Thesis (Ph. D.)--University of Wisconsisn--Madison, 1936. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references ([5] leaves at end).

Thesis (M.A.)--University of Wisconsin--Madison, 1929. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [91-96]).

<p> Digital elevation models (DEMs) are critical components of coastal flood models. Both present-day storm surge models and future flood risk models require these representations of the Earth&rsquo;s elevation surface to delineate potentially flooded areas. The National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) develops DEMs for United States&rsquo; coastal communities by seamlessly integrating bathymetric and topographic data sets of disparate age, quality, and measurement density. A current limitation of the NOAA NCEI DEMs is the accompanying non-spatial metadata, which only provide estimates of the measurement uncertainty of each data set utilized in the development of the DEM.</p><p> Vertical errors in coastal DEMs are deviations in elevation values from the actual seabed or land surface, and originate from numerous sources, including the elevation measurements, as well as the datum transformation that converts measurements to a common vertical reference system, spatial resolution of the DEM, and interpolative gridding technique that estimates elevations in areas unconstrained by measurements. The magnitude and spatial distribution of vertical errors are typically unknown, and estimations of DEM uncertainty are a statistical assessment of the likely magnitude of these errors. Estimating DEM uncertainty is important because the uncertainty decreases the reliability of coastal flood models utilized in risk assessments.</p><p> I develop methods to estimate the DEM cell-level uncertainty that originates from these numerous sources, most notably, the DEM spatial resolution, to advance the current practice of non-spatial metadata with NOAA NCEI DEMs. I then incorporate the estimated DEM cell-level uncertainty, as well as the uncertainty of storm surge models and future sea-level rise projections, in a future flood risk assessment for the Tottenville neighborhood of New York City to demonstrate the importance of considering DEM uncertainty in coastal flood models. I generate statistical products from a 500-member Monte Carlo ensemble that incorporates these main sources of uncertainty to more reliably assess the future flood risk. The future flood risk assessment can, in turn, aid mitigation efforts to reduce the vulnerability of coastal populations, property, and infrastructure to future coastal flooding.</p><p>

With growing concerns over future climate change, the need to understand past climate variability has become an important topic of research. In this thesis, a gap in knowledge of the transition to modern climatic conditions during the mid-Holocene is identified and addressed. Mid-Holocene atmospheric moisture availability has been reconstructed from five raised mires (Kortlandamossen, Tore Hill Moss, Raeburn Flow, Gällseredsmossen, and Misten Bog) located on geographical and climatological gradients across northwest Europe. In this thesis, a new testate amoebae-based palaeohydrological transfer function for south-central Sweden and an improved indicator-weighted Hydroclimatic Index (HCI) were created in order to establish univariate measures of mid-Holocene bog surface wetness (BSW). Together with detrended correspondence analysis, the HCI and testate amoebae transfer function were applied to palaeoecological data from the five bogs, in order to reconstruct climatic variability across northwest Europe from c. 9000 before present (BP) until c. 3500 BP. A series of wet and dry excursions of the bog surfaces were identified on all five bogs. These BSW changes were compared with palaeoclimatic evidence from the wider literature on a local, regional, continental and hemispheric scale. Throughout the early- to mid-Holocene, increased BSW on Misten Bog closely coincided with episodes of reduced SST in the North Atlantic. A similar link was established between SST and BSW on Raeburn Flow and Gällseredsmossen, following the end of the Holocene Thermal Maximum (HTM). The results from the analysis demonstrate that the HTM occurred asynchronously across northwest Europe. Reconstructions from all five bogs, except Misten Bog, showed a prolonged dry phase on the bog surface starting prior to c. 7000 BP. The end of the HTM occurred between c. 5600 BP and c. 4800 BP on all sites except Kortlandamossen, where regional environmental mechanisms delayed the end of the HTM. A climatic boundary at the end of the HTM was detected around 57ºN, with sites south of 57ºN experiencing the termination between c. 5600 BP and c. 5300, while it occurred between c. 4800 BP and c. 4400 BP on the sites north of this latitude. The only period when all five sites displayed similar BSW changes was between c. 4400 BP and c. 4000 BP, a period of global climatic change. A major wetting on the bogs during this time coincided with increased BSW and glacial advances across Europe as well as high lake levels in France and Switzerland.

