• Journal of the Korean association of regional geographers
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• v.4 no.2
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• pp.49-64
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• 1998

Bing-gye valley(Kyongbuk Province, South Korea) is well known as a tourist attraction because of its meteorologic characteristics that show subzero temperature during midsummer. Also, there are some interesting geomorphic features in the valley area. Therefore, the valley is worth researching in geomorphology field. The aim of this paper is to achieve two purposes. These are to clarify geomorphic features on talus within Bing-gye valley area, and to infer the origin of Bing-gye valley. The main results are summarized as follows. 1) The formation of Bing-gye valley It would be possible to infer the following two ideas regarding the formation of Bing-gye valley. One is that the valley was formed by differential erosion of stream along fault line, and the other is that the rate of upheaval comparatively exceeded the rate of stream erosion. Especially, the latter may be associated with the fact that the width of the valley is much narrow. Judging that the fact the width of the valley is much narrow, compared with one of its upper or lower valley, it is inferred that Bing-gye valley is transverse valley. 2) The geomorphic features of talus (1) Pattern It seems to be true that the removal of matrix(finer materials) by the running water beneath the surface can result in partly collapse hollows. Taluses are tongue-shaped or cone-shaped in appearance. They are $120{\sim}200m$ in length, $30{\sim}40m$ in maximum width. and $32{\sim}33^{\circ}$ in mean slope gradient. The component blocks are mostly homogeneous in size and shape(angular), which reflect highly jointed free face produced by frost action under periglacial environment. (2) Origin On the basis of previous studies, the type of the talus is classified into rock fall talus. When considered in conjunction with the degrees of both weathering of blocks and hardness of blocks, it can be explained that the talus was formed under periglacial environment in pleistocene time. (3) The inner structure of block accumulation I recognize a three-layered structure in the talus as follows: (a) superficial layer; debris with openwork texture at the surface, 1.3m thick. (b) intermediate layer: small debris(about 5cm in diameter) with fine matrix(including humic soil), 70cm thick. (c) basal layer: over 2m beneath surface, almost pure soil horizon without debris (4) The stage of landform development Most of the blocks are now covered with lichen, and/or a mantle of weathering. It is believed that downslope movement by talus creep well explains the formation of concave slope of the talus. There is no evidence of present motion in the deposit. Judging from above-mentioned facts, the talus of this study area appears to be inactive and fossil landform.

• The Korean Journal of Petroleum Geology
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• v.10 no.1_2 s.11
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• pp.10-17
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• 2004

The Doowoo-ri tidal flat in the southwestern Korean coast is a typical open-coast tidal flat which has no barriers in the offshore such as barrier island and sand bars. The difference of induced wave energy with seasons is affected directly on the distribution of surface sediment and the formation of sedimentary structures because the sedimentation by wind wave is relatively much important element in this open-coast tidal flat. This open-coast tidal flat can be classified into tidal beach, intertidal flat and lower mudflat according to the pattern of geomorphology and sediment type. The intertidal flat can be again divided into 3 types: sand flat, mixed flat and mud flat based on the primary sedimentary structure and sand/mud ratio. Doowoori tidal flat shows a seasonal change in the surface sedimentary facies based on sediment composition and primary sedimentary structure. The change is closely related to the direction and magnitude of monsoon wind and also to storm frequency. In winter and spring, when northwesterly wind is most dominant and strong and also storms are common, sand-flat facies is largely distributed on the intertidal flat, whereas mud-flat facies is most dominant during summer when weak southeasterly wind is common. In the fall season, mixed-flat facies is dominant on the flat. The Doowoori intertidal flat is covered by mud sediment which is ca. 20 cm in thickness in summer season. In winter season, surface sediment is changed from mud to sand because the summer mud is mostly eroded by strong wave action. Can-core peels in the intertidal flat show that parallel laminated mud or sand/mud and climbing ripple cross-laminated sandy silt are dominant on the upper intertidal flat $(0-1.3 {\cal}km)$ during summer season. On the other hand, on lower intertidal flat $(1.7-2.3 {\cal}km)$, dominant sedimentary facies is homogeneous mud. In winter, it is changed into parallel laminated and ripple cross-laminated sand facies.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.237-237
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• 2015

