Water Surface Elevation Data Research Articles

A spatially based area–time inundation index model developed to assess habitat opportunity in tidal–fluvial wetlands and restoration sites

A geographic information system (GIS)-based Area-Time Inundation Index Model (ATIIM) was developed to predict and evaluate availability of hydrologically connected habitats in estuarine and tidal–fluvial regions. The model establishes and describes patterns in the spatial and temporal relationships of the land and water including non-dimensional area–time and volume–time inundation indices. The processing integrates in situ or modeled water-surface elevation (WSE) data with high-resolution elevation data, using established terrain generation and spatial hydrologic analysis methods which are applied in a new geographic domain: the low-relief microtopography characteristic of coastal wetlands. The ATIIM links these data to newly developed, spatially continuous wetted-area algorithms in a GIS module and determines site average bankfull elevation, two- and three-dimensional inundation extent, and other spatial, tabular, and graph-based metrics. It is a cost-effective, rapid assessment tool suitable for the desktop planning environment, and represents an advance over methods that estimate inundation but do not enforce hydrological connectivity. Example model outputs for 11 tidal wetland areas in the lower Columbia River floodplain and estuary illustrate habitat opportunity for threatened and endangered salmon. Outputs for wetland reference sites (tidal marshes and tidal forested wetlands) are compared with river-restoration sites where objectives include increasing salmon access to beneficial habitats by hydrologically reconnecting channels in diked areas of the floodplain. Hydrological process metrics produced by the model, both new and commonly used, support the prioritization of proposed restoration sites, pre-construction planning, and post-construction evaluation. For example, the model can help determine relationships between WSE and habitat opportunity, contrast alternative restoration designs, predict impacts of altered flow regimes, estimate nutrient and biomass fluxes, and provide standardized site comparisons to support effective monitoring of the developmental trajectories of restoration sites.

Fortnightly tidal asymmetry inversions and perspectives on sediment dynamics in a macrotidal estuary (Charente, France)

Tidal asymmetry is a phenomenon that characterises estuarine hydrodynamics and has a strong impact on sediment dynamics. Extensive research has been dedicated to studying tidal dynamics in semidiurnal macrotidal estuaries, highlighting several general principles. The ratio of flood to ebb peak velocities and differences in ebb and flood durations are often used to characterise the asymmetry encountered in estuaries.In the Charente estuary (French Atlantic coast), water surface elevation data obtained using an ADCP (Acoustic Doppler Current Profiler) and a tide gauge show that the duration asymmetry undergoes inversions during the spring-neap tidal cycle. A two-dimensional hydrodynamics model is used to investigate the connection between spring-neap inversions of the tidal asymmetry and the harmonic composition of the tide. Different constituents (M2, S2, M4 and MS4) are considered at the open boundary. The results show that M4 and MS4 play a key role in the occurrence of these inversions. The influence of the morphology is also discussed and modifications of the bathymetry are performed to evaluate its impact. In the Charente estuary, the existence of both externally and internally generated overtides thus results in a spatially and fortnightly variable tidal asymmetry.The modelled barotropic tidal currents are used to estimate the possible impact on sediment dynamics. The results suggest that asymmetry inversions tend to create sediment accumulation in an intermediate zone between the river mouth and Rochefort, located approximately 20km upstream.

Mississippi River Streamflow Measurement Techniques at St. Louis, Missouri

AbstractStreamflow measurement techniques of the Mississippi River at St. Louis have changed through time (1866–present). In addition to different methods used for discrete streamflow measurements, the density and range of discrete measurements used to define the rating curve (stage versus streamflow) have also changed. Several authors have utilized published water surface elevation (stage) and streamflow data to assess changes in the rating curve, which may be attributed to be caused by flood control and/or navigation structures. The purpose of this paper is to provide a thorough review of the available flow measurement data and techniques and to assess how a strict awareness of the limitations of the data may affect previous analyses. It is concluded that the pre-1930s discrete streamflow measurement data are not of sufficient accuracy to be compared with modern streamflow values in establishing long-term trends of river behavior.

The pattern of surface waves in a shallow free surface flow

This work presents new water surface elevation data including evidence of the spatial correlation of water surface waves generated in shallow water flows over a gravel bed without appreciable bed forms. Careful laboratory experiments have shown that these water surface waves are not well‐known gravity or capillary waves but are caused by a different physical phenomenon. In the flow conditions studied, the shear present in shallow flows generates flow structures, which rise and impact on the water‐air interface. It is shown that the spatial correlation function observed for these water surface waves can be approximated by the following analytical expression . The proposed approximation depends on the spatial correlation radius, σw, characteristic spatial period, L0, and spatial lag, ρ. This approximation holds for all the hydraulic conditions examined in this study. It is shown that L0 relates to the depth‐averaged flow velocity and carries information on the shape of the vertical velocity profile and bed roughness. It is also shown that σw is related to the hydraulic roughness and the flow Reynolds number.

