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Penelusuran Limpasan Kejadian Banjir Sungai Padolo Di Kota Bima Akson Nurhanafi; Istiarto; B. Yulistyanto
Seminar Nasional Insinyur Profesional (SNIP) Vol. 1 No. 1 (2021): Prosiding SNIP Vol.1 No.1
Publisher : Fakultas Teknik

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (157.006 KB) | DOI: 10.23960/snip.v1i1.87

Abstract

Kota Bima mengalami banjir besar tanggal 21 dan 23 Desember 2016. Banjir berasal luapan Sungai Padolo dan Sungai Melayu. Sungai Padolo memberikan dampak banjir yang lebih besar dibandingkan Sungai Melayu. Penelusuran banjir di Sungai Padolo bertujuan mengetahui karakteristik sungai terhadap kejadian banjir dan membandingkan kondisi awal sebelum banjir dan pasca banjir. Sehingga perlu dilakukan penelusuran hidraulik untuk mendapatkan data profil muka air atau debit sepanjang ruas sungai. Simulasi pemodelan banjir dilakukan dengan menggunakan alat bantu perangkat lunak (software) HEC-RAS. Tipe aliran yang dipergunakan dalam simulasi HEC-RAS dapat berupa aliran permanen (steady flow) dan aliran tidak permanen (unsteady flow). Hasil penelusuran diharapkan dapat memberi informasi yang dapat dipertimbangkan dalam melaksanakan desain mitigasi yang sudah dan akan dilaksanakan. Analisa hidrologi menunjukkan beban hujan pada tanggal 21 Desember 2016 berada pada rentang kala ulang 25 sampai dengan 50 tahun. Simulasi HEC-RAS menunjukkan pada 21 Desember 2016 debit Sungai Pedolo dan anak sungai Sadia memberikan pengaruh banjir yang relatif sama terhadap kejadian banjir, sedang pada tanggal 23 Desember 2016 anak Sungai Sadia memberikan beban banjir dominan dibandingkan dengan Sungai Pedolo. Kapasitas maksimum Sungai Pedolo aadalah 64.5 mᶟ/det, diambil berdasarkan kemampuan penampang Sta. 556 di Kelurahan Paruga yang sudah penuh (fullbank capacity) pada debit tersebut. Penempatan saluran pengelak di Sungai Pedolo mampu mengurangi sejumlah titik perlu perhatian dan melimpas. Pengaruh rata-rata penurunan jumlah lokasi penampang titik lokasi melimpas sebanyak 43%. Penempatan tanggul pada Sungai Sadia mampu mengalirkan debit banjir kala ulang 25 tahunan.
MENGENAL BERBAGAI MODEL HIDROLOGI DI INDONESIA Yulius Patrisius Kau Suni; Istiarto
Eternitas: Jurnal Teknik Sipil Vol 2 No 2 (2023): ETERNITAS : Jurnal Teknik Sipil, Vol 2, No 2 April 2023
Publisher : Program Studi Teknik Sipil Universitas Katolik Widya Mandira

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30822/eternitas.v2i2.2442

Abstract

The hydrological model is a simplification of the complexity of a real-world hydrological system of a watershed. Since 1890, various hydrological models have been developed to assist decision makers in formulating watershed management scenarios. This study examines nine hydrological models through a literature review. The nine models are HydroOffice BFI+, HEC-HMS, HEC-SSP, EPA-WMOST, EPA-AGWA, EPA-SWMM, AGNPS, ANSWERS, and ANFIS. The results of the study are briefly explained as follows. Flood analysis could apply one of the tools namely HEC-HMS, AGWA, SWMM, AGNPS, ANSWERS, and ANFIS. However, certain flood analysis programs need to be combined with GIS and HEC-SSP to get an adequate analysis. Baseflow separation analysis could use BFI+ with the daily rainfall as input data. Analysis of the rate of erosion and sedimentation could apply AGWA, AGNPS, ANSWERS. The HEC-SSP model provides assistance in correcting incomplete and inconsistent data. In terms of water resource management on a watershed scale, the WMOST and AGNPS models can be used. However, some types of models have limitations. Therefore, in applying the model, it is necessary to combine several models to get optimal results. In addition, the results of the hydrological model analysis need to be confirmed by field measurements
Alternative Method for Determining Manning's Roughness Coefficient Using Two-Point Velocity in Equilibrium and Nonequilibrium Sediment Transport Maini, Miskar; Kironoto, Bambang A.; Rahardjo, Adam P.; Istiarto
Civil Engineering Journal Vol. 11 No. 7 (2025): July
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-07-02

