Catena 

About: Catena is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Soil water & Environmental science. It has an ISSN identifier of 0341-8162. Over the lifetime, 7257 publications have been published receiving 251575 citations. The journal is also known as: Catena (Amsterdam) & Catena (Giessen).

The calculation of lead-210 dates assuming a constant rate of supply of unsupported 210Pb to the sediment

Abstract: Summary The paper describes a method of calculating sediment age from 210Pb profiles where changes in accumulation rate have affected initial 210Pb concentration. Previously published age/depth profiles derived from 210Pb measurements have assumed a constant initial concentration of unsupported 210Pb per unit dry weight at each stage of accumulation, despite variations in accumulation rates. In sediments from three sites which have experienced rapid acceleration in accumulation in recent times, the assumption is not compatible with the measured unsupported 210Pb concentrations. the alternative assumption of a constant rate of supply of unsupported 210Pb to the sediments per unit time allows calculation of age throughout the profiles irrespective of evidence for rapidly accelerating accumulation. The methods of calculation used are outlined, illustrated and discussed in the light of evidence obtained from the sediments of Lough Erne and Lough Neagh, N. Ireland and lakes Ipea and Egari in the Highlands of Papua New Guinea. They provide a means of dating variations in accumulation rate resulting from human activity in the drainage basin.

A classification of natural rivers

Abstract: A classification system for natural rivers is presented in which a morphological arrangement of stream characteristics is organized into relatively homogeneous stream types. This paper describes morphologically similar stream reaches that are divided into 7 major stream type categories that differ in entrenchment, gradient, width/depth ratio, and sinuosity in various landforms. Within each major category are six additional types delineated by dominate channel materials from bedrock to silt/clay along a continuum of gradient ranges. Recent stream type data used to further define classification interrelationships were derived from 450 rivers throughout the U.S, Canada, and New Zealand. Data used in the development of this classification involved a great diversity of hydro-physiographic/geomorphic provinces from small to large rivers and in catchments from headwater streams in the mountains to the coastal plains. A stream hierarchical inventory system is presented which utilizes the stream classification system. Examples for use of this stream classification system for engineering, fish habitat enhancement, restoration and water resource management applications are presented. Specific examples of these applications include hydraulic geometry relations, sediment supply/availability, fish habitat structure evaluation, flow resistance, critical shear stress estimates, shear stress/velocity relations, streambank erodibility potential, management interpretations, sequences of morphological evolution, and river restoration principles.

Gully erosion and environmental change: importance and research needs

Abstract: Assessing the impacts of climatic and, in particular, land use changes on rates of soil erosion by water is the objective of many national and international research projects. However, over the last decades, most research dealing with soil erosion by water has concentrated on sheet (interrill) and rill erosion processes operating at the (runoff) plot scale. Relatively few studies have been conducted on gully erosion operating at larger spatial scales. Recent studies indicate that (1) gully erosion represents an important sediment source in a range of environments and (2) gullies are effective links for transferring runoff and sediment from uplands to valley bottoms and permanent channels where they aggravate off site effects of water erosion. In other words, once gullies develop, they increase the connectivity in the landscape. Many cases of damage (sediment and chemical) to watercourses and properties by runoff from agricultural land relate to (ephemeral) gullying. Consequently, there is a need for monitoring, experimental and modelling studies of gully erosion as a basis for predicting the effects of environmental change (climatic and land use changes) on gully erosion rates. In this respect, various research questions can be identified. The most important ones are: (1) What is the contribution of gully erosion to overall soil loss and sediment production at various temporal and spatial scales and under different climatic and land use conditions? (2) What are appropriate measuring techniques for monitoring and experimental studies of the initiation and development of various gully types at various temporal and spatial scales? (3) Can we identify critical thresholds for the initiation, development and infilling of gullies in different environments in terms of flow hydraulics, rain, topography, soils and land use? (4) How does gully erosion interact with hydrological processes as well as with other soil degradation processes? (5) What are appropriate models of gully erosion, capable of predicting (a) erosion rates at various temporal and spatial scales and (b) the impact of gully development on hydrology, sediment yield and landscape evolution? (6) What are efficient gully prevention and gully control measures? What can be learned from failures and successes of gully erosion control programmes? These questions need to be answered first if we want to improve our insights into the impacts of environmental change on gully erosion. This paper highlights some of these issues by reviewing recent examples taken from various environments.

Gully erosion: Impacts, factors and control

Abstract: Gully erosion attracts increasing attention from scientists as reflected by two recent international meetings [Poesen and Valentin (Eds.), Catena 50 (2–4), 87–564; Li et al., 2004. Gully Erosion Under Global Change. Sichuan Science Technology Press, Chengu, China, 354 pp.]. This growing interest is associated with the increasing concern over off-site impacts caused by soil erosion at larger spatial scales than the cultivated plots. The objective of this paper is to review recent studies on impacts, factors and control of gully erosion and update the review on dgully erosion and environmental change: importance and research needsT [Poesen et al., 2003. Catena 50 (2–4), 91–134.]. For the farmers, the development of gullies leads to a loss of crop yields and available land as well as an increase of workload (i.e. labour necessary to cultivate the land). Gullies can also change the mosaic patterns between fallow and cultivated fields, enhancing hillslope erosion in a feedback loop. In addition, gullies tend to enhance drainage and accelerate aridification processes in the semi-arid zones. Fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion. In this respect, tracers such as carbon, nitrogen, the nuclear bomb-derived radionuclide 137 Cs, magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment. Recent studies conducted in Australia, China, Ethiopia and USA showed that the major part of the sediment in reservoirs might have come from gully erosion. Gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess (European belt, Chinese Loess Plateau, North America) and sandy soils (Sahelian zone, north-east Thailand) or in soils prone to piping and tunnelling such as dispersive soils. Most of the time, the gullying processes are triggered by

Rapid urbanization in China: A real challenge to soil protection and food security

Abstract: To feed its 1.3 billion population with a per capita cultivated land far below the world average, China is already facing a great challenge of land scarcity. Accelerated urbanization along with explosive economic growth has further worsened the shortage of agricultural land over the last two decades. Increasing concern over land is expressed in terms of soil availability for grain production and soil quality degradation. Based on official statistics and data derived from satellite imagery, dynamics of China's cultivated land over the past two decades is outlined and the causes and destinations of cultivated land loss are analyzed in this paper. Particularly, urbanization-related land-use changes and their spatial variation across the country are demonstrated. Furthermore, impacts of urbanization and associated waste disposals, consequent shifts of soil utilization on areal soil quality are expatiated. It is initially concluded that China's cultivated land is shrinking at a rather shocking rate. Although conversion to urban and industrial uses took up a comparatively small share of total cultivated land loss, urbanization should still be considered as a great threat to future agricultural production for several reasons. Urbanization is increasing the risk of soil pollution through waste disposal and acid deposition derived from urban air pollution. Facing rapid urbanization, China is making positive policy responses to the challenge of decreasing availability of cultivated land and offering unremitting efforts towards the goal of national food security.