• Title/Summary/Keyword: Meandering Stream

Search Result 52, Processing Time 0.025 seconds

Formative Ages and Processes by Types of Natural Abandoned Channels in Korea (우리나라 자연 구하도의 유형별 형성시기와 형성과정)

  • LEE, Gwang-Ryul
    • Journal of The Geomorphological Association of Korea
    • /
    • v.19 no.2
    • /
    • pp.1-15
    • /
    • 2012
  • The formative ages and processes of five natural abandoned channels in three types in Korea are studied. The former meandering channel in Seongsandong, Uljin-gun was abandoned due to the neck-cutoff of incised meander, Wangpi River in approximately 2.5~2.6ka and the abandoned channel in Bulyeong Temple, Uljin-gun was formed by the neck-cutoff of Wangpi River in approximately 90ka. Deduced from these results, it is judged to favorable for formation of abandoned channels by incised meander cutoff in interglacial or interstadial stages that had a better condition for meander cutoff because of active lateral erosion. Due to the corrosion of limestone joints in the underground of ridges between Hwangji River and Cheolam River, the channel in Gumumso, Taebaek-si was abandoned by the stream piracy connecting and combining the rivers into a limestone cave in approximately 40ka and higher lower reaches of Dong River than Banbyeon River in Seonbawi, Yeongyang-gun was turned to the abandoned channel throughout the stream piracy between the rivers in approximately 1.4ka. During Last Glacial Maximum in Jangcheon-ri, Chungju-si, Namhan River was divided into the eastern and western tributaries due to the alluvial island in approximately 10ka and then the western tributary was abandoned recently.

Influence of Environmental Characteristics on the Community Structure of Benthic Macroinvertebrates in Stream-type Waterways Constructed at Upper Reaches of Guem River (금강 상류 구간 내 샛강형 수로의 서식환경 특성이 저서성 대형무척추동물 군집 구조에 미치는 영향)

  • Son, Se-Hwan;Choi, Jong-Yun
    • Korean Journal of Ecology and Environment
    • /
    • v.54 no.1
    • /
    • pp.24-38
    • /
    • 2021
  • Microhabitat In the upper stream is created by various environment variables such as the bottom substrate and the physicochemical factors, and may influence the distribution of benthic macroinvertebrates. We investigated the bottom substrate and environmental variables influencing the distribution of benthic macroinvertebrate in 26 stream-type waterways established at upper reaches of Geum River. During study period, total 85 families, 160 species, 9305 individuals of benthic macroinvertebrates were recorded. The stream-type waterways, where the bottom substrates consist mainly of pebble (16~64 mm) and cobble (64~256 mm) or with rapid water velocity (more than 0.2 m/s) and high dissolved oxygen (more than 120%), were supported by high species diversity of benthic macroinvertebrate. Hierological cluster analysis and the nonparametric multidimensional scale (NMDS) divided 26 stream-type waterways into a total of three clusters. In Cluster 1, the invertebrate species, such as Branchiura sowerbyi, Cloeon dipterum, Ischnura asiatica, Paracercion calamorum, and Radix auricularia, closely related to aquatic macrophytes, and Chironomidae spp., Limnodrilus gotoi, and Tanypodinae sp. were abundant in waterways, with high coverage of silt and clay as well as high turbidity and total nitrogen. The benthic macroinvertebrate species (Cheumatopsyche brevilineata, Drunella ishiyamana, Dugesia japonica, Ephemera orientalis, Gumaga KUa, Macrostemum radiatum, Potamanthus formosus, Semisulcospira libertine, Stenelmis vulgaris, and Teloganopsis punctisetae) included in Cluster 2 were dominated in sites with high cover rates of pebble and gravel. Cluster 3 was predominantly covered by the Cobbles, was supported by Simulium sp. Such a clear distinction in the study sites means that each stream-type waterways is governed by a clear habitat environment. In the case of some sites with low species diversity, improvement measures are required to restore nature, such as improving the function of inflows and outflows, creating meandering channel, and inducing the settlement of littoral vegetation.

