This dissertation has primarily been an exercise in surveying interdisciplinary opportunities for further research within the doctoral program's overarching mandate of Geospatial and Environmental Analysis. To this end I have dedicated my efforts to the investigation of topics and themes that are relevant to my three specializations: physical geography, biogeography, and geospatial science. I share these efforts in the three following chapters, one of which is already published (Chapter 2), and the other two presented as manuscripts suitable for publication. These themes include historical and present hydrological patterns and drivers, hurricane disturbance of coastal forest, and evaluation of a Wisconsin geosite as a possible candidate for UNESCO Geopark designation. I chose study areas located in the eastern United States, including Appalachia, the Gulf Coast, and the Great Lakes region. Every chapter's work has been supported by an interdisciplinary array of methods with which I have striven to generate high-quality research from excitingly novel perspectives. All of my research has been pursued, and each resultant manuscript has been crafted, using methods and techniques from remote sensing and GIS including in-person fieldwork, smartphonesupported geolocation and photodocumentation, pattern analysis, statistical rigor, and indepth review and citation of extant literature. This research was carried out with deliberately minimal budgets that help offset costs of transportation and labor. I offer this dissertation as the ultimate fruits of my labor while here at Virginia Tech, composed of three interrelated yet reasonably stand-alone manuscript chapters that in turn more specifically address questions within the broader fields of biogeomorphology, dendrotempestology, and finally the geohumanities. Chapter 2 was published in an open-source peer-reviewed journal (Land, 2021: https://doi.org/10.3390/land10121333). My coauthors and I intend to publish the remaining two chapters in peer-reviewed journals. Therefore each manuscript herein provides its own Introduction, Methods, Results, Discussion, Conclusion, and References sections as set forth in the Table of Contents. Chapter 2 is a recently published study of historical beaver activity and hydrological patterns at the rare and imperiled Cranberry Glades Botanical Area, a high-elevation peatland in the Allegheny highlands of West Virginia. We used Lidar and Geomorphon analysis to reconstruct shifting patterns of surface hydrology associated with Beaver ponds and dams over the past three decades. Beavers play a large role in the formation and maintenance of peatland conditions and our work provides a novel method (geomorphons) for monitoring beaver activity into the future. In Chapter 3, we take advantage of wind-damaged leaning pine trees to reconstruct characteristics of landfalling Hurricane Sally (2020) along the Gulf coast of Florida/Alabama (USA). We employed a smartphone to measure and record the direction of lean on 556 pine trees in five sites in the eyewall-struck region. Using geometric analysis, we were able to locate the geographic center of the storm and the position and size of the area of highest speed winds in Sally's eyewall. We validated our results with independent data from official sources and found that our simple field-based analysis was surprisingly accurate. We think that our low-cost and relatively low-tech approach may be useful to inform hindcasts, provide quality input to models of future stand-damaging events, and even to enhance teaching and outreach efforts. Chapter 4 represents research aimed at producing an inventory and assessment of the Baraboo Hills in south-central Wisconsin (USA) as a potential candidate for a UNESCO Geopark. The basis for designation is a geographical area that contains geological heritage of international significance, but such a park's fuller mission according to its website is to "explore, develop and celebrate the links between that geological heritage and all other aspects of the area's natural, cultural and intangible heritages." We followed a published method, including field study, to inventory and assess 62 sites in and around the Hills for their scientific, educational, and touristic merit, and their risk of degradation. We provide these data and through spatial analysis, a proposed perimeter of the area that would benefit from unified protection. / Doctor of Philosophy / This dissertation has primarily been an exercise in surveying interdisciplinary opportunities