Effect rainfall season on coastal flood in Semarang City, Central Java, Indonesia

Abstract

Floods of rain always occur on the coast of Semarang City every time there is a change of season. The coastal city of Semarang has a flat topography with 13 rivers passing through, causing flood insecurity. The purpose of the study is reviewing rainfall patterns in Semarang City, and reviewing the relationship of rainfall with flood events in coastal parts of Semarang City. The materials used are secondary data (rainfall from BMKG, flood information from online media and newspapers) and field surveys (flood measurement and observation). Rainfall data processed with Excel, flood events (place, time, and height of puddles) are associated with the magnitude of rainfall. Analysis of the interrelationship of rainfall and flooding is associated with aspects of environmental conditions (topography, hydrology, geology). The results showed that during the period June 2018-June 2019 daily rainfall above 100 mm has caused flooding. Monthly rainfall above 100 mm occurs in December, January, February. The conclusion that the rainfall pattern in Semarang City is unimodal with the November-March rainy period and the peak occurs in January.