한강하류지형면의 분류와 지형발달에 대한 연구 (양수리에서 능곡까지)

  • Park, No-Sik
    • Journal of the Speleological Society of Korea
    • /
    • no.68
    • /
    • pp.23-73
    • /
    • 2005
  • Purpose of study; The purpose of this study is specifically classified as two parts. The one is to attempt the chronological annals of Quaternary topographic surface through the study over the formation process of alluvial surfaces in our country, setting forth the alluvial surfaces lower-parts of Han River area, as the basic deposit, and comparing it to the marginal landform surfaces. The other is to attempt the classification of micro morphology based on the and condition premising the land use as a link for the regional development in the lower-parts of Han river area. Reasons why selected the Lower-parts of Han river area as study objects: 1. The change of river course in this area is very serve both in vertical and horizontal sides. With a situation it is very easy to know about the old geography related to the formation process of topography. 2. The component materials of gravel, sand, silt and clay are deposited in this area. Making it the available data, it is possible to consider about not oかy the formation process of topography but alsoon the development history to some extent. 3. The earthen vessel, a fossil shell fish, bone, cnarcoal and sea-weed are included in the alluvial deposition in this area. These can be also valuable data related to the chronological annals. 4. The bottom set conglometate beds is also included in the alluvial deposits. This can be also valuable data related to the research of geomorphological development. 5. Around of this area the medium landform surface, lower landform surface, pediment and basin, are existed, and these enable the comparison between the erosion surfaces and the alluvial surfaces. Approach : 1. Referring to the change of river beds, I have calculated the vertical and horizontal differences comparing the topographic map published in 1916 with that published in 1966 and through the field work 2. In classifying the landform, I have applied the method of micro morphological classification in accordance with the synthetic index based upon the land conditions, and furthermore used the classification method comparing the topographic map published in 1916 and in that of 1966. 3. I have accorded this classification with the classification by mapping through appliying the method of classification in the development history for the field work making the component materials as the available data. 4. I have used the component materials, which were picked up form the outcrop of 10 places and bored at 5 places, as the available data. 5. I have referred to Hydrological survey data of the ministry of Construction (since 1916) on the overflow of Han-river, and used geologic map of Seoul metropolitan area. Survey Data, and general map published in 1916 by the Japanese Army Survbey Dept., and map published in 1966 by the Construction Research Laboratory and ROK Army Survey Dept., respectively. Conclusion: 1. Classification of Morphology: I have added the historical consideration for development, making the component materials and fossil as the data, to the typical consideration in accordance with the map of summit level, reliefe and slope distribution. In connection with the erosion surface, I have divided into three classification such as high, medium and low-,level landform surfaces which were classified as high and low level landform surfaces in past. furthermore I have divided the low level landform surface two parts, namely upper-parts(200-300m) and bellow-parts(${\pm}100m$). Accordingly, we can recognize the three-parts of erosion surface including the medium level landform surface (500-600m) in this area. (see table 22). In condition with the alluvial surfaces I have classified as two landform surfaces (old and new) which was regarded as one face in past. Meamwhile, under the premise of land use, the synthetic, micro morphological classification based upon the land condition is as per the draw No. 19-1. This is the quite new method of classification which was at first attempted in this country. 2. I have learned that the change of river was most severe at seeing the river meandering rate from Dangjung-ni to Nanjido. As you seee the table and the vertical and horizontal change of river beds is justly proportionable to the river meandering rate. 3. It can be learned at seeing the analysis of component materials of alluvial deposits that the component from each other by areas, however, in the deposits relationship upper stream, and between upper parts and below parts I couldn't always find out the regular ones. 4. Having earthern vessel, shell bone, fossil charcoal and and seaweeds includen in the component materials such as gravel, clay, sand and silt in Dukso and Songpa deposits area. I have become to attempt the compilation of chronicle as yon see in the table 22. 5. In according to hearing of basemen excavation, the bottom set conglomerate beds of Dukso beds of Dukso-beds is 7m and Songpa-beds is 10m. In according to information of dredger it is approx. 20m in the down stream. 6. Making these two beds as the standard beds, I have compared it to other beds. 7 The coarse sand beds which is covering the clay-beds of Dukso-beds and Nanjidobeds is shown the existence of so-called erosion period which formed the gap among the alluvial deposits of stratum. The former has been proved by the sorting, bedding and roundness which was supplied by the main stream and later by the branch stream, respectively. 8. If the clay-beds of Dukeo-bed and Songpa-bed is called as being transgressive overlap, by the Eustatic movement after glacial age, the bottom set conglomerate beds shall be called as being regressive overlap at the holocene. This has the closest relationship with the basin formation movement of Seoul besides the Eustatic movement. 9. The silt-beds which is the main component of deposits of flood plain, is regarded as being deposited at the Holocene in the comb ceramic and plain pottery ages. This has the closest relationship with the change of river course and river beds.