FIELD OBSERVATIONS AND MODEL PREDICTIONS OF WAVE TRANSFORMATION ON A MACRO-TIDAL BEACH, KOREA

Macro-tidal beach processes are influenced by complicated interactions of tide actions, coastal waves and morphological changes. Tidal cycles may be a primary forcing responsible for specific characteristics of hydrodynamic and morphological processes complicated on the intertidal flat in space and time. Macro-tidal sandy beaches are frequently developed in the west coast of Korea, experiencing seasonal variations of inter-tidal processes caused by a monsoonal climate in the Yellow Sea. Large winter waves tend to excite active beach morphological processes, inducing beach erosion and seaward-directed sediment transports. This study is intended to investigate and characterize intertidal hydrodynamics including wave dynamics in a macro-tide environment in Korea, by using a numerical model named COBRAS. The measured water surface elevation data are divided into wave and tidal components, in order to be used as inputs of the model. Tidal components in terms of water level change are implemented in the model by adding constant currents at the offshore boundary. Comparisons of the measurements and the predictions show a good performance of the model for wave height transformation and wave set-up across the macro-tidal beach

APPLICATION OF AN AUTONOMOUS ROBOT FOR THE COLLECTION OF NEARSHORE TOPOGRAPHIC AND HYDRODYNAMIC MEASUREMENTS

Beach topographic and hydrodynamic measurements are essential for coastal geology and engineering studies as well as sustainable coastal management. Standard approaches involve either time-consuming manual data acquisition usually with limited coverage or remote sensing techniques which are usually characterized by low resolution or increased costs. The present contribution reports the results from the application of the autonomous robot RTS-Hanna with a calibrated sensor setup including 3D laser range scanners, a camera, a Differential GPS and an inertial measurement unit which significantly facilitates field data collection. RTS-Hanna was tested at the Wadden Sea Barrier Island Langeoog, Northern Germany, for two days and was proven capable of autonomously collecting topographic scans. 175 GB of dense topographic and water surface elevation data were collected, including RBG images, while RTS-Hanna covered a total of 21 km of coastline in approximately 3 hours. Scans of the surf/swash zone allowed continuous measurements of topographic changes at the beachface, wave propagation velocities and wave breaking heights.

Perancangan Program Peramalan Kanal Banjir Barat Jakarta Menggunakan Autoregresi Multivariant

This paper discusses the design of computer programs that is able to discern the characteristics description of water surface elevation data in Manggarai water gate, which variable is the most influential on the water surface elevation model and find a proper flood forecasting model using multivariate autoregressive model. The result of this study is able to assist the water gate officer in delivering early warning, prevention and anticipation of flood countermeasure. The forecast equation model obtained is Yt = 109,.7828 + 0,9291 CHt-6 – 24,484 T t-2 – 0,06245 PM t-2 + 1,4706 KB t-2 in which temperature and water surface elevation is a variable that owns the strongest correlation. This variable owns negative correlation which means that if the temperature falls, the water levels will rise. The coefficient of determination has a value of R2 = 0.4056 and the Durbin Watson statistics for DW = 0.7429.

Model Evaluation of Shoaling and Morphologic Response to Storms at Moriches Inlet, Long Island, New York

A model and field investigation of hydrodynamic processes and morphological change at a sand-substrate tidal inlet is presented in order to describe conditions that can lead to shoaling and channel constriction. The Coastal Modeling System (CMS) developed at the Coastal and Hydraulics Laboratory of the U.S. Army Engineer Research and Development Center (ERDC) employs a depth-integrated two-dimensional circulation and sediment transport model, CMS-Flow, coupled with a phase-averaging, steady-state wave model, CMS-Wave, to simulate hydrodynamics and morphodynamics at Moriches Inlet in Long Island, New York. Short-term model simulations were conducted with measured water surface elevation and time-varying wave forcing to examine the capability of the model to simulate storm versus typical forcing. Model calibration and verification was performed by comparing calculations to measured water surface elevation and current velocity data collected during a field study at Moriches Inlet in 2004. Shoal development and relative movement of morphological features were reproduced in the model simulations. During simulated storm conditions, a vortex with a weak velocity field off the tip of the east jetty caused sediment to accumulate on the eastern boundary of the inlet channel. The alignment of the channel prevents the shoal from being scoured clear of the jetty. These modeled results were verified by observed morphologic response of Moriches Inlet to extratropical storms consisting of shoaling and channel constriction along the flank of the entrance channel and inlet throat. A 14-month long-term simulation also reproduced observations of channel infilling on the outer channel and accretion on the ebb tidal delta.

