Judul: Analyisis of the Effectiveness of Retention Ponds as Flood Prevention in Simpang Polda Area Palembang
Abstrak: Kota Palembang merupakan salah satu kota metropolitan yang terletak di Provinsi Sumatera Selatan. Proses urbanisasi dan meningkatnya pertumbuhan penduduk memberikan dampak pada penggunaan lahan sebagai daerah resapan air hujan. Penelitian ini bertujuan untuk mengetahui efektivitas kolam retensi di kawasan Simpang Polda Palembang yang berfungsi sebagai kolam penampungan air hujan dari Sungai Bendung menuju ke Sungai Musi. Tahapan penelitian meliputi beberapa tahapan seperti tahap persiapan, inventarisasi dan pengumpulan data, serta analisis dan sintesis. Hasil analisis hidrologi menunjukkan bahwa wilayah tertentu di Kota Palembang memiliki rata-rata curah hujan harian maksimum sebesar 56,34 mm, dengan daerah resapan air (catchment area) seluas 1.978.723,05 m2 (sebagian wilayah dari total luas DAS Bendung). Analisis hidrolika menunjukkan Qinflow sebesar 0,76 m3 /detik dan Qoutflow sebesar 20,28 m3 /detik. Hasil analisis kapasitas maksimum kolam retensi menunjukkan kolam retensi simpang Polda Palembang memiliki kapasitas maksimum 8.482,5 m3 hingga kolam penuh dalam waktu 186 menit. Berdasarkan hasil analisis tersebut dapat disimpulkan bahwa kolam retensi simpang Polda Palembang seharusnya dapat dengan optimal menampung air hujan yang jatuh di Kelurahan 20 Ilir D IV dan mengendalikan genangan air di kawasan Simpang Polda Palembang. Menurut Tim BBWS VIII Sumatera Selatan, pengendalian luapan air di Kawasan Simpang Polda dapat dilakukan dengan melakukan normalisasi terhadap kolam retensi dan aliran sub das secara rutin. Namun, untuk menjaga keseimbangan alam, diperlukan beberapa perencanaan lain, salah satunya dengan memperbaiki saluran drainase di sekitar kolam retensi., Palembang City is one of the metropolitan cities located in South Sumatra Province. The process of urbanization and increasing population growth has an impact on land use as a rainwater catchment area. This study aims to determine the effectiveness of retention ponds in the Simpang Polda Palembang area which function as rainwater storage ponds from the Bendung River to the Musi River. The stages of the research include several stages such as preparation, inventory and data collection, as well as analysis and synthesis. The hydrological analysis results show that certain areas in Palembang City have an average maximum daily rainfall of 56.34 mm, with a catchment area of 1,978,723.05 m2 (part of the total area of the Bendung River Basin). Hydraulics analysis showed that Qinflow was 0.76 m3 /second and Qoutflow was 20.28 m3 /second. The results of the analysis of the maximum capacity of the retention pond show that the retention pond of the Palembang Police intersection has a maximum capacity of 8,482.5 m3 until the pool is full in 186 minutes. Based on the results of this analysis, it can be concluded that the retention pond for the Palembang Police intersection should be able to optimally accommodate rainwater that falls in 20 Ilir D IV Village and control standing water in the Palembang Police Intersection area. According to the South Sumatra BBWS VIII Team, controlling water overflow in the Polda Simpang Area can be done by routinely normalizing the retention pond and sub-watershed flows. However, to maintain the natural balance, several other plans are needed, such as by improving the drainage channels around the retention pond.
Keyword: Analisis hidrologi, Kolam retensi, pengendalian banjir, Hydrological analysis, retention Pond, flood control

Judul: Review of Runoff in the Context of  Construction of the Baranangsiang Retention Pool in Bogor City
Abstrak: Beberapa faktor penyebab banjir, seperti berkurangnya daerah tangkapan air akibat peralihan fungsi lahan dan curah hujan tinggi menjadi dasar dalam perencanaan kolam retensi. Pengkajian ulang limpasan untuk pembangunan kolam retensi Baranangsiang dilakukan seiring dengan perubahan landuse dan curah hujan. Penelitian ini bertujuan menganalisis volume limpasan serta merekomendasikan kapasitas dan dimensi kolam retensi yang sesuai dengan volume limpasan. Digunakan metode Hidrograf Satuan Sintetik Nakayasu dan diperoleh debit puncak runoff dengan kala ulang 5 tahun sebesar 7,26 m3/detik dan volume kumulatif limpasan sebesar 69.187,13 m3 sedangkan kapasitas tamping kolam hasil kaji awal hanya 38.573,48 m3. Efektivitas tampungan kolam retensi hasil kaji awal terhadap volume limpasan diperoleh sebesar 55,75 % sehingga perlu dilakukan perubahan dimensi tampungan kolam dari 9.643,37 m3 menjadi 11.531,19 m3 untuk luas kolam dan kedalaman kolam retensi diubah dari 4 m menjadi 6 m sehingga efektivitas kolam retensi menjadi 100%. Dinding kolam retensi menggunakan tipe kantilever di inlet kolam. Beda tinggi antara inlet dan outlet sekitar 7 m sehingga pada titik keluar (outlet) dibangun konstruksi tubuh bendungan dengan tinggi 7 m dan lebar bentang pondasi 9,61 m., Several factors that cause flooding, such as reduced water catchment areas due to landuse changes and high rainfall, are the basis for planning retention ponds. The review of runoff for the construction of the Baranangsiang retention pond was carried out in line with changes in landuse and rainfall. This research aims to analyze runoff volume and recommend the capacity and dimensions of retention ponds that are appropriate to the runoff volume. The Nakayasu Synthetic Unit Hydrograph method was used and the peak runoff discharge with a return period of 5 years was 7.26 m3 /second and the cumulative runoff volume was 69,187.13 m3 , while the tamping capacity of the pond from the initial study was only 38,573.48 m3 . The effectiveness of the retention pond storage from the initial study on runoff volume was found to be 55.75% so it was necessary to change the dimensions of the retention pond from 9,643.37 m3 to 11,531.19 m3 for the area of the pond and the depth of the retention pond to be changed from 4 m to 6 m so that the effectiveness of the pond retention to 100%. The retention pool wall uses a cantilever type at the pool inlet. The height difference between the inlet and outlet is around 7 m so that at the outlet point a dam body construction is built with a height of 7 m and a foundation span width of 9.61 m.
Keyword: discharge, runoff volume, retention pond, effectiveness, dimensions

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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