Derivation of Meandering for Close-to-Nature Stream Improvement (자연 친화적인 하천 정비사업 구간의 사행 유도 방안)

  • Han, Man-Shin;Choi, Gye-Woon;Lee, Young-Heun;Ahn, Sang-Jin
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2012.05a
    • /
    • pp.766-766
    • /
    • 2012
  • 최근 진행되고 있는 자연형 하천 조성사업과 관련하여 하천 복원 계획 및 실무에 있어 우선적으로 고려되어야 할 사항은 여러 가지가 있지만, 그 중에서 유역의 복합적인 요인(기후, 지형특성, 수리 수문특성, 식생특성, 유사 특성 등)들에 의하여 영향을 받게 되는 하천의 지형형태학적 측면의 경우에는, 안정 하도 형성에 직접적인 영향을 미치게 되므로 계획의 예비조사 단계서부터 충분한 검토가 이루어져야 함에도 불구하고, 국내에서는 하천 지형형태학적인 측면을 고려한 하천 복원의 연구는 아주 미미한 것이 사실이다. 자연하천 조성에 있어서 획일적으로 직선화된 하천보다 사행화를 유도함으로써 얻어지는 장점들이 더 많지만, 하천설계기준 등에서 제시하고 있는 사행화에 대한 정확한 지침이 부재하여 설계자의 판단에 의하여 사행화를 유도하는 경우가 대부분이다. 사행현상은 유심의 변화가 이루어지기 때문에 전단면에 걸친 수심의 유지가 어렵고, 취수구의 기능저하, 제방의 파괴, 국소세굴에 따른 하천재해 등의 문제가 발생하기도 한다. 자연 상태의 하천형상은 대부분 호우로 인한 홍수로 인하여 자연스럽게 만들어지게 되며, 대부분 사행하천의 형태를 띠게 된다. 자연적으로 형성된 사행하천은 하천 정비시 경제적인 측면을 고려하여 직선화로 계획하는 경우가 많으며, 하천 주변 지형과 토지이용 등의 제약 조건 등으로 인하여 만곡구간을 그대로 두고 하천설계를 계획하는 경우도 있다. 그러나 경제적인 측면만을 고려하여 하천을 직선화하는 것은 상류부 홍수를 하류부로 전가시켜 하류 홍수피해를 가중시키는 결과를 초래하므로 바람직하지 않을 뿐만 아니라 직선화된 수로에서는 하천의 생태계가 제대로 이루어지지 않으므로 하천은 만곡구간을 갖는 것이 바람직하다. 본 연구에서는 자연하천 조성시 하천의 사행화를 유도할 수 있는 방안으로 호안 공법의 적용을 통한 사행화 유도 방법을 제안하였으며, 길이 20m, 폭 2m, 높이 1m의 크기를 갖는 개수로 장치를 이용하여 수리모형실험을 실시하였고, 이동상 실험을 통하여 호안 공법의 배열에 따른 사행화 영향 정도를 분석하였다. 또한, 소프트 백과 같은 유연한 소재뿐만 아니라 돌이나 돌망태와 같은 강성 소재에 대한 사행화 영향을 검토함으로써 다양한 호안기법을 통한 영향범위를 제시하였다.