Modeling tidal circulation and stratification in Skagit River estuary using an unstructured grid ocean model

Tidal circulation and river plume dynamics in shallow-water estuarine systems with large intertidal zones are complex. Strong asymmetries in tidal currents and stratification often occur in the intertidal zones and subtidal channels over a tidal cycle. The Skagit River is the largest estuary with respect to the discharge of a significant amount of freshwater and sediment into Puget Sound, Washington. It consists of a large intertidal zone with multiple tidal channels near the mouth of the estuary. To simulate the tidal circulation and salinity stratification accurately in the intertidal region, an unstructured grid numerical model with wetting–drying capability and the capability to accurately represent the bathymetry of tidal flats and the geometry of shallow distributary channels is necessary. In this paper, a modeling study for the Skagit River estuary using a three-dimensional unstructured grid, finite-volume coastal ocean model (FVCOM) supported by high-resolution LIDAR data is presented. The hydrodynamic model was validated with observed water surface elevation, velocity, and salinity data over spring and neap tidal cycles under low-river-flow and high-river-flow conditions. Wetting and drying processes in the intertidal zone and strong stratification in the estuary were simulated successfully by the model. Model results indicate that the Skagit River estuary is a highly stratified estuary, but destratification can occur during flood tide. Tides and baroclinic motion are the dominant forcing in the Skagit River estuary, but strong wind events can affect the currents in the intertidal zone significantly. Preliminary analysis also indicated that the salinity intrusion length scale is proportional to the river flow to the −¼ power.

Predicting hourly-based flow discharge hydrographs from level data using genetic algorithms

This study developed a genetic algorithm model to predict flow rates at sites receiving significant lateral inflow. It predicts flow rate at a downstream station from flow stage measured at upstream and downstream stations. For this purpose, it constructed two different models: First is analogous to the rating curve model (RCM) of Moramarco et al. [Moramarco, M., Barbetta, S., Melone, F., Singh, V.P., 2005. Relating local stage and remote discharge with significant lateral inflow. J. Hydrologic Eng., ASCE, 10(1)] and the second is based on summation of contributions from upstream station and lateral inflows using kinematic wave approximation. The model was applied to predict flow rates at three different gauging stations located on Tiber River, Upper Tiber River Basin, Italy. The model used average wave travel time for each river reach and obtained average set of parameter values for all the events observed in the same river reach. The GA model was calibrated, for each river reach and for each formulation, by three events and tested against three other events. The results showed that the GA model produced satisfactory results and it was superior over the most recently developed rating curve method. This study further analyzed the case where only water surface elevation data were used in the input vector to predict flow rates. The results showed that using elevation data produces satisfactory results. This has an implication for predicting flow rates at ungauged river sites since the surface elevation data can be obtained without needing the detailed geometry of river section which could change significantly during a flood.

Capability of SRTM C- and X-band DEM Data to Measure Water Elevations in Ohio and the Amazon

We analyze Shuttle Radar Topography Mission (SRTM) water surface elevation data to assess the capacity of interferometric radar for future surface water missions. Elevations from three Ohio reservoirs and several Amazon floodplain lakes have standard deviations, interpreted as errors, that are smaller in C-band compared to X-band and are smaller in Ohio than in the Amazon. These trends are also evident when comparing water surface elevations from the Muskingum River in Ohio with those of the Amazon River. Differences are attributed to increased averaging in C-band compared to X-band, greater sensitivity to surface water motion in X-band, and generally larger off-nadir look angles in X-band. Absolute water surface elevations are greater in the C-band DEM for much of the two study areas and yield expected slope values. Height and slope differences are attributed to differing usage of geoids and ellipsoids. These SRTM measurements suggest the great possibility for space-based, laterally-spatial (2D) measurements of water surface elevations.

沖合水面変動記録を用いた津波成分即時抽出法に関する研究

This paper introduces a newly developed real time tsunami detection system using offshore water surface elevation data obtained from GPS buoys or seabed installed acoustic/pressure wave gauges. In order to eliminate high frequency components caused by wind waves and swells, shape of the numerical low-pass-filter was determined with consideration of its real-time efficiency. To eliminate lower frequency phenomena caused by astronomical tides and other causes such as water temperature change, 6 days continuous passed data were found to be necessary to obtain harmonic constants of the 4 principal tide components and averaged sea level. Miss-fixed and data-loss phenomena, which may appear in the GPS buoy observation, were also considered to elaborate the automatic system.Proposed system was checked with the actual offshore tsunami observation data caused by the 2004 Tokaido-off and 2005 Miyagi-off earthquake tsunami events, and the applicability was well confirmed with exception during a huge typhoon caused abnormal waves and sea-level events.

