Studi Perencanaan Dinding Penahan Sebagai Upaya Pengendalian Banjir Sungai Meduri Kabupaten Pekalongan Jawa Tengah

Permasalahan yang sering ditimbulkan oleh banjir adalah karena adanya daya rusak air. Bangunan dinding penahan menjadi salah satu upaya dalam pengendalian banjir. Dalam merencanakan bangunan dinding penahan diperlukan beberapa analisis baik hidrologi, hidrolika, maupun keamanan struktur bangunan dengan memperhatikan aspek ekonomis. Pada studi ini, perhitungan debit banjir rancangan digunakan Hidrograf Satuan Sintetik Nakayasu dengan debit kala ulang Q25 th sebesar 258,807 m 3 /dt pada sungai Meduri dan sebesar 201,544 m 3 /dt pada sungai Bremi. Penentuan tinggi tanggul didapatkan dari analisis tinggi muka air banjir dengan bantuan aplikasi HEC-RAS pada kondisi eksisting dengan debit kala ulang Q25 th, didapatkan tinggi muka air banjir 2,22 m dan direncanakan tinggi tanggul 7,5 m dari dasar sungai. Analisis terhadap keamanan struktur bangunan dinding penahan yang diperhitungkan pada stabilitas bangunan baik keadaan normal maupun gempa, daya dukung tanah, penulangan, maupun reaksi pondasi didapatkan desain telah memenuhi persyaratan. Didapatkan Rencana Anggaran Biaya (RAB) dalam merencanakan dinding penahan sepanjang 6,78 km sebesar Rp  156.882.300.000 (Seratus Lima Puluh Enam Milyar Delapan Ratus Delapan Puluh Dua Juta Tiga Ratus Ribu Rupiah). Flooding is often causing a problem because of its destructive power. Retaining wall structure is one among the efforts to control the floods. This study aims to determine the problem of flooding that occurs in the Meduri river in Pekalongan regency so that an appropriate treatment can be planned, for example a retaining wall. Several analysis are required in order to plan retaining wall structure, such as hydrology, hydraulics, and safety factor of its structure regarding to economic aspect. This study is using a Nakayasu Synthetic Unit Hydrograph for its design flood discharge with Q25 return flowrate at 258.807 m3/s in Meduri River and 201.544 m3/s in Bremi River. The height of the embankment is obtained from analysis of flood water level using HEC-RAS with this following existing conditions: Q25 return flowrate, flood water level at 2.22 m, and height of dyke is planned at 7.5 from riverbed. The safety analysis of this retaining wall is calculated by stability normal, earthquake, soil bearing capacity, reinforcement, and also foundation reaction are already meet the criteria standard.  The budget plan at this planning of 6.78 km retaining wall is IDR 156,882,300,000