Historically, wildfires in mixed conifer forests of Southwestern sky islands were frequent events. Dendrochronological methods were used to reconstruct fire regimes and stand age structures in the Huachuca Mountains of Southeastern Arizona. Pre-settlement (i.e., before ca. 1870) fire intervals ranged from 4 to 10 years, with many fires spreading over the entire sample area. Stand age distributions show an increase in more shade-tolerant tree species. Although ponderosa pine is still the dominant overstory tree species, recent recruitment is predominantly southwestern white pine and Douglas-fir. Establishment of Ft. Huachuca in 1877 was a precursor to extensive use of timber, mineral, range and water resources in the Huachuca Mountains. The fire regime was altered at this time, with only one subsequent widespread surface fire recorded in 1899. Settlement era land-use practices may be responsible for changes in stand structure and composition.

This thesis considers the geochemical links between geophysical survey results from, and responses of barley crop growth to, the existence of plough-levelled archaeological sites. It takes as a starting point the results of magnetic and resistivity surveys undertaken at three sites in the Upper Clyde Valley, Lanarkshire, Scotland. Two of the three sites produced geophysical results that closely matched the evidence for archaeological remains recorded using oblique aerial photography. The third site was largely unresponsive to geophysical prospection techniques. These mixed responses prompted a closer examination of why barley crops respond to plough-levelled remains, and why the geophysical data gathered tend to correlate with the growth responses. To allow an examination of the growth responses, a series of pot-based growth experiments were carried out under glasshouse conditions, and these were followed up by ICP-MS analysis of the plants and the archaeological soils in which they had grown, in an attempt to link any changes in elemental compositions with the growth responses, and to the geophysical responses recorded at the soil sampling points or for the features from which the soils were taken. The results of the experimental work revealed that although soil moisture content has a role in the development of both crop marks and geophysical anomalies, other factors are also involved, including changes in elemental concentrations in soils and plant material, soil pH changes and the redox potential of the archaeological soils.

A baseline study has been undertaken to assess the environmental impact of heavy metals within the fluvial environment of the River Stour, E. Kent, U.K. The occurrence of metal enrichment in surface waters and bed sediments coincides mainly with areas of urbanisation and high density traffic in addition to point source discharges including STW and industrial effluent outlets. Non-tidal surface water samples exhibiting Pb, Co, Cu, Fe and Zn concentrations intermittently elevated above EQS List I and II values largely correspond with bed sediment samples exhibiting metal concentrations above background values and commonly partitioned to the mobile exchangeable/acid soluble and reducible fractions. In the tidal reaches surface water samples exhibiting As, Cd, Co, Cu, Cr, Ni, Pb, V and Zn concentrations above EQS List I and II values are generally associated with bed sediment samples exhibiting partitioning to the immobile oxidisable fraction, suggesting that estuarine processes effectively promote the liberation of elements from the sediment compartment to surface waters. Total catchment annual suspended sediment yield, (190 t/km2/yr), is consistent with previous research work detailing the annual yield of U.K. rivers which in conjunction with suspended sediment concentration data highlights the importance of the transport and distribution of associated elements throughout the river system. Research highlights a requirement to improve point source management measures and control non-point sources and dredging activities and provides an index in which to assess the future impact of anthropogenic sources of metals to the fluvial environment of the River Stour.

A baseline survey of contemporary fluvial sediments in the Kentish Stour, east Kent, England, has been undertaken to document the sources and distribution patterns of anthropogenic PGE in an attempt to constrain some of the physical and chemical parameters that may influence the distribution of these elements. Nine sedimentary rocks, four motorway-runoff sediments and twenty-one river sediments were analysed for PGE by NiS fire assay pre-concentration and ICP-MS. The highest element abundances occur in a sample of ashed sewage sludge (total PGE content of 392 ng/g), whilst the lowest values were recorded in the soils and sedimentary rocks. The total PGE content of the river sediments ranged from 0.4 to 14.2 ng/g in 1999 and from 0.6 to 167 ng/g in 2001, and exhibited significant variation along the river. This variation corresponds strongly with land use changes (urban versus rural) and with points of discharge from sewage treatment works. The PGE and trace element concentrations of the river sediments, sedimentary rocks, motorway runoff sediments and ashed sewage sludge were normalised against their average crustal abundance to identify characteristic normalisation patterns. With this technique, high Pd concentrations in the River Stour sediments were found to be indicative of sewage inputs. The partitioning of Pt, Pd and Rh was investigated in a novel combination of Tessier’s (1979) sequential extraction technique and a Te coprecipitation. The partitioning in the sediments of a sediment retention lagoon progressed from more to less mobile sediment phases. The PGE are emitted in a form (possibly particulate) that becomes predominantly associated with the silicates fraction. The behaviour of the PGE in the River Stour is predicted to be controlled predominantly by physical processes.