for further research within the doctoral program's overarching mandate of Geospatial and Environmental Analysis. To this end I have dedicated my efforts to the investigation of topics and themes that are relevant to my three specializations: physical geography, biogeography, and geospatial science. I share these efforts in the three following chapters, one of which is already published (Chapter 2), and the other two presented as manuscripts suitable for publication. These themes include historical and present hydrological patterns and drivers, hurricane disturbance of coastal forest, and evaluation of a Wisconsin geosite as a possible candidate for UNESCO Geopark designation. I chose study areas located in the eastern United States, including Appalachia, the Gulf Coast, and the Great Lakes region. Every chapter's work has been supported by an interdisciplinary array of methods with which I have striven to generate high-quality research from excitingly novel perspectives. All of my research has been pursued, and each resultant manuscript has been crafted, using methods and techniques from remote sensing and GIS including in-person fieldwork, smartphonesupported geolocation and photodocumentation, pattern analysis, statistical rigor, and indepth review and citation of extant literature. This research was carried out with deliberately minimal budgets that help offset costs of transportation and labor. I offer this dissertation as the ultimate fruits of my labor while here at Virginia Tech, composed of three interrelated yet reasonably stand-alone manuscript chapters that in turn more specifically address questions within the broader fields of biogeomorphology, dendrotempestology, and finally the geohumanities. Chapter 2 was published in an open-source peer-reviewed journal (Land, 2021: https://doi.org/10.3390/land10121333). My coauthors and I intend to publish the remaining two chapters in peer-reviewed journals. Therefore each manuscript herein provides its own Introduction, Methods, Results, Discussion, Conclusion, and References sections as set forth in the Table of Contents.

No description available.

Thesis (Ph. D.)--School of Geosciences, Faculty of Science, University of Sydney, 2004. / Degree awarded 2004; thesis submitted 2003. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Geosciences, Faculty of Science. Title from title screen (viewed 13 January 2009). Includes bibliographical references. Also available in print form.

Abstract The main goal of this study is to examine mechanisms controlling valley asymmetry development at two locations with distinctly differing environmental parameters and to develop a model for the two locations. As a secondary aim the knowledge gained from the main goal is thought to help understand the very uncertain glacial past of the high Drakensberg as it can be compared to the much accepted glacial history of Abisko. Parameters studied were slope angle, landforms, vegetation cover, block abundance, available moisture, bedrock characteristics, temperature and soil moisture. Some parameters were not studied in the field due to time issues; these were instead gathered by literature study. These parameters were structural weakness, soil depth and glaciation. Results show that the environmental differences noted between each sites north and south facing slope are clear. The side facing the equator is at both locations less steep, warmer and has more diverse vegetation. Temperature development with elevation was statistically analyzed and showed no correlation or not statistically significant correlation on all slopes. The expectation the south facing side of the Sani Pass transect showed where a statistically significant decline in temperature with elevation. The main conclusion drawn is that valley asymmetry development at both locations is controlled by the increased intensity of denudational processes on the side facing the equator as a result of the larger input of radiative energy there. It is also suggested that internal feedback mechanisms are related to the hastening of asymmetric development. The main constraint of the study is that not large enough data sets were gathered and that some important parameters like soil depth could not be included in the study. More research is needed in the field of vegetation’s role in interacting with physical processes on mountain slopes. The role of vegetation as an enhancer or retarder of geomorphic processes is not sufficiently understood. / Sammanfattning Denna studies huvuduppgift var att