THERMAL BEHAVIOR OF URBAN LANDSCAPES AND THE URBAN HEAT ISLAND

The cause or causes of urban heat islands have puzzled scientists for more than a century. Investigators have observed a close relation between urban land cover and urban temperature patterns. A proposed explanation of this relation is that the thermal inertia of urban surfaces is larger than rural interface thermal inertia. However, recent METROMEX and remote sensor satellite observations do not appear to support this view. The thermal inertia model of the urban interface ignores urban canopy structure and composition. Specifically the hollow structure of buildings reduces the thermal mass and thus the apparent thermal inertia of these structures compared with pavements. Numerical modeling results of the thermal behavior of a two-layer interface and aircraft far-infrared remote sensor observations of urban landscapes demonstrate the differential thermal behavior of buildings versus pavements. Accounting for the structure and configuration of urban canopies explains observed urban landscape thermal behavior and should assist in explaining the urban heat island phenomenon.     

Municipal initiatives for managing dunes in coastal residential areas: a case study of Avalon, New Jersey, USA

The characteristics of foredunes created in a municipal management program on a developed barrier island are evaluated to identify how landforms used as protection structures can be natural in appearance and function yet compatible with human values. Shoreline management zones include a naturally evolving, undeveloped segment; a noneroding, developed segment; eroding and noneroding segments of an “improved beach” where dunes have been built by artificial nourishment; and a privately built, artificially nourished dune on the shoreline of an inlet.A disastrous storm in 1962 resulted in an aggressive program for building dunes using sand fences, vegetation plantings, purchase of undeveloped lots, and sediment backpassing to maintain beach widths and dune elevations. The present nourished and shaped foredune in the improved beach is higher, wider, and closer to the berm crest than the natural dune. Restricted inputs of aeolian sand keep the surface flat and poorly vegetated. A stable section of this engineered shore has a wider beach, and sand fences have created a higher foredune with greater topographic diversity. The cross shore zonation of vegetation here is more typical of natural dunes, but the environmental gradient is much narrower. The privately built dune is low, narrow, and located where it could not be created naturally. Foreshore and aeolian sediments in the undeveloped segment and the improved beach are similar in mean grain size (0.16–0.21 mm) and sorting (0.31–0.39φ), but sediment on the surface of the nourished dune is coarser (28.1% gravel) with a more poorly sorted sand fraction (1.30φ) representing lag elements on the deflation surface.Willingness to enhance beaches and dunes for protection has reduced insurance premiums and allowed the municipality to qualify for funds from the Federal Emergency Management Agency (FEMA) to replace lost sediment, thus placing an economic value on dunes. Success of the management program is attributed to: (i) timing property-purchase and dune-building programs to periods immediately after storms (causing residents to accept high dunes that restrict access or views); (ii) instituting a vigorous education program (reminding residents of hazards during nonstorm periods); (iii) maintaining control over local sediment supplies (to keep pace with erosion and create new shoreline environments); (iv) investing private and municipal economic resources in landforms (qualifying them for external funds for replacement); and (v) maintaining, augmenting, or simply tolerating biodiversity and natural processes (retaining a natural heritage).     

THE FALL LINE: A PHYSIOGRAPHIC‐FOREST VEGETATION BOUNDARY*

ABSTRACT. The range boundaries for many tree species in the southeastern United States correspond to the Fall Line that separates the Coastal Plain from the Appalachian Highlands. Trees in the Coastal Plain with northern range boundaries corresponding to the Fall Line occur exclusively in alluvial valleys created by lateral channel migration. These species grow mostly on lower bottomland sites characterized by a high water table, soils that are often saturated, and low annual water fluctuation. In contrast to the Coastal Plain, the southern Appalachian Highlands are occupied mostly by bedrock streams that have few sites suitable for the regeneration of these species. The Fall Line is also an approximate southern boundary for trees common in the southern Appalachians that typically occur on either dry, rocky ridgetops or in narrow stream valleys, habitats that are uncommon on the relatively flat Coastal Plain. The ranges for many trees in eastern North America are controlled by large‐scale climatic patterns. Tree species with range boundaries corresponding to the Fall Line, however, are not approaching their physiological limits caused by progressively harsher climatic conditions or by competition. Instead, the Fall Line represents the approximate boundary of habitats suitable for regeneration.     

