Flood inundation uncertainty: The case of a 0.5% annual probability flood event

During the first week of July 2018, widespread flooding caused extensive damage across several river basins in western Japan. Among the affected basins were the Mabicho district of Kurashiki city in the lower part of the Oda river basin of the Okayama prefecture. An analysis of such a historical flood event can provide useful input for proper water resources management. Therefore, to improve our understanding of the flood inundation profile over the Oda river basin during the period of intense rainfall from 5–8 July 2018, the Rainfall-Runoff-Inundation (RRI) model was used, with radar rainfall data from the Japan Meteorological Agency (JMA) as the input. River geometries—width, depth, and embankments—of the Oda river were generated and applied in the simulation. Our results show that the Mabicho district flooding was due to a backwater effect and bursting embankments along the Oda River. The model setup was then redesigned, taking into account these factors. The simulated maximum flood-affected areas were then compared with data from the Japanese Geospatial Information Authority (GSI), which showed that the maximum flood inundation areas estimated by the RRI model and the GSI flood-affected area matched closely. River geometries were extracted from a high-resolution digital elevation model (DEM), combined with coarser resolution DEM data (global data), and then utilized to perform a hydrological simulation of the Oda river basin under the scenarios of backwater effect and embankment failure. While this approach produced a successful outcome in this study, this is a case study for a single river basin in Japan. However, the fact that these results yielded valid information on the extent of flood inundation over the flood-affected area suggests that such an approach could be applicable to any river basin.

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Optimizing Digital Elevation Model Resolution Inputs and Number of Stream Gauges in Geographic Information System Predictions of Flood Inundation: a Case Study Along the Illinois River, Usa

Environmental and Engineering Geoscience ◽

10.2113/gseegeosci.23.4.345 ◽

2017 ◽

Vol 23 (4) ◽

pp. 345-357

Author(s):

Anas Rabie ◽

Eric Peterson ◽

John Kostelnick ◽

Rex Rowley

Keyword(s):

Spatial Analysis ◽

Interpolation Method ◽

Geographic Information ◽

Geological Survey ◽

Illinois River ◽

Flood Event ◽

Potential Hazard ◽

Flood Inundation ◽

Digital Elevation ◽

River Region

Abstract Spatial analysis using Geographic Information Systems (GISs) is evaluated for its ability to predict the potential hazard of a flood event in the Illinois River region in the state of Illinois. The data employed in the analysis are available to the public from trusted organizations such as the Illinois State Geological Survey and the U.S. Geological Survey. Since available GIS data may be limited for flood risk modeling in some parts of the world, the purposes of this study are to examine the use of spatial analysis in a GIS to determine flood inundation risk and to produce an accurate flood inundation vulnerability map employing the least amount of data. This study concentrates on areas that have stream gauge data with definable flood stage(s) and utilizes the inverse distance weighted interpolation method on different digital elevation models (DEMs) with different spatial resolutions (1 m, 10 m, and 30 m) to determine the extent of flooding over the study area. Resulting maps created for the Illinois River region yielded about 80 percent agreement with the effects of an actual flood event on the Illinois River near Peoria, IL, on April 23, 2013. A four-gauge distribution scenario using a 10-m DEM produced the most accurate results, but all scenarios generated reasonable flood simulation. Thus, we speculate that it is possible to create a flood prediction map with a reasonable amount of accuracy using only two initial input data layers: stream gauges and a DEM.

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Simulation of Flood Event in Kelantan on December 2014 as revealed by the HEC-HMS

Journal of the Civil Engineering Forum ◽

10.22146/jcef.34020 ◽

2018 ◽

Vol 4 (3) ◽

pp. 215

Author(s):

Muhamad Zulhilmi Abdul Latif

Keyword(s):

Heavy Rain ◽

Flood Disaster ◽

Water Levels ◽

Flood Event ◽

Analysis Tool ◽

Flood Inundation ◽

Similar Magnitude ◽

Extreme Flood ◽

Flood Analysis ◽

Peak Discharges

A devastating flood disaster occurred at Kuala Krai, Kelantan on December 2014. The flood disaster had given a significant destructive impact on the infrastructure and as a result, almost 1,600 homes were lost or destroyed. This extreme flood event killed 25 villages and forced 45,467 people in Kuala Krai, Kelantan to be evacuated from their homes. Continuous heavy rain for over three days from the 21st to the 23rd of December, 2014 was set a rainfall record of 1,295 mm, equivalent to the amount of rain usually seen in a span of 64 days. As a result, the water levels of three major rivers, the Sungai Galas in Dabong, the Sungai Lebir in Tualang and the Sungai Kelantan in Jambatan Gueillemard, rose above the dangerous water levels. It is essential to estimate the extent of flood inundation. The objective of this study is to simulate flood event in December 2014 by using HEC-HMS. The results show the peak discharges and inundations occurred approximately on the 25th December 2014; 18,575.7 m3/s to be almost similar magnitude as reported by DID 2014 Flood Report. These findings led to the conclusion that the HEC-HMS model is useful as a flood analysis tool.