undersöka de mekanismer som kontrollerar uppkomsten av dalgångsasymmetri vid två områden som innehar vitt skilda naturliga förutsättningar och att skapa en modell för platserna. Informationen som ges från huvuduppgiften tros kunna hjälpa förstå den osäkra glaciala historien för Sani Pass eftersom den då direkt kan jämföras med Abiskos väldokumenterade historia. Undersökta parametrar vid båda platserna är sluttningsvinkel, landformer, vegetation, blockmängd, vattenmängd, berggrundskaraktär, temperatur och markfukt. Vissa parametrar kunde inte mätas i fält och fick därför hämtas från facklitteratur. Exempel på sådana parametrar är svagheter i berggrunden, jorddjup och glacial historia. Resultaten visar att det finns tydliga skillnader mellan nord och sydsluttningarna vid båda platser. Den sida som vetter mot ekvatorn har lägre sluttningsvinkel, är varmare och har mer varierande vegetation. Temperaturutveckling vid ökande höjd över havet undersöktes statistiskt där resultaten inte påvisade någon signifikant korrelation mellan ökande höjd och lägre temperatur vid alla områden utom en. Denna plats, Sani Pass nordliga sluttning, påvisades en statistiskt signifikant sänkning av temperaturen med stigande elevation. Den huvudsakliga slutsatsen som utgår från studien är den att utvecklingen av dalgångsassymetri vid båda platserna är kontrollerad av den ökade intensiteten av de nedslitande processerna på den sida som vetter mot ekvatorn. Detta sker på grund av den större mängd solenergi som denna sida mottar. Interna feedback processer verkar även vara kopplade till skapandet av dalgångsasymmetri. Den största motgången i denna studie är att inte nog med data har samlats samt att vissa viktiga parametrar som jorddjup inte kunnat studeras. Mer forskning behövs inom vegetations roll i interaktionen med fysiska processer på bergssluttningar. Om vegetation intensifierar eller motverkar dessa geomorfiska processer är inte tillräckligt förstått.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2011. / AFRIKAANSE OPSOMMING: Min aandag is al gegee aan biogeomorfologiese interaksies in glasiale en periglasiale omgewings. Nietemin is hierdie interaksies, wat op die skeidingsvlak tussen ekologie en geomorfologie fokus, baie belangrik in hierdie omgewings, waar organismes in noue verband met die abiotiese omgewing saamleef. In hierdie tesis bestudeer ek die interaksies tussen die vaskulêre plantspesies met die hoogste voorkoms op sub-Antarktiese Marion Eiland, Azorella selago Hook. (Apiaceae), en die omringende geomorfologiese landskapsvorme, -prosesse en meettegnieke. Verder verskaf die tesis voorstelle om toekomstige geïntegreerde biogeomorfologiese navorsing te vergemaklik. Om die gevolge van A. selago-plante vir sedimentbeweging en -verspreiding te verstaan, het ek die verspreiding van sedimentgroottes om hierdie plante gemeet deur middel van 'n kombinasie van fotografiese analise-metodes. Deur as sedimentbewegingsobstruksies te dien, het plante 'n waarneembare effek op die omringende sedimentverdeling. Dit is veral belangrik om hierdie interaksies tussen A. selago en sy omgewing te verstaan in die lig van onlangse klimaatsverandering op die eiland, omdat sedimentgrootte belangrike grondeienskappe soos waterretensiekapasiteit en vriesgevoeligheid beïnvloed. Om die effek wat A. selago plante op die omringende mikroklimaat het beter te verstaan, is die kleinskaalse variabiliteit in grondtemperature om A. selago plante bestudeer. Grootskaalse grondligting as gevolg van fors is gemeet, ten spyte van relatief ligte forseienskappe. Dit dui daarop dat naaldys ook by temperature bo -2°C kan vorm. Wintergrondtemperature aan die oostekant van plante was effens laer en minder veranderlik as aan die westekant van plante, waarskynlik as gevolg van laer windsnelhede en/of sneeu wat ophoop aan die oostelike, lykant van plante. Die resultate benadruk dat A. selago plante 'n belangrike rol speel in die verandering van mikroklimate en dat dit belangrik is om die gevolge van sulke veranderings, soos die skep van mikrohabitatte vir grondorganismes, te verstaan. Daar word vermoed dat positiewe plantinteraksies negatiewe interaksies oorheers in omgewings met hoe abiotiese druk. Gevolglik wys ek dat daar 'n positiewe verband bestaan tussen A. selago plante en saailinge van beide A. selago self, asook van die meerjarige gras Agrostis magellanica Lam. (Poaceae). Ek stel voor dat beide plante en klippe sade, wat deur wind, reenval en/of afdraande sedimenttransportering as gevolg van vriesprosesse vervoer word, opvang. Verder