  • PDF

A Sensitivity Analysis of Cell Size on a Distributed Non-Point Source Pollution Model (분산형 비점오염원 모델에서 단위유역 크기의 민감도 분석)

  • Bae, In-Hee;Park, Jung-Eun;Park, Seok-Soon
    • Journal of Korean Society of Environmental Engineers
    • /
    • v.27 no.9
    • /
    • pp.952-957
    • /
    • 2005
  • A sensitivity analysis study was performed to examine the effects of cell size on a distributed non-point source pollution model. The model, AnnAGNPS, whiff is a modified version of USDA's AGNPS, was applied to Eung stream watershed, a tributary of Cheongmi stream located in the South Branch of Han River System. The model components and results, such as channel length, slope, land use, and delivery ratio, were analyzed according to the various cell sizes from 10 to 200 ha. As cell sire increases, channel length decreases due to short-circuiting of meandering creek. The decreased channel length has more significant effects on the model results than any other geomorphological change. When the effects of land use and soil distribution are excluded, sediment delivery loads increase due to shorter time to reach the outlet of the watershed in larger tell size. When those effects are included, however, sediment delivery loads decrease in larger fell size because the variety of land use types can not be inputted. The predominant land use in the applied watershed is forest with very low soil erosion such that the predicted sediment delivery might be much lower than real system. The cell size of 30 ha was determined to produce the most appropriate resolution. Surface runoff and non-point source loads of TN, TP and BOD were predicted and the results agree well with the field measurements. From this study, it was shown that the model results would be very dependent on variations of topography, land use, and soil distribution, as a function of cell size, and the optimum cell size is very important for successful application of distributed non-point source pollution model.

The Development of the Hantan River Basin, Korea and the Age of the Sediment on the top of the Chongok Basalt (한탄강유역의 발달과정과 전곡현무암 위의 퇴적물의 연대)

  • Bae, Kidong
    • 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.

  • PDF

Analysis on Fluvial Geomorphological Characteristics based on Past and Present Data for River Restoration: An Application to the Miho River and the Naesung River (하천 복원을 위한 과거 및 현재 자료 기반의 하천지형학적 특성 분석: 미호천과 내성천을 중심으로)

  • Lee, Chan Joo;Kim, Ji Sung;Kim, Kyu Ho;Shin, Hyoung Sub
    • Journal of Korea Water Resources Association
    • /
    • v.48 no.3
    • /
    • pp.169-183
    • /
    • 2015
  • As a basic work for river restoration, analysis on fluvial geomorphological characteristics is made using past and present data to understand close-to-nature geomorphic status. The Miho and the Naesung Rivers are targets of this study. Fluvial geomorphic variables including valley-floor width, sinuosity, bankfull width, channel gradient, bed material size, bankfull discharge and unit stream power are evaluated with dominant processes. Though common sand-bed rivers with similar catchment area, the Miho and the Naesung Rivers are different in terms of valley-floor width, channel shape variables and dominant processes related with longitudinal location. In addition, analyses on interrelationship among the geomorphological variables are carried. Bankfull width is shown to be proportional to bankfull discharge, as is in a rough agreement with the previous studies. Relationship of bankfull discharge and channel gradient shows meandering and braiding are prevalent in the Miho River, whereas the most of the sub-reaches of the Naesung River fall to braiding. Relationship of channel gradient with width-depth ratio indicates dune-ripple processes are dominant in the Miho River, while the Naesung River shows longitudinal diversity from braiding in the downstream sub-reaches to riffle-pool and plane-bed along the upper ones. Analyses based on the past data on a river in a close-to-nature status are thought to be rather reasonable in comparison with those on the same river in a engineered condition.

