Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Journal of Ecological Engineering

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Impact of Landslides Induced by the 2018 Palu Earthquake on Flash Flood in Bangga River Basin, Sulawesi, Indonesia

Tunas I. Gede, Tanga Arody, Oktavia Siti Rahmi

Journal of Ecological Engineering

2020

Vol. 21, nr 2

190--200

High magnitude flash flood has occurred several times in some areas in Central Sulawesi Province after the 2018 Palu Earthquake, one of them is in the Bangga River, Sigi Regency, Indonesia. It has caused massive impacts such as damaging agricultural and plantation areas and submerging public facilities and infrastructure and even causing fatalities. The flood carries a variety of materials, especially high concentration sediments which are thought to originate from eroded soils due to landslides induced by a 7.5 magnitude earthquake. These materials are eroded and transported by the flow at the upstream watershed due to heavy rainfall. This study intends to investigate the potential of landslides, factors that trigger floods and increased flooding after the earthquake. This research was conducted by investigating the landslides potency based on field surveys and interpretation of the latest satellite imagery, analyzing the characteristics of rainfall as a trigger for flooding, and predicting the flood potency as the primary impact of these two factors. Rainfall-flood transformation was simulated with the HEC-HMS Model, one of the freeware semi-distributed models commonly used in hydrological analysis. The model input is the configuration of river networks generated from the National DEM (DEMNAS), hourly rainfall during floods and other watershed parameters such as land cover, soil types and river slope. The similar simulation was also carried out on the condition of the watershed before the earthquake. Based on the results of the analysis, It can be inferred that flash floods in the Bangga River are mainly caused by heavy rainfall with long duration and landslide areas in the upper watershed triggered by the 2018 Palu Earthquake with an area of approximately 10.8 km2. The greatest depth of rainfall as a trigger for flooding is 30.4 mm with a duration of 8 hours. The results of the study also showed that landslides in the upper watershed could increase the peak flood by 33.33% from 118.56 m3/s to 158.08 m3/s for conditions before and after the earthquake.

The Application of ITS-2 Model for Flood Hydrograph Simulation in Large-Size Rainforest Watershed, Indonesia

Tunas I. Gede

Journal of Ecological Engineering

2019

Vol. 20, nr 7

112--125

Nowadays, the increasing intensity of extreme rainfall and changes in land use have triggered massive floods in various regions of Indonesia. The changes in the characteristics of these two parameters cause an increase in the peak and duration of the flood over time. Peak and duration of flood estimation might be very useful for the national and local government because it is closely related to the effectiveness of prevention and mitigation plan in the future. A hydrograph-based model constitutes one approach to estimating them simultaneously. The objective of this research is to examine the application of ITS-2 – a synthetic unit hydrograph (SUH) model which was developed at Sepuluh Nopember Institute of Technology (ITS) in 2017 – for estimating the peak flood discharge as a basis for planning disaster mitigation programs. This study was carried out by testing the reliability of the ITS-2 Model using the Nash-Sutcliffe Efficiency (NSE) indicator by comparing the measured unit hydrograph and synthetic unit hydrograph derived using the model, optimizing the parameters of the model, and then analyzing the transformation of rainfall-flood discharge in the Gumbasa Watershed, one of the major watersheds in Central Sulawesi Province, Indonesia. This catchment is part of the Palu watershed, which is largely a tropical rainforest conservation area known as the Lore Lindu National Park. The input model is based on the design rainfall with a certain return period using the frequency analysis where the data was obtained from the rainfall stations in the study area. The results of the research showed that the performance of the ITS-2 model was still very good with the NSE above 80%. The difference in the peak discharge of these two unit hydrographs is relatively low, with a deviation below 10%. The optimal values of the ITS-2 Model parameter coefficients consisting of C1, C2, and C3 were achieved at 1.29, 0.33 and 1.88, respectively. The results of the hydrograph analysis based on a 1-year to 100-year return period indicate that peak flood discharge ranges from 100 m3/sec to 550 m3/sec. From a series of analyses and tests that have been conducted in the previous and current research, it can be concluded that the ITS-2 Model can be applied to various watershed sizes, especially in Indonesia.