dui verhoogde A. selago saailinggetalle om plante, maar nie om klippe nie, daarop dat plante een of ander biologiese voordeel aan A. selago saailinge bied. Dit is bekend dat die verspreidingspatrone van plantspesies as gevolg van abiotiese stresgradiente varieër. Met hierdie bevinding in gedagte, is moontlike faktore verantwoordelik vir A. selago saailinggetalle en -verspreidingspatrone, soos hoogte bo seespieël en substraatbedekking, bestudeer. Alhoewel dit wil voorkom asof daar 'n verband tussen saailinggetalle en hoogte bo seespieël is, is saailinggetalle en verpreidings meestal afhanklik van ongemeette perseel-spesifieke eienskappe. Plante kan die omringende geomorfologie beïnvloed, maar ook geomorfologiese meettegnieke. Om die potensiaal van kosmogeniese dateringsmetodes as geomorfologiese hulpmiddels in fellfield habitatte te verken, is die akkumulasietempo van die kosmogeniese isotoop ¹ºBe onder en langs 'n A. selago plant bepaal. Die resultate dui daarop dat ¹ºBe nie ten volle in die grondprofiel behoue bly nie en verskeie potensiële redes word bespreek. Verder dui die resultate daarop dat ¹ºBe konsentrasies in fellfield habitatte versigtig geïnterpreteer moet word, aangesien A. selago plante effektief ¹ºBe opvang in hulle grondryke kern. Om vordering in biogeomorfologie te vergemaklik, is dit belangrik om bewus te wees van die verskillende metodes wat geomorfoloë en ekoloë volg. Ekologiese benaderings is dikwels op strenger statistiese tegnieke gebaseer, terwyl geomorfoloë eerder fokus op 'n meer beskrywende benadering en teoretiese beredenering. Ek verduidelik hoekom die twee velde sulke uiteenlopende benaderings volg, benadruk moontlike struikelblokke en verskaf voorstelle om samewerking te vergemaklik. / ENGLISH ABSTRACT: There are few scientific publications that relate to biogeomorphological interactions in glacial and periglacial environments. Interactions that focus on the interface between ecology and geomorphology are very important in these environments, as a tight coupling often exists between organisms and their abiotic surroundings. In this thesis the interactions between the dominant vascular cushion plant species on sub-Antarctic Marion Island, Azorella selago Hook. (Apiaceae), and the surrounding geomorphological landforms, processes and measuring techniques were studied. In addition, the thesis provides suggestions to facilitate future integrated biogeomorphological research. To understand the consequences of A. selago cushions for substrate movement and sorting, the grain size distribution of sediment surrounding these cushions was quantified using a combination of image analysis approaches. Through obstructing frost-related sediment transport, A. selago cushions are shown to affect the grain size sorting of the surrounding sediment. Particle size affects soil properties such as water-holding capacity and frost susceptibility. It is therefore important to understand the interactions between A. selago cushions and sediment distributions, especially in the light of recent warming and drying on the island. Fine scale variability in soil temperature parameters was studied around cushions to improve understanding on how A. selago affects the surrounding soil microclimate. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms above the previously suggested required temperature of -2°C. Lower and less variable winter temperatures were found on eastern than on western cushion sides, probably as a result of lower wind speeds or leeside snow accumulation on eastern cushion sides. These research findings highlight the importance of A. selago cushions in modifying site microclimates. Such modifications could have important potential consequences, such as providing microhabitats for soil microorganisms and seedlings. Positive plant interactions have been suggested to dominate over negative interactions in environments with high abiotic stress. Positive associations were found between A. selago and both its own seedlings and those of the perennial grass, Agrostis magellanica Lam. (Poaceae) on Marion Island. It is suggested that both cushions and rocks trap seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect to seedlings of their own kind. Plant species' distributions have been known to vary in response to abiotic stress gradients. In light of this, determinants of A. selago seedling distributions and abundance, such as altitude and substrate cover, were explored. Although there appears to be some altitudinal trend, seedling distributions and abundance patterns