• Journal of Korea Water Resources Association
• /
• v.52 no.12
• /
• pp.1057-1066
• /
• 2019

The storage function method is used as a flood prediction model for four flood control offices in Korea as a method to analyze the actual rainfall-runoff relationship with non-linearity. It is essential to accurately estimate the parameters of the storage function method for accurate runoff analysis. However, the parameters of the storage function method currently in use are estimated by the empirical formula developed by the limited hydrological analysis in 2012; therefore, they are somewhat inaccurate. The kinematic wave method is a method based on physical variables of watershed and channel and is widely used for rainfall-runoff analysis. By adopting the two-term storage function method by the conversion of the kinematic wave method, parameters can be estimated based on physical variables, which can increase the accuracy of runoff calculation. In this research, the reproducibility of the kinematic wave method by the two-term storage function method was investigated. It is very easy to estimate the parameters because equivalent roughness, which is an important physical variable in watershed runoff, can be easily obtained by using land use and land cover, and the physical variable of channel runoff can be easily obtained from the basic river planning report or topographic map. In addition, this research examined the applicability of the two-term storage function method to runoff simulation of Naechon Stream, a tributary of the Hongcheon River in the Han River basin. As a result, it is considered that more accurate runoff calculation results could be obtained than the existing one-term storage function method. It is expected that the utilization of the storage function method can be increased because the parameters can be easily estimated using physical variables even in unmeasured watersheds and channels.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.18 no.2
• /
• pp.4116-4120
• /
• 1976

With the use of many rivers increased nearly to the capacity, the need for information concerning daily quantities of water and the total annual or seasonal runoff has became increased. A systematic record of the flow of a river is commonly made in terms of the mean daily discharge Since. a single observation of stage is converted into discharge by means of rating curve, it is essential that the stage discharge relations shall be accurately established. All rating curves have the looping effect due chiefly to channel storage and variation in surface slope. Loop rating curves are most characteristic on streams with somewhat flatter gradients and more constricted channels. The great majority of gauge readings are taken by unskilled observers once a day without any indication of whether the stage is rising or falling. Therefore, normal rating curves shall show one discharge for one gauge height, regardless of falling or rising stage. The above reasons call for the correction of the discharge measurements taken on either side of flood waves to the theoretical steady-state condition. The correction of the discharge measurement is to consider channel storage and variation in surface slope. (1) Channel storage As the surface elevation of a river rises, water is temporarily stored in the river channel. There fore, the actual discharge at the control section can be attained by substracting the rate of change of storage from the measured discharge. (2) Variation in surface slope From the Manning equation, the steady state discharge Q in a channel of given roughness and cross-section, is given as {{{{Q PROPTO SQRT { 1} }}}} When the slope is not equal, the actual discharge will be {{{{ { Q}_{r CDOT f } PROPTO SQRT { 1 +- TRIANGLE I} CDOT TRIANGLE I }}}} may be expressed in the form of {{{{ TRIANGLE I= { dh/dt} over {c } }}}} and the celerity is approximately equal to 1.3 times the mean watrr velocity. Therefore, The steady-state discharge can be estimated from the following equation. {{{{Q= { { Q}_{r CDOT f } } over { SQRT { (1 +- { A CDOT dh/dt} over {1.3 { Q}_{r CDOT f }I } )} } }}}} If a sufficient number of observations are available, an alternative procedure can be applied. A rating curve may be drawn as a median line through the uncorrected values. The values of {{{{ { 1} over {cI } }}}} can be yielded from the measured quantities of Qr$.$f and dh/dt by use of Eq. (7) and (8). From the 1/cI v. stage relationship, new vlues of 1/cI are obtained and inserted in Eq. (7) and (8) to yield the steady-state discharge Q. The new values of Q are then plotted against stage as the corrected steadystate curve.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.12
• /
• pp.453-458
• /
• 2016

While the design of weirs requires a scour-considered strategy, research on the analysis of the effectiveness of hydraulic energy dissipaters and design criteria are scarce due to the limited experimental facilities and restraint in the experiment conduction period. The study analyzed the scour dissipation effect of multidirectional dissipaters to improve the scour problems of a weir downstream and suggests design criteria to minimize scour. A hydraulic model experiment was conducted for Nakdong River Hapcheon-Changnyeong Weir and a model in 1/25 of horizontal accumulation and 1/25 of vertical accumulation was produced. The experimental equipment was classified into channels and a flow rate supply and an underwater pump were installed to enable flow at a maximum of 2.0 m3/s. The experimental inflow was 1.3 m3/s, the upstream water level was 0.36 m, downstream water level was 0.24 m, and a cylinder wooden baffle, a dissipater, with a diameter of 0.05 m was made. A 3D scanner was also used for an accurate scour depth comparison for a length change of the baffle before and after installing the baffle. When the baffle was arranged in the shape of a V, the depth of scour decreased by 36% while the scour length decreased by 49% due to flow reduction compared to that before installing the baffle.

