• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.117-125
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• 2016

Current cities encounter various types of water problems due to rapid urbanization and climate change. The increasing significance of urban water problems calls for the establishment of resilient alternatives to prevent and minimize social loss that results from these phenomena. As a background research for establishing resilient infrastructures for the mitigation of urban water problems, we evaluated the robustness of structural alternatives for urban flood as a representative case. Combining the robustness index (RI) and the cost index (CI), we suggested the robustness-cost index (RCI) as an indicator of the robustness of structural alternatives, and applied the index to assess the existing infrastructures and structural alternatives (i.e., sewer network expansion, additional storage tank construction, and green roof construction) at a site prone to floods located around Gangnam-station, Seoul, Korea. At a rainfall intensity frequency range of 2 to 20 years, the usage of a storage tank and a green roof showed relatively high RCI value, with a variation of an alternative showing greater RCI between the two depending on the size of design rainfall. For a rainfall intensity frequency of 30 years, installing a storage tank with some green roofing was the most resilient alternative based on the RCI value. We proposed strategies for establishing resilient infrastructures for the mitigation of urban floods by evaluating the robustness of existing infrastructures and selecting optimal structural alternatives with the consideration of scales of design disaster.

• Journal of Aquaculture
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• v.14 no.2
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• pp.73-79
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• 2001

Testicular development of the male African lungfish, Protopterus annectens (Owen) was investigated histologically. The testis was found to be an elongated structure that possessed two distinct portions: an anterior spermatogenic part that was made up of a system of testicular tubules and a posterior vesicular part that invaded the kidney tissue. Spermatogenesis can be divided into five stages; primary spermatogonia, secondary spermatogonia, spermatocyte, spermatids and spermatozoa. Based on the gonadosomatic index (GSI) and histological changes observed, the reproductive cycle can be divided onto four distinct stages: resting and quiescent (December to February), growing (March to June) ripe and spent (July to August) and postspawning (September to November). The GSI was the maximum on July when reproductive cells were mature, ripe and ready for spawning; and the minimum in August after fish spawned.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.283-283
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• 2016

기후변화의 지역적 영향으로 호우의 강도와 빈도가 증가하고 있는 상황에서 수재해 대응을 위하여 다양한 기술들이 필요하며 특히 홍수 취약성에 대한 분석과 평가가 선행되어야 한다. 본 연구에서는 기존의 PSR(Pressure-State-Response) 모형과 DPSIR(Driving force-Pressure-StateImpact-Response 모형을 다중선형회귀 기법을 사용하여 최적화하였다(Fig. 1). 대상기간은 2008년부터 2013년까지이며, mod 1에서는 연도별로 다중선형회귀기법을 사용하여 최적 가중치를 산정하였고, mod 2에서는 대상기간(2008 ~ 2013) 전체에 대해 다중선형회귀기법을 사용하여 최적 가중치를 산정하는 방법을 적용하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.281-281
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• 2021

본 연구에서는 재해와 홍수 발생에 대한 대응성을 높이고자 강우레이더 격자 기반으로 홍수 및 침수 위험도 정도를 산정하고자 한다. 홍수 위험 지수는 중소하천 상류 지역에 내린 비로 인해 하류 지점의 홍수 위험도가 얼마나 변화하는지 상대적으로 파악하기 위한 지표이며, 침수 위험 지수는 내수침수에 대한 위험도를 나타내는 것으로 단기간 강한 비에 의한 상대적인 침수 위험도의 증가를 파악하기 위한 지표를 말한다. 강우레이더 기반 전국 단위 홍수 및 침수 위험 지수 개발을 통해 기존 하천홍수예보에 국한된 홍수예보의 제공 범위를 중소하천유역 및 도시지역까지 확대할 수 있을 것으로 예상된다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.3
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• pp.35-45
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• 1984

