Hydrogeomorphic Effects of River Training Works: the Case of the Allyn River,NSW

Since 1955 the NSW Department of Water Resources has undertaken extensive river training works on many NSW streams. In the Hunter Valley alone over $23 million have been spent and more than 850 km of channel have been treated Published work suggests that river training works are usually undertaken in response to a pre-existing problem of river instability but can also induce adverse hydrogeomorphic effects. One of the treated streams, the Allyn River, had been supposedly degraded by the constructed works. It was alleged that vegetation clearing, channel excavations, alignment straightening and bank protection works had decreased roughness thus increasing velocity and flood frequency. As a result, what were thought to be relatively moderate floods were eroding the banks and destroying the floodplain. A critical evaluation of the available hydraulic, hydrologic and geomorphic data revealed that the river training works were a response to, rather than a cause of river instability.     

Water,Wind, Wood,and Trees: Interactions,Spatial Variations,Temporal Dynamics,and their Potential Role in River Rehabilitation

Recent Australian research has quantified the role of large wood (wood of any origin and length with a diameter greater than 0.1 m) in dissipating stream energy, forming pool habitats by local bed scour, protecting river banks from erosion, and damming rivers with long rafts causing avulsions. Large wood in Australian streams is sourced by a range of processes from the nearby riparian zone which has usually been degraded by post‐European settlement vegetation clearing. Large wood loadings within the bankfull channel are dependent not only on the type and quality of the riparian plant community but also on bankfull specific stream power, channel width, and the processes of large wood delivery to the stream. While bank erosion and floodplain stripping by catastrophic floods are obvious and important delivery mechanisms, treefall and trunk and branch breakage by strong winds during tropical cyclones and severe storms are also significant in the tropics. Furthermore, wood decay and downstream transport produce temporally dynamic large wood distributions. The longevity of natural large wood structures in rivers, such as rafts, debris dams, and log steps, requires determination. River rehabilitation programs need to not only include the reintroduction of large wood, but also carefully plan the spatial distribution of that wood, the most appropriate type and range of large wood structures, and, most importantly, the revegetation of the riparian zone to ensure a natural long‐term source of large wood. Exotic species management is an essential part of river rehabilitation.     

Assessment of Riparian Revegetation Trials on In-Channel Benches in the Hunter Valley of Southeast Australia

Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.     

Estimates of Historical Tree Densities in the North Lachlan River Catchment,New South Wales,Australia

Vegetation structure and composition during the pre‐ and early‐European period in Australia is often proposed as a benchmark against which to measure the effects of modern landscape management practices. However, little quantifiable information exists for that historical period. One potential source of information is the land survey record, used in this study to provide estimates of tree densities that existed during the period 1870 to 1900 in part of central New South Wales. Estimates were obtained for 23 parishes in the north Lachlan River valley, between the towns of Condobolin and Tottenham. Densities were calculated from portion corner to nearest tree data obtained from historical survey plans, using the plotless, closest individual method. Densities ranged from 6.0 to 31.4 trees per hectare for parishes with enough data points for reliable calculation. These figures would account for trees of a diameter large enough to be blazed with a survey mark. Any smaller trees would be additional and, although no quantitative data existed for this, qualitative evidence suggested that the figures obtained were more likely to be underestimates due to the presence of such small trees. The study area was predominantly covered by woodlands which varied in density across the landscape, in comparison to the modern landscape where much of the native vegetation has been cleared for agriculture. Although the tree density figures should be considered to be indicative rather than precise, they provide quantifiable historical figures for past conditions in an area where the historical record is otherwise sparse. Such information is valuable for interpreting ecological changes brought about by modern land management.     

Allometric Analysis and Stream Channel Morphometry

The concept of allometric change, developed and widely applied in biology, is outlined, and the nature of static allometric changes in stream channel size, relative to drainage area, is considered at a variety of scales. Field observations from Devon, England, allow analysis of the allometric variations along individual channels, between tributaries within a network, and between streams within a region. Data collected from the literature allow these to be viewed in a global perspective. The analysis confirms the applicability and value of the concept of allometric change to channel form studies and suggests a tendency for streams to reach a steady-state allometric situation when channel capacity increases at the same rate as drainage area. The importance of a range of factors in affecting the nature of the allometric relationships is also assessed.     

