• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.58-64
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• 2020

Large-scale flooding due to extreme weather and typhoons causes heavy damage. This is especially true in urban areas where accumulated debris prevents the smooth drainage of rainwater in sewage facilities such as rain gutters installed near roads. In this study, to improve the drainage performance and effectively remove foreign substances by applying the dust screen used in rivers, the rain gutter with Coanda effect was simulated and compared with the experiment. The simulation was performed by setting the parameters to the fillet radius R₁ and R₂ at the top of the screen filter, the fillet radius R₃ at the bottom of the screen filter, and the height H of the gap W from the bottom. W is the gap at the backside of screen filter which is applied to stimulate the Coanda effect. According to the simulation results, the highest drain performance was 87.99% derived from R₁= 30mm, R₂= 5mm, R₃= 85mm, H= 75mm, and W= 2mm. The error rate of simulation results refer to the 4.89%~7.36% compared to the experimental results. In the future, by considering the slope according to the installation environment, the simulation results can be applied to the actual roadside to help prevent flood damage.

• Land and Housing Review
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• v.2 no.3
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• pp.299-305
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• 2011

Streams and rivers are among the most fascinating and complex ecosystems on Earth. Recently, many plans of ecological streams are developed and performed in several regions. In spite of obtaining of instream water is most important problem to composite an ecological stream, assessment methods for instream water are too various to estimate an optimal result. In this study, we developed decision support system so that decision-maker may can be supported decision making for composite an ecological stream with connecting the satisfaction of residents in stream. Decision support system is composed of hydraulic, water quality, eco-river simulation model and can show optimal instream flow assessment and water quality improvement.

• Journal of Environmental Impact Assessment
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• v.7 no.2
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• pp.53-64
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• 1998

This study was performed to build up the ecological guidelines to grasp the structure of the vegetation change which is due to river rehabilitation. Anyway, river ecosystem and function has been destroyed owing to river development. It is important that river vegetation supplies ecological corridor and biotope. Two survey sites(Wonsungcheon and Pungseocheon)were investigated in the aspect of plant ecosystem and structure to settle the practical concept of river ecosystem. Each survey site was subdivided to five plots. The site was surveyed through the belttransect method. Wonsungcheon gets more seriously polluted as it runs to the urban area. In other words, there are On the other hand, Pungseocheon has more naturality but its downstream is under the pressure of various wood plants in the upstream area, but downstream area is dominated by naturalized plants such as Bidens frondosa, Panicum dichotomiflorum, etc. Riverbank of downstream has been changed into farm and parking lot. development. It should be preserved definitely because it still has abundant naturality and wetland which formed a biotope. The objective of the research is to find out the river retrogression and maintenance methods based on the riparian vegetation structure. To manage the river ecologically, hydrophytes should be induced partly for natural purification after the riverside is rehabilitated. The vegetation should be induced step by step to restore natural river and steady monitoring and research are required.

• Journal of Environmental Impact Assessment
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• v.20 no.5
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• pp.705-716
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• 2011

For the efficient discovery of knowledge and information from the observed systems, data mining techniques can be an useful tool for the prediction of water quality at intake station in rivers. Deterioration of water quality can be caused at intake station in dry season due to insufficient flow. This demands additional outflow from dam since some extent of deterioration can be attenuated by dam reservoir operation to control outflow considering predicted water quality. A seasonal occurrence of high ammonia nitrogen ($NH_3$-N) concentrations has hampered chemical treatment processes of a water plant in Geum river. Monthly flow allocation from upstream dam is important for downstream $NH_3$-N control. In this study, prediction models of water quality based on multiple regression (MR), artificial neural network and data mining methods were developed to understand water quality variation and to support dam operations through providing predicted $NH_3$-N concentrations at intake station. The models were calibrated with eight years of monthly data and verified with another two years of independent data. In those models, the $NH_3$-N concentration for next time step is dependent on dam outflow, river water quality such as alkalinity, temperature, and $NH_3$-N of previous time step. The model performances are compared and evaluated by error analysis and statistical characteristics like correlation and determination coefficients between the observed and the predicted water quality. It is expected that these data mining techniques can present more efficient data-driven tools in modelling stage and it is found that those models can be applied well to predict water quality in stream river systems.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.863-871
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• 2007

Spectroscopic characteristics of river water from four major watersheds in the Ulsan area were measured to examine their potential for estimating water quality parameters. The total 176 river samples were collected from 44 sites of small streams within the watersheds during the year 2006. Spectroscopic characteristics investigated included protein-like fluorescence (FLF) intensity, fulvic-like fluorescence (FLF) intensity, terrestrial humic-like fluorescence (TLF) intensity, UV absorbance at 254 nm, and UV absorbance difference at 220 nm and 254 nm. Protein-like fluorescence intensity showed linear relationships with biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorous (TP) concentrations of the samples with the correlation of 0.784, 0.779, and 0.733, respectively. Due to the UV absorption characteristics of nitrate at 220 nm, UV absorbance difference at 220 nm and 254 nm was selected to represent total nitrogen (TN) concentration. Exclusion of some samples with PLF intensity higher than 5.0 improved the correlation between the UV absorbance difference and TN as demonstrated by the increase of the correlation coefficient from 0.392 to 0.784. Instead, for the samples with PLF intensity lower than 5.0, the highest correlation of TN was achieved with UV absorbance at 254 nm. The results suggest that PLF intensity could be used as the estimation index for BOD, COD, and TP concentration of river water, and as the primary screening index for the prediction of TN using UV absorbance difference. Some BOD-based water quality levels among the river water were statistically discriminated by the PLF intensity. Low p-values were obtained from the t-tests on the samples with the first level and the second level (p=0.0003) and the samples with the second and the third levels (p=0.0413). Our combined results demonstrated that the selected spectroscopic characteristics of river water could be utilized as a tool for on-site real-time monitoring and/or the primary estimation of water quality.