were largely attributed to unaccounted variation between sites. Plants can affect the surrounding geomorphology, but also geomorphological measuring techniques. To explore the potential of cosmogenic dating techniques as geomorphological tools in fellfield habitats, accumulation rates of the cosmogenic isotope ­¹ºBe were assessed underneath and adjacent to an A. selago cushion. The results show that ¹ºBe is not fully retained in the soil profile and various reasons are discussed. Furthermore, the results suggest that ¹ºBe concentrations should be interpreted cautiously in fellfield habitats, as A. selago cushions effectively intercept the isotope in their soil-rich core. To facilitate the integration of geomorphological and ecological principles, as was attempted in this thesis, it is important to understand the philosophies behind the different research approaches that ecologists and geomorphologists employ. Ecologists often employ a more statistics-based approach, whereas geomorphologists focus on a more descriptive approach and reasoning based on established theories. I attempt to explain why the two fields follow such different approaches, highlight some potential challenges and provide suggestions to facilitate progress in the interdisciplinary field of biogeomorphology.

Urbanisation is increasingly recognised as a major ecological pressure at the coast. By 2035, the Department for Environment, Food and Rural Affairs will have to spend £1 billion each year on flood defence and erosion control infrastructure if current levels of protection are to be sustained in England and Wales; this represents a substantial commitment to building new hard structures. Ecological research has shown that structures like seawalls, breakwaters, and harbour and port infrastructure are poor surrogates for undisturbed rocky shores. This, alongside substantial international policy drivers, has led to an interest in the ways in which structures might be enhanced for ecological gain. Virtually all of this research has been undertaken by ecologists, while the contribution of geomorphological understanding has not been fully recognised. This thesis presents an assessment of the two-way interactions between colonising organisms and the materials used to build hard coastal structures under a framework of biogeomorphology. The influence of material type and small-scale surface texture on early colonisation is assessed alongside detailed observations of the ways in which biota are involved in the alteration of substratum properties and behaviours through weathering and erosion in the intertidal zone. The research demonstrates that biotic (organisms) and abiotic (material substrata) components of coastal structures are inherently linked at various spatial and temporal scales through complex biogeomorphic interactions and feedbacks. Importantly, these interactions have consequences for the subsequent operation of ecological and geomorphological processes that are of relevance to urban marine ecology, weathering and rock coast geomorphology, and engineering. This thesis demonstrates the considerable potential to manipulate substratum-biota interactions on artificial structures for ecological gain, both directly and indirectly. More broadly, the explicitly interdisciplinary methodological approach adopted shows the value and necessity of integrated research for achieving useful, applied outcomes.

Recent studies within the past decade or so have shown the importance of algae in geomorphic and hydrologic processes of lotic systems. However, the ecohydraulic role of algae in bedrock systems has largely been ignored. In addition, the utility of algae as indicators of channel dynamics have often been assumed by geomorphologists, but relatively few studies have examined this relationship. The purpose of this study was to determine whether algae, specifically diatoms, are useful indicators of channel geomorphological dynamics, and to examine if distinct habitats or biotopes typical in fluviokarst and bedrock systems provide unique habitat space for diatoms, and to address the potential ecohydraulic implications. The investigation was performed in a 100 m reach of Shawnee Run, a limestone, fluviokarst tributary to the Kentucky River in Mercer County, KY. The results of the study showed that periphyton are not useful indicators of channel dynamics, and that biotopes and other distinct habitats, including riffles, bedforms, and fine sediment, do not provide unique habitat in terms of diatom community composition.

