A rating curve provides a functional relationship between water height (i.e. stage) and discharge at a specified cross-section in a river. Used in combination with a time series of stage, rating curves become one of the central components for generating continuous records of streamflow. Since developing and maintaining rating curves can be time consuming, hydraulic models have shown potential to reduce the effort required for developing rating curves. A central challenge with modeling procedures, however, is the acquisition of accurate stream channel and floodplain topography. From this perspective, this thesis focuses on the real-world application of close-range remote sensing techniques such as laser-based ranging technologies (i.e. Light detection and ranging or LiDAR) or acoustic based ranging technologies (i.e. acoustic Doppler current profiler or ADCP) to capture topographic information for hydraulic modeling applications across various spatial scales. First, a review of the current LiDAR literature was carried out to identify potential ways to take full advantage of these novel data and technologies in the future. This was followed by four interconnected studies whereby: (i) a low-cost custom laser scanning system was designed to capture grain size distributions for a small stream; (ii) synthetically thinned airborne laser scanning (ALS) data was applied in a physically-based hydraulic modelling framework to develop rating curves; (iii) low-resolution national-scale ALS was coupled with ADCP bathymetry to be used in conjunction with a hydraulic model to develop rating curves; and (iv) the impact of measurement uncertainties on generating rating curves with a hydraulic model were investigated. This thesis highlights the potential of close-range remote sensing techniques for capturing accurate stream channel topography and derive from these data, the necessary parameters required for hydraulic modeling applications. / En avbördningskurva tillhandahåller ett funktionellt förhållande mellan vattendjup (dvs. vattenstånd) och flöde vid ett specifikt tvärsnitt i ett vattendrag. Avbördningskurvan blir en central komponent för generering av kontinuerliga tidsserier av vattenföring från tidsserier av vattenstånd. Eftersom det är tidskrävande att utveckla och underhålla avbördningskurvor erbjuder hydrauliska modeller attraktiva möjligheter att minska den insats som krävs för att utveckla avbördningskurvorna. En central utmaning för sådana modelleringsförfaranden är emellertid tillgången till noggrann topografidata av strömfåran och de omgivande stränderna. Den här avhandlingen fokuserar på tillämpningen av fjärranalystekniker för avståndsmätning på nära håll, såsom laserbaserade teknik (dvs. Light detection and ranging eller LiDAR) och akustisk baserat teknik (dvs. acoustic Doppler current profiler eller ADCP), för att fånga topografisk information för hydraulisk modellering av vattendrag i olika rumsliga skalor. Först presenteras en litteraturstudie av den nuvarande LiDAR-litteratur för att identifiera potentiella sätt att dra full nytta av dessa nya data och tekniker i framtiden. Detta följs av fyra sammanlänkade studier: (i) tillämpning av ett lågkostnads-laseravsökningssystem för att fånga kornstorleksfördelningar i ett litet vattendrag, (ii) syntetiskt förtunnad flygburen laserskanningsdata (ALS) applicerad i en fysiskt baserad hydraulisk modell för att utveckla avbördningskurvor, (iii) lågupplösta ALS från Svensk nationell höjdmodell kopplade med ADCP-batymetri för att ta fram en avbördningskurva med en hydraulisk modell, och (iv) undersökning av effekterna av osäkerheter på mätdata för att generera avbördningskurvor med en hydraulisk modell. Denna avhandling belyser potentialen för fjärranalystekniker för avståndsmätning på nära håll, för att fånga strömfårans exakta topografi och ifrån dessa data härleda de parametrar som krävs för hydrauliska modelleringstillämpningar. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.</p>

The flow velocity in a river is three-dimensional (3D), turbulent, and varies in time and space. Capturing this variability in field measurements to support studies of river processes has proven particularly challenging. While originally developed to measure discharge, boat-mounted acoustic Doppler current profilers (ADCP) are increasingly used in field studies to quantify flow features including mean velocity, boundary shear stress, and sediment motion. Two survey procedures are typically employed with an ADCP. Moving-vessel (MV) measurements provide spatially-rich velocity data while temporally-rich data are obtained with fixed-vessel (FV) procedures. Given the relative ease of MV measurements, recent work has focused on developing MV procedures that produce comparable results to FV measurements. At the present, results of this work are inconclusive. Additionally, there is a lack of reported data and procedures for FV measurements. This work seeks to develop techniques to present 3D velocity data obtained in natural rivers in a unified framework. This framework is based on a stream-fitted coordinate system defined by the flow direction at a cross section and allows for 3D velocity to be decomposed into streamwise, spanwise, and vertical components. Procedures are developed to assure that the velocity profiles measured at fixed locations are (1) not negatively impacted by the inevitable motion of the ADCP, (2) statistically stationary, and (3) of sufficient record length to determine the mean velocity. The coordinate system allows time-averaged velocity from FV procedures to be compared with spatially-averaged velocity from MV vessels. Significant differences are found between the two survey procedures, particularly for secondary velocity components. Ultimately, integrating results of the two survey procedures leads to an improved representation of the mean flow field. The techniques are applied to data obtained on a study reach on the lower Roanoke River, located in eastern North Carolina. / Ph. D.