Surface albedo is one of the critical parameters required by studies of surface energy balance and climate models. Albedo is defined as the ratio of outgoing radiances to incoming irradiances over hemispherical view-illumination geometry. Remotely sensed albedo is usually based on multiple view angle observations and a Bidirectional Reflectance Distribution Function (BRDF) model. The accuracy of remotely sensed albedo depends on a variety of factors of which the main ones are the accuracy of atmospherically corrected observations, the reliability of observations, and the validity of the applied BRDF model. Fine spatial resolution airborne and satellite data are valuable for the validation of coarse spatial resolution satellite albedos as they may be validated using field measurements with higher reliability. In this study, a variety of remote sensing data and field measurements were used to estimate, validate and analyse albedo at different spatial resolutions. The main aim was to validate the MODIS albedo product under UK conditions using the methods of direct and indirect comparisons with other available data. The source of the fine spatial resolution data used was the NCAVEO Field Campaign 2006 that took place at the Chilbolton calibration test site in southern England. The CHRIS/PROBA albedo was used as a fine spatial resolution (34 m) albedo map to investigate the spatial variation of albedo. The results of this investigation provided valuable information about the possibility of the extension of the obtained albedo map from CHRIS/PROBA data. The MODIS albedo product with a coarser spatial resolution (500 m), relative to the NCAVEO datasets, was compared with the CHRIS/PROBA albedo map to examine the effect of spatial scale on the accuracy of albedo (direct comparison). The uncertainties in the obtained albedo maps, from both MODIS and CHRIS/PROBA, were mainly examined by testing the accuracy of the input reflectance data and the applied BRDF model (indirect comparison). The results showed the accuracy of the MODIS albedo product inferior to that claimed by the MODIS team.

River bank erosion models are a fundamental requirement for understanding the migration and evolution of river meanders, estimating the potential for land-loss and threat to floodplain infrastructure, and predicting the delivery of contaminated floodplain sediments to aquatic ecosystems. While progress has recently been made in understanding and modelling processes controlling large-scale mass failure, less attention has been paid to the role that fluvial erosion plays in bank retreat. This project aims to address this gap by developing a new fluvial erosion model. Recent developments in bank erosion monitoring technology, and in the quantification of the bank erodibility parameters using jet-testing devices, offer the means of determining fluvial erosion rates and bank erodibility. However, the missing link remains the need to obtain highresolution, spatially distributed, flow data to characterize the near-bank fluid shear stresses that drive bank erosion. One possible solution is to use Computational Fluid Dynamics (CFD) models as a substitute for empirical data. Herein I evaluate a series of three-dimensional CFD simulations for a meander loop on the River Asker at Bridport in southern England. CFD models under specific steady peak flow conditions were developed using Fluent 6.2, with peak flow discharge estimates obtained from an adjacent gauging station. All the models obtained from the three examined flow events were successfully verified and validated using clearly defined and structured procedures. The modelling results indicated that the main qualitative features of the flow remain even as flow discharge varies. However, notable differences were observed between the examined flow events, such as, a general increasing of velocity and shear stress throughout the reach as flow stage is gradually increased, a slight reduction in the size and extent of separation zones at bank full stage, a movement of impingement points further downstream, and a continuation of the secondary flow within the fast streamtube further towards the bends exits. Bed/bank shear stress is mostly seen to decrease at shallow riffles as discharge approaches bankfull, while pools experience an increase in bed/bank shear stress with increase in discharge. Zones of higher bed/bank shear stress extend and combine, while marginal recirculation zones and areas of relatively low bed/bank shear stress generally reduce in area to form discrete locations for erosion and deposition phenomena. At bank full stage, the magnitudes of velocity and simulated shear stresses within the inner bank separation zones are found to be higher than those observed under low flow conditions and they may be sufficient to result in the removal of accumulated sediments into the main downstream flow. The presence of regions of high velocity in the form of a streamtube, especially along the outer banks, creates high shear stresses within these areas. As a result, outer bank migration rates are likely to be relatively high in bends with inner bank separation zones.