Generally speaking, agriculture exist in a climatic environment of uncertainty. Namely, normal rainfall value, as given by the mean values, does not exist. Thought on exists, itl does not affect like extreme Precipitation value on the part of agriculture and of others. Therefore, it is important that we measure the duration and severity index of drought caused by extreme precipitation deficit. In this purpose, this study was dealt with the calculation of drought duration and severity indexs by the method of monthly weighting coefficient. There is no quantitive definition of drought that is universally acceptable. Most of the criteria was used to identify drought have been arbitrary because a drought is a 'non-event' as opposed to a distinct event such as a flood. Therefore, confusion arises when an attempt is made to define the drought phenomenon, the calculation of duration, drought index is based on the following four fundamental question, and this study was dealt with the answers of these four questions as they related to this analytical method, as follows. First, the primary interest in this study is to be the lack of precipitation as it relates to agricultural effective rainfall. Second, the time interval was used to be month in this analysis. Third, Drought event, distinguished analytically from other event, is noted by monthly weighting coefficient method based on monthly rainfall data. Fin-ally, the seven regions used in this study have continually affected by drought on account of their rainfall deficit. The result from this method was very similar to the previous papers studied by many workers. Therefore, I think that this method is very available in Korea to identify the duration of drought, the deficit of precipitation and severity index of drought, But according to the climate of Korea exist the Asia Monsoon zone. The monthly weighting coefficient is modify a little, Because get out of 0.1-0.4 occasionally.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.516-520
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• 2004

Stream Naturalness means the index of natural state in stream's ecosystem. The evaluation of stream naturalness can evaluate relatively the effect of environmental damages by human and to show how significantly current stream has been apart from its natural state. And it could be show what is the meaning of importance in stream's ecosystem by such distinctions and it Is done by showing the need how a large scale of action for restoration to be restored to natural state of stream system. In this study, a set of index for Stream Naturalness evaluation is proposed, which is referred to and modified problems with domestic and foreign study cases. This methodology is supposed to show well the characteristics of stream in Korea. A case study of Hong-Chun River shows how this methodology is applied to the Stream Naturalness evaluation. For improving the function of river which are water use and flood control and for preserving the function of inhabitation, the proposed methodology is expected to be used a index of direction for a environmental project related stream improvement by evaluation of ecologically sound function in streams.

• Journal of Korea Water Resources Association
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• v.48 no.2
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• pp.105-114
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• 2015

In the case of rapidly developed urban and industrial complex, the most area becomes impervious, which causes the increasing runoff and high probability of flooding. SWMM model has been widely used to calculate stormwater runoff in urban areas, however, the model is limited to interpreting the actual natural phenomenon. It has the uncertainty in the model structure, so it is difficult to calculate the accurate runoff from the urban basin. In this study, the model parameters were investigated and uncertainty was quantified using Uncertainty Quantification Index (UQI). As a result, pipe roughness coefficient has the largest total uncertainty and largest effect on the total runoff. Therefore, when the stormwater pipe network is designed, pipe roughness coefficient has to be calibrated accurately. The quantified uncertainty should be considered in the runoff calculation. It is recommended to understand the characteristics of each parameter for the prevention and mitigation of urban flood.

• KIEAE Journal
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• v.10 no.1
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• pp.3-10
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• 2010

Riverside forests make a river bank stable because trees of them hold together the stone and soil by roots and decrease the speed of running fluid by trunks. So they become known to have positive effects on flood prevention. So This study will be a basic study to preserve and restore of riverside forests. The goal of this study is to classify types of Han riverside forests between Yangpyeng and Yeoju gun. and find out sites of planting. Results of this study can be summarized as follows; The evaluation indicators were set up based on literature review and site survey. Two indicator categories were developed: natural environment and human environment. And they were divided into 5 sub-categories for calculating weights. As for the major indicator categories, the weighted index of natural environment is at 0.5. And the weighted index of human environment is at 0.5 followed by access at 0.15, the range of user at 0.15, cultivated land at 0.1 and legislation at 0.1. This study selected 53 sites for riverside forests planting. They were classified with types of bank(11), level-upped riverside(32), island(10). The amount of the length of 11 bank types is 23,050m, the area of 32 level-upped riverside types is $4,490,000m^2$ and the area of 10 island types is $4,590,000m^2$. After the evaluation of 53 riverside forests, this study selected 12 sites of riverside forests. They were two bank types, nine level-upped riverside types, and one island type. Rebuilding riverside forests are to accomplish the green network which links and divides region. It will be one of the best ecological methods to construct friendly environmental region.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.458-458
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• 2012