In the Spring of 2012, hydraulic data was collected to calibrate three types of discharge models: stage-discharge, single-regression and multi-regression index velocity models. Unsteady flow conditions were observed at the site (â H/â t = 0.75 cm/min), but the data did not indicate hysteresis nor variable backwater effects on the stage-discharge relation. Furthermore, when corrected with a datum offset (α) value of -0.455, the stage-discharge relation r2 was equal to 0.98. While the multiple regression index velocity models also showed high correlation (r2 = 0.98) values, high noise levels of the parameter index velocity (Vi) complicated their use for the determination of discharge. Because of its reliability, low variance and accessibility to students, the stage-discharge model [Q = 5.459(H-0.455)^2.487] was selected as the model to determine discharge in real-time for LEWAS. Caution should be used, however, when applying the equation to stages above 1.0m. The selected discharge model was applied to ADCP stage (H) data collected during three runoff events in July 2012. Other LEWAS models showed similar discharge values (coefficient of variation = 0.14) while the on-site weir also produced similar discharge values. Precipitation estimates for July 19 and 24 rain events over the Webb Branch watershed were derived from IDW interpolated rain data and rainfall-runoff analyses from this data yielded an average ratio of 0.23, low for the urbanized watershed. However, since the three LEWAS models were very similar, and the on-site weir showed a lower value to LEWAS, it was concluded that any error in the ratio would be attributed to the precipitation estimate, and not the discharge models developed in this study. / Master of Science

A seasonal and long-term analysis of the vertical structure of currents in the nearshore is conducted to determine the role of the wind in driving currents and consequently affecting littoral transport processes. Approximately ten years (January, 2002 – October, 2011) of nearshore current profiles are examined using the data collected with an Acoustic Doppler Current Profiler (ADCP) installed off of Spessard Holland North Beach Park located in Melbourne Beach, Florida. Additionally, wind data collected with a directional anemometer from September, 2002, until October, 2008, are used to further characterize the long-term hydrodynamic forcing. With the shoreline oriented nominally 17o west of magnetic north, both the current profiles and the wind vectors have been rendered into longshore and cross-shore components. The water level record from a NOAA tide station located at the Trident Pier at nearby Port Canaveral is utilized in establishing the water depth and conditioning the data for statistical analysis. Monthly mean vertical profiles reveal that during the winter months the surface currents are usually toward the south, and toward the north in the summer. In spring and fall, they are mixed, demonstrating a clear seasonality in both direction and intensity of the longshore current. Subjecting the longshore and cross-shore current data to Empirical Orthogonal Function Analysis reveals that the first spatial Eigenfunction accounts for more than 98% of the variability in the vertical profile of the longshore current, and more than 86% of the variability in the profile of the cross-shore current. However, there is a rotation of the current to the right (clockwise) with the rotation angle increasing and the variance decreasing with depth below the surface. The spiral structure of the water column follows a surface Ekman veering, but for very shallow water. The upper layer of the current is almost aligned with the direction of the wind. Monthly correlations between 2-hour average time series of longshore current and 2-hour average time series of wind speed reveal the seasonal patterns of the wind and longshore current in which the upper layer of the water column is highly correlated with the longshore component of the wind speed for most of the year and slightly less correlated for the lower layer of the water column. Most importantly, on average, wave height (Hmo) is larger when the longshore current is heading to the south (Hmo=0.95 m) than when the current is going to the north (Hmo=0.73 m). Additionally, there is a stronger correlation between southerly directed currents and incident wave energy flux than northerly directed currents and wave energy flux. These results indicate that the net long-term north-to-south sediment transport known to characterize the region is heavily influenced by wind-driven currents.