scholarly journals Baur dam breach analysis using various manning’s roughness values

2020 ◽  
Vol 4 (6) ◽  
pp. 293-297
Author(s):  
Jyothi Prasad
Keyword(s):  
High Impact ◽  
Agricultural Area ◽  
Flood Mapping ◽  
Command Area ◽  
Dam Breach ◽  
Inundation Maps ◽  
Modelling Procedure ◽  
Breach Parameters ◽  
Analysis System

This paper describes the importance of flood mapping in terms of saving downstream agricultural area. Flood can cause high impact on the nearby crops productivity which further affects the country’s economy. The Baur dam has a Culturable Command Area of 31453,6572 hectares. It’s key focus is on describing the importance of Manning’s roughness value in dam breach modelling and shows it’s bad impact on downstream areas of dam. In this work hypothetical breach modelling of Baur dam is performed by using Hydrologic Engineer’s Centre- River Analysis System (HEC-RAS). Details about study area, breach parameters, modelling procedure, and outflow flood values are also described in this paper. Flow hydrographs are plotted at different Manning’s roughness value for the two populated downstream areas of dam and it has been observed from results that as roughness value increases flow decreases which justifies Manning’s theory. As a Final result Inundation maps are plotted with the detail of inundated area values for different Manning’s values so that the effect of roughness can be analysed numerically on study area. The Manning’s roughness value of 0.030 causes 37.75km2 inundated area in the downstream of dam.1

Exploring Sentinel-1 and Sentinel-2 diversity for Flood inundation mapping using deep learning

2021 ◽  
Author(s):  
Goutam Konapala ◽  
Sujay Kumar
Keyword(s):  
Flood Mapping ◽  
Attractive Alternative ◽  
Flood Inundation ◽  
Positive Role ◽  
Inundation Maps ◽  
Flood Inundation Mapping ◽  
Sar Imagery ◽  
Operational Errors ◽  
Water Indices ◽  
Sentinel 2

<p>Identification of flood water extent from satellite images has historically relied on either synthetic aperture radar (SAR) or multi-spectral (MS) imagery. But MS sensors may not penetrate cloud cover, whereas SAR is plagued by operational errors such as noise-like speckle challenging their viability to global flood mapping applications. An attractive alternative is to effectively combine MS data and SAR, i.e., two aspects that can be considered complementary with respect to flood mapping tasks. Therefore, in this study, we explore the diverse bands of Sentinel 2 (S2) derived water indices and Sentinel 1 (S1) derived SAR imagery along with their combinations to access their capability in generating accurate flood inundation maps. For this purpose, a fully connected deep convolutional neural network known as U-Net is applied to combinations of S1 and S2 bands to 446 (training: 313, validating: 44, testing: 89) hand labeled flood inundation extents derived from Sen1Floods11 dataset spanning across 11 flood events. The trained U-net was able to achieve a median F1 score of 0.74 when using DEM and S1 bands as input in comparison to 0.63 when using only S1 bands highlighting the active positive role of DEM in mapping floods. Among the, S2 bands, HSV (Hue, Saturation, Value) transformation of Sentinel 2 data has achieved a median F1 score of 0.94 outperforming the commonly used water spectral indices owing to HSV’s transformation’s superior contrast distinguishing abilities. Also, when combined with Sentinel 1 SAR imagery too, HSV achieves a median F1 score 0.95 outperforming all the well-established water indices in detecting floods in majority of test images.</p>

scholarly journals An integrated evaluation of the National Water Model (NWM)–Height Above Nearest Drainage (HAND) flood mapping methodology

2019 ◽  
Vol 19 (11) ◽  
pp. 2405-2420 ◽  
Author(s):  
J. Michael Johnson ◽  
Dinuke Munasinghe ◽  
Damilola Eyelade ◽  
Sagy Cohen
Keyword(s):  
Absolute Error ◽  
Low Complexity ◽  
Water Model ◽  
Flood Mapping ◽  
Roughness Coefficient ◽  
University Of Texas ◽  
Inundation Maps ◽  
Elevation Data ◽  
High Level ◽  
National Water

