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

Judul: Evaluation of Topographic Wetness Index and Normalized
Difference Water Index for Identifying Flood-Prone Areas in Ciliwung Watershed
Abstrak: Bencana banjir dapat memberikan dampak besar dan merugikan beberapa wilayah di Indonesia. Salah satu penyebab banjir adalah penutupan lahan dan topografi. Penelitian ini dilakukan untuk mengevaluasi penggunaan Topographic Wetness Index (TWI) dan Normalized Difference Water Index (NDWI) dalam memetakan daerah rawan banjir. Pemetaan kerawanan banjir dilakukan berdasarkan nilai TWI dan NDWI, serta hasil gabungan kedua indeks tersebut yang kemudian dilakukan overlay terhadap jenis tutupan lahan untuk melihat tingkat kebasahan berdasarkan jenis tutupan lahan. Proses random sampling dilakukan untuk melihat tingkat kebasahan masing-masing penutupan lahan secara adil. Hasil penelitian menunjukkan mayoritas tutupan lahan di wilayah kajian memiliki tingkat kebasahan sedang hingga tinggi. Hal tersebut disebabkan oleh topografi yang cenderung landai dan tingkat kerapatan vegetasi yang cenderung sedikit., Flood disasters can have significant and detrimental impacts on several regions in Indonesia. One of the main causes of floods are land use and topography. This study aims to evaluate the use of Topographic Wetness Index (TWI) and Normalized Difference Water Index (NDWI) in mapping flood-prone areas. Flood vulnerability mapping is conducted based on TWI and NDWI values, as well as the combined results of these two indices, which are then overlaid with land cover types to assess moisture levels based on land cover types. Random sampling is performed to assess the moisture levels of each land cover type. The research findings indicate that the majority of land cover types in the study area have moderate to high moisture levels. This is attributed to the relatively flat topography and low vegetation density.
Keyword: banjir, tutupan lahan, topografi, TWI, NDWI

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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