The Impact of Typhoon on Coastal Dikes

 2023.11.18.

The respected Comrade Kim Jong Un said:

"Efficient sea and coastal management is important in our country, which is bounded on three sides by the sea and has many rivers, lakes and reservoirs."

In recent years, climate changes induced by global warming have led to frequent and extreme natural hazards such as typhoons and floods which cause severe damages to lives and properties in coastal regions all around the world.

We combined SW module, the spectral wave model of DHI, and HD module to simulate the effect of waves on stability of sea dikes in West Korean Bay in the period of typhoon. The simulation results show that the stability of dikes was greatly affected by the wave characteristics figures of dikes at seaside since they rapidly increase due to reclamation. Thus, the changes in wave characteristics should be considered as an important issue in building dikes.

The present study focused on the impact of typhoon on the sea off Honggondo on the northern coast, where the coasts are relatively indented based on the construction project (stages 1 and 2) in the area. The study used Typhoon No. 8 in 2020, which had serious impact on West Korean Bay in late August, 2020. Figure shows the study area, path of selected typhoon in the study and dike construction stages for the tidal flat reclamation.

The assessment point 1 was set on the dike in front of Jopdo, which is heavily affected by waves in the first-stage of dike construction schedule, and the assessment point 2 was set on the dike between Sinmi Islet and Ung Islet. The significant wave height and energy at the assessment points are estimated by taking the maximum values in the period of the typhoon. This is because we want to evaluate the impact of waves on the stability of dikes when wave impact is greatest.

As shown in the table, the maximum significant wave height at point 1 was 2.2 m, the maximum wave energy was 14.9 kW/m, the maximum significant wave height at point 2 was 2.7 m, and the maximum wave energy was 22.3 kW/m. The results showed that the significant wave height and wave energy in front of dike increased as dikes are built in accordance with the stages of tidal flat reclamation plan. Significant wave height and wave energy are heavily dependent on the water depth. The farther the dikes, the greater the significant wave height and wave energy.

After all, the simulation results of wave characteristics in front of dikes have emphasized that the stability of dikes subjected to wave attack in the period of typhoon should be considered before construction in deep water.

These results have been reported in the paper entitled "Influence of Tidal Flat Reclamations on Storm Surge in West Korean Bay of DPR Korea"(https://doi.org/10.1007/s11852-022-00895-y) published in "Journal of Coastal Conservation".