abstract: Ephemeral streams in Arizona that are perpendicularly intersected by the Central Arizona Project (CAP) canal have been altered due to partial or complete damming of the stream channel. The dammed upstream channels have experienced decades long cycles of sediment deposition and waterlogging during storm events causing the development of "green-up" zones. This dissertation examines the biogeomorphological effects of damming ephemeral streams caused by the CAP canal by investigating: (1) changes in the preexisting spatial cover of riparian vegetation and how these changes are affected by stream geometry; (2) green-up initiation and evolution; and (3) changes in plant species and community level changes. To the author's knowledge, this is the only study that undertakes an interdisciplinary approach to understanding the environmental responses to anthropogenically-altered ephemeral stream channels. The results presented herein show that vegetation along the upstream section increased by an average of 200,872 m2 per kilometer of the CAP canal over a 28 year period. Vegetation growth was compared to channel widths which share a quasi-linear relationship. Remote sensing analysis of Landsat TM images using an object-oriented approach shows that riparian vegetation cover gradually increased over 28 years. Field studies reveal that the increases in vegetation are attributed to the artificial rise in local base-level upstream created by the canal, which causes water to spill laterally onto the desert floor. Vegetation within the green-up zone varies considerably in comparison to pre-canal construction. Changes are most notable in vegetation community shifts and abundance. The wettest section of the green-up zone contains the greatest density of woody plant stems, the greatest vegetation volume, and a high percentage of herbaceous cover. Vegetation within wetter zones changed from a tree-shrub to a predominantly tree-herb assemblage, whereas desert shrubs located in zones with intermediate moisture have developed larger stems. Results from this study lend valuable insight to green-up processes associated with damming ephemeral streams, which can be applied to planning future canal or dam projects in drylands. Also, understanding the development of the green-up zones provide awareness to potentially avoiding flood damage to infrastructure that may be unknowingly constructed within the slow-growing green-up zone. / Dissertation/Thesis / Ph.D. Geography 2014

The plants and animals that inhabit river channels may act as zoogeomorphic agents affecting the nature and rates of sediment recruitment, transport and deposition. The impact of benthic-feeding fish, which disturb bed material sediments during their search for food, has received little attention, even though benthic feeding species are widespread in rivers and may collectively expend significant amounts of energy foraging across the bed. A series of experiments were conducted to investigate the impacts of benthic feeding fish on the structure and composition of gravel-bed river sediments, and the implications for bed material transport. An ex-situ experiment was conducted to investigate the impact of a benthic feeding fish (European Barbel Barbus barbus) on particle displacements, bed sediment structures, gravel entrainment and transport fluxes. In a laboratory flume, changes in bed surface topography were measured and grain displacements examined when an imbricated, water-worked bed of 5.6-16 mm gravels was exposed to feeding juvenile Barbel. For substrates that had been exposed to feeding fish and control substrates which had not, grain entrainment rates and bedload fluxes were measured under a moderate transport regime. On average, approximately 37% of the substrate, by area, was modified by foraging fish during a four-hour treatment period, resulting in increased microtopographic roughness and reduced particle imbrication. Structural changes caused by fish increased bed load flux by 60% under entrainment flows, whilst on average the total number of grains transported during the entrainment phase was 82% higher from substrates that had been disturbed by Barbel. An ex-situ experiment utilising Barbel and Chub Leuciscus cephalus extended this initial study by considering the role of fish size and species as controls of sediment disturbance by foraging. Increasing the size of Barbel had a significant effect on measured disturbance and bedload transport. Specifically, the area of disturbed substrate, foraging depth, microtopographic roughness and sediment structure all increased as functions of fish size, as did bedload flux and total transported mass. In a comparison of the foraging effects of like-sized Barbel and Chub 8-10 in length, Barbel foraged a larger area of the riverbed and had a greater impact on microtopographic roughness and sediment structure. Foraging by both species was associated with increased sediment transport, but the bed load flux after foraging by Barbel was 150% higher than that following foraging by Chub and the total transported mass of sediment