Flood Management in the Babon River Watershed, Semarang City

Abstract

Floods are natural disasters that often occur during the rainy season, Apart from that, there are also tidal floods which are caused by global warming. This problem occurs in the city of Semarang, especially northern Semarang, specifically the northern coast floods that occurred in 2021 in the city of Semarang including Genuk, Kaligawe, Tawang Station, Tanjungmas, and Karangayu. Flood disasters are caused by high rainfall, while tidal floods are caused by high tides and inundate the roads and houses of residents on the north coast of Semarang city. To handle this problem, the current government has built embankments in the Sringin River, which is equipped with a ponpa, Tenggang River, Babon River, Semarang River, Banger River, and others. The embankment is equipped with a pump so that when the water from upstream to downstream is high, the water is pumped into the sea. The aim is to determine one of the annual discharges of the Baboon river, as well as to determine the capacity of the Baboon river’s longstorage capacity. Apart from that, there is a method for dealing with tidal floods, namely using Baboon River Longstorage which is equipped with a pump. If high tide floods roads and houses, the pump is turned on, whereas if the water recedes and does not inundate residential areas, the pump is turned off. Flood control analysis was calculated using the HEC-RAS program simulation using a return period of 50 years. Based on calculations using the HEC-RAS program, the flood discharge is 2,529 m³/sec. The high tide elevation is + 1.67 m, while the normal water level is -0.5 m. The implication of the results of this research is to provide input to local governments when discussing flood management meetings in the city of Semarang. Keywords: babon, longstorage, hec-ras