WESTERN RANGE BOUNDARIES OF FLOODPLAIN TREES IN THE SOUTHEASTERN UNITED STATES

Forest vegetation in the southeastern United States extends westward beyond the Ozark and Ouachita plateaus in Arkansas and Missouri into the Central Plains. Along this transect, luxuriant forests give way to mixed forests and grasslands that include smaller trees and progressively fewer tree species and eventually to grassland‐dominated landscapes in central Kansas, Oklahoma, and Texas. This transition is directly related to decreasing precipitation with distance to the west of the Mississippi River valley. Many species, however, have abrupt western range boundaries related to physiography and hydrogeomorphic processes. The western range limits for many trees correspond to Coastal Plain boundaries that at a regional scale impose sharper range boundaries than would be expected on the basis of decreasing precipitation. Also, riparian habitats within stream valleys extending westward from the Coastal Plain provide suitable habitats for trees in the dry regions of the Great Plains. The presence of riparian trees in this region is determined largely by the presence or absence of groundwater conditions necessary for survival. For floodplain trees, then, it is primarily habitat—not climate—that determines the location of range boundaries.     

Phases of blowout initiation and stabilization on Padre Island revealed through ground-penetrating radar and remotely sensed imagery

Abstract

Blowouts cover a large section of North Padre Island, Texas, and have previously been associated with overgrazing and vehicles driving between the low water line and the toe of the foredune. In the current study, the evolution and migration of 18 blowouts within Padre Island National Seashore are tracked using aerial photographs and satellite images since 1969. Representative active and stabilized trough blowouts are also examined using ground-penetrating radar surveys and remotely sensed imagery to identify the phases of blowout initiation and stabilization between 1969 and 2010. At least five distinct phases can be identified in the radar surfaces and facies of the active blowout, including both the stabilization and reactivation of the blowout throat, whereas only four phases can be identified in the surfaces and facies of a blowout that completely stabilized in 2010. Results suggest that blowout evolution on Padre Island is episodic and is initiated by the opening and closing of the blowout throat during periods with elevated storm surge. The lack of reflectors at depth is evidence that the development of blowouts on Padre Island is a relatively new phenomenon initiated by overgrazing and maintained by compaction of the beach and backshore by vehicles.     

Evidence of aeolian sediment transport across an Ammophila arenaria‐dominated foredune,Mason Bay,Stewart Island

Aeolian sedimentation across an Ammophila arenaria‐dominated foredune was assessed for eight months using sand traps. This research aimed to ascertain if such foredunes act as a barrier to transport between beaches and hinterland dune systems. At Mason Bay, sand was transported across the foredune at rates of up to 10 kg.hour^?1per 100 m length of coast at wind velocities of 31 m.s^?1. Results were compared with computational fluid dynamics modelled airflows and foredune volume changes. Saltation was important for up to 17 m past the stoss face. Rates of transport were well short of rates of volume gain. Approximately 2% or less of stoss face suspended sediment transport reached the hinterland. The foredune is primarily a sand sink.     

闽江口海岸沙丘的形成与演化

闽江口海岸沙丘的物质来源于以闽江泥沙为沙源的海滩沙，宽广的海滩、强劲的向岸风与干旱的时空耦合，适宜的地形空间构成了海岸沙丘发育的基本条件。海岸沙丘起源于约２５００ａＢ．Ｐ．，其活动是多幕次的，唐、宋及近代几次气候干冷期的出现，人口陡增以及垦荒规模扩大等人为因素，促进了海岸沙丘的发育进程。海岸沙丘从海向陆按雏形沙丘，岸前沙丘，横向沙丘及沙丘链，圆形、抛物线型或Ｕ型沙丘及风积平原依次演化。     

海平面上升与海滩侵蚀

世纪性的海平面持续上升，加大了海岸水下斜坡深度，逐渐减小波浪对沉溺古海岸的扰动作用而形成海底的横向供沙减少，却加强激浪对上部海滩的冲刷。逐渐上升的海平面，降低了河流坡降而减少了入海沙量。因此世界海滩普遍出现沙量补给匮乏。海平面上升伴随着厄尔尼诺现象与风暴潮频率的增加，水动力加大。这两者的综合效应，使海滩遭受冲刷，沙坝向陆移动。如按ＩＰＣＣ估计，至２１００年海面上升５０ｃｍ时，中国主要旅游海滨的沙滩将损失现有面积的１３％─６６％。主要对策是海岸防护与海滩人工喂养。     

Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana

Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 10⁶ m³/a before 1964 (pre-Akosombo dam) to about 7 × 10⁶ m³/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast. There is the need, therefore, to ensure that catchment management plans and coastal management plans are integrated or interconnected.     

