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• Accurately and Timely Flash Flood Forecasting Accurately and Timely Flash Flood Forecasting Seok Hwan Hwang (Research Fellow, Flash Flood Research Center) Overview Korea and the rest of East Asia have suffered massive damage this year after experiencing the longest rainy season on record as well as repeated torrential downpours. These challenging experiences have highlighted the importance of being able to accurately predict sudden flash floods. The Flash Flood Research Center at the KICT is currently developing a system for predicting localized flash floods and providing early warning notifications for urban inundation. Once implemented, the system will be able to quickly and accurately identify flash floods at least one hour before they actually occur, giving residents a chance to evacuate or take other precautions. The system is expected to help drastically reduce the loss of life and property due to water damage during the summer. Flood Forecasting in Populated Areas Numerous water-related disasters have occurred in Korea in the summer of 2020. Rivers flowing through the city overflowed, landslides buried human dwellings in mud and soil, and apartment complexes were inundated with flood water. This type of water damage happens every year, resulting in the loss of both lives and property. These accidents occur suddenly, without warning, making them even more damaging. Dr. Seok Hwan Hwang(Ph.D.), who is the head of the Flash Flood Research Center, has met with numerous public servants working for related authorities, and they have unanimously stated that even less than an hour’s warning would be hugely effective in preventing the loss of human life. “Public servants working with related authorities have consistently called for threat prediction information for disaster response operations. Predicting threats may be difficult, but it is also essential. At this point in time, flood forecasts are provided only for the country’s major rivers, but flood damage reaches far beyond these major rivers. That is why there is a need for flash flood warnings to cover the entire country. How safe Koreans feel should not be dependent on where they live.” ▲ [{hoto 1] Head of the Flash Flood Research Center, Dr. Seok Hwan Hwang(Ph.D.) The Flash Flood Research Center at the KICT is currently developing a system to predict localized flash floods and provide early warnings for urban inundation. Effective forecasting of localized flash flooding across vast areas involves the use of rainfall data gathered remotely using radar technology. Accurate flash flood forecasting is only possible using highly accurate rainfall measurements obtained remotely by radar. The Flash Flood Research Center is currently developing technology to enhance the accuracy of such technologies. “The Flash Flood Forecasting System uses meteorological radar data to predict rainfall. However, the accuracy ofradar-based predictions decreases significantly when making forecasts more than hour into the future. In order to overcome these limitations, we are developing a technology that combines short-term radar prediction data with numerical weather prediction data so that we can ensure accurate rainfall predictions up to three hours in advance.” The localized flash flooding prediction system under development is currently undergoing field testing at the Ministry of Environment’s Flood Control Office with the aim of putting the system into field operations by 2021. Dr. Hwang introduces the localized flash flooding prediction system as a technology that brings flood forecasting into people’s“everyday living sphere.” Once implemented, the technology will be able to provide a one-hour warning for flash floods anywhere in the country. “Another characteristic of the system is that it analyzes open information on the web and social media to self-diagnose flood threat prediction errors. This will allow the accuracy of the system’s flood predictions to increase as the system matures. We are also developing techniques to track torrential rainfall to predict the spread and proliferation of flood risk. We are also working to develop techniques to calculate, early on, based on cloud formations, whether there is a possibility that the resulting rainfall will develop into torrential downpours that are likely to cause flash flooding.” Dual-polarization Technology for Enhanced Accuracy Flash floods are caused by convective precipitation, which develops vertically, or by precipitation fronts, which develop in one area and then move to another. The flooding that happened in Busan and Daejeon this summer developed in this same way. This past summer, many people wondered why flooding happened in the heart of the city, away from the rivers. Dr. Hwang explains that flood characteristics, damage, and risk levels vary substantially depending on the topology. “In low-lying urban areas, such as the Gangnam district of Seoul, the amount of water that gathers in one place and the speed at which it flows will be completely different than in a village on Mt. Jirisan. That is why current special weather reports based on precipitation data often fail to predict the flash flood conditions that people actually experience in real life. This type of data is insufficient in providing early warning for sudden flash floods.” Localized flash flood forecasting isa process that is divided into three steps: 1) First, rainfall is observed using meteorological radars, and rainfall predictions are made up to three hours in advance using observed data; 2) Second, any flood (inundation) risk is calculated using predicted rainfall and the hydrologic characteristics of each region, including topography; 3) Third, the predicted rainfall and flood (inundation) risk data is used to assess flash flood risk levels and provide flash flood warnings in realtime. The system under development by the Flash Flood Research Center uses existing flood damage data and detailed regional flood characteristics to extract factors that determine flood depth and degree of