Abstract. Flood maps are needed for emergency response, research, and planning. The Height Above Nearest Drainage (HAND) technique is a low-complexity, terrain-based approach for inundation mapping using elevation data, discharge–height relationships, and streamflow inputs. The recent operational capacities of the NOAA National Water Model (NWM) and preprocessed HAND products from the University of Texas offer an operational framework for real-time and forecast flood guidance across the US. In this study, we evaluate the integrated National Water Model –Height Above Nearest Drainage (NWM–HAND) flood mapping approach using 28 remotely sensed inundation maps and 54 reach-level catchments. The results show the NWM–HAND method tends to underpredict inundated cells in 4th-order and lower-order reaches but does better with a slight tendency to overpredict in high-order reaches. An evaluation of the roughness coefficient used in the production of synthetic rating curves suggests it is the most important parameter for correcting these errors. Persistent inaccuracies do occur when NWM streamflow predictions are substantially biased (>60 % mean absolute error between NWM and observed streamflow) and in regions of low relief. Overall, the NWM–HAND method does not accurately capture inundated cells but is quite capable of highlighting regions likely to be at risk in 4th-order streams and higher. While NWM–HAND should be used with caution when identifying flood boundaries or making decisions of whether a cell is dry or wet, its applicability as a high-level guidance tool along larger rivers is noteworthy.

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

Hydrology ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 89
Author(s):  
Mihretab G. Tedla ◽  
Younghyun Cho ◽  
Kyungsoo Jun
Keyword(s):  
Land Surface ◽  
Meteorological Data ◽  
Dam Break ◽  
Maximum Depth ◽  
Dam Failure ◽  
Flood Mapping ◽  
Return Periods ◽  
Maximum Duration ◽  
Analysis System

In this study, we conducted flood mapping of a hypothetical dam break by coupling the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) models under different return periods of flood inflow. This study is presented as a case study on the Kesem embankment dam in Ethiopia. Hourly hydrological and meteorological data and high-resolution land surface datasets were used to simulate the design floods for piping dam failure with empirical dam breach methods. Based on the extreme inflows and the dam physical characteristics, the dam failure was simulated by a two-dimensional, unsteady flow hydrodynamic model. As a result, the dam will remain safe for up to 50-year return-period inflows, but it breaks for 100- and 200-year return periods and floods the downstream area. For the 100-year peak inflow, a 208 km2 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 km2 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.

scholarly journals GIS derived synthetic rating curves and HAND model to support on-the-fly flood mapping

2021 ◽  
Author(s):  
Blair William Gerald Scriven ◽  
Heather McGrath ◽  
Emmanuel Stefanakis
Keyword(s):  
Water Level ◽  
Cost Effective ◽  
Flood Mapping ◽  
Roughness Coefficient ◽  
Inundation Maps ◽  
Hand Model ◽  
Cost Effective Method ◽  
Rating Curves ◽  
Land Covers ◽  
Many Sources

AbstractA timely and cost-effective method of creating inundation maps could assist first responders in allocating resources and personnel in the event of a flood or in preparation of a future disaster. The Height Above Nearest Drainage (HAND) model could be implemented into an on-the-fly flood mapping application for a Canada-wide service. The HAND model requires water level (m) data inputs while many sources of hydrological data in Canada only provide discharge (m3/sec) data. Synthetic rating curves (SRCs), created using river geometry/characteristics and the Manning’s formula, could be utilized to provide an approximate water level given a discharge input. A challenge with creating SRCs includes representing how multiple different land covers will slow impact flow due to texture and bulky features (i.e., smooth asphalt versus rocky river channel); this relates to the roughness coefficient (n). In our study, two methods of representing multiple n values were experimented with (a weighted method and a minimum-median method) and were compared to using a fixed n method. A custom ArcGIS tool, Canadian Estimator of Ratings Curves using HAND and Discharge (CERC-HAND-D), was developed to create SRCs using all three methods. Control data were sourced from gauge stations across Canada in the form of rating curves. Results indicate that in areas with medium to medium–high river gradients (S > 0.002 m/m) or with river reaches under 5 km, the CERC-HAND-D tool creates more accurate SRCs (NRMSE = 3.7–8.8%, Percent Bias = −7.8%—9.4%), with the minimum-median method being the preferred n method.

