Although large hydraulic facilities such as sea dike, breakwater bank and river bank, can protect a lot of lives and various industrial facilities from flood. The extreme weather events including changes in land use, localized heavy rains, extraordinary floods and earthquakes; rapid water discharge from upstream dams; and dam destruction may cause inundation damage like flood flow and debris flow. Such disasters by outburst floods result in not only loss of mass lives and property but also different social problems. In this regard, it is essential to establish flood forecasting, warning and evacuation strategy for proper flood measures against such disasters.
Organizations in charge of controlling reservoirs and sea dikes have developed and operated Emergency Action Plan (EAP) by scenarios of emergency situations caused by floods exceeding the design flood amount or unpredictable reasons such as earthquakes.EAP classifies emergency levels issued for emergency situations including collapse of reservoirs and sea dikes into 4 stages-Attention (Blue), Caution (Yellow), Alert (Orange), Serious (Red) - to determine and respond to the symptom by situation.
For areas where EAP for sea dikes has been established, the development of emergency situations or countermeasures are classified, while there is no index to separate them. In this case, if a manager conducts the phased measures with only “forecasting” in the situation stage, they are highly likely to have limitations to their active responses.
This research aims to perform hydraulic and hydrologic safety review on sea dikes according to inflow of extraordinary floods from upstream of sea dikes and tributaries. Changes in water level flowing into the lake according to flood amount by frequency is used to investigate if it can be utilized as a disaster management index for EAP for sea dikes. For this, EAP index is developed by simulating flood level changes and time to reach flood level at the point of selected sea dikes from 100, 200 and 500-year and PMF flood amounts centering around the sea dikes. Targeting Saemangeum Lake, the study set the range required for numerical model, entered model composition and data using Delft3D numerical analysis model, verified the credibility of the model through calibration and established operational conditions of the model.
Assuming that Saemangeum Master Plan had been completed, the study also conducted comprehensive operations. For inflow of floods by each frequency according to management water level in the lake, time to reach the flood level and flood stage were simulated.
EAP index was established using the flood level and travel time. If the initial stage among the emergency levels, ‘Attention,’ was set as 『from extraordinary flood to management water level EL-1.5m』, it would be beneficial to respond to initial disasters. Also, it would be easier to set ‘Caution’ as 『from management water level EL-1.5m to management flood level inside the lake EL+1.5m』; ‘Alert’ as 『from management flood level inside the lake EL+1.5m to riprap protection flood level inside the bank』; and ‘Serious’ as 『flood level over riprap protection inside the bank (Mangyeong EL+4.5m, Dongjin EL+2.5m)』 for responding to initial disasters.
The research aims to provide sea dike operators with more accurate information by presenting index by emergency situation stage. The result, as hydraulic and hydrological data on flood level, travel time, etc., is expected to be useful for sea dikes with or without EAP as a response index required for disaster management of sea dikes.