# A Numerical Framework for Evaluating Flood Inundation Hazard under Different Dam Operation Scenarios—A Case Study in Naugatuck River

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Study Area

#### 2.2. Data

#### 2.2.1. LIDAR Terrain Elevation Data

#### 2.2.2. NLDAS Reanalysis Forcing Data

#### 2.3. Methodology: Flood Vulnerability Framework

#### 2.3.1. Hydrological Simulation

#### 2.3.2. Flood Frequency Analysis

#### Adjustment Technique for Flood Frequency Estimation

#### LPIII Method

#### 2.3.3. Constructing Synthetic Hydrograph

^{3}/s (~1-year return period) were considered. This method was used to construct synthetic hydrographs for flood events at 50-, 100-, 200-, and 500-year return periods used as upstream boundary conditions in river reaches “U” and “D”. The same procedure is conducted for both upstream and downstream except that no observation is available for the flow contributed by the downstream part alone. Therefore, the timing structure is retrieved from simulated flow contributed by the downstream drainage area alone. The constructed synthetic hydrographs are finally inputted to HEC-RAS to simulate inundation.

#### 2.3.4. Hydraulic Simulation

## 3. Results

#### 3.1. Validation of Stream Flow Simulations

_{m}is the total measured volume and V

_{obs}is the total observed volume.

#### 3.2. Validation of Hydraulic Simulations

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References and Notes

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**Figure 1.**(

**a**) The Naugatuck River Basin, (

**b**) the subdivision of the Naugatuck River Basin, (

**c**) satellite imagery of critical infrastructure in Waterbury, Connecticut.

**Figure 3.**Deriving median durations for each exceedance percentile to determine median hydrograph shape.

**Figure 4.**Upstream river reach “U” and downstream river reach “D” modeled in the HEC-RAS domain displayed over LIDAR derived DEM.

**Figure 5.**The Coupled Routing and Excess Storage–Soil–Vegetation–Atmosphere–Snow (CREST-SVAS) daily streamflow validation against observation for Naugatuck River Basin at the inlet of Thomaston Dam.

**Figure 6.**Model simulated gate discharge validated against Thomaston Dam posted ratings curves. Line A represents the intersection between the maximum flood stage (22.76 m or 74.67 ft) and the rating curve for one gate that is 3 ft open. Line B represents the intersection between the maximum flood stage and the rating curve for one gate that is 5 ft open.

**Figure 7.**Model simulated dam output streamflow validated against observations from USGS station (01206900) Naugatuck River at Thomaston, CT, USA.

**Figure 12.**Simulated maximum water depth (meter) at critical infrastructure “A” and “B” for the various flooding and dam operation scenarios examined.

Dam Peak Streamflow Contribution (cms) | ||
---|---|---|

Flooding Scenario | Half Open Gates | Fully Open Gates |

50 Year | ||

Empty Reservoir | 649.3 (9.94%) | 704.8 (16.90%) |

Half Filled Reservoir | 661.7 (11.52%) | 732.3 (20.07%) |

No Dam | 969.4 (66.89%) | |

100 Year | ||

Empty Reservoir | 722.5 (9.20%) | 780.4 (15.78%) |

Half Filled Reservoir | 734.0 (10.52%) | 805.7 (18.45%) |

No Dam | 1088.1 (66.86%) | |

200 Year | ||

Empty Reservoir | 797.6 (8.56%) | 857.7 (14.80%) |

Half Filled Reservoir | 808.4 (9.67%) | 881.1 (17.07%) |

No Dam | 1210.5 (66.83%) | |

500 Year | ||

Empty Reservoir | 900.8 (7.83%) | 963.5 (13.68%) |

Half Filled Reservoir | 910.7 (8.73%) | 984.7 (15.52%) |

No Dam | 1379.2 (66.78%) |

Return Period | Dam Operation | Reservoir Level | Results |
---|---|---|---|

50 years | No Dam | N/A | 24 FLOOD INUNDATION MAPS |

Closed Dam | |||

Half Open Gates | Both: Empty and Half Filled | ||

Fully Open Gates | |||

100 years | No Dam | N/A | |

Closed Dam | |||

Half Open Gates | Both: Empty and Half Filled | ||

Fully Open Gates | |||

200 years | No Dam | N/A | |

Closed Dam | |||

Half Open Gates | Both: Empty and Half Filled | ||

Fully Open Gates | |||

500 years | No Dam | N/A | |

Closed Dam | |||

Half Open Gates | Both: Empty and Half Filled | ||

Fully Open Gates |

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**MDPI and ACS Style**

Hardesty, S.; Shen, X.; Nikolopoulos, E.; Anagnostou, E.
A Numerical Framework for Evaluating Flood Inundation Hazard under Different Dam Operation Scenarios—A Case Study in Naugatuck River. *Water* **2018**, *10*, 1798.
https://doi.org/10.3390/w10121798

**AMA Style**

Hardesty S, Shen X, Nikolopoulos E, Anagnostou E.
A Numerical Framework for Evaluating Flood Inundation Hazard under Different Dam Operation Scenarios—A Case Study in Naugatuck River. *Water*. 2018; 10(12):1798.
https://doi.org/10.3390/w10121798

**Chicago/Turabian Style**

Hardesty, Sage, Xinyi Shen, Efthymios Nikolopoulos, and Emmanouil Anagnostou.
2018. "A Numerical Framework for Evaluating Flood Inundation Hazard under Different Dam Operation Scenarios—A Case Study in Naugatuck River" *Water* 10, no. 12: 1798.
https://doi.org/10.3390/w10121798