The district of Marlborough has had more than its share of river management projects over the past 150 years, each one uniquely affecting the geomorphology and flood hazard of the Wairau Plains. A major early project was to block the Opawa distributary channel at Conders Bend. The Opawa distributary channel took a third and more of Wairau River floodwaters and was a major increasing threat to Blenheim. The blocking of the Opawa required the Wairau and Lower Wairau rivers to carry greater flood flows more often. Consequently the Lower Wairau River was breaking out of its stopbanks approximately every seven years. The idea of diverting flood waters at Tuamarina by providing a direct diversion to the sea through the beach ridges was conceptualised back around the 1920s however, limits on resources and machinery meant the mission of excavating this diversion didn't become feasible until the 1960s. In 1964 a 10 m wide pilot channel was cut from the sea to Tuamarina with an initial capacity of $700m^3/s$. It was expected that floods would eventually scour this 'Wairau Diversion' to its design channel width of 150 m. This did take many more years than initially thought but after approximately 50 years with a little mechanical assistance the Wairau Diversion reached an adequate capacity. Using the power of the river to erode the channel out to its design width and depth was a brilliant idea that saved many thousands of dollars in construction costs and it is somewhat ironic that it is that very same concept that is now being used to deal with the aggradation problem that the Wairau Diversion has caused. The introduction of the Wairau Diversion did provide some flood relief to the lower reaches of the river but unfortunately as the Diversion channel was eroding and enlarging the Lower Wairau River was aggrading and reducing in capacity due to its inability to pass its sediment load with reduced flood flows. It is estimated that approximately $2,000,000m^3$ of sediment was deposited on the bed of the Lower Wairau River in the time between the Diversion's introduction in 1964 and 2010, raising the Lower Wairau's bed upwards of 1.5m in some locations. A numerical morphological model (MIKE-11 ST) was used to assess a number of options which led to the decision and resource consent to construct an erodible (fuse plug) bank at the head of the Wairau Diversion to divert more frequent scouring-flows ($+400m^3/s$)down the Lower Wairau River. Full control gates were ruled out on the grounds of expense. The initial construction of the erodible bank followed in late 2009 with the bank's level at the fuse location set to overtop and begin washing out at a combined Wairau flow of $1,400m^3/s$ which avoids berm flooding in the Lower Wairau. In the three years since the erodible bank was first constructed the Wairau River has sustained 14 events with recorded flows at Tuamarina above $1,000m^3/s$ and three of events in excess of $2,500m^3/s$. These freshes and floods have resulted in washout and rebuild of the erodible bank eight times with a combined rebuild expenditure of $80,000. Marlborough District Council's Rivers & Drainage Department maintains a regular monitoring program for the bed of the Lower Wairau River, which consists of recurrently surveying a series of standard cross sections and estimating the mean bed level (MBL) at each section as well as an overall MBL change over time. A survey was carried out just prior to the installation of the erodible bank and another survey was carried out earlier this year. The results from this latest survey show for the first time since construction of the Wairau Diversion the Lower Wairau River is enlarging. It is estimated that the entire bed of the Lower Wairau has eroded down by an overall average of 60 mm since the introduction of the erodible bank which equates to a total volume of $260,000m^3$. At a cost of $$0.30/m^3$ this represents excellent value compared to mechanical dredging which would likely be in excess of $$10/m^3$. This confirms that the idea of using the river to enlarge the channel is again working for the Wairau River system and that in time nature's "excavator" will provide a channel capacity that will continue to meet design requirements.

• The Journal of the Petrological Society of Korea
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• v.28 no.3
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• pp.195-215
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• 2019

