Judul: Flood Vulnerability Assessment at Various Rainfall Return Periods in the Jeneberang Watershed, South Sulawesi Province
Abstrak: Daerah Aliran Sungai (DAS) Jeneberang merupakan salah satu DAS kritis prioritas nasional di Sulawesi Selatan. Salah satu faktor yang menyebabkan DAS kritis adalah perubahan tutupan lahan dari kawasan hutan menjadi lahan terbangun. Hal ini menyebabkan fungsi DAS menurun ditunjukkan oleh frekuensi kejadian banjir yang sering terjadi. Upaya meminimalisir dampak bencana banjir adalah penyediaan peta kerawanan banjir yang akurat. Penelitian ini dilakukan untuk mengidentifikasi tingkat kerawanan banjir DAS Jeneberang pada berbagai periode ulang curah hujan. Tingkat kerawanan banjir dihitung berdasarkan parameter Topographic Wetness Index (TWI), tutupan lahan, dan periode ulang curah hujan dengan nilai pembobotan berdasarkan Standar Nasional Indonesia yang dimodifikasi yaitu 35%, 35%, dan 30% untuk TWI, tutupan lahan, dan curah hujan secara berurutan. Hasil analisis menunjukkan bahwa tingkat kerawanan banjir berdasarkan parameter curah hujan dengan kelas daerah tidak rawan terdapat di bagian hulu, daerah rawan terdapat di bagian tengah menuju hilir, dan daerah sangat rawan terdapat di area yang dekat dengan jaringan sungai. Daerah rawan banjir DAS Jeneberang berkorelasi tinggi dengan nilai TWI yang tinggi, tutupan lahan didominasi oleh pemukiman dan persawahan, serta curah hujan > 76 mm/hari. Identifikasi kerawanan banjir menggunakan parameter TWI, tutupan lahan, dan periode ulang curah hujan mampu memetakan tingkat kerawanan banjir di DAS Jeneberang dan berdasarkan hasil analisis bahwa ketiga parameter tersebut dapat digunakan untuk memetakan tingkat kerawanan banjir suatu wilayah, tetapi kajian kerawanan banjir yang lebih akurat memerlukan tambahan parameter sesuai dengan faktor yang mempengaruhi kejadian banjir wilayah tersebut., The Jeneberang watershed is categorized as the critical watershed and has become the national priority for restoration in South Sulawesi. The critical condition of watershed was due to the high rate of land use change that converts forest to other uses. This has led to decreased hydrological watershed functions as indicated by frequent flood events. To minimize the impact of flood, the availability of an accurate flood vulnerability map is required. This research aimed to identify the level of flood vulnerability of the Jeneberang watershed at various return periods of rainfall. The flood mapping required information on the Topographic Wetness Index (TWI), land cover, and return period of rainfall, which were weighted based on modified Indonesian Standard National as follows 35%, 35%, and 30% for TWI, land cover, and rainfall consecutively. The results showed that based on rainfall information, the low level of vulnerability was found in upstream area, whereas the vulnerable class was located in the middle downstream and the very vulnerable class was located at adjacent to river networks. Flood vulnerability areas of the Jeneberang watershed were highly correlated with high TWI values, land cover dominated by building area and rice fields, and rainfall > 76 mm/day. The findings reveal that identification of flood vulnerability based on our approach (with parameters TWI, land cover, and return period of rainfall) is able to characterize the level of flood vulnerability. Further, more robust approach by considering other important parameters that influence flood events will improve the prediction of the map of flood vulnerability.
Keyword: flood vulnerability, land cover, rainfall, return period, TWI