Reconstructing late Holocene palaeoenvironments in Bangladesh: phytolith analysis of archaeological soils from Somapura Mahavihara site in the Paharpur area,Badalgacchi Upazila,Naogaon District,Bangladesh

Palaeoenvironmental reconstruction based on phytolith analysis of late Holocene-aged soils in and around the Somapura Mahavihara archaeological monastery site in the Paharpur area, Badalgacchi Upazila of Naogaon District in northwestern Bangladesh was undertaken. Results indicate five climate zones marked by alternatively cool and temperate events. The phytolith assemblages of Zones 1, 3 and 5 are clearly characterized by a higher proportion of Pooideae phytoliths. The climate indices for these zones are all greater than 50, indicating cooler climatic conditions. In contrast, the phytolith assemblages of Zones 2 and 4 are typified by a higher proportion of Panicoideae phytoliths; their climate indices are 42 and 44, respectively, indicating the presence of a warmer, more temperate climate. In general, the dominance of grasses over broad- leaved trees throughout the sequences suggests that generally cool to temperate and dry conditions with some cyclical variability persisted around Paharpur and the surrounding region throughout the Pala Dynasty from AD 730 to 1080. The question of whether these shifts in vegetation might be linked with El Niño Southern Oscillation events, and whether these might in turn have cultural responses, is raised.     

Marshes and Estuaries in Different Latitudes

Abstract

Physiographic features in estuaries and marshes are deeply influenced by differences in climate. The study of these contrasts demands interdisciplinary teams of climatologists, botanists, hydrologists, geochemists, oceanographers, human geographers, geomorphologists and geologists. In temperate countries a dense carpet of herbaceous vegetation grows on high marshes, while low marshes bear plants which disappear in winter; mud-flats have no flowering plants. In colder regions, for example Quebec and the surrounding areas in north-east America, sea waters freeze for a long time every winter. This results in a particular evolution of tidal marshes, as ice rafts either pick up blocks of sediment from marshes, or, conversely, drop on them stones of foreign origin. In intertropical areas mangrove trees grow instead of herbaceous vegetation, although in some places true marshes can be found.     

Broom (Cytisus scoparius) at Barrington Tops,New South Wales

Broom was introduced to the northern part of the Barrington Tops plateau in the 1840s Particularly since 1969, when cattle grazing and associated burning ceased in the area, Broom has spread over c 10,000 hectares, mostly in the State Forest and National Park In eucalypt-dominated vegetation, Broom invasion is shown to cause substantial reduction in species richness and foliage projective cover of native understorey vegetation, including number of eucalypt seedlings Reasons for Brooms success, and possible outcomes, are discussed Control measures to date have been ineffective; biological control appears to offer the best future prospects.     

Morphological Impacts and Implications of a Trial Release on the Wingecarribee River,New South Wales

A trial, monitored release on the Wingecarribee River over 27 days had a peak discharge below the Wingecarribee Dam of 1090 ML/d, which had a flow duration of 0.95 per cent. Morphological impacts on 29 km of channel below the dam included bank erosion, concentrated neck overflow, bed degradation and channel widening at recent cutoffs, sedimentation in weir pools and overbank flow, particularly at discharges greater than 800 ML/d. Prolonged operational releases at bankfull discharge (400–800 ML/d) will have the greatest morphologic impacts and should be avoided. Pulses which dissipate stream power over a broad, well-vegetated floodplain should be incorporated in the operational release policy, provided such pulses are phased to facilitate channel and vegetation recovery.     

Phytolith assaying using a micron-scale electrokinetic sorting ring

A particularly useful indicator of past vegetation are phytoliths, glassy products of plant metabolism which have distinctive size and morphology based on the plant taxa which produced them; however, their analysis is a time-consuming task. Building on investigations into mobilizing and sorting of synthetic polystyrene microspheres using a closed loop rectangular microelectromechanical systems (MEMS) electrokinetic array, we investigate these devices’ utility for sorting natural microparticles. Using phytolith samples extracted from archaeological sediment, we show that closed loop MEMS can separate the glassy bodies from both mineral contaminants and each other. Also, small differences in polarization between the phytoliths cause lateral segregation between particles of different sizes and shapes. This process facilitates manual analysis by providing a motive force to the phytoliths that translates and rotates them, showing different configurations as they are propelled by the MEMS array. The organization of the phytoliths into streams also opens the door to automated analysis using image processing. Phytolith assaying is therefore feasible using a MEMS electrokinetic ring and merits additional research to explore the potential of this innovative approach.     

Assessment of Riparian Rainforest Vegetation Change in Tropical North Queensland for Management and Restoration Purposes

Changes in riparian vegetation extent in northern Queensland, Australia were assessed using aerial photographs from 1944 and 2000. Change in riparian extent was recorded as vegetation gain or loss. Changes in density were recorded as vegetation thickening. Riparian forest coverage increased by 22 ha during this time period in the Mossman River catchment. A total of 124 ha of riparian forest were gained, while 101 ha of riparian forest were lost. A further 59 ha of forest increased in density over this time period. Clearing, changes in farm management practices and natural stream channel movement have been identified as three potential causes for these changes. Areas with little or no riparian vegetation were identified and categorised into priority levels for potential revegetation efforts.     