• Water for future
• /
• v.27 no.4
• /
• pp.123-133
• /
• 1994

The kinematic and diffusion models using simplified momentum equations of the full dynamic equation have been frequently used for numerical flow simulations, because they have several computational advantages compared to the full dynamic model. In this paper, the more generally acceptable application ranges of the kinematic and diffusion finite difference models were investigated based on three major parameters, which are channel bed slopes So, dimensionless depth increasing numbers Gw at upstream boundary and Froude numbers Fr. The applicable ranges were obtained by comparing the relative magnitudes of the local acceleration, convective acceleration, pressure, gravity and friction terms in the full dynamic equation. In the simulations, a Courant number of 0.5 was used and the channel bed slopes were changed from 0.00001 to 0.05. Also, Froude numbers of 0.1, 0.5 and 0.9 were employed. In this paper, it is indicated that the applicable ranges of kinematic models are increased with increasing of Froude numbers. However, the applicable ranges of diffusion models are decreased with increasing of Froude numbers. Finally, 9 figures were proposed as a guideline in the application of kinematic and diffusion finite difference models based upon the allowable deviation compared to the full dynamic model. With applying the proposed criteria, it is expected that the flow simulations in the channels, streams or rivers are more efficiently achieved.

• Journal of Korea Water Resources Association
• /
• v.47 no.4
• /
• pp.397-409
• /
• 2014

In this study, the assessment scheme has been developed to evaluate the ecological function of rivers which were changed by the river improvement project. The evaluating factors are composed of physical structure in river channels and ecological connectivity in river areas, and each value of the factors is quantified based on 4 and 2 variables, respectably. This scheme was applied to past (1918, before artificial river improvement) and present Mankyung River area. A GIS model was adopted for calculating, analysing, and presenting river ecological conditions using the 204 grids and 7 reaches in study area. Comparison results show that the evaluation grade was decreased in both factors after river improvement. The main causes of lower grade (from II to IV) for physical structure are the river straightening and crossing structures. The reduction (from II to III) in ecological connectivity grade effected by linear fragmentation due to roads and rails is found to be greater than areal fragmentation due to land-use. In particular, it is also found that a high degree of ecological connectivity in 1918 was distributed along the river, but that one in 2007 showed a tendency to scatter because of the construction of levee and increase of urbanized area.

• Korean Journal of Ichthyology
• /
• v.20 no.3
• /
• pp.210-219
• /
• 2008

Monthly variation in species composition of upstream-migrating fish in the Cheonjeyeon Estuary was determined by analyzing fish data collected January~September 2004 and January~August 2007. Fish migrating from the sea to freshwater through the channels were collected by a rectangular net with a mesh size of 2 mm during the day and at night in the new moon. Of 14 species collected, ayu (Plecoglossus altivelis altivelis) and mullet (Mugil cephalus) predominated in abundance. Glass eels (Anguilla japonica) occurred mainly during the night from February to May. Other fishes collected included brackish-water gobiids (Gymnogobius urotaenia, Rhinogobius giurinus, Tridentiger obscurus, and Sicyopterus japonicus), freshwater fishes (Misgurnus anguillicaudatus and Rhynchocypris oxycephalus), and coastal marine fishes (Engraulis japonicus, Pempheris japonica, Plotosus lineatus, Takifugu niphobles, and Terapon jarbua). Ayu occurred during almost all sampling periods. They ranged principally from 55 to 100 mm total length (TL), with some fish larger than 100 mm TL collected after April. Mullet also occurred during almost all sampling periods. They ranged principally 25~58 mm TL, with some larger fish of 103~240 mm TL collected in February and April. That only a few freshwater and brackish-water fishes occurred in the study area is probably related to the freshwater systems having long been isolated from the continental systems and to the poorly developed estuaries in Jeju Island reflecting limited river discharge.

• The Korean Journal of Quaternary Research
• /
• v.3 no.1
• /
• pp.87-101
• /
• 1989

The development of the Hantan river basin can be divided into three stages. The first stage include the ancient Hantan channel system prior to the Chongokni basalt which yield dates of about 0.6 mya from the K/Ar dating method. During this period the Baekuyri formation was formed. The Baekuyri formation is widely observed under the Chongokni basalt along the current river system. The second stage is the period when stream channels stayed on the top of the basalt plateau. Aggradation and deggradation were continued by meandering and braiding channel systems until major stream channel was formed. The currently remaining deposit on the top of the basalt was formed by lacustrine and fluvial systems in this period. During this period Pleistocene hominid was present on edge of water and flood plain and left Paleolithic material. This period was begun at the time of the final basalt flow dated about 300,000 BP. The third stage is designed for the time when the Hantan river channel was dropped down to a level from which the channel could not influence the top of the basalt any more No more deposit could be formed but erosion by surface water has been continued on the top of the basalt since then. The dropping of the Hantan river channel was probably not very long after the final flow of the basalt. Because of frost action and heavy concentrated precipitation in the basin area along with blocky and clumnar joint structure of the basalt, erosional process of the basalt is believed to have been carried out within a relatively short time. The lowering of the Hantan river channel was probably completed in a cycle of major fluctuation of world cimate. Also, the redclay on the top of the basalt is believed to have been formed during a warm period around 200,000 BP, which accords with the climatic change suggested above fair1y well. The Paleolithic materials in tile deposits fell accordingly into approximately same time period.