The standard model of headland formation assumes a coastline with discordant geology, where the less resistant rock is eroded at a higher rate than the more resistant geology. The indentation of the coastline will continue to increase until variations in wave energy due to refraction balance with the variation in rock strength and beach volume. On soft cliff coasts, where no systematic variations in cliff lithology or strength exist subtle headlands are still seen. Several examples of this can be seen on the southwest coast of the Isle of Wight, a coastline of complex interbedded soft rock lithology. Its relatively straight planform is punctuated by three established and one potentially emerging headland. All of these headlands are fronted by locally elevated intertidal shore platforms. It was hypothesised that these platform potentially act in three ways. Firstly by reducing the amount of wave energy reaching the cliff base, thus reducing local cliff recession rates. The second may counteract the first by increasing the wave energy directed at the cliff base due to refraction, the balance between these two effects will determine if a headland will grow, be maintained or decline. Thirdly by blocking longshore transport of beach sediment, building a protective beach up-drift, while starving the downdrift coast of sediment, potentially accelerating erosion in that area. To test these three possible mechanisms, investigation into the geological and geotechnical properties of the cliff and platform, beach volumes and sediment budget, wave refraction, and historical recession rates was undertaken. The elevation of the shore platform is controlled by their resistance to erosion, which is related to aspects of their lithology and structural geology. These include clay content, mass properties, dip and strike in relation to the orientation of the coastline and the strength of the surrounding beds. Although two of the established headlands, Hanover and Atherfield Points act as a partial barrier to sediment transport the sediment volumes along the coastline were insufficient to significantly influence recession rates. The results of the sediment budget indicate that the low sediment volumes observed are likely to have been consistent over time due to the low inputs of beach grade sediment. Wave refraction modelling revealed that concentration of wave energy occurs towards the established headlands of Hanover and Atherfield Points this is reflected in the higher than average recession rates seen at these headlands. It is concluded that the major control of the formation and evolution of headlands on the southwest coast is the geological and geotechnical properties of the intertidal platforms. Once established these headlands exist in a state of dynamic equilibrium controlled by the persistence of the platform forming beds and the balance between refraction and attenuation of wave energy across the platform surface. These results may have widespread implications on soft cliffed sediment-starved coasts where similar processes are dominant.

Estonian coastal wetlands are of international importance as they support characteristic biological diversity. Their limited extent and distribution mean that these wetlands are of high conservation concern, and as such have been identified as a priority in the European Union Habitats Directive. These wetlands are typified by a flat, extensive landscape, situated between the micro-tidal «0.02m), brackish Baltic Sea and a forest interior. Due to the low relief these wetlands may be under threat from sea level rise. This research consisted of four studies: (i) to determine and quantify the relationship between a range of coastal wetland plant community types, elevation and edaphic conditions. Results demonstrated that plant community distribution was significantly affected by micro-topography and edaphic variability. The majority of the plant communities were discernible in the field by elevation alone and elevation was found to be the factor that could distinguish the greatest number of plant communities. (ii) to determine an appropriate method of interpolating LiDAR elevation data and assess the use of LiDAR data in creating a static correlative model to determine plant community type based on elevation. Results showed that with dGPS calibration the model could accurately predict plant community location. Validation of the model in two further sites showed that the correlative model was able to predict plant community with almost perfect (K 0.81) and moderate agreement (K 0.53) dependent on the site. (iii) to determine sediment accretion rates to complete the dynamic model by analysing the level of radionuclides, 137CS and 210Pb, in discrete core sections. Results showed that during periods of greater storminess sediment accretion increased almost threefold. These sensitivity data were included in the dynamic correlative model. (iv) to assess the effects of sea level rise on plant communities in Estonian coastal wetlands under five sea level scenarios, two accretion rate scenarios and factoring in isostatic uplift rates. Results showed that local sea level will rise in some sites and decrease in others dependent on location and SLR scenario. This study has indicated that in many instances Estonian coastal wetlands will increase in extent in the future due to high rates of sediment accretion, particularly in a scenario with more frequent storms, and isostatic uplift. The study has shown that following validation, calibration and sensitivity analysis LiDAR data can be used to accurately predict plant community type in microtopographical ecosystems. The model developed in this study of Estonian coastal wetlands is likely to be transferable to other appropriate habitats such as tidal, estuarine, and floodplains wetlands.

Rivers are essential components of the earth surface. The world’s largest rivers have been studied much less than to smaller rivers. They are dominated by meandering channels – whether these are individual km-wide meander bends or ‘accessory’ meandering channels in an anabranching system. Large rivers, specifically ones with laterally migrating bends, can build a variety of floodplain elements that are represented by a complex surface topography, the dynamics and characteristics of which are not yet fully understood. This research brings a greater understanding to, and quantification of, the floodplain topography and geomorphology of large rivers. The project uses remote sensing imagery of the World’s largest rivers, LiDAR datasets of meandering scroll bar topography, and global coverage elevation data. Novel analytical methods are created, involving image manipulation and GIS processing, to quantify these landforms in a way that was not possible until recent technological and computational advancements. A new hierarchical classification schema of meandering floodplain deposits is presented and applied to quantify meandering deposits for two large rivers, the Amazon and the Ob. Both floodplains show similar downstream morphological changes to their floodplains despite their different sizes and locations. The new classification schema works well to describe meandering floodplain deposits. The geomorphology of scroll bars is investigated for the Mississippi River, revealing the heterogeneity of these deposits and that local meander bend conditions are important in determining scroll bar formation and preservation on the floodplain. The periodicity of scroll bars from a range of rivers is investigated and it is shown that scroll bars are intrinsically linked with the width of the adjacent river channel and respond to local planform changes. Floodplains of large rivers have complex overbank sedimentation processes that create spillage sedimentation phenomena. Spillage sedimentation was quantified down a 1700 km reach of the Amazon River and a 1400 km reach for the River Ob, revealing spatial discontinuities in spillage phenomena. Spillage dominance depends on diverse sediment loadings, hydrological sequencing, and morphological opportunity. Understanding spillage dynamics is important in quantifying overbank sedimentation rates and the spatial distribution of fine-grained deposits. The findings of this thesis highlight that despite the incredible complexity and heterogeneity of large river floodplains, order can be inferred via classification schemas and fundamental relationships identified. The thesis uses novel methods and conceptual models to bring a greater understanding and quantification to this complex floodplain geomorphology.