Geopark is a new system for development of the local economy through conservation, education, and tourism that is an area of scientific importance for the earth sciences and that has outstanding scenic values. The Hwaseong Geopark, the candidate for Korean National Geopark is composed of 10 geosites: Gojeongri dinosaur egg fossils, Ueumdo, Eoseom, Ddakseom, Goryeom, Jebudo, Baengmiri Coast, Gungpyeonhang, Ippado and Gukwado geosites. In this study, geosites, geoheritages, and geotrails of the Hwaseong Geopark were described in detail, and the value and significane as a geopark were also discussed. The geology of the Hwaseong Geopark area belonging to the Gyeonggi Massif consists of the Precambrian metamorphic and meta-sedimentary rocks, Paleozoic sedimentary and metamorphic rocks, Mesozoic igneous and sedimentary rocks, and Quaternary deposits, indicating high geodiversity. The Gojeongri Dinosaur Egg Fossils geosite, designated as a natural monument, has a geotrail including dinosaur egg nest fossils, burrows, tafoni, fault and drag fold, cross-bedding. Furthermore, a variety of infrastructures such as eco-trail deck, visitor center are well-established in the geosite. In the Ueumdo geosite, there are various metamorphic rocks (gneiss, schist, and phyllite) and geological structures (fold, fault, joint, dike, and vein), thus it has a high educational value. The Eoseom geosite has high academic value because of the orbicular texture found in metamorphic rocks. Also, various volcanic and sedimentary rocks belonging to the Cretaceous Tando Basin can be observed in the Ddakseom and Goryeom geosites. In the Jebudo, Baengmiri Coast, and Gungpyeonghang geosites, a variety of coastal landforms (tidal flat, seastacks, sand and gravel beach, and coastal dunes), metamorphic rocks and geological structures, such as clastic dikes and quartz veins can be observed, and they also provide various programs including mudflat experience to visitors. Ippado and Gukwado geosites have typical large-scale fold structures, and unique coastal erosional features and various Paleozoic schists can be observed. The Hwaseong Geopark consists of outstanding geosites with high geodiversity and academic values, and it also has geotrails that combine geology, geomorphology, landscape and ecology with infrastructures and various education and experience programs. Therefore, the Hwaseong Geopark is expected to serve as a great National Geopark representing the western Gyeonggi Province, Korea.

• Ecology and Resilient Infrastructure
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• v.8 no.2
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• pp.79-87
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• 2021

Because active interactions occur among vegetation, hydrology, and geomorphology in riparian systems, any changes in one of these factors can significantly affect the other two. In this study, we evaluated these interactions at four sites (two in Gajeong and two in Hahan) along the Seomjin-gang River that was substantially devastated by an extreme flood in 2020. We examined the relationship between the riparian vegetation and the hydraulic characteristics of the flood using remote sensing, hydraulic modeling, and field surveys combined. The evaluation results showed that the floods caused a record-breaking rise of up to 43.1 m above sea level at the Yeseong-bridge stage gauge station (zero elevation 27.4 m) located between the Gajeong and Hahan sites, with the shear stress being four times higher in Hahan than in Gajeong. Additionally, the water level during the flood was estimated to be a maximum of 1 m higher depending on the location in the presence of riparian plants. Furthermore, both sites underwent extensive biological damage due to the flood, with 78-80% loss in vegetation, with preferential damage observed in large willow species, compared to Quercus acutissima. The above findings imply that all plant species exhibit different vulnerabilities towards extreme floods and do not induce similar behavior towards events causing a disturbance. In conclusion, we developed strategies for effectively managing riparian trees by minimizing flood hazards that could inevitably cause damage.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.6-7
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• 2021

Vegetation development in rivers is one of the important issues not only in academic fields such as geomorphology, ecology, hydraulics, etc., but also in river management practices. The problem of river vegetation is directly connected to the harmony of conflicting values of flood management and ecosystem conservation. In Korea, since the 2000s, the issue of river vegetation and land formation has been continuously raised under various conditions, such as the regulating rivers downstream of the dams, the small eutrophicated tributary rivers, and the floodplain sites for the four major river projects. In this background, this study proposes a method for classifying the distribution of vegetation in rivers based on remote sensing data, and presents the results of applying this to the Naeseong Stream. The Naeseong Stream is a representative example of the river landscape that has changed due to vegetation development from 2014 to the latest. The remote sensing data used in the study are images of Sentinel 1 and 2 satellites, which is operated by the European Aerospace Administration (ESA), and provided by Google Earth Engine. For the ground truth, manually classified dataset on the surface of the Naeseong Stream in 2016 were used, where the area is divided into eight types including water, sand and herbaceous and woody vegetation. The classification method used a random forest classification technique, one of the machine learning algorithms. 1,000 samples were extracted from 10 pre-selected polygon regions, each half of them were used as training and verification data. The accuracy based on the verification data was found to be 82~85%. The model established through training was also applied to images from 2016 to 2020, and the process of changes in vegetation zones according to the year was presented. The technical limitations and improvement measures of this paper were considered. By providing quantitative information of the vegetation distribution, this technique is expected to be useful in practical management of vegetation such as thinning and rejuvenation of river vegetation as well as technical fields such as flood level calculation and flow-vegetation coupled modeling in rivers.