• The Journal of Engineering Geology
• /
• v.24 no.4
• /
• pp.525-534
• /
• 2014

Environmental problems typically occurring in abandoned mine lands (AML) include: contaminated and acidic surface water and groundwater; stockpiled waste rock and mill tailings; and ground subsidences due to mining operations. This study examines the effectiveness of various geophysical techniques for mapping potential hazard and contaminated zones. Four AML sites with sedimentation contamination problems, acid mine drainage (AMD) channels, ground subsidence, manmade liner leakage, and buried mine tailings, were selected to examine the applicability of various geophysical methods to the identification of the different types of mine hazards. Geophysical results were correlated to borehole data (core samples, well logs, tomographic profiles, etc.) and water sample data (pH, electrical conductivity (EC), and heavy metal contents). Zones of low electrical resistivity (ER) corresponded to areas contaminated by heavy metals, especially contamination by Cu, Pb, and Zn. The main pathways of AMD leachate were successfully mapped using ER methods (low anomaly peaks), self-potential (SP) curves (negative peaks), and ground penetrating radar (GPR) at shallow penetration depths. Mine cavities were well located based on composite interpretations of ER, seismic tomography, and well-log records; mine cavity locations were also observed in drill core data and using borehole image processing systems (BIPS). Damaged zones in buried manmade liners (used to block descending leachate) were precisely detected by ER mapping, and buried rock waste and tailings piles were characterized by low-velocity zones in seismic refraction data and high-resistivity zones in the ER data.

• Water for future
• /
• v.29 no.2
• /
• pp.249-260
• /
• 1996

There have been easily found a number of examples that misleading or unreasonable measuring data set of physical variables are often produced in the field and the laboratory. The primary reason is that the specific requirements of civil engineers are initially disregarded in designing the experimental apparatus. It results from a lack of mutual understanding and co-operating between the user group and the maker. Therefore, their fundamental knowledge and apprehension become indispensible in order to obtain measuring data with high confidence and good quality In this study it is shortly explained the basic structure and the operation system of the experimental equipments commonly used at the present. A simple measuring set is developed which is quite easy for a general civil engineer to design and operate without any other specialty of mostly electricity electronics. Based upon this requirement, one of data logger named PPDL8 is newly designed by making use of the parallel port in the personal computer, consisting of multi-channels able to measure 8 different point values simultaneously. It can also use many valuable sub-programs existing in PC because the user makes his own programs necessary for measurement, by himself. Of all things, it has a great advantage to increase the applicability of field measurements much larger when adopting the notebook computer to operate with small battery only. In addition this study gives, in fact, the excellent agreements of in-situ field variables by showing their measuring results of temperature, distance and turbidity.

• Korean Journal of Ecology and Environment
• /
• v.45 no.2
• /
• pp.252-260
• /
• 2012

The wetlands have eco-sociological values because their functions have proven to be useful to human society. Many countries are working to conserve and protect the wetland ecosystems. However, many wetlands have disappeared or have been fragmented due to a natural and/or anthropogenic disturbance. These isolated wetlands appear to work best in the landscape, as a spatially distributed system. We have analyzed the spatial-social distribution patterns of wetlands in Gyeongsangnam-do Province (GNP). We examined the frequency distribution of wetland sizes, the distances to the nearest wetlands, the shapes of the wetlands, land-use patterns, land owners, and official land values were confirmed as social characteristics for each wetland. A total of 146 wetlands (3,598.85 ha), including 76 riverine wetlands (1,955.60 ha), 49 palustrine wetlands (1,282.28 ha) and 21 mountain wetlands (1,282.28 ha) were identified in GNP. Most wetlands left for use to drainage were small (<2 ha) and located in agricultural areas. However, small and isolated wetlands were clustered, according to the location, indicating that these wetlands can be connected to each other using the linear riverine wetlands and water channels in agricultural areas. This is extremely valuable in maintaining the biodiversity, such that any loss of small wetlands will cause a direct reduction in the connectedness among populations of the remaining species. Due to most wetlands belonging to the nation or businesses, being classified as reservoirs (water storage areas), and consequently, degradation of wetlands will progress due to grand-scale engineering works. Therefore, wetland policy and ecologically sensitive laws and policies should be developed in order to promote the wise-use for wetlands.