@misc{TrinhMolkenthin, author = {Trinh, Manh Xuan and Molkenthin, Frank}, title = {Flood hazard mapping for data-scarce and ungauged coastal river basins using advanced hydrodynamic models, high temporal-spatial resolution remote sensing precipitation data, and satellite imageries}, series = {Natural Hazards}, volume = {109}, journal = {Natural Hazards}, number = {1}, issn = {0921-030X}, doi = {10.1007/s11069-021-04843-1}, pages = {441 -- 469}, abstract = {This paper presents an integrated approach to simulate flooding and inundation for small- and medium-sized coastal river basins where measured data are not available or scarce. By coupling the rainfall-runoff model, the one-dimensional and two-dimensional models, and the integration of these with global tide model, satellite precipitation products, and synthetic aperture radar imageries, a comprehensive flood modeling system for Tra Bong river basin selected as a case study was set up and operated. Particularly, in this study, the lumped conceptual model was transformed into the semi-distributed model to increase the parameter sets of donor basins for applying the physical similarity approach. The temporal downscaling technique was applied to disaggregate daily rainfall data using satellite-based precipitation products. To select an appropriate satellite-derived rainfall product, two high temporal-spatial resolution products (0.1 × 0.1 degrees and 1 h) including GSMaP_GNRT6 and CMORPH_CRT were examined at 1-day and 1-h resolutions by comparing with ground-measured rainfall. The CMORPH_CRT product showed better performance in terms of statistical errors such as Correlation Coefficient, Probability of Detection, False Alarm Ratio, and Critical Success Index. Land cover/land use, flood extent, and flood depths derived from Sentinel-1A imageries and a digital elevation model were employed to determine the surface roughness and validate the flood modeling. The results obtained from the modeling system were found to be in good agreement with collected data in terms of NSE (0.3-0.8), RMSE (0.19-0.94), RPE (- 213 to 0.7\%), F1 (0.55), and F2 (0.37). Subsequently, various scenarios of flood frequency with 10-, 20-, 50-, and 100-year return periods under the probability analysis of extreme values were developed to create the flood hazard maps for the study area. The flood hazards were then investigated based on the flood intensity classification of depth, duration, and velocity. These hazard maps are significantly important for flood hazard assessments or flood risk assessments. This study demonstrated that applying advanced hydrodynamic models on computing flood inundation and flood hazard analysis in data-scarce and ungauged coastal river basins is completely feasible. This study provides an approach that can be used also for other ungauged river basins to better understand flooding and inundation through flood hazard mapping.}, language = {en} } @inproceedings{TrinhNguyenMolkenthin, author = {Trinh, Manh Xuan and Nguyen, Mai Dang and Molkenthin, Frank}, title = {Flood risk assessment in the Tra Bong river catchment, Vietnam}, series = {International Symposium on Lowland Technology (ISLT 2018), Hanoi, Vietnam}, booktitle = {International Symposium on Lowland Technology (ISLT 2018), Hanoi, Vietnam}, publisher = {Construction Publishing House}, address = {Hanoi}, isbn = {978-604-82-2483-7}, pages = {8}, abstract = {Extreme flood events often cause tremendous damage and enormous risks to our life and nature. Flooding is one of the most costly kinds of natural disasters in Vietnam. Tra Bong is a river catchment located in Quang Ngai province, Vietnam. Due to the effect of typhoons originated from the East Sea, many extreme floods occur in this river annually. Therefore, considering the impacts of flooding and flood risk assessment in this river plays an important role in mitigating and adapting to flood risk. In this paper, a hydrological model (MIKE NAM) and some hydro-dynamic models such as the MIKE 11 HD, MIKE 21 FM and MIKE Flood models were applied as the effective tools to simulate flooding and inundation in the downstream area of the catchment. Two flood risk maps for 2009 and 100 year return period were created based on the intersection of hazard and vulnerability maps which were obtained from flood maps, land-use and population density. Accordingly, more than 80\% of total flooded area is at high and very high risk. Almost 35 km2 of the flooded area were under high and very high risk in the year 2009, while, approximately 45.5 km2 would be under high and very high risk in the design flood event of 100 year return period.