Recent research on sediment transport in gravel bed rivers shows evidence of the influence of sub-threshold flow history on values of entrainment thresholds (Paphitis and Collins, 2005; Monteith and Pender, 2005; Haynes and Pender, 2007; Haynes and Ockelford, 2008). The research presented here analyses the effect of the characteristics of hydrograph rising limbs (flow magnitude and duration) on entrainment thresholds of gravel beds, with discharges ranging from 0.25-1.6 times the estimated bed threshold flow and durations from 0.5h to 6h. This analysis uses results from flume experimentation. Entrainment thresholds were determined by two well documented methods: a) particle movement counts (visual method, Yalin, 1977); and b) the reference transport method (RTM) (Parker et al., 1982a; Shvidchenko et al., 2001). Results obtained with near-uniform and uniform bed material sizes show a clear influence of flow magnitude and duration on entrainment thresholds, with bed resistance increasing up to c. 25% for longer durations of antecedent flows when using the visual method, similarly to Paphitis and Collins (2005). The results from the unimodal gravel bed suggest an intermediate duration of rising limb (c. 2h) producing the strongest bed, with more mobile beds resulting from both shorter and longer rising limbs. Total bedload transport rates reduce with increased bed resistance, this effect is also noted during the stability test phase. These results are used to develop a new simplified method for estimating critical bed shear stress using only total bedload data. The performance of a new formulation for bedload rates derived in this thesis is tested against a number of traditional bedload transport equations and appropriately discussed. In-depth analyses of bed surface and bedload size composition and surface grain structure show that bed surface undergoes little change of size composition, with a slightly proportionally larger reduction of fine content, suggesting penetration of fines below the surface. The analysis of coarse-grain bed surface structures, mobility and clustering, based on the size class containing D90 and using digital images taken under UV light, suggests that the surface distribution of coarse grains has a primary role on bed stability.

River ecosystems can be strongly in uenced by contaminants in the water column, in the pore water and attached to sediment particles. Current models [TGD, 2003] predict exposure to sediments based on equilibrium partitioning between dissolved and suspended-particle-sorbed phase in the water column despite numerous studies showing significant direct mass transfer across the sediment water interface. When exchange across the interface (hyporheic exchange) is included in modelling the diffusion coefficient is assumed to be constant with depth. The overall aims of this research were to quantify the vertical variation in diffusion coefficient below the sediment water interface and asses the use of a modified EROSIMESS-System (erosimeter) in the study of hyporheic exchange. The modified erosimeter and novel fibre optic uorometers measuring in-bed concentrations Rhodamine WT were employed in an experimental investigation. Five different diameter glass sphere beds (0.15 to 5.0mm) and five bed shear velocities (0.01 to 0.04m/s) allowed the vertical variation in diffusion coefficient to be quantified to a depth of 0.134m below the sediment water interface. The vertical variation in diffusion coefficient can be described using an exponential function that was found to be consistent for all the parameter combinations tested. This function, combined with the scaling relationship proposed by O'Connor and Harvey [2008] allows a prediction of the diffusion coefficient below the sediment water interface based on bed shear velocity, roughness height and permeability. 1D numerical diffusion model simulations using the exponential function compare favourably with the experimental data.

Diffuse sources of sediment may have important implications for flood risk management (FRM), especially as catchment sediment yields are predicted to increase in future. UK legislation requires FRM to work with natural processes wherever possible, including accounting for sediments. However, the importance of wash-material load to FRM has been under researched and both a robust evidence-base and practical sediment models are needed to identify, prioritise and justify sediment-related catchment management. Research addressing these issues was centred on the River Tone, a sub-catchment of the Parrett, in which features excessive inputs of sediment in its upper catchment combined with high potential for deposition in its lower reaches. Links between sediment sources, water and sediment runoff, and downstream sediment sinks were established and the research examined the role played by sediment, especially wash-material load, within the fluvial system. The greatest sediment-related threats to the functioning of this lowland river stem from either: a protracted, major reduction in wash-material load; or a significant increase in bed-material load. Imbalance in the Tone fluvial-sediment system may not significantly affect flood risk directly, but has implications for FRM operations, maintenance and monitoring. Impacts on land quality result from soil loss. For example, ~2.5 million tonnes of soil has been eroded from the Parrett catchment since WWII. Water quality issues include delivery of phosphate and other pollutants into the river, and potentially more frequent dredging that remobilises contaminants. The thesis defines the key sediment-related components of sustainable, integrated catchment management and provides an improved evidence-base upon which to engage stakeholders. It tests and benchmarks sediment assessment tools including the Sediment Impact Assessment Model (SIAM). An approach to catchment-scale sediment assessment for lowland rivers is recommended, which involves a nested-approach using routinely collected and project-specific field data, stream power screening and SIAM.

