Land Use Management (land + use_management)

Distribution by Scientific Domains


Selected Abstracts


The influence of changes in habitat structure on the species composition of bird assemblages in the southern Kalahari

AUSTRAL ECOLOGY, Issue 5 2010
COLLEEN L. SEYMOUR
Abstract Land use management practices often change habitat structure, which in turn influence diversity and the composition of floral and faunal assemblages. In the southern Kalahari, southern Africa, heavy grazing after above-average rainfall has lead to bush thickening, and widespread use of arboricides and/or removal of large trees for firewood has also impacted habitat structure. At sites near Kimberley, in South Africa, we investigated the effects of these changes on bird species richness and which aspects of habitat structure most influenced bird assemblage diversity and composition. We also investigated correlations between bird life history traits and habitat characteristics using RLQ analysis. Bird species richness and abundance were both explained by vertical habitat heterogeneity and density of woody species between the heights of 0,2 m, with bird species richness also explained by the density of woody species at heights above 6 m. Large trees within bush-thickened areas dampened the effects of bush thickening on bird assemblages by enabling certain species to persist, consistent with the idea that large trees are keystone structures. Smaller insectivorous gleaners, ball- and cup-nesters, birds with parts of their range extending into arid areas and birds with long-wavelength plumage (i.e. red, orange or yellow plumage) dominated bush-thickened habitats. Seed-eaters, burrow- and ground-nesters, bark-foragers, birds that perch and sally, or perch and swoop to the ground, were all negatively associated with bush thickening. Cavity-nesters, bark-foragers, hawkers, frugivores, birds that perch and sally and species with iridescent plumage were negatively affected by the loss of large trees. Of the common species analysed, nearly 40% of species had life history traits tied to large trees; and 68% had traits negatively associated with bush thickening and removal of large trees together, suggesting that where these changes in habitat occur simultaneously, bird diversity will be strongly affected. [source]


The systematic approach to flooding problems,

IRRIGATION AND DRAINAGE, Issue S1 2006
J. (Hans) van Duivendijk
maîtrise des crues; mesures non-structurelles; gestion des inondations Abstract Since 1987 one of the working groups of the International Commission on Irrigation and Drainage (ICID) has, inter alia, been preparing two manuals concerning approaches to flooding problems. The Manual on Non-Structural Approaches to Flood Management was issued in 1999 while the Manual on the Planning of Structural Approaches to Flood Management has been issued recently (2005). In this paper a broad outline of both manuals is presented. The first manual describes in detail the various planning and response measures in flood management, which are known as non-structural measures. The latter are measures which alter the exposure of life and property to flooding but do not change the flood(ing) phenomenon as such. The said planning and response measures comprise such actions as floodplain land use management, flood forecasting and warning, flood fighting, flood proofing, etc. It is explained that such measures are sometimes the only ones feasible in the prevailing circumstances and that, moreover, non-structural measures should always be added to the so-called structural measures if the latter are considered feasible (i.e. feasible from a technical, economic, socio-economic and ecological point of view). In the second manual a methodology is presented for the planning of structural measures. This type of measure alters the physical characteristics of the floods and in this connection one must think of the operation of flood storage reservoirs, upstream catchment management, modification to river channels, construction of levees, special flood diversion channels (bypasses) and operation of hydraulics works. The idea behind this methodology is that it is difficult for planners and decision makers to select the appropriate flood protection system for a given situation including a range of possible floods if the problem is not approached in a systematic manner. Copyright © 2006 John Wiley & Sons, Ltd. Depuis 1987 un des groupes de travail de la CIID prépare, entre autres, deux manuels sur la manière d'approcher les problèmes d'inondation. Le ,Manuel d'approche non-structurelle de la gestion des crues' a été publié en 1999, tandis que le ,Manuel de la planification de l'approche structurelle de la gestion des crues' a été publié plus récemment (2005). Le présent article présente une vue d'ensemble de ces deux manuels. Le premier manuel donne une description détaillée des différentes mesures de préparation et de réponse à la gestion des crues, connues comme étant non-structurelles. Ces mesures changent l'exposition de la vie et des propriétés aux inondations mais ne modifient pas le phénomène proprement dit des crues et des inondations. Elles comprennent des actions telles que la gestion de l'espace dans les plaines d'inondations, les prévisions et alertes, la lutte contre les crues, la protection contre les inondations, etc. On y explique que ces mesures sont parfois les seules faisables dans les circonstances données et que, en outre, des mesures non-structurelles devraient toujours être ajoutées aux mesures dites structurelles si ces dernières sont considérées comme faisables (c'est-à-dire faisables d'un point de vue technique, économique, socio-économique et écologique). Dans le second manuel une méthodologie est présentée pour la planification des mesures structurelles. Ce type de mesures modifie les caractéristiques physiques des crues, comme par exemple réservoirs d'écrétage de crue, gestion des hauts bassins, modification des lits des fleuves, construction de digues, canaux spéciaux de déviation des crues (courts circuits) et fonctionnement d'ouvrages hydrauliques. L'idée qui est derrière cette méthodologie est qu'il est difficile aux planificateurs et aux décideurs de choisir le système de protection contre les crues correspondant exactement à une situation comprenant une large gamme d'inondations possibles si le problème n'est pas approché de manière systématique. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Flood control and land use management in Mengwa retention area, Huai River Basin,

