MITIGASI BANJIR STRUKTURAL MENGGUNAKAN MODEL HEC-RAS DAN GEO-STUDIO PADA WILAYAH SUNGAI TOBA-ASAHAN, SUMATERA UTARA

Abstrak Permasalahan banjir menjadi isu utama di Indonesia dan di dunia. Strategi manajemen pengendalian banjir dapat berupa upaya mitigasi struktural dan non-struktural. Adanya perkembangan penelitian menyebutkan bahwa mitigasi non-struktural memiliki dampak yang baik dalam mereduksi banjir. Penelitian ini mengambil studi kasus di daerah studi yaitu Wilayah Sungai Toba-Asahan, tepatnya di Sungai Silau. Apakah mitigasi struktural dalam pengendalian banjir signifikan? Analisis kapasitas hidrolika menggunakan software HEC-RAS adanya penurunan limpasan banjir dari kondisi eksisting ke kondisi skenario normalisasi sungai. Begitu pula nilai safety factor lereng sungai pada lokasi tinjauan menggunakan software Geo-Studio yang naik sebesar 139%. Opsi usulan desain bendungan urugan juga dapat mereduksi banjir sebesar 24,83%. Sehingga, dapat disimpulkan bahwa mitigasi struktural signifikan dalam pengendalian banjir. Namun, mitigasi struktural tidak bersifat sustainable bagi pemangku kepentingan, sehingga perlu ada skenario simulasi menggunakan mitigasi non-struktural. Kata kunci: pengendalian banjir, mitigasi struktural, mitigasi non-struktural, flood routing Abstract The problem of flooding is a major issue in Indonesia and in the world. Flood control management strategies can take the form of structural and non-structural mitigation measures. The development of research states that non-structural mitigation has a good impact in reducing flooding. This research took a case study in the study area, namely the Toba-Asahan River Basin, to be precise in the Silau River. Is structural mitigation in flood control significant? Analysis of hydraulic capacity using HEC-RAS software shows a decrease in flood runoff from existing conditions to river normalization scenario conditions. Likewise, the river slope safety factor value at the review location using Geo-Studio software increased by 139%. The proposed option for embankment dam design can also reduce flooding by 24.83%. Thus, it can be concluded that structural mitigation is significant in flood control. However, structural mitigation is not sustainable for stakeholders, so there needs to be a simulation scenario using non-structural mitigation. Keywords: flood management, structural mitigation, non-structural mitigation, flood routing