# Flood Mapping from Dam Break Due to Peak Inflow: A Coupled Rainfall–Runoff and Hydraulic Models Approach

^{1}

^{2}

^{*}

## Abstract

**:**

^{2}area will be inundated by a maximum depth of 20 m and for a maximum duration of 46 h. The 200-year inflow will inundate a 240 km

^{2}area with a maximum depth of 31 m for a maximum duration of 93 h. The 2D flood map provides satisfactory spatial and temporal resolution of the inundated area for evaluation of the affected facilities.

## 1. Introduction

#### Study Area

^{3}and a crest length of 685 m. The capacity of the reservoir is estimated at 770 hm

^{3}, of which 360–480 hm

^{3}(47–62%) is assumed to be live storage, and the spillway capacity is about 6180 m

^{3}/s. The dam is located 237 km to the northeast of Addis Ababa at 800 m above sea level.

## 2. Materials and Methods

#### 2.1. Data Acquisition

#### 2.1.1. Land Surface Data

^{2}in the Kesem watershed.

#### 2.1.2. Meteorological and Hydrological Data

#### 2.2. Estimation of the Designed Storm

_{t}= P

_{av}+ K

_{T}σ

_{t}denotes the precipitation depth of the T-year storm event; K

_{T}is the frequency factor; and P

_{av}and σ are the mean and the standard deviation of the annual maximum precipitation, respectively. The frequency factor K

_{T}is expressed as

_{t}/T

_{d}

_{d}is the rainfall duration.

#### 2.3. Hydrologic Modeling (HEC-HMS)

^{2}) is used to describe the degree of correlation between the simulated and measured data. It ranges from −1 to 1, where values close to 1 indicate the least error. The percent bias (PBIAS) measures the tendency of the average value. The Nash–Sutcliffe efficiency (NSE) is a normalized statistic showing the residual variance, where an NSE > 0.5 is considered to indicate a good fit. The mean absolute error (MAE) and root mean square error (RMSE) are absolute measures of fit. The equations that were employed in this study are shown below:

^{3}/s); Si is simulated flow (m

^{3}/s); and Oav and Sav are mean measured and simulated flow (m

^{3}/se), respectively. Afterward, the frequency method was selected to run the HEC-HMS model for specified durations under the inbuilt meteorological model in the HEC-HMS model.

#### 2.4. Hydraulic Modeling (HEC-RAS)

^{2}) for breach width, peak outflow, and breach formation time parameters: 0.68, 0.86, and 0.96, respectively [38]. The prediction equations for the parameters Bav, z, and tf were determined from multiple regression analysis of the assembled data. Logarithmic transformations of all dependent and independent variables were found to provide the best linear relationships [39]. As a result, the Froehlich method was found to be more appropriate for the simulation of the Kesem dam.

#### 2.5. 2-D Flood Mapping

_{w}∆T/∆X ≤ 1 and ∆T ≤ ∆X/V

_{w}

_{w}is the wave speed in feet per second. The flood wave speed can be calculated by

_{w}= dQ/dA

_{2}− Q

_{1}); and dA is the change in cross-sectional area over a short time interval (A

_{2}− A

_{1}).

## 3. Results

#### 3.1. Designed Storm

#### 3.2. Hydrologic Simulation (Flood Hydrograph)

^{3}/s, respectively. The use of hourly peak observed rainfall events for the flood estimation shows a relatively higher flood hydrograph, which increased the estimation accuracy of the Kesem watershed hydrographs.

#### 3.3. Hydraulic Simulation (Flood Mapping)

^{3}. The breach is estimated to begin as triangular and then stretching to reach the bottom of the breach, when the shape changes to trapezoidal. A standardized dam-breach scenario examines a range of possibilities to estimate the expected annual damages, which vary with the volume of water in the reservoir. For general planning purposes, the most useful scenario is the worst-case one in which the dam fails while the reservoir is full [42]. Therefore, in this study, the stored water in the dam and the inflow was routed to the floodplain downstream of the dam. Thus, the flood hazard maps for the 100- and 200-year return periods were generated. Figure 9 represents the model results for the return periods that show dam break and those that remain safe.