Holistic geoarchaeology in the Penobscot Valley,Maine, USA: context,scale, and interpretation

A holistic landscape approach to cultural resource analysis of a set of archaeological sites in the central Penobscot Valley led to inferences regarding the Holocene physical and biological environmental context. Targeted environmental studies include (1) examination of forest and wetland changes through time and (2) lake-level studies as a key to paleohydrology. These studies were combined with broad-scale geomorphic investigations and detailed stratigraphic analyses, and studies of archaeological sites and their artifact assemblages. Together, these studies provide a picture of dramatic changes to the physical and vegetational landscape. These included reestablishment of a major river following deglaciation, evolution of extensive lakes to uplands and peatlands, and a shifting mosaic of open and closed forest composed of a variety of hardwood and softwood species. Inferences based on buried soils exposed in archaeological excavations supported climatic interpretations based on vegetation and paleohydrology. As a result, this work allowed evaluation of (1) site formation and preservation processes and (2) occupational patterns. Site formation and preservation of Early Holocene sites can be linked to sedimentation by hydraulic damming upstream of rapids at the mouths of tributary streams. Shifting human land use reflected by changes in occupation patterns appears to correspond to changes in forest composition as well as wetland and stream evolution through time.     

The Differential Regional Effects of Monetary Policy: Evidence from the U.S. States

In this paper we use time-series techniques to examine whether monetary policy had symmetric effects across U.S. states during the 1958:1–1992:4 period. Impulse response functions from estimated structural vector autoregression models reveal differences in policy responses, which in some cases are substantial. We provide evidence on the reasons for the measured cross-state differential policy responses. The size of a state's response is significantly related to industry-mix variables, providing evidence of an interest rate channel for monetary policy, although the state-level data offer no support for recently advanced credit-channel theories.     

Satellite Remote Sensing of Archaeological Vegetation Signatures in Coastal West Africa

This article discusses how archaeological sites in Sierra Leone, and by extension much of West Africa, can be identified through vegetation patterns (vegetation signatures) detectable in very high-resolution (VHR) multispectral satellite imagery. Settlement sites typically have a differing pattern of vegetation from the surrounding landscape, including concentrations of very large trees with sociocultural and historical significance: cotton (Ceiba pentandra) and baobab (Adansonia digitata). These features are conspicuous elements of the landscape both from the ground and in aerial imagery. Two complementary methods of using VHR multispectral satellite imagery are discussed in this paper: visual interpretation and semi-automated subpixel classification. These techniques are aiding ongoing archaeological survey of the Sierra Leone River Estuary. The impact of recently renewed industrial activity at a site of probable archaeological significance is also assessed through visually interpreted VHR satellite imagery.     

The Evolution of Peat‐Swamp Channels and Organic Floodplains,Barrington Tops,New South Wales,Australia

Geomorphology, geochronology and palynology are used to assess the development and stability of two channelled swamps on the Barrington Tops plateau. While both swamps commenced peat accumulation prior to about 4000 cal BP, new stratigraphic data indicate incision between 700 and 1000 cal BP, in response to regional climate change. Two broad stratigraphic units are identified in each swamp: the upper floodplain, comprised entirely of peat, and the inset floodplain, underlain by interbedded peat and fluvial sediments. Following incision, rapid vertical growth of the inset floodplain occurred on the Barrington River between 690 and 620 cal BP, and palynological data indicate a change from more saturated pre‐incision swamp flora to less saturated post‐incision swamp flora. Bankfull stage‐height, achieved many times in a year, is remarkably consistent along the length of each swamp channel. Its elevation controls the overall elevation of the swamps by controlling the height of the water‐table and hence the growth of swamp vegetation and formation of peat. In particular, contemporary channel dimensions control the growth and height of the inset floodplain, a process that results in the formation of an organic floodplain not previously described in the geomorphic literature.     

Frequency of fast geomorphological processes in high-gradient streams: case study from the Moravskoslezské Beskydy Mts (Czech Republic) using dendrogeomorphic methods

High-gradient streams are localities with the most dynamic activity of geomorphological processes in medium-high mountains. This study of the frequency of floods and debris flows in a selected high-gradient stream in the Moravskoslezské Beskydy Mts was based on a dendrogeomorphic approach. It makes use of the most accurate methods applied in the dating of historic geomorphological processes. Individual events were reconstructed on the basis of the dating of various growth disturbances displayed in 99 samples taken from 56 predominantly broad-leaved trees.     