A Review of “The Experience of Return Migration: Caribbean Perspectives”

Abstract

Commuting in Italy has always been addressed without regard to gender differences. Following the issuance of a comprehensive database by the National Statistical Institute, it is now possible to analyze gender differences in personal mobility for the first time in Italy. For our analyses we used Local Labor Systems (LLS) zoning in lieu of administrative zoning. LLSs are territorial subdivisions based on the principle of a self-contained labor market and are widely used in Italy. This article also reports the results of a multidimensional data analysis aimed at highlighting relations between different gender-based commuting patterns and a set of variables (education level, age, household structure, occupational category, and position, etc.). The analysis points out gender differences in the relationship among commuting and socioeconomic characteristics, reveals that these relationships are in turn related to the economic structure and geographical context of different regional labor markets, and suggests to analysts that they be sensitive to singular context when interpreting the meaning of gender differences in commuting.

     

A rationale for beach selection by the public on the coast of Wales, UK

Questionnaires were completed by 2306 beach users at 19 Welsh beaches with respect to beach selection parameters. The modal group of respondents was female aged 30–39. Beach choice was primarily determined by clean litter-free sand and seawater, followed by safety. Refreshment facilities and beach awards were deemed minor considerations by the public when choosing a beach to visit. Approximately 58 per cent of respondents were aware of beach award and rating schemes. Of coastal visitors interviewed for this paper, 67 per cent rated a beach as 'important' or 'very important' to their holiday, with just 2 per cent replying that they were unimportant.     

THE MARBLE BEACHES OF TUSCANY*

ABSTRACT. Beach‐nourishment operations designed to replace sediment lost through erosion change the identity and meaning of coastal landscapes. Seven beaches in Tuscany, nourished with marble‐quarry waste, reveal how an industrial byproduct is naturalized by particle rounding and sorting and can become a positive symbol of human‐altered nature. The marble was placed on formerly sandy beaches, resulting in different grain size and color of sediments, beach morphology, and value for human use. The abrasion rate of marble makes the nourished beaches unsatisfactory when viewed solely as protection structures, but the rapid particle rounding and aesthetic appeal of marble increase the acceptability of the beaches for recreation.     

Tourist Carrying Capacity Measures: Crowding Syndrome in the Caribbean

International tourism is increasing at an unprecedented rate. Understanding the variety of national and local impacts of this increase is of importance to a growing number of governments. Butler's resort cycle model (1974, 1980, 1991) provides for several long‐term possibilities as to the relationship between crowding and growth. McElroy, de Albuquerque, and Dioguardi (1993) focus on one of those possibilities. Specifically, using their penetration ratio, they predict that as tourist crowding continues for a group of Caribbean islands, the appeal of these islands decreases in the eyes of potential tourists and that, as time increases, the growth rate of the affected islands, actually decreases. Our article indicates that such a simple, straight‐line relationship between increased crowding and a decrease in the rate of change may not be inevitable; indeed, diseconomies of scale may be avoided. The use of a curvilinear regression function reveals how both positive and negative scale economies existed in the Caribbean during the years 1992 through 1996.     

基于地貌动力学的雷州半岛海滩状态分类研究

海滩地貌动力学为理解海滩形态和海岸动力环境提供了理论框架,在海滩的保护与开发中有重要的指导意义。基于地质背景、海滩地貌形态、海滩沉积物和海洋动力要素选取7个可以量化的海滩特征指标,采用聚类分析对雷州半岛23个海滩进行分类和地貌动力特征识别,针对海滩状态分类模型Ω-RTR在雷州半岛复杂多变海岸线环境下的适用性进行了分析,结果表明：① 雷州半岛海滩可以分为六类：反射组、低潮阶地/反射组（有裂流）、沙坝-槽谷/中间状态组、沙坝消散组、超消散组和低潮阶地/反射组（无裂流）;② 波浪、潮汐、沉积物特征以及海岸地质构造背景等对雷州半岛海滩状态均有不同程度的影响,在不同岸段各要素的影响各异。地质背景是海滩状态分类不可忽视的因素。③ 由于Ω-RTR模型在判别海滩状态时更侧重于动力和沉积因素,分类结果与聚类分析结果稍有差异,但总体上可以有效区分海滩状态类型,是理解海滩动力地貌系统有效手段。     