Climate extreme variability is a major cause of disaster such as flood and drought types occurred in Korea and its effects is also more severe damage in last decades which can be danger mature events in the future. The main aim of this study was to assess the effectives of climate change on drought for an agriculture as Nakdong basin in Korea using climate change data in the future from data of General Circulation Models (GCM) of ECHO-G, with the developing countries like Korea, the developed climate scenario of medium-high greenhouse gas emission was proposed of the SRES A2. The Standardized Precipitation Index (SPI) was applied for drought evaluation. The drought index (SPI) applied for sites in catchment and it is evaluated accordingly by current and future precipitation data, specific as determined for data from nine precipitation stations with data covering the period 1980-2009 for current and three periods 2010-2039, 2040-2069 and 2070-2099 for future; time scales of 3month were used for evaluating. The results determined drought duration, magnitude and spatial extent. The drought in catchment act intensively occurred in March, April, May and November and months of drought extreme often appeared annual in May and November; drought frequent is a non-uniform cyclic pattern in an irregular repetitive manner, but results showed drought intensity increasing in future periods. The results indicated also spatial point of view, the SPI analysis showed two of drought extents; local drought acting on one or more one of sites and entire drought as cover all of site in catchment. In addition, the meteorology drought simulation maps of spatial drought representation were carried out with GIS software to generate for some drought extreme years in study area. The method applied in this study are expected to be appropriately applicable to the evaluation of the effects of extreme hydrologic events, the results also provide useful for the drought warning and sustainable water resources management strategies and policy in agriculture basins.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.629-641
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• 2021

In this study, a two-dimensional numerical model (Nays2DH) was applied to analyze the process of morphological changes in the river channel bed depending on the changes in the amount of flooding after fully opening the Sejong weir, which was constructed upstream of the Geum River. For this, numerical simulations were performed by assuming the flow conditions, such as a non-uniform flow (NF), unsteady flows (single flood event, SF), and a continuous flood event (CF). Here, in the cases of the SF and CF, the normalized hydrograph was calculated from real flood events, and then the hydrograph was reconfigured by the peak flow discharge according to the scenario, and then it was employed as the flow discharge at the upstream boundary condition. In this study, to quantitatively evaluate the morphological changes, we analyzed the time changes in the bed deformation the bed relief index (BRI), and we compared the aerial photographs of the study area and the numerical simulation results. As simulation results of the NF, when the steady flow discharge increases, the ratio of lower width to depth decreases and the speed of bar migration increases. The BRI initially increases, but the amount of change decreased with time. In addition, when the steady flow discharge increases, the BRI increased. In the case of SF, the speed of bar migration decreased with the change of the flow discharge. In terms of the morphological response to the peak flood discharge, the time lag also indicated. In other words, in the SF, the change of channel bed indicates a phase lag with respect to the hydraulic condition. In the result of numerical simulation of CF, the speed of bar migration depending on the peak flood discharges decreased exponentially despite the repeated flood occurrences. In addition, as in the result of SF, the phase lag indicated, and the speed of bar migration decreased exponentially. The BRI increased with time changes, but the rate of increase in the BRI was modest despite the continuous peak flooding. Through this study, the morphological changes based on the hydrological characteristics of the river were analyzed numerically, and the methodology suggested that a quantitative prediction for the river bed change according to the flow characteristic can be applied to the field.