## 4. Discussion

## 5. Conclusions

- The use of high-temporal-resolution hydro-meteorological data (i.e., precipitation and streamflow), for flow estimation, and high-spatial-resolution topographic data (i.e., DEM, land use, and soil), for flood inundation mapping, performs well.
- The flood hydrographs produced from event-based runoff estimation by the SCS curve number method displayed suitable results for application to peak storm events.
- The Kesem dam, from the empirical dam break simulations, shows possible failure for the 100- and 200-year return period inflows, whereas the dam remains safe for inflows up to the 50-year return period. This may indicate user-defined breaching, with the HEC-RAS models determining the dam breach time and dimension depending on the breach trigger inputs, such as inflow boundary conditions.
- The 2D flood map provides a satisfactory spatial and temporal resolution result for the inundated area. Furthermore, 2D flood mapping can be used to better understand the flood inundation extent of any type of flood.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

- Cannata, M.; Marzocchi, R. Two-dimensional dam break flooding simulation: A GIS-embedded approach. Nat. Hazards
**2012**, 61, 1143–1159. [Google Scholar] [CrossRef] - Science Engineering & Sustainability. 2019. Dam Break Simulation with HEC-RAS: Chepete Proposed Dam. Available online: https://sciengsustainability.blogspot.com/2019/03/dam-break-simulation-hec-ras.html (accessed on 5 May 2019).
- Koskinas, A.; Tegos, A.; Tsira, P.; Dimitriadis, P.; Iliopoulou, T.; Papanicolaou, P.; Koutsoyiannis, D.; Williamson, T. Insights into the Oroville Dam 2017 Spillway Incident. Geosciences
**2019**, 9, 37. [Google Scholar] [CrossRef] [Green Version] - Rotta, L.H.; Alcantara, E.; Park, E.; Negri, R.G.; Lin, Y.N.; Bernardo, N.; Mendes, T.S.; Souza Filho, C.R. The 2019 Brumadinho tailings dam collapse: Possible cause and impacts of the worst human and environmental disaster in Brazil. Int. J. Appl. Earth Obs. Geoinf.
**2020**, 90, 102119. [Google Scholar] [CrossRef] - Latrubesse, E.M.; Park, E.; Sieh, K.; Dang, T.; Lin, Y.N.; Yun, S.H. Dam failure and a catastrophic flood in the Mekong basin (Bolaven Plateau), southern Laos, 2018. Geomorphology
**2020**, 362, 107221. [Google Scholar] [CrossRef] - Dave, P. Hidroituango: Another Landslide Crisis at a Hydroelectric Dam. The Landslide Blog, AGU. 2018. Available online: https://blogs.agu.org/landslideblog/2018/05/21/hidroituango-1/ (accessed on 5 April 2019).
- Aljazeera News. 2018. Search for Survivors after Deadly Kenya Dam Collapse. Available online: https://www.aljazeera.com/news/2018/05/search-survivors-deadly-kenya-dam-collapse-180511054548148.html (accessed on 5 May 2019).
- Zin, W.W.; Kawasaki, A.; Takeuchi, W.; San, Z.M.L.T.; Htun, K.Z.; Aye, T.H.; Win, S. Flood hazard assessment of Bago River Basin, Myanmar. J. Disaster Res.
**2018**, 13, 14–21. [Google Scholar] [CrossRef] - Mao, J.; Wang, S.; Ni, J.; Xi, C.; Wang, J. Management System for Dam-Break Hazard Mapping in a Complex Basin Environment. ISPRS Int. J. Geo-Inf.
**2017**, 6, 162. [Google Scholar] [CrossRef] [Green Version] - Rodrigues, A.S.; Santos, M.A.; Santos, A.D.; Rocha, F. Dam-break flood emergency management system. Water Resour. Manag.
**2002**, 16, 489–503. [Google Scholar] [CrossRef] - Tsakiris, G.D. Flood risk assessment: Concepts, modelling, applications. Nat. Hazards Earth Syst. Sci.
**2014**, 14, 1361–1369. [Google Scholar] [CrossRef] [Green Version] - Urzică, A.; Mihu-Pintilie, A.; Stoleriu, C.C.; Cîmpianu, C.I.; Huţanu, E.; Pricop, C.I.; Grozavu, A. Using 2D HEC-RAS Modeling and Embankment Dam Break Scenario for Assessing the Flood Control Capacity of a Multi-Reservoir System (NE Romania). Water
**2020**, 13, 57. [Google Scholar] [CrossRef] - Albu, L.