• Journal of Environmental Science International
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• v.19 no.1
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• pp.115-124
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• 2010

Urban watershed can be found in the visible changes in technology, the most realistic satellite images is to use the data. Satellite image data on the indicators for progress on the nature of the change of land use is consistent and repetitive information, regular observation makes possible the detailed analysis of space-time. These remote sensing techniques and the type of course and, by using the time series history, the past, the dynamic model and the randomized prediction methodology for the conversion process if the city and river basin cooperation of the space changes effectively will be able to extrapolate. For each of the main changes in river flow, depending on the area of urbanization as determined according to reproduce the duration of the relationship between the urbanization of the area and runoff can be represented as a linear polynomial expression was, if a linear expression in the two fast slew rate of 0.858 to 0.861 showed up, and fast slew rate of 0.934 to 0.974 for the polynomial are reported. Change of land use changes in the watershed of the flow is one of the most affecting elements. Therefore, changes in land use of the correct classification of rivers is a more accurate calculation of the amount of the floodgate. In particular, using the Landsat images through the image of the land use category, land use past data and calculated using the Markov Chain model and predict the future land use plan in the water control project will be used for large likely.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.4
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• pp.347-360
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• 2014

Recently construction of large sewer tunnels used also as underground sluiceways/storages is increasing in order to prevent urban inundation, untreated sewage flow into rivers from combined sewer overflows and consequential river pollution due to climate change. Most of these large sewer tunnels are constructed with concrete and the concrete lining should be protected from corrosion caused by hydrogen sulfide($H_2S$). This paper introduced popular concrete corrosion protection methods for large sewer tunnels with 100-plus years of life cycle, and pros and cons of each corrosion protection methods were described by giving specific examples. However, it is difficult to objectively assess corrosion protection alternatives because of insufficient track record of corrosion protection methods applied to large sewer tunnels. In this paper, the evaluation process for selecting a corrosion protection alternative was introduced for large sewer tunnels using a case study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.935-942
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• 2018

Precipitation has a wide range of applications, such as the management and operation of dams and rivers, supply of dranking water for urban and industrial complex, farming and fishing, forest greening, and safety management. In order to prepare for disasters and to obtain economical effects in case of flood damage, it is necessary to measure accurate precipitation. In this study, we carried out the characteristics tests for various types of rainfall gauge using integrated verification system, which can analyze the performance of collective type rainfall gauge. The uncertainty for tipping bucket rain gauge was 0.0041 mm, where weight type and surface tension type was 0.0045 mm and 0.0039 mm respectively. Therefore, the uncertainty according to the type and characteristics of the precipitation system is not significantly different. The uncertainty is also influenced greatly by the resolution.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.4
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• pp.11-23
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• 2011

Mountain streams, which are major components of an entire river network, play an important role as the source of water, sediment, coarse and fine organic matter, and nutrients for lowland rivers. Therefore, dynamics and downstream linkages of each compartment of the mountain stream can be essential for watershed management in catchment scale. The dynamics and downstream linkages are understood as a development of step-pool sequences along a river course. Recently, stream restoration after flooding event often employ the development of step-pool sequences in the world. In this paper, we 1) examined the geomorphic characteristics and the role of step-pool sequences in steep mountain streams by reviewing the results of past studies, and 2) introduced the case studies of stream restoration using step-pool sequences, and finally 3) addressed design methods considering geometry and stability of artificial step-pool sequences for stream restoration. Step-pool sequences play an important role not only as roughness with energy dissipation but also as heterogeneity of stream feature for aquatic habitat. Step-pool sequences, even if they are constructed artificially along a stream, may be effective for small stream restoration considering eco-friendly torrent controls. So far the artificial step-pool sequences were employed for mountainous streams, but those would be applied to urban stream.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.20-25
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• 2012

New Zealand suffers from regular floods, these being the most common source of insurance claims for damage from natural hazard events in the country. This paper describes the origin and distribution of the largest floods in New Zealand, and describes the systems used to monitor and predict floods. In New Zealand, broad-scale heavy rainfall (and flooding), is the result of warm moist air flowing out from the tropics into the mid-latitudes. There is no monsoon in New Zealand. The terrain has a substantial influence on the distribution of rainfall, with the largest annual totals occurring near the South Island's Southern Alps, the highest mountains in the country. The orographic effect here is extreme, with 3km of elevation gained over a 20km distance from the coast. Across New Zealand, short duration high intensity rainfall from thunderstorms also causes flooding in urban areas and small catchments. Forecasts of severe weather are provided by the New Zealand MetService, a Government owned company. MetService uses global weather models and a number of limited-area weather models to provide warnings and data streams of predicted rainfall to local Councils. Flood monitoring, prediction and warning are carried out by 16 local Councils. All Councils collect their own rainfall and river flow data, and a variety of prediction methods are utilized. These range from experienced staff making intuitive decisions based on previous effects of heavy rain, to hydrological models linked to outputs from MetService weather prediction models. No operational hydrological models are linked to weather radar in New Zealand. Councils provide warnings to Civil Defence Emergency Management, and also directly to farmers and other occupiers of flood prone areas. Warnings are distributed by email, text message and automated voice systems. A nation-wide hydrological model is also operated by NIWA, a Government-owned research institute. It is linked to a single high resolution weather model which runs on a super computer. The NIWA model does not provide public forecasts. The rivers with the greatest flood flows are shown, and these are ranked in terms of peak specific discharge. It can be seen that of the largest floods occur on the West Coast of the South Island, and the greatest flows per unit area are also found in this location.