Simple model of sea level peak potentially trigger coastal flood on north coast of Java

Coastal flood is often a problem on the north coast of Java. The main factor that causes it is sea level rise which is triggered by several main constituents. The main triggering constituent that has long been known is the gravitational constituent of the moon and the sun. Another main trigger constituent is high waves at the sea, especially due to bad weather. Djamaluddin et al. (2022) have found empirical evidence of astronomical constituents in increasing sea level peaks in Jakarta and Surabaya from analyses of long-term tidal data from 1984 to 2004. The most dominant astronomical parameters are the combination of moon phases at new-full moon or lunar declination, the proximity of the moon to the earth (perigee), and the sun’s declination. Jakarta and Surabaya tide gauge stations are considered to represent general conditions on the north coast of Java, although there are differences in tidal characteristics. The tides in Jakarta generally have a diurnal pattern which is affected by the constituent of the moon’s declination, while the tides in Surabaya generally have a semi-diurnal pattern which is affected by the constituent of the new-full moon. On the basis of this empirical evidence, a simple model of the effect of astronomical parameters on sea level rise was made. The model is prepared by periodicity superposition of declination or moon phase, lunar perigee, and sun declination. The absolute value of the minimum cycle of the declination of the moon, moon phase, and solar declination is used, because the peak of sea level rise also occurs during the minimum phase of the moon, as well as the minimum (most southern) declination of moon and sun. This simple model is quite well suited to sea level peaks in the period 1984 - 2004. Most of the coastal flood events also correspond to the peaks of variation in the model. Thus, the developed simple model can be used as a prediction of the potential coastal flooding on the north coast of Java. Of course, other triggering factors of high waves, that cannot be predicted in advance, need to be watched out for, because they act as a strengthening factor to the potential coastal flooding.