was 98% greater. An in-situ experiment quantified the effects of foraging fish, primarily Cyprinids (specifically Barbel and Chub), on gravel-river bed sediment structures, surface grain-size distributions, sediment transport fluxes and grain entrainment in the River Idle, Nottinghamshire, UK. This was achieved by installing large experimental sediment trays seeded with food at typical densities. The experiments yielded data about 1) topographic and structural differences between pre- and post-feeding substrates using DEMs interpolated from laser scans, 2) modifications to surface and sub-surface grain-size distributions as a function of fish foraging and 3) differences in sediment entrainment from water-worked substrates exposed to feeding fish and control substrates, without fish. Small sections of the substrate trays were recovered in tact from the field and for substrates that had been exposed to feeding fish and control substrates which had not, grain entrainment rates and bedload fluxes were measured under a moderate transport regime in the laboratory. On average, approximately 74% of the substrate, by area, was modified by foraging fish during a twelve-hour period, resulting in increased microtopographic roughness and substrate coarsening which had significant implications for bed material transport during the steady entrainment flow. Together, results from these experiments indicate that by increasing surface microtopography, modifying the composition of fluvial substrates and undoing the naturally stable structures produced by water working, foraging can influence sediment transport dynamics, predominately by increasing the mobility of river bed materials. The implication of this result is that by influencing the quantity of available, transportable sediment and entrainment thresholds, benthic feeding may affect sediment transport fluxes in gravel-bed rivers. In addition, three discrete studies were performed alongside the core experiments described above. A quantitative examination of habitat conditions favoured by feeding Barbel was conducted in the River Idle (Nottinghamshire, UK) which served to supplement existing literature pertaining to Barbel ecology, and inform experimental design during the core experiments. Two further studies considered the potential importance of foraging as a zoogeomorphic activity in terms of spatial extent, at a variety of scales, thereby extending core experiments to larger spatial scales in-situ.

Signal crayfish are an internationally widespread invasive species that can have important detrimental ecological impacts. This thesis aims to determine whether signal crayfish have the potential to also impact the physical environment in rivers. A series of experiments were undertaken in purpose-built still-water aquaria using a laser scanner to obtain Digital Elevation Models (DEMs) of narrowly-graded gravel surfaces before and after exposure to crayfish. The difference between DEMs was used to quantify volumetric changes in surface topography due to crayfish activity. Two distinct types of topographic change were identified. The first was the construction of pits and mounds which resulted in an increase in surface roughness and grain exposure. The second was the rearrangement of surface material caused by crayfish brushing past grains when walking and foraging, reorientating grains and altering friction angles. A series of 80 flume runs were undertaken to quantify alterations made by crayfish to water-worked, as well as loose, gravel substrates at low velocity flows. Crayfish significantly altered the structure of water-worked substrates, reversing the imbrication of surface grains to a more random arrangement. Surfaces were entrained at a relatively high velocity flow subsequent to crayfish activity in order to directly link topographic and structural alterations to substrate stability. Nearly twice as many grains were mobilised from surfaces which had been disturbed by crayfish in comparison to control surfaces that were not exposed to crayfish. A field investigation aimed to determine the potential significance of the geomorphic impact of crayfish in rivers. Signal crayfish were tracked through a 20 m reach of a small, lowland alluvial river for 150 days using a Passive Integrated Transponder (PIT) system. Crayfish were active throughout the channel, although their activity became limited as water temperature dropped and flow stage increased. Substrate was not an important determinant of crayfish activity at this scale. Instead, crayfish tended to be found along the inner bank of a meander bend where there was a substantial cover of macrophytes. Consequently, signal crayfish were active for extended periods on substrates of a similar size to those that they could disturb in flume experiments. These results suggest that signal crayfish could have important geomorphic effects in rivers, disturbing bed structures and increasing the mobility of coarse material. This may have important implications for both the management of some rivers and benthic organisms that reside on the river bed.