Jon French

Diel surface temperature range scales with lake size

Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored.

Evolution and entropy in the organization of urban street patterns

The street patterns of cities are the result of long-term evolution and interaction between various internal, social and economic, and external, environmental and landscape, processes and factors. In this article, we use entropy as a measure of dispersion to study the effects of landscapes on the evolution and associated street patterns of two cities: Dundee in Eastern Scotland and Khorramabad in Western Iran, cities which have strong similarities in terms of the size of their street systems and populations but considerable differences in terms of their evolution within the landscape. Landscape features have strong effects on the city shape and street patterns of Dundee, which is primarily a shoreline city, while Khorramabad is primarily located within mountainous and valley terrain. We show how cumulative distributions of street lengths when graphed as log–log plots show abrupt changes in their straight-line slopes at lengths of about 120 m, indicating a change in street functionality across scale: streets shorter than 120 m are primarily local streets, whereas longer streets are mainly collectors and arterials. The entropy of a street-length population varies positively over its average length and length range which is the difference between the longest and the shortest streets in a population. Similarly, the entropies of the power law tails of the street populations of both cities have increased during their growth, indicating that the distribution of street lengths has gradually become more dispersed as these cities have expanded.

Entropy Measures of Street-Network Dispersion: Analysis of Coastal Cities in Brazil and Britain

Geographical location and landforms of various types have strong effects on the developments of many cities and associated street networks. This study presents new results of landform effects, in particular the geometry of shorelines, on the grid street networks (a total of 10,442 streets) of three Brazilian coastal cities. The results are compared with the street networks of three coastal cities in Britain (a total of 22,002 streets) that have evolved through a more natural “bottom-up” process. Gibbs/Shannon entropy (a measure of dispersion) generally has a positive linear correlation with length ranges and the average lengths of the street, and for the power-law tails in particular. The geometry of the adjacent shorelines has great effect on the spatial orientation of streets in the Brazilian cities but less so for the networks of the British cities. More specifically, the more curved the shoreline, the greater is the dispersion in the street orientation and the greater the associated entropy. The results also show that the length-entropies of the outer parts of the Brazilian cities are generally lower than those of the inner parts, whereas the entropies of outer parts of the British cities are higher than those of the inner parts, indicating dispersion during street-network growth in the British cities.

Large-scale spatial variability in the contemporary coastal sand and gravel resource, Suffolk, eastern UK

The response of coastal systems to changes in sea level and storm events is often dependent on the availability of sediment and sustainability of sediment supply. This paper analyses the changing sediment resource of a driftaligned shoreline in eastern England, UK, over centennial and decadal timescales. Spatial variability in cross-shore extent and elevational distribution of this mixed sand and gravel system exerts a significant control on the ability of different stretches of this shoreline to respond dynamically to changes in marine forcing. Furthermore, anthropogenic interference has led to the development of unnaturally high beach ridges in some places, which contrasts with the absence of intertidal or supratidal sediment along stretches dominated by seawalls.

Sediment sorting and mixing in the Camel Estuary, UK

ABSTRACT Oyedotun, T.D.T., Burningham, H. and French, J. R., 2013. Sediment sorting and mixing in the Camel Estuary, UK The Camel estuary, north Cornwall, UK, is characterised by extensive intertidal flats and saltmarsh that grade into beach and sand dunes at the mouth. This and other Cornish estuaries have received considerable attention in terms of the impact of mining (principally for Sb and Sn) on sedimentation. Significant changes in sediment supplied to these systems from the local catchment occurred as a result of mining activity. The primary impacts were on supply, sedimentology and mineralogy, and the peak of these impacts occurred in the 19th century. Although pollution and chemistry indicators have been considered extensively in past studies, very little consideration has been given to the nature of estuary-coast linkages in terms of sedimentary processes. This study focuses on the sedimentological characteristics of surface and shallow intertidal sediments within the Camel estuary system. Short (15cm) sediment cores obtained from 44 sample sites were sliced at 1cm intervals and grain size analysis (using a Malvern Mastersizer 2000) was undertaken on these subsamples. A wide range of grain size parameters is examined to explore the evidence for sediment mixing and extensive sediment transport processes within the estuarine system. Results show that the sediments are dominated by medium to fine sands throughout except in the inner estuary. Sediment is moderately well sorted in the outer and mid-estuary and poorly sorted in the inner estuary. It is possible that valley shape influences sediment transport processes and inhibits the supply and active reworking of marine sands in the inner estuary.

Correction to: Implementation of a 3D ocean model to understand upland lake wind-driven circulation

The article “Implementation of a 3D ocean model to understand upland lake wind-driven circulation”, written by L.A. Morales-Marín, J.R. French and H. Burningham, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 12 October 2017 without open access.

Evaluating Broadscale Morphological Change in the Coastal Zone Using a Logic-Based Behavioural Systems Approach

Climate change will have pervasive effects on the world’s coasts, but at broad scales these changes have typically proven difficult to analyse in a quantifiable manner. Consequently, individual management decisions are often taken without consideration of the wider, regional coastal system with its physical linkages between geomorphological elements.