scholarly journals Flood Assessment and Identification of Emergency Evacuation Routes in Seti River Basin, Nepal

Land ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 82
Author(s):  
Bhabana Thapa ◽  
Teiji Watanabe ◽  
Dhananjay Regmi
Keyword(s):  
River Basin ◽  
Low Income ◽  
Land Use Planning ◽  
Emergency Evacuation ◽  
Inundation Maps ◽  
Flooding Hazards ◽  
And Migration ◽  
Analysis System ◽  
Evacuation Routes ◽  
Evacuation Route

Sudden floods frequently occur in the Himalayas under changing climates. Rapid glacial melt has resulted in the formation of glacial lakes and associated hazards. This research aimed to (1) identify flood-prone houses, (2) determine pedestrian emergency evacuation routes, and (3) analyze their relationships to socioeconomic status in the Seti River Basin. Detailed hazard maps were created using field survey results from unmanned aerial vehicle photogrammetry and the Hydrologic Engineering Center River Analysis System. Questionnaire, focus-group, and key-informant surveys helped identify the socioeconomic situation. Inundation maps revealed that most residents are exposed to future flooding hazards without proper evacuation routes. Highly impoverished and immigrant households were at the highest risk in terms of income inequality and migration rate (p < 0.001) and were located on the riverside. The locations of 455 laborers’ houses were significantly correlated with inundation hazards (p < 0.001). Governmental and associated agencies must develop adequate plans to relocate low-income households. Group discussions revealed the need for stronger adaptive capacity-building strategies for future risk management. Pokhara requires better systematic and scientific land-use planning strategies to address this issue efficiently. A similar approach that combines flood modeling, proper evacuation route access, and socioeconomic survey is suggested for this river basin.

scholarly journals Anticipating of Potential Climate and Land Use Change Impacts on Floods: A Case Study of the Lower Nam Phong River Basin

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1158 ◽  
Author(s):  
Kittiwet Kuntiyawichai ◽  
Winai Sri-Amporn ◽  
Sarayut Wongsasri ◽  
Prinya Chindaprasirt
Keyword(s):  
Land Use ◽  
River Basin ◽  
Climate Models ◽  
Land Use Changes ◽  
Flood Damage ◽  
Mitigation Strategies ◽  
Inundation Maps ◽  
Rcp 8.5 ◽  
Analysis System

This study aimed at quantifying the impacts of climate and land use changes on flood damage on different flood occurrences. A Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) model was calibrated for the period 2005–2011 and validated in the period 2012–2017, and was used to generate hydrographs using rainfall during the period 2020–2039 from CNRM-CM5, IPSL-CM5A-MR, and MPI-ESM-LR climate models under Representative Concentration Pathways (RCPs) 4.5 and 8.5. A Hydrologic Engineering Center’s River Analysis System (HEC-RAS) model for use in generating inundation maps from hydrographs produced by HEC-HMS was calibrated and validated for 2010 and 2011 period, respectively. The climate and land use changes showed insignificant impacts on the extent of floods during 25-, 50-, and 100-year flood events, i.e., inundation in 2039 under RCP 4.5 is smaller than baseline (2000–2017) by 4.97–8.59 km2, whereas a larger difference of inundation is found for RCP 8.5 (0.39–5.30 km2). In contrast, the flood damage under RCP 4.5 (14.84–18.02 million US$) is higher than the baseline by 4.32–5.33 million US$, while the highest was found for RCP 8.5 (16.24–18.67 million US$). The agriculture was the most vulnerable, with a damage of 4.50–5.44 million US$ in RCP 4.5 and 4.94–5.72 million US$ in RCP 8.5, whereas baseline damages were 4.49–6.09 million US$. Finally, the findings are useful in the delivery of flood mitigation strategies to minimize flood risks in the lower Nam Phong River Basin.

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