Abstract

Understanding flow resistance equations, such as Manning’s roughness equation, is essential for river design and improvement. Estimating Manning’s roughness coefficient becomes more complicated when sediment transport is involved. This study takes an alternative approach by using velocity profiles to examine how sediment transport affects Manning’s roughness coefficient. To achieve this goal, 1200 velocity profiles with sediment-feeding (SF) and non-sediment-feeding (NSF) flows are evaluated to determine the (composite) Manning’s roughness coefficient. Sediment-feeding flows describe sediment flow under equilibrium conditions, whereas non-sediment-feeding flows represent sediment flow under nonequilibrium conditions. A Sontek 16-MHz Acoustic Doppler Velocimeter is used to measure the velocity (and turbulence) profiles. In addition to the present data, 225 secondary velocity profile data sets are analyzed in this study. The research findings indicate that the composite Manning’s roughness coefficient nco can be determined from Manning’s roughness coefficient nz/B at z/B in the transversal direction, using two points of the velocity profile at y/H = 0.2 and 0.4 in the vertical direction. The differences in the velocity profile shape (u/U) due to sediment feeding, particularly in inner regions (y/H ≤ 0.2), affect the value of nz/B. nco for sediment-feeding flows are generally higher than the cross-section Manning roughness coefficient n. As nco (based on nz/B) is based on the velocity profile, the nco values change with sediment transport. Meanwhile, the n values remain unchanged because the equation variables cannot detect the presence of sediment transport. For non-sediment-feeding flow, the differences in nco with n are 14.80% for a fixed bed (FB) and 18.17% for a movable bed (MB). The differences are even more pronounced for sediment-feeding flow at 33.01% for a fixed bed and 36.52% for a movable bed. The point where nz/B/nco = 1 occurs at z/B = 0.2 from the channel sidewall. This suggests that nz/B, measured at z/B = 0.2 from the channel sidewall, provides a good representation of nco for the section.
Scour Morphology Comparison Around Oblong Bridge Pier: Clear-Water and Live-Bed Flow Conditions Darajat, Achmad Rafi’ud; Kironoto, Bambang A.; Istiarto
Civil Engineering Journal Vol. 12 No. 2 (2026): February
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2026-012-02-023

Abstract

Bridge pier scour is a significant contributor to structural instability in riverine infrastructure, particularly in sediment-laden tropical rivers. Streamlined shapes such as oblong piers generally produce smaller scour depths than bluff-body piers, offering potential safety advantages. However, the morphological evolution of scour under different sediment-transport regimes and its implications for structural stability remain insufficiently documented. This study experimentally compares clear-water (CW) and live-bed (LB) scour around an oblong pier, with emphasis on equilibrium depth, temporal development, three-dimensional morphology, velocity structure, and safety relevance. Flume tests were performed using a 5-cm × 10-cm oblong pier under steady subcritical flow (Q = 50 L/s, h = 10 cm, d50 = 2.21 mm, Fr < 1), with CW simulated by eliminating upstream sediment supply and LB by continuous sediment recirculation. Velocity measurements using an Acoustic Doppler Velocimeter (ADV) were conducted at equilibrium scour geometry to characterize flow structures. Results show CW scour reached a deeper equilibrium (z/D = 1.70), developed 36.4% faster (T* = 666 min) than LB (z/D = 1.52, T* = 909 min). CW formed a symmetric, steep-walled scour hole with 14.1% greater volume and 15.6% wider planform area, creating an immediate risk of vertical undermining. LB produced a shallower, more elongated scour with partial downstream backfilling, leading to gradual longitudinal undermining and slower foundation settlement. Velocity measurements revealed stronger vertical and lateral fluctuations under LB, explaining its more irregular scour morphology. Although the reduced scour depth confirms previous findings for streamlined piers, the elongated downstream scour and partial backfilling under LB provide new insights for countermeasure design. Among the tested predictors, Sheppard's Equation performed best with 8% (CW) and 3% (LB) deviations. These findings confirm that streamlined oblong piers reduce the maximum scour depth compared with circular shapes, but reveal contrasting mechanisms: CW promotes rapid, concentrated erosion, whereas LB induces slower, more widespread scour. The results emphasize that countermeasure design must explicitly account for the sediment-transport regime to ensure long-term foundation stability.
Co-Authors Akson Nurhanafi alyasari, claudia nur B. Yulistyanto Darajat, Achmad Rafi’ud Kironoto, Bambang A. Miskar Maini Noberta Rahardjo, Adam P. Rahmatullah, Ilham Suwignyo Wesi Fatmawati Yulius Patrisius Kau Suni