was proposed. All models that related the local transverse bed slope to mean flow characteristics were alike in the sense that they predicted the local transverse bed slope to be proportional to the ratio between depth and radius of curvature. The difference among the models was related with the factor of proportionality, K. Also, measured transverse bed slope was correlated to mean velocity, maximum depth, and density Froude number in channel bend. In this paper selected models were compared for the prediction of the transverse bed slope using Odgaard's experiment (obtained in Sacramento River bend), so Odgaard89 model was closely related with real transverse bed slope.

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Relationship between Stream Geomophological Factors and the Vegetation Abundance - With a Special Reference to the Han River System - (하천의 지형학적 인자와 식생종수의 관계 -한강수계를 중심으로-)

  • 이광우;김태균;심우경
    • Journal of the Korean Institute of Landscape Architecture
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    • v.30 no.3
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    • pp.73-85
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    • 2002
  • The purpose of this study was to develop prediction models for plant species abundance by stream restoration. Generally the stream plant is affected by stream gemophology. So in this study, the relationship between the vegetation abundance and stream gemophology was developed by multiple regression analysis. The stream characteristics utilized in this study were longitudinal slope, transectional slope, micro-landforms through the longitudinal direction, riparian width and geometric mean diameter and biggest diameter of bed material, and cumulated coarse and fine sand weight portion. The Pyungchang River with mountainous watershed and the Kyungan stream and the Bokha stream in the agricultural region were selected and vegetation species abundance and stream characteristics were documented from the site at 2~3km intervals from the upper stream to the lower. The Models for predicting the vegetation abundance were developed by multiple regression analysis using SPSS statistics package. The linear relationship between the dependant(species abundance) and independant(stream characteristics) variables was tested by a graphical method. Longitudinal and transectional slope had a nonlinear relationship with species abundance. In the next step, the independance between the independant variables was tested and the correlation between independant and dependant variables was tested by the Pearson bivariate correlation test. The selected independant variables were transectional slope, riparian width, and cumulated fine sand weight portion. From the multiple regression analysis, the $R^2$for the Pyungchang river, Kyungan stream, Bokga stream were 0.651, 0.512 and 0.240 respectively. The natural stream configuration in the Pyungchang river had the best result and the lower $R^2$for Kyunan and Bokha stream were due to human impact which disturbed the natural ecosystem. The lowest $R^2$for the Bokha stream was due to the shifting sandy bed. If the stream bed is fugitive, the prediction model may not be valid. Using the multiple regression models, the vegetation abundance could be predicted with stream characteristics such as, transection slope, riaparian width, cumulated fine sand weigth portion, after stream restoration.

Estimation methods of maximum scour depth in steep gravel-bed bend channel (급경사 자갈하상 만곡수로의 최대세굴심 산정공식 평가)

  • Cho, Jaewoong;Nam, A-Reum;Woo, Tae Young;Park, Sang Deog
    • Journal of Korea Water Resources Association
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    • v.49 no.6
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    • pp.529-536
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    • 2016
  • The existing methods to estimate the maximum scour depth in the bend of steep gravel bed channel have been evaluated by the hydraulic movable-bed experiments. In the $90^{\circ}$ bend steep-slope channel paved with the fluvial gravels which are uniform in size and have a mean diameter of 43mm, the maximum scour depths due to the flow discharge and the gradient of bed slope have been investigated and compared with the scour depth computed from the equations. The local scour has occurred in conditions that the bed slope is steeper than 0.02 and the $F_r$ is greater than 0.95. Except Lacey's equation and Zeller's equation, the existing methods computing the maximum scour depth overestimate the maximum scour depth in the steep channel with the very coarse gravel bed. However, Lacey's equation with the bed material size and Zeller's equation considering the approach channel gradient and the bend angle may be relatively used to estimate the scour depth in bend of the steep gravel-bed river.

Application of Slope-area Discharge Estimation Method using Continuously Observed Water Level Data in a Gravel Bed River -Case Study of the Dal Cheon River- (자갈하천에서 연속적인 수위 자료를 이용한 경사면적법 유량 산정 -달천 사례연구-)

  • Lee, Chan-Joo;Kim, Ji-Sung;Kim, Chi-Young;Kim, Dong-Gu
    • Journal of Korea Water Resources Association
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    • v.41 no.5
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    • pp.503-515
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    • 2008
  • In this study we calculate discharge by slope-area method using continuously observed water level data and analyse the results. This study is performed in the Dalcheon river reach of 960 m length including riffles and a pool, which is located downstream of the Goesan Dam. Three values of roughness coefficient are applied to discharge calculation, which are established using bed material size analysis. Another roughness coefficient value obtained from the river improvement plan is also used. Calculated discharges by slope-area method are compared with dam discharges. Relative difference from dam discharges appears to be largely affected by roughness values and a value of 0.042 or more seems most suitable for the entire study reach. Smaller roughness value is suitable to the reach which has gentler water surface slope than mean channel slope of the entire study reach, while a larger value to steeper reach. In case roughness value is set considering overall slope of the channel, it is desirable to select the entire calculation reach including both gentler and steeper sub-reaches. Since relative difference becomes nearly constant at over 500 cms, in case that verification of applied roughness is conducted with other directly measured discharge, accuracy of measurement by slope-area method for larger discharge may be improved.

An Application of Stream Classification Systems in the Nam River, Korea (남강에 대한 하천분류체계의 적용 연구)

  • Kim, Kiheung;Jung, Heareyn
    • Ecology and Resilient Infrastructure
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    • v.2 no.2
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    • pp.118-127
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    • 2015
  • Because streams have a great diversity of morphological features according to their reaches, it is necessary to classify the types of streams in order to assess their characteristics of channel. In addition, a quantitative assessment system for channel characteristics should be reflected in the stream type properties. Therefore, this study compares two stream classification system (Rosgen's and Yamamoto's) to review their applicability on Korean streams, and the two classification systems were applied on the Nam River. In order for the mean bed slope and the longitudinal connectivity of the provincial and national streams to be reflected in the assessment system of channel characteristics, the Yamamoto system is considered highly adaptable in the stream geomorphology side. In addition, it has been found the Rosgen system has a low correlation of bed slope compared to the Yamamoto system in the view of bed materials. On the other hand, the Yamamoto system was found to be capable of reflecting sediment sorting (hydraulic sorting) of the bed slope. According to the results obtained at the Nam River, the Rosgen system could not classify a type of stream by relationship between bed material and bed slope, but the Yamamoto system can verify the correlation of stream type. However, further review is needed with respect to the applicability of natural rivers. Three types of stream that can be applied to the assessment system of channel characteristics were proposed.

Estimation of Rivers Discharge by Probabilistic Velocity Function Considering Hydraulic Characteristics (하천 수리특성을 고려한 확률론적 유속공식에 의한 하천유량 산정)

  • Choo, Tai Ho;Lee, Sang Jin;Park, Sang Woo;Oh, Ryun Su
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.6B
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    • pp.537-542
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    • 2009
  • To improve stage-discharge curve equation considering water level's function, this study suggested the method that can efficiently compute rivers discharge based on hydraulic characteristics such as river width, area, channel bed slope and entropy concept adopting probabilistic approach. This scheme is proposed to estimate discharge from the velocity formulation based on the entropy function in the equilibrium state derived from the relation between mean and maximum flow velocity. It has been tested using field and laboratory hydraulic data collected from the Alberta university in Canada. As a result it was found that the method proposed in this study was more efficient and accurate comparing with the traditional stage-discharge curve equation.