Detailed sedimentological studies, using coastal and inland exposures, were carried out at formation and bed levels on the Ashdown and Wadhurst Clay formations (Late Berriasian-Valanginian) in the Weald, southeast England. Field descriptions of outcrops were conducted at seven sites and supplemented by borehole and 2D seismic data. Field samples were studied in detail using hand specimen analysis. The sandstones were described in hand specimen and via optical microscopy. Clay mineral and geochemical analyses on mudstones, shales, and ironstones were conducted using XRD, XRF, and SGR methods while SEM analyses were conducted on selected sandstones and ironstones. Porosity and permeability of selected sandstones were measured using pycnometry and gas permeametry respectively. The dominance of quartz arenites and kaolinite and the presence of thorium and Zr in the sediments suggest that they were sourced mainly from granitic and/or gneissic rocks. Materials from metamorphic sources appear to be secondary in abundance. The mineralogical and textural maturity of the sediments coupled with relatively short travel distance (~300km) suggests reworking from secondary or matured sources. The two formations received sediments from at least two sources. The clay mineral assemblage, sandstone composition, and gamma-ray data confirm that the main source of the sediments is the London Massif in the north and north east while sediments were also sourced from Armorica in the south based on the presence of detrital zircon. The palaeoclimatic conditions at the source area as revealed by the dominance of quartz arenites and kaolinite and the presence of thorium were warm and humid which led to intensive weathering. The mineralogy and geochemistry of the sediments suggest that they may have been directly or indirectly sourced from a stable craton. The lithology (sandstones, siltstones, mudstones, shales and ironstones); facies (channel and floodplain/overbank); sedimentary structures (channels, cross stratification, flaser bedding, ripples and planar laminations); sedimentary architecture (repeated cycles and vertically stacked multi-storey successions), and gamma ray data (more radioactive sandstone facies) confirm that the sediments within the two formations were deposited in predominantly fresh water environments although tidal and lagoonal conditions were clearly evident in the Ashdown Formation and Wadhurst Clay Formation respectively. The lithology and sedimentary facies show that deposition occurred in both braided and meandering river systems although meandering facies are more prominent in the lower Ashdown Formation. The presence of abundant load and slump structures and fresh green glauconite in the sandstones provide evidence that deposition was rapid while the water depth was shallow and not beyond 2 metres based on the widespread occurrence of colour mottling and frequent exposure of the sediments to the air. Early diagenesis was confirmed by the precipitation of sideritic ironstones while diagenetic alteration is minimal based on the clay mineral assemblage. Evidence from the shallow burial nature of sideritic ironstone, the proportion of illite-smectite and the nature of diagenesis confirm that the sediments have experienced shallow burial not beyond 2km. Enrichments in redox sensitive trace elements such as Mo, U, V and Co suggest anoxic conditions in the sediments. The highest levels of anoxia were in the lower sections of the formations. Palaeosalinity as indicated by sideritic ironstone indicates a pH between 6 and 10. Porosity ranges from 6.8% to 13. 2% with an average of 9.9% while permeability ranges from 0.4mD to 11.9mD with an average of 3.1mD. The main controls on porosity and permeability are grain sizes, grain shapes, and sorting and the porosity is mainly primary. The main control on sedimentation is the local tectonics at the source areas while palaeoclimatic conditions, sea level, river dynamics, and subsidence are secondary. The proximal part of the modern Niger Delta is proposed as an analogue for the palaeoenvironments of the Ashdown and Wadhurst Clay formations. More generally, the results presented in this thesis highlight the usefulness of integrating field, petrographic, mineralogical, and geochemical data, and the use of modern analogue to fully assess the depositional environments, stratigraphic variability, post depositional changes and controls on deposition within sedimentary basins.