Observations of Hydraulic Controls on the Olentangy River, Columbus, Ohio

The Lower Olentangy River in Columbus, Ohio has a sharp change in slope and width near the crossing of the Henderson Rd. bridge. This sudden change in morphology had not been directly addressed, but previous studies suggest that these changes are results of the low-head dam near North Broadway, three kilometers downstream. The water surface elevation (WSE) is modeled by solving a gradually varied flow equation with input data collected by 16 stream gages in 2014, a nearby USGS gage station, and bathymetry data collected with a depth sounder in 2015. Two WSE profiles are computed, one using observed water elevation at the dam as a boundary condition, and the second using a boundary condition representing water elevation without the dam. The simulations using observed and lowered boundary conditions converge 2.2 and 1.7 km upstream at low and high flow. The effect of the dam does not extend to the sharp change in slope. At low flow, widths increase 15.5% in the influence of the dam, but at high flow width decreases by 1.65%. Bathymetry data show a 22.9% decrease in bed slope downstream of Henderson Rd., which contributes to the decreasing slope and increasing width.NASA JPL grant NNX13AD96GNo embarg

ADVANCING REMOTE SENSING OF FLUVIAL SEDIMENT TRANSPORT AND STORAGE

Abundant satellite imagery and increased processing power has changed the way hydrologists and geomorphologists study rivers by providing access to continental and global- scale datasets. These rich datasets allow us the opportunity to test and expand existing theory at large scales but require a whole new set of methodologies. Sediment transport research has lagged behind other applications of remote sensing to surface hydrology and fluvial geomorphology, likely due to the complexity of the remote sensing methods and scarcity of in- situ data. In the first chapter of this dissertation, I develop new methods to track the movement of riverbanks over two decades for all rivers wider than 150 meters. With these new data, I confirm well-established theory on the scaling relationship between river size and bank mobility and find uncertainty in the global applicability of more recent theories of the hierarchy of scaling relationships. In the second chapter, I develop an open-source turbidity sensor that allows us to monitor watersheds at a scale that would not be cost-effective with commercial sensors. In the third and final chapter, I combine new algorithms for estimating river discharge and suspended sediment concentration, the sensor developed in chapter two, and existing models to evaluate our ability to use remote sensing to estimate the suspended sediment flux of an Arctic river. What connects these chapters is an overall advancement of our ability to use remote sensing data and techniques to measure the transport and storage of sediment through rivers.Doctor of Philosoph

A High-Resolution Airborne Color-Infrared Camera Water Mask for the NASA ABoVE Campaign

The airborne AirSWOT instrument suite, consisting of an interferometric Ka-band synthetic aperture radar and color-infrared (CIR) camera, was deployed to northern North America in July and August 2017 as part of the NASA Arctic-Boreal Vulnerability Experiment (ABoVE). We present validated, open (i.e., vegetation-free) surface water masks produced from high-resolution (1 m), co-registered AirSWOT CIR imagery using a semi-automated, object-based water classification. The imagery and resulting high-resolution water masks are available as open-access datasets and support interpretation of AirSWOT radar and other coincident ABoVE image products, including LVIS, UAVSAR, AIRMOSS, AVIRIS-NG, and CFIS. These synergies offer promising potential for multi-sensor analysis of Arctic-Boreal surface water bodies. In total, 3167 km2 of open surface water were mapped from 23,380 km2 of flight lines spanning 23 degrees of latitude and broad environmental gradients. Detected water body sizes range from 0.00004 km2 (40 m2) to 15 km2. Power-law extrapolations are commonly used to estimate the abundance of small lakes from coarser resolution imagery, and our mapped water bodies followed power-law distributions, but only for water bodies greater than 0.34 (±0.13) km2 in area. For water bodies exceeding this size threshold, the coefficients of power-law fits vary for different Arctic-Boreal physiographic terrains (wetland, prairie pothole, lowland river valley, thermokarst, and Canadian Shield). Thus, direct mapping using high-resolution imagery remains the most accurate way to estimate the abundance of small surface water bodies. We conclude that empirical scaling relationships, useful for estimating total trace gas exchange and aquatic habitats on Arctic-Boreal landscapes, are uniquely enabled by high-resolution AirSWOT-like mappings and automated detection methods such as those developed here