<p> The Lake Titlow watershed (approximately 35,000 acres) in south-central Minnesota is part of the Minnesota River Basin. The lake is listed in the draft 2010 Clean Water Act Section 303d for nutrient pollution, eutrophication, and biological indicators for impairment of aquatic life and recreational use. Over 90 percent of pre-settlement wetlands are currently drained for agricultural land use. The Lake Titlow watershed is over 80 percent row crops and land use is implicated as a primary cause of impairment in the lake. </p><p> Water samples were collected from the Lake Titlow tributaries McLeod-Sibley Judicial Ditch Number 18 (JD18), Sibley County Ditch Number 18 (CD18), and Ditch 250 (D250) during 2009 and 2010 and were analyzed for total suspended solids (TSS), total phosphorus (TP), and nitrate-nitrite nitrogen (NOx). Investigative methods included continuous recording stream stage and through the use of rating curves, discharge. Runoff, sediment loads, and nutrient loads were then determined from the field data. Four rain gauges collected precipitation each year and were used to assess the impact of precipitation on runoff and loading. Four characteristic precipitation events were selected for each of the calendar years 2009 and 2010 to estimate the loads of sediment and nutrients to the lake and more fully understand the specific roles that land use, hydrologic soil group, slope, and precipitation play with regard to causing sediment and nutrient loading in the lake. </p><p> Results indicate runoff and loads are significant and highly variable by position within the watershed, areas referred to herein as subsheds. The row crop land use, soils characteristics, and precipitation do contribute to overall runoff and loads; however, they do not control subshed variability. Although the low-sloping land surfaces of the watershed should not contribute to overall runoff and loads, results indicate that subtle slope changes in the JD18Lo and CD18Lo subsheds could contribute to the variability of loads seen in these portions of the watershed. </p><p> The location and type of best management practices to implement is debatable because the results of this study indicate that large runoffs and loads could originate within any given subshed during any given rainstorm event. This study was unable to precisely identify the root cause of the variability in subshed runoff and loading. Therefore, it is suggested to look at other factors (e.g., antecedent soil moisture, rainfall intensity, mass wasting, etc.) to explain the subshed variability in the sediment and nutrient loading in future studies of this lakeshed.</p>

The purpose of this study is to analyse the impact of the 2010 Chile earthquake and tsunami on community resilience. Specifically, the thesis examines the role of community resilience in coping with and recovery from natural disasters, and the capacities and external factors that enhance or undermine the levels of community resilience. Furthermore, this study focuses on developing a model suitable for analysing community resilience in the context of natural disasters in Chile. In 2010, a magnitude 8.8 earthquake and tsunami struck Chile. Coastal areas were particularly affected by the disaster; fishing villages were completely destroyed and many people were injured and killed by the tsunami. However, exceptionally, only one fishing village entirely survived the tsunami impact in Talcahuano, one of the worst affected regions by the disaster. This is the case of the ‘El Morro’ community where, despite their boats and houses being swept away by the destructive waves, no one died. This community, considered the most successful experience in coping effectively with the disaster in the country, is the case analysed in this thesis. The results of a primary research conducted in the ‘El Morro’ case study (through methods of semi-structured interviews, observation, informal conversations, documentary review and social media) show that communities have the power to activate internal resources and capacities to cope with and recover from natural disasters. The research highlights that communities are not simply passive victims of disasters; rather, they are active agents. Furthermore, it shows that external factors, specifically political ones can have a detrimental effect on community resilience. Additionally, an integrated model of community resilience was developed which provides new insights into measuring community resilience in the context of natural disasters. Finally, these findings could be useful for designing effective disaster risk reduction programmes and promoting community resilience in Chile and in other developing countries.

Uppsatsen analyserar didaktisk hur väl geografiska exkursionshandledningar besvarar det centrala innehållet för Geografi 2 på gymnasieskolan. Uppsatsen syftar till att undersöka hur geografiska exkursioner motsvarar och reflekterar mål och styrdokument för Geografi 2 på gymnasieskolan samt varför materialet ser ut som det gör. Den ska också undersöka behovet av hjälpmedel för geografiska exkursioner. Exkursionshandledningarna analyseras utifrån en typ av systematisk analys som klargör idéstrukturer. Resultaten undersöks med hjälp av semi-strukturerade intervjuer. Studien visar att det finns få exkursionshandledningar att tillgå som hjälper läraren att besvara det centrala innehållet för Geografi 2. Tidigare forskning och intervjuer pekar på att det finns en tydlig naturgeografisk exkursionstradition som inte finns inom kulturgeografin. Detta leder till att Geografi 2, som är kulturgeografisk, inte kan förlita sig på de exkursionshandledningar som finns att tillgå. Utöver det tycks det också finnas en generationsskillnad bland geografer och geografilärare som länge gjort att de två geografiska skolorna hållits isär. Samtidigt visar studien att trots att behovet av kulturgeografiska exkursionshandledningar är stort är utbudet desto mindre.