• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.1
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• pp.106-119
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• 2016

Flood risk map, flood damage map, disaster information map, inundation trace map are involved with the cartographic analysis of flood inundation based on prevention, preparation, restoration, response from natural disasters such as flood, flooding, etc. In this study, the analysis for channel and basin characteristics Chungju dam to Paldang dam of South han river after four river project. Flood scenario is selected to take advantage of design flood level of schematic design for river. Flood inundation of one dimensional non-uniform flow by using HEC-RAS with basin characteristics is accomplished and two dimensional unsteady flow was interpreted by using FLUMEN. Frequency analysis is carried out about each abundance of South han river for 100 year period, 200 year period and 500 year period. Flooding disaster area of 100 year period on 0.5m damage functions is 2378.8ha, 200 year period on 0.5m damage functions is 3155.2ha, 500 year period on 0.5m damage functions is 3995.3ha respectively. It will be significant data for decision making to establish inundation trace map for providing basic plan for river maintenance, land use plan, flood protection plan, application plan and getting information of flood expectation area.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.48-59
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• 2019

This study analyzed the water quality characteristics and developed empirical models prior to and after the construction of Baekje Weir, in the Geum River watershed between 2004-2017. The comparative evaluation of the surface water chemistry before and after the four major river projects on the weirs indicated that total phosphorus (TP), based on annual data, rapidly decrease after the construction of the weir while the total nitrogen(TN) decreased. Conversely, chlorophyll-a (CHL) concentration, which is a good indicator of primary productivity, increased after the construction of the weir together with an increase in specific conductivity. Simply put, the construction of the weir led to the decrease in concentrations of N and P due to the increased water residence time (WRT), whereas the CHL :TP ratio greatly increased in magnitude. The regression analysis of the empirical model indicated that CHL had no significant relation (r=0.068, p=0.6102, n=58) with TP before the weir construction, but had a relation with TP after the weir construction (r=0.286, p<0.05, n=56). Therefore, such conditions resulted in an increase in primary productivity on a given unit of phosphorus, resulting in frequent algal blooms. In contrast, seasonal suspended solids (SS) and TP increased during the monsoon period, compared to the pre-monsoon, thereby showing positive correlations (r>0.40, p<0.01, n=163) with precipitation. If the government consistently discharges water from the weir, the phosphorus concentration will be increased due to its reversion to a lotic waterbody from a lentic waterbody hereby reducing algal blooms in the future.

• Journal of Korea Water Resources Association
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• v.57 no.2
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• pp.87-97
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• 2024

This study analyzed the water shortage hotspot areas in South Korea using spatial clustering analysis for water shortage estimates in 2030 of the Master Plans for National Water Management. To identify the water shortage cluster areas, we used water shortage data from the past maximum drought (about 50-year return period) and performed spatial clustering analysis using Local Moran's I and Getis-Ord Gi*. The areas subject to spatial clusters of water shortage were selected using the cluster map, and the spatial characteristics of water shortage areas were verified based on the p-value and the Moran scatter plot. The results indicated that one cluster (lower Imjin River (#1023) and neighbor) in the Han River basin and two clusters (Daejeongcheon (#2403) and neighbor, Gahwacheon (#2501) and neighbor) in the Nakdong River basin were found to be the hotspot for water shortage, whereas one cluster (lower Namhan River (#1007) and neighbor) in the Han River Basin and one cluster (Byeongseongcheon (#2006) and neighbor) in the Nakdong River basin were found to be the HL area, which means the specific area have high water shortage and neighbor have low water shortage. When analyzing spatial clustering by standard watershed unit, the entire spatial clustering area satisfied 100% of the statistical criteria leading to statistically significant results. The overall results indicated that spatial clustering analysis performed using standard watersheds can resolve the variable spatial unit problem to some extent, which results in the relatively increased accuracy of spatial analysis.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.163-173
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• 2022