Anticipated Improvements to River Surface Elevation Profiles From the Surface Water and Ocean Topography Mission

Existing publicly available digital elevation models (DEMs) provide global-scale data but are often not precise enough for studying processes that depend on small-scale topographic features in rivers. For example, slope breaks and knickpoints in rivers can be important in understanding tectonic processes, and riffle-pool structures are important drivers of riverine ecology. More precise data (e.g., lidar) are available in some areas, but their spatial extent limits large-scale research. The upcoming Surface Water and Ocean Topography (SWOT) satellite mission is planned to launch in 2021 and will provide measurements of elevation and inundation extent of surface waters between 78° north and south latitude on average twice every 21 days. We present a novel noise reduction method for multitemporal river water surface elevation (WSE) profiles from SWOT that combines a truncated singular value decomposition and a slope-constrained least-squares estimator. We use simulated SWOT data of 85–145 km sections of the Po, Sacramento, and Tanana Rivers to show that 3–12 months of simulated SWOT data can produce elevation profiles with mean absolute errors (MAEs) of 5.38–12.55 cm at 100–200 m along-stream resolution. MAEs can be reduced further to 4–11 cm by averaging all observations. The average profiles have errors much lower than existing DEMs, allowing new advances in riverine research globally. We consider two case studies in geomorphology and ecology that highlight the scientific value of the more accurate in-river DEMs expected from SWOT. Simulated SWOT elevation profiles for the Po reveal convexities in the river longitudinal profile that are spatially coincident with the upward projection of blind thrust faults that are buried beneath the Po Plain at the northern termination of the Apennine Mountains. Meanwhile, simulated SWOT data for the Sacramento River reveals locally steep sections of the river profile that represent important habitat for benthic invertebrates at a spatial scale previously unrecognizable in large-scale DEMs presently available for this river

ANTICIPATED IMPROVEMENTS TO RIVER SURFACE ELEVATION PROFILES FROM THE SURFACE WATER AND OCEAN TOPOGRAPHY MISSION

Existing publicly available digital elevation models (DEMs) provide global-scale data but are often not precise enough for studying processes that depend on small-scale topographic features in rivers. The upcoming Surface Water and Ocean Topography (SWOT) satellite mission is planned to launch in 2021 and will provide surface water elevation and inundation extent at high resolution for most of the Earth surface. We present a novel noise reduction method for multitemporal river water surface elevation profiles that combines a truncated singular value decomposition and a slope-constrained least-squares estimator. We use simulated SWOT data of 85-145 km sections of the Po, Sacramento, and Tanana Rivers to show that 3-12 months of simulated SWOT data can produce elevation profiles with mean absolute errors of 5.38-12.55 cm at 100-200 m along-stream resolution. Last, we consider case studies in geomorphology and ecology to demonstrate the scientific value of more accurate water surface elevation profiles