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Improving assessment of flood inundation of Navsari (India) via open-source data and HEC-RAS model

10.5194/egusphere-egu21-4187 ◽

2021 ◽

Author(s):

Azazkhan Ibrahimkhan Pathan ◽

Dr.Prasit Girishbhai Agnihotri ◽

Dr. Dhruvesh Patel ◽

Dr. Critina Prieto

Keyword(s):

Boundary Condition ◽

Open Source ◽

Coastal Area ◽

Arabian Sea ◽

Flood Event ◽

Flood Inundation ◽

Open Source Data ◽

Source Data ◽

Gauge Station ◽

The City

<p>Flooding seems to be the most widespread and common catastrophe in a tropical country such as India. Efficient rainfall, industrial development, huge population, the effect of the tide, and urban growth are actual reasons for flooding in urban coastal regions. Navsari, the city of Gujarat, located 19 km upstream of the Arabian Sea. The city has experienced a devastating flood on 4rth August 2004. Flash flooding and maximum discharge estimated at the Mahuva gauge station of about 8836 m3/sec were responsible for a disaster that resulted in massive damage to property and lives. A two dimensional (2D) flood simulation model is carried out to assessment of flood inundation in an urban coastal area. HEC-RAS is one of the most popular open-source hydraulic software having 2D capabilities including GIS features. In the present study, the distance between the Mahuva gauge station to the Arabian sea was considered for flood inundation assessment, whereas the SRTM 30 m DEM was used for grid generation for Navsari city. The inflow hydrograph was used as the upstream boundary condition, and normal depth was used as the downstream boundary condition during the 4th August 2004 flood event. The unsteady flow simulation was performed and validated for the year of 2004 flood event. The simulated outcomes show that major areas such as Viraval, Kachiawad, Jalalpore, near Railway station, Kaliawad, Tavdi village, and Near TATA School were flooded with 2-4 m depth. Furthermore, the simulated result demonstrates that, if the discharge exceeds 8836 m3/sec in the area of a floodplain, it may take 11 to 13 hours to make the city inundated. The R<sup>2 </sup>value for the model is 0.9679, which shows that the observed value is the best match with the simulated value. The research study illustrates the accurate flood inundation assessment in the urban coastal area using open-source 2D HEC-RAS model. The present study described the applicability of open-source data and model in flood inundation assessment. The study will fill the gap of flood assessment through 2D HEC-RAS model worldwide areas, which are situated nearby coastal region, accompanied by the benefits of open-source dataset and model.</p>

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Modelling of Flood Inundation due to Levee Breaches: Sensitivity of Flood Inundation against Breach Process Parameters

Water ◽

10.3390/w12123566 ◽

2020 ◽

Vol 12 (12) ◽

pp. 3566

Author(s):

Yohannis Birhanu Tadesse ◽

Peter Fröhle

Keyword(s):

Numerical Model ◽

Process Parameters ◽

Flood Plain ◽

Flood Event ◽

Flood Inundation ◽

Inundation Maps ◽

Levee Breach ◽

Negligible Influence

This paper analyses the sensitivity of flood inundation due to river levee breach against breach process parameters using the 1996 Awash River levee breach case at Wonji, Ethiopia. A parametric levee breach model integrated into the 2D hydrodynamic numerical model Telemac-2D is used to simulate a levee breach flood event at Wonji, Ethiopia. Levee breach process parameters are systemically varied to find out their effect on the flood inundation. The analysis of the model results shows that the flood inundation is sensitive to the final breach dimensions and breach location. However, the parameters describing the levee breach development have negligible influence on the flood inundation. This implies that final breach dimension and breach location in an event of levee breach are the most important and decisive parameters affecting the resulting inundation of the flood plain, and as such should be given due consideration when creating flood inundation maps due to levee breach.

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Application of GIS, Hydraulic and Hydrologic Modelling to Investigate the Changes of Flood Inundation Characteristics due to the Construction of Dams for different scenarios

International Journal of Computational Physics Series ◽

10.29167/a1i2p61-77 ◽

2018 ◽

Vol 1 (2) ◽

pp. 61-77

Author(s):

Hossameldin M. Elhanafy

Keyword(s):

Fluid Mechanics ◽

Flood Control ◽

Reduction Rate ◽

Hydraulic Modeling ◽

Direct Result ◽

Flood Inundation ◽

High Ability ◽

The West ◽

Hydrologic Modelling ◽

New Location

The novelty of the research project reported in this paper is the coupling of hydrological and hydraulic modeling which are based on the first principal of fluid mechanics for the simulation of flash floods at Wadi Elarish watershed to optimize the a new location of another dam rather than Elrawfa dam which already exist. Results show that, the optimum scenario is obtained by the construction of the west dam. As a direct result of this dam, the downstream inundated area can be reduced up to 15.7 % as function of reservoir available storage behind the dam. Furthermore, calculations showed that the reduction rate of inundated area for 50-year floods is largely more than 100-year floods, implies the high ability of west dam on flood control especially for floods with shorter return period.

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