Struggling to Save Cash: Seasonal Migration and Vulnerability in West Bengal,India

This article concerns an important but overlooked means by which able‐bodied poor people get hold of lump sums of cash in rural West Bengal: seasonal migration for agricultural wage work. Drawing on a regional study of four migration streams, our main focus here is on the struggle to secure this cash by landless households in just one of those streams, originating in Murshidabad District. Case studies are used to illustrate the importance for women in nuclear families of maintaining supportive networks of kin for periods when men are absent. A parallel analysis is made of the negotiations between male migrant workers and their employers, at labour markets, during the period of work, and afterwards. The article then briefly discusses some of the contrasting ways in which remittances are used by landless households and owners of very small plots of land, in the context of rapid ecological change, demographic pressure and growing inequality.     

抗战期间广东省银行沟通潮梅汇路之研究

论文利用广东省档案馆藏近代侨汇档案,集中考察了1939年6月汕头沦陷后,广东省银行沟通潮梅汇路的成因、成效及局限,进而分析其对华南抗战的作用及贡献。研究显示,抗战期间汕头的陷落,是广东省银行沟通这一汇路的重要契机;其自身所具有的经营特色和优势,是其能够肩负这一历史使命的重要保证;而海内外各方则是促成汇路沟通的重要参与者。在此过程中,广东省银行发展壮大,并惠及数百万潮梅侨眷生计。同时为厚实国家外汇储备及赢取华南抗战的最终胜利做出了重要贡献。然而,国民政府严格限制其海外拓展的政策,英、法、荷等国在南洋属地实施的外汇管制以及英、美对中国资金的封存,都在一定程度上制约了它吸收侨汇的成效。     

Human Adaptive Responses to Catastrophic Landscape Disruptions During the Holocene at Numundo,PNG

Prehistoric land use and social activity in West New Britain, PNG, are well documented, although the landscapes – largely shaped by catastrophic volcanic eruptions – in which these took place, and the relationships people had with these landscapes, are poorly understood. We define the evolving landscape at Numundo, from prior to the Witori-Kimbe 2 eruption (W-K2, ca. 3600 BP) to after the Witori-Kimbe 4 eruption (W-K4, ca. 1400 BP), using fossil phytolith and coral evidence at eight archaeological sites to provide environmental evidence of the human responses to periodic catastrophic events. From ca. 5900 to 3600 BP, all the sites were coastal and disturbed. Early disturbance reflected natural forest recovery after W-K1 (ca. 5900 BP), whereas the later landscape was largely shaped by human activity. In contrast, forest regrowth was limited after W-K2 and open environments typical of human activity with a mosaic of regenerating, disturbed and managed vegetation, persisted until W-K3. Environmental recovery from W-K3 and W-K4 (ca. 1700 BP and ca. 1400 BP) differed completely, reflecting severity of the volcanism and the short time between eruptions. The landscape after W-K3 was largely a naturally recovering landscape, in contrast to effective vegetation recovery and significant human exploitation of the landscape – again a mosaic of regenerating, disturbed and managed vegetation – after W-K4. The social history is one in which people evolved increasingly flexible land-use practices, enabling them to re-settle this periodically disrupted landscape, and to take advantage of an increasingly broad range of habitats suitable for cultivation. The human response to this highly dynamic landscape represents a close relationship between social and natural processes, as people became increasingly better at re-settling an unpredictably disrupted landscape; both the social and environmental processes within this landscape become equally influential and instrumental in shaping the effects of the other.     

Preservation of old‐growth forests: a case study of Big Timber Park,Whistler, BC

This paper explores the concepts of old‐growth forests, preservation and natural disturbance and demonstrates how contemporary biogeographic theory contributes to successful preservation of old‐growth forests. The case study analyzes the composition, structure, age and growth histories of trees in Big Timber Park, Whistler, British Columbia. Composition. The structure of the forest was diverse and tree ages ranged from 122 to 305 years. The densities of large old Douglas‐fir, shade‐tolerant trees and all snags are indicative of old‐growth forests; however, maximum tree diameters and densities of large snags and logs do not meet quantitative criteria for old‐growth forests. The abundance of tree regeneration and understory vegetation are relatively low. We conclude that some aspects of Big Timber Park are transitional between the mature and old‐growth stages of forest development. In the future, fine‐scale canopy gaps caused by tree senescence and interactions among insects, pathogens and wind are expected to dominate stand dynamics. Forest structure will become increasingly complex, exemplifying the dynamic nature of old‐growth forests. To successfully preserve Big Timber Park and La préservation des forêts other old‐growth forests in Canada requires understanding of natural disturbances. Preservation and the criteria and indicators used to measure successful preservation must explicitly include elements of natural change.