Remote Sensing of Sea Surface Wave by Using CW X-Band Microwave Doppler Radar at Sagami-Bay

2008 ◽  
Author(s):  
Chang-Kyu Rheem
Keyword(s):  
Surface Waves ◽  
Wave Height ◽  
Water Surface ◽  
Doppler Radar ◽  
Sea Surface ◽  
Surface Elevation ◽  
Sagami Bay ◽  
Water Surface Elevation ◽  
Water Particle ◽  
Sea Surface Waves

Sea surface waves had been observed remotely by using a continuous wave (CW) X-band microwave Doppler radar at the off Hitatsuka of Sagami-bay in Japan. A new algorithm was applied to retrieve sea surface elevation from radar output Doppler signals. The sea surface waves observed by the microwave Doppler radar had been compared with the waves measured by a supersonic wave height meter. There were good correlations in both the wave height and the wave period between the waves observed by the microwave Doppler radar and that measured by a supersonic wave height meter. The correlation of wave heights was better than that of wave periods. The microwave irradiation width on sea surface does a role of space filter. It seems that the filtering effect is a kind of aliasing, the energy of short wavelength waves moves to low wave number region. The algorithm to retrieve a sea surface elevation is described by the relation of the water surface elevation and the orbital velocity of water particle on water surface that generated by water surface waves. A linear superposition method has been used to retrieve sea surface elevation. No empirical parameters are used in the algorithm, because the water surface elevation can be obtained from the water particle velocity on water surface by using the mathematical relation of the water surface elevation and the orbital motion of water particle. Water particle motion on sea surface is affected by sea surface wind, currents, and sea surface waves. Water particle motion generated by sea surface waves can be separated by the difference of the fluctuation scale of each physical process.

scholarly journals Deep visual domain adaptation and semi-supervised segmentation for understanding wave elevation using wave flume video images

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jinah Kim ◽  
Taekyung Kim ◽  
Sang-Ho Oh ◽  
Kideok Do ◽  
Joon-Gyu Ryu ◽  
...  
Keyword(s):  
Time Series ◽  
Water Level ◽  
Wave Height ◽  
Water Surface ◽  
Domain Adaptation ◽  
Surface Elevation ◽  
Nearshore Processes ◽  
Water Surface Elevation ◽  
Wave Flume ◽  
Visual Domain

AbstractAccurate water surface elevation estimation is essential for understanding nearshore processes, but it is still challenging due to limitations in measuring water level using in-situ acoustic sensors. This paper presents a vision-based water surface elevation estimation approach using multi-view datasets. Specifically, we propose a visual domain adaptation method to build a water level estimator in spite of a situation in which ocean wave height cannot be measured directly. We also implemented a semi-supervised approach to extract wave height information from long-term sequences of wave height observations with minimal supervision. We performed wave flume experiments in a hydraulic laboratory with two cameras with side and top viewpoints to validate the effectiveness of our approach. The performance of the proposed models were evaluated by comparing the estimated time series of water elevation with the ground-truth wave gauge data at three locations along the wave flume. The estimated time series were in good agreement within the averaged correlation coefficient of 0.98 and 0.90 on the measurement and 0.95 and 0.85 on the estimation for regular and irregular waves, respectively.

scholarly journals The FLOod Probability Interpolation Tool (FLOPIT): A Simple Tool to Improve Spatial Flood Probability Quantification and Communication

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 666
Author(s):  
Mahkameh Zarekarizi ◽  
K. Joel Roop-Eckart ◽  
Sanjib Sharma ◽  
Klaus Keller
Keyword(s):  
Flood Risk ◽  
Water Surface ◽  
The United States ◽  
Surface Elevation ◽  
Exceedance Probability ◽  
Water Surface Elevation ◽  
Inundation Maps ◽  
Probability Maps ◽  
Flood Probability ◽  
Floodplain Development

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.

Morphodynamic stability and characteristic length scales of bifurcations and confluences loops

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>

Sign in / Sign up

Export Citation Format

Share Document