美国海滩养护与海滩经济对中国 滨海旅游产业发展的启示

根据美国最新的海滩经济和旅游研究的数据资料,分析了其海滩养护的概况、管理、对滨海旅游经济增长的贡献和当前面临的困境,对照分析了中国滨海旅游产业发展所面临的海岸侵蚀加剧、海滩环境污染、海滩养护投入力度不够、政府职能分散、旅游开发破坏公众利益等一系列问题,借鉴美国海滩旅游开发经验并结合中国实际情况,分别从海滩养护、海滩开发研究与评估、政府管理、动态监测几个层面提出中国未来海滩旅游开发的建议。     

The environmental envelope of fires in the Colombian Caribbean

Fire is an important disturbance agent for terrestrial ecosystems, particularly in tropical and subtropical regions where its occurrence is controlled by multiple biophysical and anthropogenic variables. We assessed the temporal and spatial patterns of active fire detections (MODIS product MCD14ML) in the Caribbean region of Colombia between 2003 and 2015, using time series, cross-correlation, hot spot and density techniques. We also assessed the environmental envelope of active fires by evaluating the effect of multiple biophysical and anthropogenic variables on fire presence/absence using generalized linear models (GLMs). Results show that fires follow a clear intra-annual cycle, with 86% of fire events taking place during the region's main dry season (December–March). There is also inter-annual variability related to the Tropical North Atlantic (TNA) quasi-decadal climatic oscillation. Active fires exhibit a distinctive spatial pattern, with regional hotspots. The set of variables that best explain fire presence/absence include biophysical (TNA, temperature annual range, dry quarter precipitation), anthropogenic (minimum distance to towns and roads) and composite (NDVI) variables. The extensive and ongoing land cover transformation of this region, from forest to pasture and agriculture, will likely increase the extent of burned areas and future carbon fire emissions to the atmosphere.     

中国低碳治理的制约因素和相应对策

作为全球碳排放大国,中国低碳治理的发展方向对全球气候变化有深远的影响,值得深入研究。通过中国低碳治理的制约因素及其成因的分析,提出地方政府行为是中国低碳治理的主要制约因素。这主要表现在地方政府鼓励不符合低碳发展的粗放式经济增长和城市开发及地方政府制定与执行低碳政策的积极性不高。而地方政府行为背后是各种制度环境因素。因此,改善中国低碳治理需要从制度改革入手。对制度改革提出3个建议：① 强化节能目标责任制;② 缓和地方政府过于强烈的发展意愿;③ 加强公民参与低碳治理。     

An evolutionary model for sabkha development on the north coast of the UAE

The north coast of the United Arab Emirates (UAE) provides a typical example of coastal sabkha (supratidal flat) formation. Various stages of sabkha development can be recognized along this coast. This paper combines previous studies of sabkha environment with the results of field investigation of sabkha geomorphology, sedimentology, and stratigraphy on the north coast of UAE, to formulate a model of sabkha evolution.The model has six stages in the evolution of coastal sabkhas following the early Holocene sea-level rise. These are: Stage 1: sea-level rise results in the formation of an embayment. Stage 2: involves subsequent spit development and progradation across the bay as a result of sediment availability. Stage 3: coincident with spit evolution is the development of a khor (tidal inlet) with or without mangrove. Channel depth of Khors varies from 4 to 6 m. Stage 4: sediment accumulates in the khor reducing the khor depth, turning it into a lagoon. There are three sub-stages of the lagoon stage. (a) With lagoon depths of 1–2 m, (b) with lagoon depths 0.5 m or less, (c) when the lagoon floor is exposed at low tide. Stage 5: is sabkha formation; development occurs in two sub-stages. In the first the sabkha is immature and flooded during rain storms and spring tides (0.1 m above present sea-level). Later the sabkha is only flooded after rainstorms, when it reaches an elevation of about 1 m or more above present sea-level. Stage 6: in sabkha development is the coastal plain, which results when large sabkhas are linked together.