-M.; Enea, A.; Iosub, M.; Breabăn, I.-G. Dam Breach Size Comparison for Flood Simulations. A HEC-RAS Based, GIS Approach for Drăcșani Lake, Sitna River, Romania. Water
**2020**, 12, 1090. [Google Scholar] [CrossRef] - Cho, Y. Application of NEXRAD Radar-Based Quantitative Precipitation Estimations for Hydrologic Simulation Using ArcPy and HEC Software. Water
**2020**, 12, 273. [Google Scholar] [CrossRef] [Green Version] - Tahmasbinejad, H.; Feyzolahpour, M.; Mumipour, M.; Zakerhoseini, F. Rainfall-runoff Simulation and Modeling of Karon River Using HEC-RAS and HEC-HMS Models, Izeh District, Iran. J. Appl. Sci.
**2012**, 12, 1900–1908. [Google Scholar] [CrossRef] [Green Version] - Horritt, M.; Bates, P. Evaluation of 1D and 2D numerical models for predicting river flood inundation. J. Hydrol.
**2002**, 268, 87–99. [Google Scholar] [CrossRef] - Jayakrishnan, R.; Srinivasan, R.; Arnold, J. Comparison of raingage and WSR-88D Stage III precipitation data over the Texas-Gulf basin. J. Hydrol.
**2004**, 292, 135–152. [Google Scholar] [CrossRef] - CEIWR-HEC. HEC-RAS, River Analysis System: Hydraulic Reference Manual; US Army Corps of Engineers Hydrologic Engineering Center: Davis, CA, USA, 2016. [Google Scholar]
- Bhandari, M.; Nyaupane, N.; Mote, S.R.; Kalra, A.; Ahmad, S. 2D Unsteady Flow Routing and Flood Inundation Mapping for Lower Region of Brazos River Watershed. In World Environmental and Water Resources Congress 2017; Digital Scholarship@UNLV: Sacramento, CA, USA, 2017; pp. 292–303. [Google Scholar] [CrossRef]
- Brunner, M.I.; Seibert, J.; Favre, A. Bivariate return periods and their importance for flood peak and volume estimation. Wiley Interdiscip. Rev. Water
**2016**, 3, 819–833. [Google Scholar] [CrossRef] [Green Version] - Yang, Z.; Chen, W.-P. Earthquakes along the East African Rift System: A multiscale, system-wide perspective. J. Geophys. Res. Solid Earth
**2010**, 115. [Google Scholar] [CrossRef] - Ayele, A.; Ebinger, C.J.; van Alstyne, C.; Keir, D.; Nixon, C.W.; Belachew, M.; Hammond, J.O.S. Seismicity of the central Afar rift and implications for Tendaho dam hazards. Geol. Soc. Lond. Spéc. Publ.
**2016**, 420, 341–354. [Google Scholar] [CrossRef] [Green Version] - Yared, M.G.; Nigussie, T.; Yohannis, B.T. Dam Breach Modeling and Flood Inundation Mapping a Case Study on Kesem Dam. ACADEMIA. 2016. Available online: https://www.academia.edu/27150269/Dam_Breach_Modelling_and_Flood_Inundation_Mapping_A_Case_Study_on_Kesem_Dam (accessed on 5 May 2019).
- CEIWR-HEC; HEC-HMS. Hydrological Modeling System: Application Guide; US Army Corps of Engineers Hydrologic Engineering Center: Davis, CA, USA, 2017; pp. 3.1–3.19. [Google Scholar]
- MoWIE, Kesem Kebena Dam and Irrigation Project Final Feasibility study and Dam Design Report. Available online: http://www.fao.org/3/ar867e/ar867e.pdf (accessed on 12 April 2019).
- Ross, C.W.; Prihodko, L.; Anchang, J.; Kumar, S.; Ji, W.J.; Hanan, N.P. HYSOGs250m, global gridded hydrologic soil groups for curve-number-based runoff modeling. Sci. Data
**2018**, 5, 180091. [Google Scholar] [CrossRef] [PubMed] - USDA NRCS. Urban Hydrology for Small Watersheds; US Dept. of Agriculture, Soil Conservation Service, Engineering Division: Washington, DC, USA, 1986.
- National Catalog Service for Geographic Information. Globeland30. Available online: http://www.webmap.cn/main.do?method=index (accessed on 3 February 2019).