Climate change is a key factor that greatly influences changes in the biological seasons and geographical distribution of species. In the ecological field, the BioClimatic predictor (BioClim), which is most related to the physiological characteristics of organisms, is used for vulnerability assessment. However, BioClim values are not provided other than the future period climate average values for each GCM for the Shared Socio-economic Pathways (SSPs) scenario. In this study, BioClim data suitable for domestic conditions was produced using 1 km resolution SSPs scenario detailed data produced by Rural Development Administration, and based on the data, a species distribution model was applied to mainly grow in southern, Gyeongsangbuk-do, Gangwon-do and humid regions. Appropriate habitat distributions were predicted every 30 years for the base years (1981 - 2010) and future years (2011 - 2100) of the Acer pictum subsp. mono. Acer pictum subsp. mono appearance data were collected from a total of 819 points through the national natural environment survey data. In order to improve the performance of the MaxEnt model, the parameters of the model (LQH-1.5) were optimized, and 7 detailed biolicm indices and 5 topographical indices were applied to the MaxEnt model. Drainage, Annual Precipitation (Bio12), and Slope significantly contributed to the distribution of Acer pictum subsp. mono in Korea. As a result of reflecting the growth characteristics that favor moist and fertile soil, the influence of climatic factors was not significant. Accordingly, in the base year, the suitable habitat for a high level of Acer pictum subsp. mono is 3.41% of the area of Korea, and in the near future (2011 - 2040) and far future (2071 - 2100), SSP1-2.6 accounts for 0.01% and 0.02%, gradually decreasing. However, in SSP5-8.5, it was 0.01% and 0.72%, respectively, showing a tendency to decrease in the near future compared to the base year, but to gradually increase toward the far future. This study confirms the future distribution of vegetation that is more easily adapted to climate change, and has significance as a basic study that can be used for future forest restoration of climate change-adapted species.

• Journal of Korea Water Resources Association
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• v.42 no.12
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• pp.1069-1077
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• 2009

Lately, it is an important concern in water resources research to maintain a stable water supply according to a future climate change and an increase in water use. In Han-River basin, approximately 10 % of water resources that is provided the capital region (Gyeonggi, Seoul etc.) has been reduced as a consequence of the construction of Imnam Dam (storage volume: 27 billion $m^3$) located in the upper Hwacheon Dam upstream area. Therefore, streamflows have decreased in Bukhangang basin, but it could not be evaluated quantitatively. In this study, SWAT-K which is the physically based long-term runoff simulation model, was used in order to evaluate the effect of Imnam Dam on the reduced inflow to Hwacheon Dam according to the change of hydrological condition in the upstream area of Hwacheon Dam. For the model input data of North Korea area, meteorological data of GTS (Global Telecommunication System) were used, and soil maps by FAO/UNESCO (2003) were applied. Temporal variations of water resources is investigated with comparison of observed and simulated inflows at Hawcheon Dam site. Also, annual, monthly, seasonal decreases in water resources were evaluated using the flow duration analysis of simulated streamflows with or without Imnam dam.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.28-38
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• 2019

Climate change on the Korean peninsula is progressing faster than the global average. For example, typhoons, extreme rainfall, heavy snow, cold, and heatwave that are occurring frequently. North Korea is particularly vulnerable to climate change-related natural disasters such as flooding and flooding due to long-term food shortages, energy shortages, and reckless deforestation and development. In addition, North Korea is classified as an unmeasured area due to political and social influences, making it difficult to obtain sufficient hydrologic data for hydrological analysis. Also, as interest in climate change has increased, studies on climate change have been actively conducted on the Korean Peninsula in various repair facilities and disaster countermeasures, but there are no cases of research on North Korea. Therefore, this study selects watershed characteristic variables that are easy to acquire in order to apply localization model to North Korea where it is difficult to obtain observed hydrologic data and estimates parameters based on meteorological and topographical characteristics of 16 dam basins in South Korea. Was calculated. In addition, as a result of reviewing the applicability of the parameter estimation equations calculated for the fifty thousand, Gangneungnamdaecheon, Namgang dam, and Yeonggang basins, the applicability of the parameter estimation equations to North Korea was very high.

• Journal of the Korean association of regional geographers
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• v.16 no.2
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• pp.100-109
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• 2010

The study examines two different sites to analyze the difference of stream channel profile between two different landuse areas on Neponset River, Boston, MA. Landuse represents the current status of land in terms of human, agricultural or forest, industry and environmental activity types. According to the previous research, forest and urban area are significantly distinguished in chemical characteristic, shape and bed load of the stream. On the chosen sites, I look at the cross-section profile, the slope, velocity, and roughness of the channels. With the data collected at the site I determined the value for the channel bed material using Manning's equation, and compared with the result of HEC-RAS model with the cross-section profile data I measured. In the forest area, water surface elevation and bed material obtained through Manning's equation are very close to HEC-RAS model result. However, in the resident area the Manning's 'n' value calculated much higher than assumption which was considered as cobble whose 'n' value is 0.03-0.06. The difference could be caused by unusual steep elevation on the site and the dam present down further. With the steep elevation upside of dam, there is critical-depth condition occurs. The difference of Manning's 'n' value reflects the difference of depth. HEC-RAS model was run to analyze the difference and the result shows that depth is 0.36 much less than 0.688 what I computed when the Manning's n value is 0.03(cobble) instead of the result of the study (0.13292). Beside, dam is a major source of fragmentation and degradation of stream, and it's possibly inferred upstream water levels are increased and stream velocity is decreased. This study is meaningful for introduction of HEC-RAS in geography field to analyze different sites with channel bed material, and it is going to be used more actively to manage river and river side.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.235-247
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• 2012