flood damage in various regions under varied conditions. The formula derived using this process is used to predict flash flooding risk for areas with no prior flooding data. A dual-polarized radar system is employed to boost the accuracy of the observation data. “Dual polarization is a method of emitting radar beams to observe airborne precipitation particles. In the past, a single-polarized beam that oscillates only in a horizontal direction was emitted to observe precipitation. Even though single-polarized radar is able to measure the intensity of precipitation based on the strength of the reflected radar signals, this technology is unable to distinguish between different types of precipitation, such as rain, snow, or sleet. However, a dual-polarized radar simultaneously emits horizontally and vertically oscillating beams, which allows for the accurate determination of the type of precipitation, including rainfall.” Dr. Hwang also points out that flood risk is manifested through a dynamic process of precipitation, flooding, surging, and landslides. This process was also seen in the flood damage caused by extended periods of torrential rainfall this past summer. Dr. Hwang also notes that the special rainfall alerts, flooding risk alerts, river overflow warnings, and landslide risk forecasts that are currently provided to the public are given individually, and fail to take into consideration all the factors of a given region. With such poor warning systems, people who live in areas with underdeveloped disaster response infrastructure cannot be expected to effectively cope with flood-related disasters. Dr. Hwang also stresses that the state needs to provide general flood risk forecast data to local governments and municipalities, so that they can also engage in disaster prevention and response efforts for small river overflows and landslide risks in upstream areas as well as for flood risks in downstream urban areas. “Local governments need to be able to utilize this information and provide feedback on its effectiveness, as well as to give suggestions for improvement. An organically-linked system allows for the continual enhancement of prediction accuracy. By implementing an accurate prediction system, we will be able to prevent overlapping government investments in disaster prevention systems, and ensure that all Koreans are guaranteed the same standards of safety, regardless of their economic standing.” ▲ [Photo 2] Datafrom meteorological radars used to predict precipitation Efforts Toward a Stronger Forecasting System The Flash Flood Research Center is working on developing original flash flood forecasting technologies, based on quaternary convergence technologies, and implementing a national flash flood forecasting hub under the motto “Confidence in Technology Toward a Better Life.” Once implemented, the flash flood forecasting system currently under development will be capable of generating applied forecasting data that considers regional and user characteristics. This will enable optimized flood forecasting tailored to each user type (i.e. industrial or agricultural). It will also allow the central and local governments to provide accurate and detailed flash flood forecasts one to three hours in advance at the local level. These advancements are expected to greatly improve the general safety of the Korean public in the face of flood risks. “We assessed the system using urban flooding cases from 2020 and found that the system was capable of accurately predicting flood risks in numerous cases. However, our assessments also helped us identify a number of areas for improvement. After we address these areas, the system will be able to more accurately and reliably predict flash flood risks. Differences in urban and mountain village environments mean that calculated risk levels may be manifested entirely differently in real life depending on the area. Differences between areas are caused by artificial structures and varying degrees of urbanization. The flash flood forecasting system we are currently developing will be even more accurate next year as we make further improvements to address area differences.” ▲ [Photo 3] Radar meteorology station onSeodaesan Mountain Flash Flood Research Center Date2020-07-30 Hit 93
• Development of next-generation seawater desalination technology to address water shortages ㅇ Overview - Use of next-generation hollow fiber membrane distillation technology in seawater desalination to overcome the limitations of conventional desalination technologies, for the implementation of the world’s first and largest pilot plant for the testing of next-generation desalination technology ㅇ Research contents - Design and implementation of the membrane distillation (MD) process using hollow fiber modules; design of a hybrid desalination process using the membrane distillation method; development of technologies to reduce water concentrates from seawater desalination using membrane distillation; development of low-energy forward osmosis seawater desalination techniques World’s first and largest membrane distillation pilot plant (400 ㎥/day) ㅇ Research Achievement - Development of the world’s first and highest-capacity (400 ㎥) membrane distillation technology through the use of an exclusive hollow fiber-type membrane distillation module - Development of next-generation seawater desalination process technology with a 1,000 ㎥/day capacity by combining reverse osmosis and membrane desalination - Development of a low-energy seawater desalination technology using forward osmosis - Quantitative achievements: 36 press releases, 10 papers (3 domestic, 7 SCI(E)), 2 patents, and 16 academic presentations 1,000 ㎥/day next-generation seawater desalination pilot plant ㅇ Expected effects - Reduction in the large volume of water concentrates resulting from the desalination of seawater and a 30% increase in freshwater production - Reduced volume of water concentrates for compliance with environmental regulations and the increased protection of maritime ecosystems - Increased seawater desalination cost savings by securing low-energy seawater desalination technology - Improved technological competitiveness and development of new markets through the early securing of next-generation seawater desalination technologies Department of Land, Water and Environment Research Date2019-01-16 Hit 585
