Perencanaan Sistem Drainase Kebon Agung Kota Surabaya, Jawa Timur

Saluran Kebon Agung membentang dari Surabaya bagian selatan, Kecamatan Jambangan dan bermuara di sisi laut Surabaya bagian Timur, Kecamatan Rungkut. Saluran ini memiliki panjang 11 kilometer dan lebar berkisar antara 7 – 12 meter. Pada saluran Kebon Agung terdapat 2 rumah pompa, yaitu Pompa Kutisari dan Pompa Kebon Agung. Rumah pompa ini sudah berfungsi agar dapat mengurangi banjir di Surabaya, namun masih kurang maksimal, sehingga masih terjadi genangan di beberapa lokasi. Menurut BAPPEKO (Badan Perencanaan Pembangunan Kota) Surabaya tahun 2015, terjadi genangan setinggi 10-40 cm di Kecamatan Wonocolo dan setinggi 10-50 cm di Kecamatan Gununganyar. Perencanaan sistem drainase Kebon Agung dilakukan dengan meninjau kondisi saluran eksisting terlebih dahulu, kemudian melakukan analisa hidrologi dengan menggunakan program bantu HEC-HMS untuk mendapatkan debit banjir rencana. Sedangkan, analisa hidrolika menggunakan program bantu HEC-RAS dengan dua kali simulasi aliran tidak tetap (unsteady flow), yaitu simulasi kondisi saluran eksisting dan hasil perencanaan. Berdasarkan hasil analisa kondisi eksisting diperoleh bahwa genangan air terjadi karena kapasitas saluran yang tidak mampu mengalirkan debit banjir, seperti dimensi saluran yang kurang sesuai, dan adanya sedimentasi, sampah, tanaman liar di saluran. Kapasitas saluran Kebon Agung saat ini tidak dapat mengalirkan debit banjir rencana, sehingga dibutuhkan perencanaan baru. Lebar saluran primer yang diperlukan berkisar antara 8 meter sampai 20 meter dengan kedalaman 3 meter sampai 4,5 meter, lebar saluran sekunder yang diperlukan berkisar antara 5 meter sampai 8 meter dengan kedalaman 2 meter sampai 2,5 meter, dan untuk lebar saluran tersier yang diperlukan berkisar antara 1 meter sampai 2,5 meter dengan kedalaman 1 meter sampai 2 meter. Jumlah pompa yang dibutuhkan adalah sebanyak 5 dengan kapasitas 10 m3/detik dan 3 buah pompa dengan kapasitas 1,5 m3/detik. ================================================================================== Kebon Agung channel is in the southern part of Surabaya in Jambangan district to the eastern part of Surabaya in Rungkut district. This channel is 11 kilometers long and about 7 – 12 meters wide. Today there are 2 pump houses serving the Kebon Agung channel, they are Kutisari pump house and Kebon Agung pump house. These pump houses have been operated to reduce the flood in Surabaya, however this facilities aren’t sufficient yet since the inundation continue to occur in several locations. Based on Surabaya High Flood Risk Region Map 2014, a neighborhood with high flood risk was found in Jambangan district as the result of Kali Surabaya overflow. In addition, as stated by BAPPEKO (Badan Perencanaan Pembangunan Kota) Surabaya year 2015, inundation with height of 10-40 cm in Wonocolo district and of 10-50 cm in Gununganyar district happened to occur as well.. Kebon Agung drainage system planning is carried out by considering the existing channel condition, then continued by analyzing the hydrology aspect using HEC-HMS software in order to obtain the flood discharge. The hydraulic aspect is analyzed next using HEC-RAS software with two-times unsteady flow simulations, by means the simulation of existing channel condition and the result of channel design. According to the result of existing channel analysis, it is proved that the inundation occured because the channel capacity was not able to stream the current discharge. This innapropriate condition is caused by the following factors; channel dimensions that did not correspond to the discharge, and the existence of sedimentation/trashes/water plants along the channel. The new design of channel dimensions are required as the current capacity of Kebon Agung channel was no longer suitable to stream the flood discharge. The width required for the primary channel is about 7 meter to 15 meter with 3 meter depth. For the secondary channel, the dimension is designed is about 5 meter to 8 meter wide and 2,5 meter deep. The last is the tertiary channel, which requires dimension 1,2 meter to 2 meter wide and 1 meter to 2 meter deep. The new total of pump facilities are 5 pumps with 10 m3/sec capacity and 3 pumps with with 1,5 m3/sec