• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.132-137
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• 2018

Compared with general rivers, fluctuations of the water level and the river bed are severe in the tidal river. In hydro-dynamic aspect, such fluctuation gives different river-bed data to us according to observing period. The time-dependent river-bed data and pre-estimation of the Manning's roughness coefficient which is the key factor of numerical modelling induces uncertainty of evaluating the design flood level. Thus it is necessary to pay more attention to calculate the flood level at tidal rivers than at general rivers. In this study, downstream of the Imjin River where is affected by tide of the West Sea selected as a study site. From the numerical modelling, it was shown that the unsteady simulation gave considerable mitigation of the water level from the starting point to 15 km upstream compared to the steady simulation. Either making a detention pond or optional dredging was not effective to mitigate the flood level at Gugok - Majung region where is located in the downstream of the Imjin River. Therefore, a more sophisticated approach is required to evaluate the design flood level estimation before constructive measures adopted in general rivers when establishing the flood control plan in a tidal river.

• Journal of Korea Water Resources Association
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• v.50 no.9
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• pp.617-625
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• 2017

In this study, it was examined that a methodology for evaluating the design flood level reasonably at Imjin River estuary affected by the tide periodically. First of all, the change of the flood level was observed by performing unsteady simulation which can take into account the characteristics of the tidal rivers. And the variations of the flood level was analyzed by change of the Manning's roughness coefficient which is sensitive to the water level calculation. The results were compared with the design flood level at Imjin River estuary announced in the 2011 Imjin River Basic Plan Report. For reference, the design flood level reported in 2011 has been calculated by using a section of a huge riverbed dredging section as input data. From the simulation results, it was found that the flood level evaluated by this study was able to satisfy the freeboard of the levee without the riverbed dredging when the roughness coefficient was assigned to the same value as that of the Han river estuary in the calculation of the flood level, and the unsteady flow simulation was carried out to reflect on the tidal river.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.1
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• pp.118-123
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• 2015

There have been various studies on measurements of flood risk and forecasting models. For river and dam region, PDF and FVI has been proposed for measurement of flood risk and regression models have been applied for forecasting model. For Bo region unlikely river or dam region, flood risk would unexpectedly increase due to outgoing water to keep water amount under the designated risk level even the drain system could hardly manage the water amount. GFI and general linear model was proposed for flood risk measurement and forecasting model. In this paper, FVI with the consideration of duration on GFI was proposed for flood risk measurement at Bo region. General linear model was applied to the empirical data from Bo region of Nadong river to derive the forecasting model of FVI at three different values of Base High Level, 2m, 2.5m and 3m. The significant predictor variables on the target variable, FVI were as follows: ground water level based on sea level with negative effect, difference between ground altitude of ground water and river level with negative effect, and difference between ground water level and river level after Bo water being filled with positive sign for quantitative variables. And for qualitative variable, effective soil depth and ground soil type were significant for FVI.

• Journal of the Korean Society of Safety
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• v.38 no.2
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• pp.81-86
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• 2023

In this study, a one-dimensional numerical model was constructed to propose a flood control plan linked with the dam and river basin for the flood events of the Seomjin River in 2020. The flood level reduction of the downstream river was tested based on a scenario operation of the Seomjingang Dam and was also analyzed when a storage pocket was newly constructed as one of the river basin measures. It was confirmed that Seomjingang Dam's flood control capacity would be increased if the flood limit level was drastically lowered from the current EL. 196.5 m to EL. 188.0 m. In addition, if the upper area of the (old) Geumgok Bridge (which suffered great damage due to the loss of the levee) is used as a storage pocket, it would be effective in preventing floods in the lower area of it. In the era of the climate crisis, more integrated flood management is needed and basic river management must be observed.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.173-173
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• 2015