BACKGROUND: Gohyeon Stream is the municipal eco-stream of 7.1km in total length which flows through the downtown area of Gohyeon in Geoje city, rising from the watershed of Mundong Water Fall. Gohyeon district in Geoje city has been a rapid growing area centering in Geoje city and then experienced an rapid increase in population. Large amounts of sewage pollutants have been spewed into Gohyeon Stream from its tributaries, due to the lack of sewer system. Gohyeon Stream is laced with unhealthy levels of fecal coliform (FC). Restoration of water quality in Gohyeon Stream is no less inevitable in behalf of its ecosystem and the citizen. In this study, the water quality of Gohyeon Stream and its tributaries was examined temporally and spatially, and their relationships were comparatively analyzed to give useful basic data applying to a restoration project of the water quality of Gohyeon Stream. METHODS AND RESULTS: The samples ware taken at 20 points in Gohyeon Stream and 19 points in its tributaries during the rainy and dry seasons, respectively, and examined on the parameters of pH, temperature, salinity, dissolved oxygen (DO), suspended solid (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN; $NH_3$-N, $NO_3$-N, $NO_2$-N), disolved inorganic phosphorus (DIP; $PO_4$-P) and FC. The data were analyzed using a comparative analysis and Pearson's correlation analysis among the parameters. During the rainy season, the concentration of SS was high in the upper region of Gohyeon Stream, and the concentrations of COD, DIN and DIP were low in the upper region and high in the middle and lower regions. During the dry season, the concentration of SS was low and the concentrations of COD, DIN, DIP and FC were high in all regions. The Pearson's correlation analyses showed that the relationships between DO and FC, COD and DIP, and DIN and FC during the rainy season as well as between DO and DIN, SS and FC, COD and DIP, and DIN and DIP during the dry season were significant. CONCLUSION: During the rainy season, the upper region of Gohyeon Stream flowed the high level of SS, the middle region the high level of nutrients due to an agricultural run-off, and the lower region the high level of nutrients due to a sewage inflow. During the dry season, the water quality of Gohyeon Stream was directly and sensitively influenced on the inflow of sewage from the tributaries.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.431-444
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• 2020

The relationship between dam construction and water quality has recently come to be considered an important issue. A dam is a physical factor which causes changes to the river system around it. Considering these points, this study was conducted to obtain basic data by analyzing the relationship between water level fluctuations and water quality parameters in the short-term. In terms of methodology, the new construction of the Yeongju Dam (M5) in 2016 was divided into Stage 1 as the lotic system and Stage 2 as the lentic system, with four years in each period, and the water level fluctuations and water quality were analyzed using official data. As a result of this study, M5, a stagnant area in which organic matter and nutrients accumulate, was found to be an important factor in water quality management. In addition, the water level changed rapidly (0.9±0.2 m → 10.9±7.1 m) as the river environment condition was converted from the lotic system to the lentic system. In addition, water quality parameters such as BOD, COD, TOC, and Chl-a significantly changed in the short-term. Further, since the transport of organic matter and nutrients occurred well in the lotic system, sedimentation was expected to be dominant in the lentic system. Therefore, it was determined that when the river flow is blocked, autochthonous organic matter is an important factor for long-term water quality management in the future. This process can increase the trophic state of the water body. As a result of this study, the TSI_KO value was converted from mesotrophic in Stage 1 to eutrophic in Stage 2. Eventually, short-term changes in the river environment will affect not only changes in water level but also changes in water quality. Thus, a comprehensive and strategic approach is needed for long-term water quality management in the future.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.5
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• pp.11-18
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• 2016

The objective of this study was to develop the simple method to estimate ungauged river section for flood stage analysis. Damage prediction should be prioritized using hydrological modeling to reduce flood risk. Mostly, the geographical data using hydrological modeling depends on national river cross-section survey. However because of the lack of measured data, it is difficult to apply to many local streams or small watersheds. For this reason, this study suggest the method to estimate unguaged river cross-section. Simple regression equations were derived and used to estimate river cross-section by analyzing the correlation between the river cross-sectional characteristics (width, height and area). The estimated cross-sections were used to simulate flood level by HEC-RAS (Hydrologic Engineering Center's River Analysis System). The applicability of this method was verified by comparing simulated flood level between measured and estimated cross-section. The water surface elevation of the flood stage analysis was 6.56-7.24 m, 5.33-5.95 m and 6.12-6.75 m for measured cross section, for estimated cross section and for estimated cross section based on DEM elevation, respectively. Further study should consider other factors for more accurate flood stage analysis. This study might be used one of the guidelines to estimate ungauged river section for flood stage analysis.