Water slope and discharge in the Amazon River estimated using the shuttle radar topography mission digital elevation model

We find that the standard deviation, hence error, of the water surface elevation data from the Shuttle Radar Topography Mission (SRTM) is 5.51 m for basin‐wide, regional and local Amazon mainstem reaches. This error implies a minimum reach length of 733km in order to calculate a reliable water‐surface slope. Resulting slopes are 1.92 ± 0.19 cm/km for Manacapuru, 2.86 ± 0.24 cm/km for Itapeua and 3.20 ± 0.34 cm/km for Tupe. Manning's equation is applied with these slopes and with channel width measurements from the Global Rain Forest Mapping project synthetic aperture radar mosaics (GRFM SAR), channel depths averaged from nautical charts, and reasonable estimates of Manning's n. Resulting discharge values are 84,800 m3/s at Manacapuru, 79,800 m3/s at Itapeua, and 62,900 m3/s at Tupe averaged over the SRTM mission period. These values are within 6.2% at Manacapuru, 7.6% at Itapeua, and 0.3% at Tupe of the in‐situ gage‐based estimates for the same or similar time period.

Comparison of two modes of surface water control using a soil water model and surface elevation data

In large parts of the Netherlands, agricultural potential is largely determined by water table depth. In turn, the water table depth is controlled by the surface water levels of a network of drainage ditches. Consequently, the gross return from agricultural production can be maximised by manipulating the surface water levels in these ditches. The traditional mode of surface water control consists of a weir with a fixed crest level at the outlet of a control area or catchment. A recent development is the use of groundwater dependent surface water control: the crest level of an adjustable weir is set according to measurements of the water table depth. For both modes of surface water control the crest levels of the controlling weir are adapted to the surface elevation at some reference location. The gross return from agricultural production thus depends on both the mode of surface water control and the choice of the reference location. A method is developed to estimate the performance of a mode of surface water control when adapted to a given reference location. Performance is measured in terms of the estimated average gross return of a control area (in Dutch guilders per ha per year). The method combines a soil water model with detailed surface elevation data from laser scanning and accounts for the unknown spatial variation of soil-physical and hydrological properties by means of a Monte Carlo approach. Although it is developed for the specific purpose of evaluating modes of surface water control, the method presented here is more generic. It is in fact a general procedure that uses densely sampled auxiliary information for mapping the results of expensive model calculations and the associated uncertainty. The method is applied in a control area in the north of the Netherlands. It is used to compare the performance of a traditional mode of surface water control with a groundwater dependent mode of surface water control and to estimate the best reference location for both modes. It is found that the traditional mode of surface water control is best adapted to a reference location from the higher parts of the control area, while the groundwater dependent surface water control is best adapted to a reference location from the lower parts. Maximum values of estimated average gross return that can be obtained for both modes of surface water control are approximately the same. However, contrary to the traditional mode of surface water control, the maximum value for groundwater dependent surface water control is obtained almost without adversely affecting the farmers in the lower parts of the control area.

Avulsion and anastomosis in the panhandle region of the Okavango Fan, Botswana

GPS water-surface elevation data from the panhandle region of the Okavango Fan (northwestern Botswana) show that a prominent anastomosed reach occurs within a relative valley-gradient depression inferred to represent a small graben structure. The Okavango River undergoes an abrupt change in pattern as it approaches the upstream fault zone of the graben, developing small meander loops and higher sinuosity in response to increased valley slope induced by faulting. Four channels split from and ultimately rejoin the Okavango trunk channel to define the anastomosed reach. The oldest (Filipo channel) diverted from the Okavango on the upstream horst block, rejoining the trunk channel 26 km downstream within the graben. The younger channels B, C and D all developed subsequent to the Filipo avulsion by forming linkages between the Okavango trunk and floodplain tributaries that had evolved by headward extension and incorporation of older abandoned channel segments. Diversion of the three younger anastomosed channels was likely abetted by increased aggradation of the trunk channel following down-faulting. Neotectonic movement, although involving only slight displacement, is seen to be the underlying cause of avulsion, anastomosis, and certain channel pattern changes in the Okavango panhandle. This contrasts with other parts of the Okavango Fan system where avulsion appears to result more from autogenic in-channel sedimentation conditioned by various roles of vegetation.

A field study of wave reflections from an exposed dissipative beach

This paper describes a field study of wave reflections from an exposed dissipative beach, using only water-surface elevation data from five wave height sensors. Many insights were gained into beach reflections and their detection. A technique normally reserved for laboratory use was successfully applied to surf zone data to separate incident and reflected infragravity wave-energy spectra. The reflected wave energy was found to be significant for all wave periods greater than 20 seconds, and often total for wave periods greater than 30 seconds. The evidence was heavily weighted towards the observed reflected wave activity being essentially two dimensional with the influence of three-dimensional edge waves being minimal. Other findings relate to the value of wave energy spectra computed from a single surf-zone sensor, the relevance of single slope approximations of beach profiles and the relationship between incident infragravity wave-activity and the longer-period swash excursions on a beach face.