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Retention Ponds (retention + pond)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Variability of dry sediment bulk density between and within retention ponds and its impact on the calculation of sediment yields

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2001
Gert Verstraeten
Abstract Monitoring sediment yields from catchments is important for assessing overall denudation rates and the impact of environmental change. One of the methods used to assess sediment yield is by quantifying sedimentation rates in reservoirs, lakes or small ponds. Before reliable sediment yield values (t ha,1 a,1) can be computed from such sedimentation records, the measured sediment volumes need to be converted to sediment masses using representative values of the dry sediment bulk density. In textbooks, simple relations predicting dry sediment bulk density from sediment texture, time since deposition and hydrologic condition are presented. In this study, 13 small flood retention ponds in central Belgium were sampled to reveal the variability in dry sediment bulk density and to test the commonly used relations to predict dry sediment bulk density. Dry sediment bulk density varies not only between the selected ponds (0·78,1·35 t,m,3) but also within individual ponds (coefficient of variation at 95 per cent ranges from 7 to 80 per cent). The observed variability can be attributed primarily to the hydrologic condition of the retention pond and, also, to sediment texture. The existing relations are not a reliable predictor for the observed dry bulk densities, because they are primarily based on sediment texture. Thus, when using volumetric sedimentation data from small ponds with varying hydrologic condition to predict sediment yield, existing relations predicting dry sediment bulk density cannot be applied. Instead, frequent and dense sampling of sediments is necessary to calculate a representative value of the dry sediment bulk density. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A short history of muddy floods

LAND DEGRADATION AND DEVELOPMENT, Issue 4 2010
J. Boardman
Abstract The term ,muddy flood' has been used widely in the lowland, arable areas of western and central Europe to describe muddy runoff from arable fields that causes damage to property. There is some evidence that muddy floods are much more frequent in the last two decades than previously. It is clear though that there is very substantial under-reporting of the phenomena even in areas where they have been recognised for 20 years e.g. UK and France. Reconstructions based on questionnaires, news media and local authority records have had some success in historical analysis of muddy flood frequency but there is still a huge data deficiency. Records from some countries are woefully lacking e.g. Germany, Spain and Italy. Costs of muddy flooding are substantial especially in the loess belt of Belgium. The number of properties flooded in France suggests also that costs are high; similarly in England (UK) where costs for case studies are known but not for the country as a whole. There are two quite different solutions to the problem of muddy flooding. Protection can be provided by engineering devices: retention ponds, dams, trenches. This is an ,end of pipe' solution with severe cost implications and risks with regard to the design return period. Alternatively, land use change on relatively small areas of catchments, can be shown to be effective at reducing flood-risk hazard. A combination of the two has proved most effective at several sites in Europe. Copyright © 2010 John Wiley & Sons, Ltd. [source]