IRRIGATION AND DRAINAGE, Issue 4 2004
Han Ruiguang
Contrôle des crues; gestion de l'occupation du sol; aire d'épandage Abstract Retention areas have a very important role in flood alleviation in the Huai River Basin. With economic and societal development the former retention areas have been developed and some of them even became very important urban areas. When floods come, there is a lot of damage. The government has realized that the flood control standards in the whole river basin are low and has made a plan to increase flood control standards for the Mengwa retention area. The design water level will be 28.00,m+MSL at Runheji. In light of this the use of the Mengwa retention area needs to be considered. To arrive at decisions that reduce flood damage, one should take into account the following uncertainties: the river discharge, the flood damage given the discharge, the downstream water level given the discharge, and the costs of constructing embankments and dredging the river. By using the DUFLOW model and a GIS model, the present situation and the alternative development options have been analysed. How to use the Mengwa retention area is also discussed. Copyright © 2004 John Wiley & Sons, Ltd. Les zones d'expansion jouent un rôle important dans la réduction des crues du fleuve Huia. Ces zones ont connu le même développement économique et social que le reste de la région, et certaines sont maintenant fortement urbanisées. Les crues y provoquent beaucoup de dégâts. Le gouvernement a pris conscience que les critères pour contrôler les crues dans le bassin versant sont insuffisants, et a élaboré un plan pour améliorer ce contrôle dans l'aire d'épandage de Mengwa. Le niveau d'eau de référence retenu est à la cote 28,m, prise à Runheji. Ceci implique de reconsidérer l'utilisation de la zone d'expansion. Les décisions permettant de réduire les dégâts dus aux crues ont été élaborées à partir des paramètres suivants: débit du fleuve, relation entre le débit et les dégâts dus aux crues, niveau d'eau en aval, coûts de renforcement des digues, coût du dragage. La situation actuelle et les possibilités d'amélioration ont été analysées avec le modèle DUFLOW et un SIG. L'utilisation de la zone d'expansion de Mwenga est examinée également. Copyright © 2004 John Wiley & Sons, Ltd. [source]


ASSESSING LAND USE IMPACTS ON WATER QUALITY USING MICROBIAL SOURCE TRACKING,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004
Sharon C. Long
ABSTRACT: A renewed emphasis on source water protection and watershed management has resulted from recent amendments and initiatives under the Safe Drinking Water Act and the Clean Water Act. Knowledge of the impact of land use choices on source water quality is critical for efforts to properly manage activities within a watershed. This study evaluated qualitative relationships between land use and source water quality and the quantitative impact of season and rainfall events on water quality parameters. High levels of specific conductance tended to be associated with dense residential development, while organic carbon was elevated at several forested sites. Turbidity was generally higher in more urbanized areas. Source tracking indicators were detected in samples where land use types would predict their presence. Coliform levels were statistically different at the 95 percent confidence levels for winter versus summer conditions and dry versus wet weather conditions. Other water quality parameters that varied with season were organic carbon, turbidity, dissolved oxygen, and specific conductance. These results indicate that land use management can be effective for mitigating impacts to a water body; however, year- round, comprehensive data are necessary to thoroughly evaluate the water quality at a particular site. [source]


Agricultural trajectories in a Mediterranean mountain region (Priorat, NE Spain) as a consequence of vineyard conversion plans

LAND DEGRADATION AND DEVELOPMENT, Issue 1 2009
R. Cots-Folch
Abstract In mountain regions of Mediterranean European countries, recent economic and technologic changes have involved the intensification of crops, based on heavy land levelling and/or terracing, and the abandonment or marginalization of traditional land use management. These trends have been reinforced by the subsidy policies of the European Union. The objectives of the present research were: (a) to contribute to the understanding of agricultural trajectories and farming systems that are entirely transforming the social and environmental characteristics of Mediterranean mountain areas, focusing on the analysis of the main agricultural trajectories in a sample area of this environment (the Priorat region, NE Spain) over the last 20 years (1986,2005); and (b) to analyse the farming systems that coexist in the region with regard to the landscape impacts they involve and the influence of CAP subsidies in each one. A methodological approach based on the combination of multivariate statistical techniques was used to obtain a better knowledge of the heterogeneity of farming systems on a local scale. The results show that, although most farms cultivate a mosaic of traditional crops and have small mechanized areas, a minority group follows a high intensification and specialization strategy based on new mechanized-terraced vineyards. This group only comprises 12 per cent of the farmers in the region, but owns 61 per cent of the new vineyard plantations and 42 per cent of the total agricultural land, receiving most of the subsidies from the EU vineyard conversion and restructuring policy (68 per cent of total Common Agricultural Policy (CAP) subsidies assigned to the region). Copyright © 2008 John Wiley & Sons, Ltd. [source]