Sedimentary Environments and Geochemical Characters of the Core Sediments Near Naju-Yeongam Area in the Lower Part of the Yeongsan River, Cheonnam, Korea (전남 나주-영암지역의 영산강 하류 시추퇴적물의 퇴적환경과 지구화학적 특성)

  • Eun, Go-Yeo-Na;Koh, Yeong-Koo;Youn, Seok-Tai;Oh, Kang-Ho;Kim, Dong-Ju;Kim, Joo-Yong
    • Journal of the Korean earth science society
    • /
    • v.22 no.4
    • /
    • pp.301-316
    • /
    • 2001
  • To consider the vertical variations of sedimentary environments and geochemical characters in the core sediments in Naju-Yeongam area od the lower part of Yeongsan River, grain-size and metal components of the sediments were analyzed. The sediments are pebble to mud and show fining upward. The core sediments are poorly to very poorly sorted and positively skewed. On the basis of grain size distributions, the sediments of the study areas were thought to have been deposited in a meandering stream. The metallic contents of sediments were presumably controlled by carbonate contents of sediments and weakly controlled by fining upward grain size distribution pattern. Enrichment factors indicating metal concentration in the sediments did not suggest any meaningful concentrations for metallic elements.

  • PDF

Distribution Characteristics of Quaternary Geology and Aggregate Resources in Geumsan-gun, Chungcheongnam-do (충청남도 금산군 일대 제4기 지질 및 골재자원 분포 특성)

  • Kim, Jin Cheul;Kim, Ju Yong;Lee, Jin-Young
    • Economic and Environmental Geology
    • /
    • v.54 no.5
    • /
    • pp.595-603
    • /
    • 2021
  • Sand layer distribution, which is the main target of river and land aggregate resources, mainly belongs to alluvial and river sedimentary environments among the Quaternary sedimentary environments. The distribution of aggregate resources in the area of Geumsan-gun, Chungcheongnam-do is characteristically developed around a sedimentation environment in which intrusive meandering river dominate. Although the area around Bonhwangcheon Stream and the area near the confluence of small streams are small, the river floodplain develops and corresponds to the aggregate distribution area. The sedimentary layer formed in the sedimentary environment such as colluvial deposits or alluvial fan deposits has a relatively low distribution rate of aggregate resources. The vertical distribution of the Quaternary sedimentary layers in the Geumsan-gun region ranges from about 5 to 12 m and has an average Quaternary sedimentary thickness of 8 m. The aggregate-bearing section has an average thickness of 3.6 m, and the average grain size is about 21% clay-silt, 67% sand, and 12% gravel. The main characteristics of the aggregate-bearing section are that coarse-grained sand predominates, and gravel is sub-angular or sub-rounded, and the sorting is generally poor and has a massive form of deposits, and the soil colour ranges from dark grey to yellowish-brown. In Geumsan-gun, the most likely distribution area for aggregate development is the alluvial sedimentary and river sedimentary layers distributed along the current and former riverbeds of the main Geumgang River, Bonhwangcheon and small River tributaries.

Modeling 2D residence time distributions of pollutants in natural rivers using RAMS+ (RAMS+를 이용한 하천에서 오염물질의 2차원 체류시간 분포 모델링)

  • Kim, Jun Song;Seo, Il Won;Shin, Jaehyun;Jung, Sung Hyun;Yun, Se Hun
    • Journal of Korea Water Resources Association
    • /
    • v.54 no.7
    • /
    • pp.495-507
    • /
    • 2021
  • With the recent industrial development, accidental pollution in riverine environments has frequently occurred. It is thus necessary to simulate pollutant transport and dispersion using water quality models for predicting pollutant residence times. In this study, we conducted a field experiment in a meandering reach of the Sum River, South Korea, to validate the field applicability and prediction accuracy of RAMS+ (River Analysis and Modeling System+), which is a two-dimensional (2D) stream flow/water quality analysis program. As a result of the simulation, the flow analysis model HDM-2Di and the water quality analysis model CTM-2D-TX accurately simulated the 2D flow characteristics, and transport and mixing behaviors of the pollutant tracer, respectively. In particular, CTM-2D-TX adequately reproduced the elongation of the pollutant cloud, caused by the storage effect associated with local low-velocity zones. Furthermore, the transport model effectively simulated the secondary flow-driven lateral mixing at the meander bend via 2D dispersion coefficients. We calculated the residence time for the critical concentration, and it was elucidated that the calculated residence times are spatially heterogeneous, even in the channel-width direction. The findings of this study suggest that the 2D water quality model could be the accidental pollution analysis tool more efficient and accurate than one-dimensional models, which cannot produce the 2D information such as the 2D residence time distribution.