Maximizing Multi‐Decadal Water Surface Elevation Estimates with Landsat Imagery and Elevation/Bathymetry Datasets

Understanding flood probabilities is essential to making sound decisions about flood-risk management. Many people rely on flood probability maps to inform decisions about purchasing flood insurance, buying or selling real-estate, flood-proofing a house, or managing floodplain development. Current flood probability maps typically use flood zones (for example the 1 in 100 or 1 in 500-year flood zones) to communicate flooding probabilities. However, this choice of communication format can miss important details and lead to biased risk assessments. Here we develop, test, and demonstrate the FLOod Probability Interpolation Tool (FLOPIT). FLOPIT interpolates flood probabilities between water surface elevation to produce continuous flood-probability maps. FLOPIT uses water surface elevation inundation maps for at least two return periods and creates Annual Exceedance Probability (AEP) as well as inundation maps for new return levels. Potential advantages of FLOPIT include being open-source, relatively easy to implement, capable of creating inundation maps from agencies other than FEMA, and applicable to locations where FEMA published flood inundation maps but not flood probability. Using publicly available data from the Federal Emergency Management Agency (FEMA) flood risk databases as well as state and national datasets, we produce continuous flood-probability maps at three example locations in the United States: Houston (TX), Muncy (PA), and Selinsgrove (PA). We find that the discrete flood zones generally communicate substantially lower flood probabilities than the continuous estimates.

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Morphodynamic stability and characteristic length scales of bifurcations and confluences loops

10.5194/egusphere-egu21-8017 ◽

2021 ◽

Author(s):

Niccolò Ragno ◽

Marco Redolfi ◽

Marco Tubino

Keyword(s):

Froude Number ◽

Water Surface ◽

Characteristic Length ◽

Coupled Model ◽

Surface Elevation ◽

Momentum Balance ◽

Water Surface Elevation ◽

Control Volumes ◽

Almost All ◽

Fluvial Environments

<p>The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.</p>

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Effects of the Oscillating Water Channel Length on the Water Surface Elevation within Seawater Exchange Breakwater

Ocean and Polar Research ◽

10.4217/opr.2003.25.spc3.423 ◽

2003 ◽

Vol 25 (spc3) ◽

pp. 423-426

Author(s):

Dal-Soo Lee ◽

Young-Min Oh ◽

In-Sik Chun ◽

Chang-Il Kim

Keyword(s):

Water Surface ◽

Water Channel ◽

Channel Length ◽

Surface Elevation ◽

Water Surface Elevation ◽

Seawater Exchange

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standing water (surface) elevation

Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik ◽

10.1007/978-3-642-41714-6_196700 ◽

2014 ◽

pp. 1298-1298

Keyword(s):

Water Surface ◽

Surface Elevation ◽

Water Surface Elevation ◽

Standing Water

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Study on Backwater Effect Due to Polavaram Dam Project under Different Return Periods

Water ◽

10.3390/w12020576 ◽

2020 ◽

Vol 12 (2) ◽

pp. 576 ◽

Cited By ~ 1

Author(s):

Amarnath C R ◽

Shashidhar Thatikonda

Keyword(s):

Unsteady Flow ◽

Water Surface ◽

Water Levels ◽

Surface Elevation ◽

Flood Frequency Analysis ◽

Discharge Data ◽

Gate Operation ◽

Water Surface Elevation ◽

Flow Simulations ◽

Flood Discharge

In this study, we present a scenario to evaluate the backwater impacts on upstream of the Polavaram dam during floods. For this purpose, annual peak discharges across the different gauge stations in river stretch considered for flood frequency analysis. Statistical analysis is carried out for discharge data to estimate probable flood discharge values for 1000 and 10,000 years return period along with 0.1 and 0.14 million m3/s discharge. Furthermore, the resulting flood discharge values are converted to water level forecasts using a steady and unsteady flow hydraulic model, such as HEC-RAS. The water surface elevation at Bhadrachalam river stations with and without dam was estimated for 1000 and 10,000 years discharge. Unsteady 2D flow simulations with and without the dam with full closure and partial closure modes of gate operation were analysed. The results showed that with half of the gates as open and all gates closed, water surface elevation of 62.34 m and 72.34 m was obtained at Bhadrachalam for 1000 and 10,000 years. The 2D unsteady flow simulations revealed that at improper gate operations, even with a flow of 0.1 million m3/s, water levels at Bhadrachalam town will be high enough to submerge built-up areas and nearby villages.

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Case Study of Transient Dynamics in a Bypass Reach

Water ◽

10.3390/w12061585 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1585

Author(s):

Anton J. Burman ◽

Anders G. Andersson ◽

J. Gunnar I. Hellström ◽

Kristian Angele

Keyword(s):

Water Surface ◽

Operating Conditions ◽

Surface Elevation ◽

Water Surface Elevation ◽

Positive Effects ◽

Downstream Distance ◽

Hydropower Plants ◽

Wetted Area ◽

Bed Stability

The operating conditions of Nordic hydropower plants are expected to change in the coming years to work more in conjunction with intermittent power production, causing more frequent hydropeaking events. Hydropeaking has been shown to be detrimental to wildlife in the river reaches downstream of hydropower plants. In this work, we investigate how different possible future hydropeaking scenarios affect the water surface elevation dynamics in a bypass reach in the Ume River in northern Sweden. The river dynamics has been modeled using the open-source solver Delft3D. The numerical model was validated and calibrated with water-surface-elevation measurements. A hysteresis effect on the water surface elevation, varying with the downstream distance from the spillways, was seen in both the simulated and the measured data. Increasing the hydropeaking rate is shown to dampen the variation in water surface elevation and wetted area in the most downstream parts of the reach, which could have positive effects on habitat and bed stability compared to slower rates in that region.