The flood water level in tidal river is determined by the joint effects of flood discharge and tidal water levels at downstream boundary. Due to the variable tidal boundary conditions, the evaluated design water levels associated with a certain flood event can be significantly different. To avoid determining of design water levels just by a certain tidal boundary condition and remove the influence of variability in boundary condition from the evaluation of design water levels, a probabilistic approach is considered in this study. This study focuses on the development of a method to evaluate the realistic design water levels in tidal river with taking into account the combined effects of river discharge and tidal level. The flood water levels are described by the joint probability of two driving forces, river discharge and tidal water levels. The developed method is applied to determine design water levels for the tidal reach of the Han River. An unsteady flow model is used to simulate the flow in the reach. To determine design water levels associated with a certain flood event, first, possible boundary conditions are obtained by sampling starting times of tidal level time series; then for each tidal boundary condition, corresponding peak water levels along the channel are computed; and finally, design water levels are determined by computing the expectations of the peak water levels. Two types of tides which are composed by different constituents are assumed (one is composed by $M_2$, and the other one is composed by $M_2$ and $M_2$) at downstream boundary, and two flood events with different maximum flood discharges are considered in this study. It is found that (a) the computed design water levels with two assumed tides have no significant difference for a certain flood event, though variability of peak water levels due to the tidal effect is considerably different; (b) tidal effect can reach to the Jamsil submerged weir and the effect is obvious in the downstream reach of the Singok submerged weir; (c) in the tidally affected reach, the variability of peak water levels due to the tidal effect is greater if the maximum flood discharge is smaller.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.649-652
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• 2008

In urban area, flood risk is getting higher because of inland flood risk has grown up by changing rainfall intensity, rainfall pattern, changing land use and so on. Urban area is needed higher flood protection level to protect accumulated people, buildings and other infrastructures. However, even though former flood protection has focused on overflow from river, there is not a guide line for evaluating proper flood protection level. Thus, it is necessary to protect flood from inland flooding as well as overflow from river and need a proper method to evaluating flood protection level. This study present a method of determining flood protection elevation by using GIS tools for deciding proper flood protection level. The study result may contribute to urban flood protection measures in which inland flood risk increases.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.2
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• pp.198-203
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• 2020

In this paper, we propose an artificial water level prediction system for small river flood prediction. River level prediction can be a measure to reduce flood damage. However, it is difficult to build a flood model in river because of the inherent nature of the river or rainfall that affects river flooding. In general, the downstream water level is affected by the water level at adjacent upstream. Therefore, in this study, we constructed an artificial intelligence model using Recurrent Neural Network(LSTM) that predicts the water level of downstream with the water level of two upstream points. The proposed artificial intelligence system designed a water level meter and built a server using Nodejs. The proposed neural network hardware system can predict the water level every 6 hours in the real river.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.405-408
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• 2008

Up to now, a lot of houses, roads and other urban facilities have been damaged by natural disasters such as flash floods and landslides. It is reported that the size and frequency of disasters are growing greatly due to global warming. In order to mitigate such disaster, flood forecasting and alerting systems have been developed for the Han river, Geum river, Nak-dong river and Young-san river. These systems, however, do not help small municipal departments cope with the threat of flood. In this study, a real-time urban flood forecasting service (U-FFS) is developed for ubiquitous computing city which includes small river basins. A test bed is deployed at Tan-cheon in Gyeonggido to verify U-FFS. It is found that U-FFS can forecast the water level of outlet of river basin and provide real-time data through internet during heavy rain. Furthermore, it is expected that U-FFS presented in this study can be applied to ubiquitous computing city (u-City) and/or other cities which have suffered from flood damage for a long time.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1533-1537
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• 2005

The recent rainfall has happened to exceed the design rainfall after 1990 often, due to the characteristic of the rain to be changed. So, it is failing the ability safety of flood defense equipments to exist. This study analyzed the rainfall of Busan in 2003 since 1961 through the FARD2002(Frequency Analysis of Rainfall Duration). The result is equal to the thing which the design rainfall increased a little since 1991. The change of design rainfall created the result to be a flood discharge increase. This study investigated about the impact to influence on the river bank according to the change of flood discharge, the rainfall pattern change as well. This study used the program of HEC-RAS with HEC-HMS and calculated flood discharge with flood level of river. The result is equal to the thing which the computation became a flood level which exceed 50year(River design criteria-Korea water resources association 2002) criteria with 30year(River establishment criteria-Ministry of construction & transportation 1993), because of an area of impermeability increased of model basin.

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.465-472
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• 2012

Recently, as the development of water front and natural type river is gradually increasing, it is mostly the case in that the flow analysis is implemented by only the flood level of the starting point without the tidal effect when the flood water level of the starting point is highly estimated than the high tidal water level in the design of river adjacent to an estuary. This research has analyzed the variation of tidal current for Oncheon river in Busan using Delft-3D program, considering that the tidal effect can cause the change of the flood water level of the starting point although the flood water level is higher than the flood tide level. As a result, considering the tidal effect at downstream boundary condition, water level indicates a periodicity of tide in particular region and the fluctuation range of water level is extended to upstream.