Athabasca River Avulsion Underway in the Peace-Athabasca Delta, Canada

Avulsions change river courses and transport water and sediment to new channels impacting infrastructure, floodplain evolution, and ecosystems. Abrupt avulsion events (occurring over days to weeks) are potentially catastrophic to society and thus receive more attention than slow avulsions, which develop over decades to centuries and can be challenging to identify. Here, we examine gradual channel changes of the Peace-Athabasca River Delta (PAD), Canada using in situ measurements and 37 years of Landsat satellite imagery. A developing avulsion of the Athabasca River is apparent along the Embarras River–Mamawi Creek (EM) distributary. Its opening and gradual enlargement since 1982 are evident from multiple lines of observation: Between 1984 and 2021 the discharge ratio between the EM and the Athabasca River more than doubled, increasing from 9% to 21%. The EM has widened by +53% since 1984, whereas the Athabasca River channel width has remained stable. The downstream Mamawi Creek delta is growing at a discharge-normalized rate roughly twice that of the Athabasca River delta in surface area. Longitudinal global navigation satellite systems field surveys of water surface elevation reveal the EM possesses a ∼2X slope advantage (8 × 10−5 vs. 4 × 10−5) over the Athabasca River, and unit stream power and bed shear stress suggest enhanced sediment transport and erosional capacity through the evolving flow path. Our findings: (a) indicate that a slow avulsion of the Athabasca River is underway with potentially long-term implications for inundation patterns, ecosystems, and human use of the PAD; and (b) demonstrate an observational approach for identifying other slow avulsions at river bifurcations globally.Plain Language SummaryAvulsions shift river courses and move water and sediment to new channels, which affect infrastructure, floodplains, and ecosystems. Slow avulsions take decades to develop and are more difficult to identify. Using on-the-ground measurements and 37 years of Landsat satellite imagery, we analyze gradual channel changes in the Peace-Athabasca River Delta (PAD), Canada. The Athabasca River is changing course such that more of its water enters its westernmost outlet, the Embarras River–Mamawi Creek (EM) channel. Multiple lines of evidence demonstrate that the EM channel has been gradually opening since 1982. Between 1984 and 2021, the water entering the EM channel increased from 9% to 21% of the river’s total flow. Since 1984, the EM channel has widened by 53%, while the Athabasca River channel has remained stable. The delta forming at the EM mouth (i.e., Mamawi Creek delta) has grown twice as fast as the Athabasca River delta. Field measurements of water surface elevation show the slope of the EM channel is twice as steep as the slope of the lower Athabasca River (8 × 10−5 vs. 4 × 10−5). Because water tends to flow down the steepest slope, we expect more water to flow down the EM channel in the future. Our findings indicate a slow capture of Athabasca River water into its EM channel, with potential long-term implications for the delta’s inundation pattern, ecosystems, and traditional Indigenous activities.Key PointsWe assess a potential avulsion of the Athabasca River in the Peace-Athabasca Delta, Canada using field measurements and remote sensingAnalysis of hydrological and morphological observations affirm that a slow avulsion is currently underwayThe avulsion may accelerate in the future and cause transformative effects on the delta’s vegetation, habitat, and ecosystemsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/175946/1/wrcr26488.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/175946/2/wrcr26488_am.pd

Peace-Athabasca Delta water surface elevations and slopes mapped from AirSWOT Ka-band InSAR

In late 2023 the Surface Water and Ocean Topography (SWOT) satellite mission will release unprecedented high-resolution measurements of water surface elevation (WSE) and water surface slope (WSS) globally. SWOT’s exciting Ka-band near-nadir wide-swath interferometric radar (InSAR) technology could transform studies of surface water hydrology, but remains highly experimental. We examine Airborne SWOT (AirSWOT) data acquired twice over Canada’s Peace-Athabasca Delta (PAD), a large, low-gradient, ecologically important riverine wetland complex. While noisy and susceptible to “dark water” (low-return) data losses, spatially averaged AirSWOT WSE observations reveal a broad-scale water-level decline of ~44 cmn (σ =271 cm) between 9 July and 13 August 2017, similar to a ~56 cm decline (σ=33 cm) recorded by four in situ gauging stations. River flow directions and WSS are correctly inferred following filtering and reach-averaging of AirSWOT data, but ~10 km reaches are essential to retrieve them. July AirSWOT observations suggest steeper WSS down an alternate flow course (Embarras River–Mamawi Creek distributary) of the Athabasca River, consistent with field surveys conducted the following year. This signifies potential for the Athabasca River to avulse northward into Mamawi Lake, with transformative impacts on flooding, sedimentation, ecology, and human activities in the PAD. Although AirSWOT differs from SWOT, we conclude SWOT Ka-band InSAR observations may detect water level changes and avulsion potentials in other low-gradient deltas globally.</p