• Development of Korean Hanji filter ㅇ Overview - Development of high added value new material for removing environmental pollutants by combining state-of-the-art science and technology with traditional Hanji cellulose fiber - Addressing the social problem of major pollutants such as fine particulate matter and VOCs, and developing environmental material production technologies, thereby gaining a competitive edge over advanced economies ㅇ Research Contents ￮ Development of Hanji filter and activated charcoal-infused Hanji filter - Developed technology: Cellulose fiber is dispersed in a solvent by adding non-polar material such as tertiary butyl alcohol to prevent the wind-up phenomenon. Free-drying is used to evaporate the solvent to prepare a porous (porosity: 90%) Hanji filter with layered cellulose fibers. A cation bonding agent is used to evenly and electrostatically bind powdered activated charcoal to the cellulose Hanji fiber, resulting in an activated charcoal-infused Hanji filter from which the powdered activated charcoal does not come loose and which is able to simultaneously remove fine particulate matter and VOCs. ￮ Synthesis of porous aluminosilicate zeolite containing a regenerable iron component - Developed technology: Ammonium iron citrate is chemically bound to an aluminosilicate frame to synthesize porous zeolite containing an iron component that is able to absorb and remove VOCs. VOCs adsorbed by zeolite are radiated with UV light, causing electrons to be released from the iron component within the porous material. This, in turn, causes oxidation (photo-fenton oxidation) of the VOCs. Absorption and oxidation (regeneration) can be carried out on-site, allowing infinite reuse. Porous Hanji Filter ㅇ Research Achievements ￮ Technological value - The commercialized fine particulate matter removal technologies currently used worldwide involve electrical dust collection devices that are primarily for industrial use only. Dust filters produced by companies such as Samsung and LG for the removal of fine particulate matter in household environments use discontinuous fiber spinning (melting blown, electro spinning, etc.) technology. This technology is used to coat a non-woven fabric with synthetic fibers; the non-woven fabric is then folded into a metal enclosure through which air can freely pass. A widely used adsorbent for the removal of VOCs is activated charcoal; however, the greatest problem associated with activated charcoal is the high cost of facilities used for regeneration. The technologies currently used cause environmental pollution, and production has been migrated to developing economies such as China and India. - A “porous Hanji filter” and “activated charcoal-infused porous Hanji filter” have been developed as part of this study. This technology, which is unique to Korea, involves the simultaneous removal of fine particulate matter and VOCs using a single flat sheet/filter. “Photo-fenton oxidation” technology using iron-containing zeolite and UV irradiation is a new concept in VOC removal and allows for absorption and filter absorbent regeneration. This newly developed technology is designed to replace many of the preexisting technologies developed by advanced economies. - The fine particulate matter (1 um – 10 um) removal efficiency of a single “activated charcoal-infused porous filter” is 99% at 1m/sec flux. Up to 99% BTEX removal is also possible. The “iron-containing zeolite + UV irradiation” technology is able to readily remove pollutants and is easy to regenerate, allowing for semi-permanent use. iron-containing zeolite + UV irradiation ￮ Scientific value - Approximately 16 articles have been published in SCI(E) journals on the Hanji filter and its iron-containing zeolite technology, which serves as further proof of the scientific value of the technology. In particular, an article relating to iron-containing zeolite and UV irradiation was published in J. of Hazardous Materials (I/F:6.5). ￮ Social value - In recent times, fine particulate matter, volatile carcinogens, and new house & building syndrome have been keywords in some of the social issues in Korea. - To remove fine particulate matter and VOCs using current technologies, a dual filter combining a non-woven fabric filter and an activated charcoal filter is necessary. However, using the activated charcoal-infused Hanji filter, both fine particulate matter and VOCs can be removed using a single filter. The iron-containing zeolite can be regenerated and reused. - The technology developed through this study is significant in that it uses unique Korean traditional technology to provide a solution to problems experienced by our society, allowing it to replace technologies currently being used by other advanced countries. ￮ Economic value (10) - The price of indoor dust filters, including non-woven fabric filters and activated charcoal filters, is approximately KRW 200,000 per set, but the price of a Hanji filter is KRW 10,000/filter, approximately 1/10 of conventional filters. Also, whereas activated charcoal filters require housings, no particular housing is required when using iron-containing zeolite. ㅇ Expected Effects ￮ Technological value - Development of Korean Hanji filter able to simultaneously remove fine particulate matter and VOCs - Development of iron-containing absorbents capable of regeneration, replacing technologies used by advanced economies ￮ Social benefits - Indoors: Can be used in the manufacture of air conditioner and air purifier filters (for simultaneous removal of fine particulate matter and VOCs) - Outdoors: Filters for HVAC system air intakes for public facilities such as schools and department stores Department of Land, Water and Environment Research Date2019-11-26 Hit 289

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