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Experimental Study of a Moored Floating Oscillating Water Column Wave-Energy Converter and of a Moored Cubic Box

Energies ◽

10.3390/en12101834 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1834 ◽

Cited By ~ 3

Author(s):

Minghao Wu ◽

Vasiliki Stratigaki ◽

Peter Troch ◽

Corrado Altomare ◽

Tim Verbrugghe ◽

...

Keyword(s):

Water Column ◽

Wave Energy ◽

Water Surface ◽

Wave Energy Converter ◽

Surface Elevation ◽

Mooring Line ◽

Oscillating Water Column ◽

Energy Converter ◽

Large Wave ◽

Water Surface Elevation

This paper describes experimental research on a floating moored Oscillating Water Column (OWC)-type Wave-Energy Converter (WEC) carried out in the wave flume of the Coastal Engineering Research Group of Ghent University. This research has been introduced to cover the existing data scarcity and knowledge gaps regarding response of moored floating OWC WECs. The obtained data will be available in the future for the validation of nonlinear numerical models. The experiment focuses on the assessment of the nonlinear motion and mooring-line response of a 1:25 floating moored OWC WEC model to regular waves. The OWC WEC model motion has 6 degrees of freedom and is limited by a symmetrical 4-point mooring system. The model is composed of a chamber with an orifice on top of it to simulate the power-take-off (PTO) system and the associated damping of the motion of the OWC WEC model. In the first place, the motion response in waves of the moored floating OWC WEC model is investigated and the water surface elevation in the OWC WEC chamber is measured. Secondly, two different mooring-line materials (iron chains and nylon ropes) are tested and the corresponding OWC WEC model motions and mooring-line tensions are measured. The performance of these two materials is similar in small-amplitude waves but different in large wave-amplitude conditions. Thirdly, the influence of different PTO conditions is investigated by varying the diameter of the top orifice of the OWC WEC model. The results show that the PTO damping does not affect the OWC WEC motion but has an impact on the water surface elevation inside the OWC chamber. In addition, an unbalanced mooring configuration is discussed. Finally, the obtained data for a moored cubic model in waves are presented, which is a benchmarking case for future validation purposes.

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Calibrating 1D hydrodynamic river models in the absence of cross-section geometry using satellite observations of water surface elevation and river width

Hydrology and Earth System Sciences ◽

10.5194/hess-25-6359-2021 ◽

2021 ◽

Vol 25 (12) ◽

pp. 6359-6379

Author(s):

Liguang Jiang ◽

Silja Westphal Christensen ◽

Peter Bauer-Gottwein

Keyword(s):

Cross Section ◽

Water Surface ◽

Power Laws ◽

Satellite Observations ◽

Surface Elevation ◽

Flow Area ◽

Water Surface Elevation ◽

Hydraulic Roughness ◽

River Models ◽

Cross Section Geometry

Abstract. Hydrodynamic modeling has been increasingly used to simulate water surface elevation which is important for flood prediction and risk assessment. Scarcity and inaccessibility of in situ bathymetric information have hindered hydrodynamic model development at continental-to-global scales. Therefore, river cross-section geometry is commonly approximated by highly simplified generic shapes. Hydrodynamic river models require both bed geometry and roughness as input parameters. Simultaneous calibration of shape parameters and roughness is difficult, because often there are trade-offs between them. Instead of parameterizing cross-section geometry and hydraulic roughness separately, this study introduces a parameterization of 1D hydrodynamic models by combining cross-section geometry and roughness into one conveyance parameter. Flow area and conveyance are expressed as power laws of flow depth, and they are found to be linearly related in log–log space at reach scale. Data from a wide range of river systems show that the linearity approximation is globally applicable. Because the two are expressed as power laws of flow depth, no further assumptions about channel geometry are needed. Therefore, the hydraulic inversion approach allows for calibrating flow area and conveyance curves in the absence of direct observations of bathymetry and hydraulic roughness. The feasibility and performance of the hydraulic inversion workflow are illustrated using satellite observations of river width and water surface elevation in the Songhua river, China. Results show that this approach is able to reproduce water level dynamics with root-mean-square error values of 0.44 and 0.50 m at two gauging stations, which is comparable to that achieved using a standard calibration approach. In summary, this study puts forward an alternative method to parameterize and calibrate river models using satellite observations of river width and water surface elevation.

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Transformation of Water Wave Spectra into Time Series of Surface Elevation

Earth ◽

10.3390/earth2040059 ◽

2021 ◽

Vol 2 (4) ◽

pp. 997-1005

Author(s):

Phelype Haron Oleinik ◽

Gabriel Pereira Tavares ◽

Bianca Neves Machado ◽

Liércio André Isoldi

Keyword(s):

Time Series ◽

Time Domain ◽

Water Surface ◽

Large Scale ◽

Wave Spectrum ◽

Ocean Waves ◽

Surface Elevation ◽

Sea Waves ◽

Water Surface Elevation ◽

Input Spectrum

Spectral wave modelling is widely used to simulate large-scale wind–wave processes due to its low computation cost and relatively simpler formulation, in comparison to phase-resolving or hydrodynamic models. However, some applications require a time-domain representation of sea waves. This article proposes a methodology to transform the wave spectrum into a time series of water surface elevation for applications that require a time-domain representation of ocean waves. The proposed method uses a generated phase spectrum and the inverse Fourier transform to turn the wave spectrum into a time series of water surface elevation. The consistency of the methodology is then verified. The results show that it is capable of correctly transforming the wave spectrum, and the significant wave height of the resulting time series is within 5% of that of the input spectrum.

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