- Subyani, A.M. Hydrologic behavior and flood probability for selected arid basins in Makkah area, western Saudi Arabia. Arab. J. Geosci.
**2011**, 4, 817–824. [Google Scholar] [CrossRef] - CEIWR-HEC. Hydrologic Modeling System HEC-HMS, Technical Reference Manual; U.S. Army Corps of Engineers, Hydrologic Engineering Center (HEC): Davis, CA, USA, 2000. [Google Scholar]
- Maidment, D.R.; Morehouse, S. Arc Hydro: GIS for Water Resources; ESRI, Inc.: Redlands, CA, USA, 2002. [Google Scholar]
- CEIWR-HEC; HEC-GeoHMS. Geospatial Hydrologic Modeling Extension: Hydraulic Reference Manual; US Army Corps of Engineers Hydrologic Engineering Center: Davis, CA, USA, 2013. [Google Scholar]
- Getahun, Y.S.; Gebre, S.L. Flood hazard assessment and mapping of flood inundation area of the Awash River basin in Ethiopia using GIS and HEC-GeoRAS/HEC-RAS model. J. Civ. Environ. Eng.
**2015**, 5, 1. [Google Scholar] [CrossRef] - Behailu, S. Stream Flow Simulation for the Upper Awash Basin. Ph.D. Thesis, Faculty of Technology Department of Civil Engineering, Addis Ababa University, Addis Ababa, Ethiopia, 2004. [Google Scholar]
- Kisi, O.; Shiri, J.; Tombul, M. Modeling rainfall-runoff process using soft computing techniques. Comput. Geosci.
**2013**, 51, 108–117. [Google Scholar] [CrossRef] - CEIWR-HEC; HEC-GeoRAS. GIS Tools for Support of HEC-RAS Using ArcGIS. [Online] Version 4.3.93; US Army Corps of Engineers, Institute of water Resources: Davis, CA, USA, 2011. [Google Scholar]
- Froehlich, D.C. Embankment Dam Breach Parameters and Their Uncertainties. J. Hydraul. Eng.
**2008**, 134, 1708–1721. [Google Scholar] [CrossRef] - Wahl, T. Evaluation of Erodibility-Based Embankment Dam Breach Equations (Hydraulic Laboratory Report HL-2014-02); US Department of the Interior Bureau of Reclamation: Denver, CO, USA, 2014; p. 99.
- Thornton, C.I.; Pierce, M.W.; Abt, S.R. Enhanced Predictions for Peak Outflow from Breached Embankment Dams. J. Hydrol. Eng.
**2011**, 16, 81–88. [Google Scholar] [CrossRef] - Yu, D.; Lane, S.N. Urban fluvial flood modelling using a two-dimensional diffusion-wave treatment, part 1: Mesh resolution effects. Hydrol. Process.
**2005**, 20, 1541–1565. [Google Scholar] [CrossRef] - Chow, V.T. Open-Channel Hydraulics; McGraw-Hill Civil Engineering Series; McGraw-Hill Book Company Inc.: New York, NY, USA, 1959. [Google Scholar]
- Michaud, J.; Johnson, C.; Iokepa, J.; Marohnic, J. Methods for Estimating the Impact of Hypothetical Dam Break Floods. In Chemistry for the Protection of the Environment; Springer: Boston, MA, USA, 2005; pp. 195–199. [Google Scholar] [CrossRef]
- Onyutha, C.; Tabari, H.; Taye, M.T.; Nyandwaro, G.N.; Willems, P. Analyses of rainfall trends in the Nile River Basin. J. Hydro-Environ. Res.
**2016**, 13, 36–51. [Google Scholar] [CrossRef] - Basheer, T.A.; Wayayok, A.; Yusuf, B.; Kamal, M. Dam Breach parameters and their influence on flood hydrographs for Mosul Dam. J. Eng. Sci. Technol.
**2017**, 12, 2896–2908. [Google Scholar] - Awal, R.; Nakagawa, H.; Kawaike, K.; Baba, Y.; Zhang, H. Experimental study on piping failure of natural dam. J. Jpn. Soc. Civ. Eng. Ser. B1 Hydraul. Eng.
**2011**, 67, I_157–I_162. [Google Scholar] [CrossRef] [Green Version] - Psomiadis, E.; Tomanis, L.; Kavvadias, A.; Soulis, K.; Charizopoulos, N.; Michas, S. Potential Dam Breach Analysis and Flood Wave Risk Assessment Using HEC-RAS and Remote Sensing Data: A Multicriteria Approach. Water
**2021**, 13, 364. [Google Scholar] [CrossRef] - Wu, M.; Ge, W.; Li, Z.; Wu, Z.; Zhang, H.; Li, J.; Pan, Y. Improved Set Pair Analysis and Its Application to Environmental Impact Evaluation of Dam Break. Water
**2019**, 11, 821. [Google Scholar] [CrossRef] [Green Version]