}, language = {en} } @misc{TrinhMolkenthin, author = {Trinh, Manh Xuan and Molkenthin, Frank}, title = {Numerical Modeling of Extreme Flooding for Flood Risk Assessment in the Tra Bong River Basin, Vietnam}, series = {Recent Trends in Environmental Hydraulics : 38th International School of Hydraulics}, journal = {Recent Trends in Environmental Hydraulics : 38th International School of Hydraulics}, editor = {Kalinowska, Monika B. and Mrokowska, Magdalena M. and Rowiński, Paweł M.}, publisher = {Springer Nature}, address = {Switzerland}, isbn = {978-3-030-37105-0}, issn = {2190-5193}, doi = {10.1007/978-3-030-37105-0_26}, pages = {299 -- 308}, abstract = {Flooding and inundation are of the most concerns in Vietnam. Many extreme floods have been occurring in Vietnam frequently, especially during the period of 1999-2009. Considering the impacts of flooding plays an important role in mitigating and adapting to flood risks. In this study, a rainfall-runoff model, two hydrodynamic models, and a coupling model were successfully applied as effective tools to simulate flooding and inundation in the Tra Bong River Basin, which is located in central Vietnam and considered as an ungauged basin. These models simulated the high flows accurately by depicting all of the peak flow discharges in accordance with observed high flows. The low flows were also simulated fairly well. In general, there is a good fit between the observed and simulated hydrographs for both calibration and validation. According to the model performance, 80\% of the floodplain area would be flooded during the future extreme flood event. Eventually, the model results indicate that the integration of these models is significantly suitable for the flood risk assessment in the basin.}, language = {en} } @misc{TrinhMolkenthin, author = {Trinh, Manh Xuan and Molkenthin, Frank}, title = {Flood Risk Assessment in the Tra Bong River Catchment, Vietnam}, series = {Advances in Hydroinformatics - SimHydro 2019 - Models for Extreme Situations and Crisis Management}, journal = {Advances in Hydroinformatics - SimHydro 2019 - Models for Extreme Situations and Crisis Management}, editor = {Gourbesville, Philippe and Caignaert, Guy}, publisher = {Springer Nature}, address = {Singapore u.a.}, isbn = {978-981-15-5435-3}, issn = {2364-6934}, doi = {10.1007/978-981-15-5436-0_45}, pages = {575 -- 592}, abstract = {Extreme flood events often cause tremendous damage and enormous risks to people, infrastructure and nature worldwide and especially in Vietnam. Therefore, flooding is considered as one of the most costly kinds of natural disasters in this country. Tra Bong is an ungauged river catchment located in Quang Ngai province, Vietnam. Annually, due to the effect of typhoons that originate from the South China Sea, many extreme floods occur in the river system every year. Considering the impacts of severe flooding in the Tra Bong River Catchment plays an important role in mitigating and adapting flood risk. In this paper, the hydrological model MIKE11 NAM and some hydro-dynamic models such as the MIKE 11 HD, MIKE 21 FM, and MIKE Flood models were applied as effective tools to simulate the flooding and inundation in the downstream area of the catchment. These models simulated the high flows accurately by depicting all of the peak flow discharges in accordance with observed high flows. Two flood risk maps for the year of 2009 and the design flood events (100 year return period) were created based on the intersection of hazard and vulnerability maps which were obtained from flood maps, land-use and population density. Accordingly, more than 80\% of the total flooded area is at high and very high risk. Almost 35 km2 of the flooded area were at high and very high risk in the year 2009, while, approximately 45.5 km2 would be at high and very high risk in the 100 year return period flood event.}, language = {en} }