**Figure 1.**Locations and characteristics of the study area: (

**a**) Ethiopian river basins and the Kesem watershed in the Awash river basin; (

**b**) elevation, Hydro-Met observation stations, and Kesem dam location; (

**c**) hydrologic soil group; and (

**d**) land-use map of the Kesem watershed.

**Figure 5.**Depth duration frequency (DDF) for the Kesem watershed with rainfall estimation of seven return periods.

**Figure 7.**Model calibration and validation results: hydrographs of storm events after calibration in (

**a**) 2012, (

**b**) 2013, and (

**c**) 2016; and validation in (

**d**) 2014 and (

**e**) 2015.

**Figure 9.**Hydraulic model outputs of inundation areas for various return periods: (

**a**) the main infrastructure and flooded area locations; and the (

**b**) 50-year, (

**c**) 100-year, and (

**d**) 200-year return periods.

**Figure 10.**Maximum velocity of flood flow from the dam in the cases of (

**a**) 100-year and (

**b**) 200-year return period inflows.

Land Use | Contents | Area (km^{2}) |
---|---|---|

Agriculture | Land used for agriculture, horticulture and gardens | 2242.7 |

Bare land | Land covered by natural grass, shrubs and with vegetation less than 10% | 1095.9 |

Forest | Land covered with trees, with vegetation cover over 30% | 148.8 |

Built-up | Lands modified by human activities | 11.1 |

Water | Water bodies in the land area | 1.4 |

Type | Name | Latitude (Decimal Degrees) | Longitude (Decimal Degrees) | Period (Years) |
---|---|---|---|---|

Precipitation | Addis Ababa | 9.02 | 38.77 | 2012–2018 |

Precipitation | Metehara | 8.86 | 39.92 | 2012–2018 |

Precipitation | Debre Birhan | 9.63 | 39.50 | 2012–2018 |

Stream flow | Kesem Arerti | 9.04 | 39.56 | 2012–2018 |

Type | Storm Event Period | NSE | MAE | RMSE | R^{2} | PBIAS |
---|---|---|---|---|---|---|

Calibration | 16–19 August 2012 | 0.81 | 75.45 | 117.63 | 0.90 | 22.36 |

22–24 August 2013 | 0.50 | 66.51 | 130.25 | 0.66 | −20.34 | |

22–24 August 2016 | −0.30 | 109.79 | 179.80 | 0.21 | −39.74 | |

Validation | 7–9 August 2014 | 0.61 | 21.19 | 86.51 | 0.64 | −9.01 |

18–20 August 2015 | 0.75 | 94.92 | 171.33 | 0.86 | 35.24 |

Return Period | Inundation Area (km^{2}) | Depth (m) | Duration (h) | ||
---|---|---|---|---|---|

Maximum | Mean | Maximum | Mean | ||

100 years | 208 | 20.06 | 2.04 | 46 | 10 |

200 years | 240 | 31.20 | 2.84 | 93 | 39 |

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**MDPI and ACS Style**

Tedla, M.G.; Cho, Y.; Jun, K.
Flood Mapping from Dam Break Due to Peak Inflow: A Coupled Rainfall–Runoff and Hydraulic Models Approach. *Hydrology* **2021**, *8*, 89.
https://doi.org/10.3390/hydrology8020089

**AMA Style**

Tedla MG, Cho Y, Jun K.
Flood Mapping from Dam Break Due to Peak Inflow: A Coupled Rainfall–Runoff and Hydraulic Models Approach. *Hydrology*. 2021; 8(2):89.
https://doi.org/10.3390/hydrology8020089

**Chicago/Turabian Style**

Tedla, Mihretab G., Younghyun Cho, and Kyungsoo Jun.
2021. "Flood Mapping from Dam Break Due to Peak Inflow: A Coupled Rainfall–Runoff and Hydraulic Models Approach" *Hydrology* 8, no. 2: 89.
https://doi.org/10.3390/hydrology8020089