Siltation

About: Siltation is a research topic. Over the lifetime, 1420 publications have been published within this topic receiving 20983 citations.

The capacity of seagrasses to survive increased turbidity and siltation: The significance of growth form and light use

Abstract: Seagrasses are submerged or intertidal angiosperms that form extensive meadows in shallow coastal waters. Tropical as well as temperate seagrass beds are subject to man's interference. Most human activities affect seagrasses either through reductions in light availability or changes in sediment dynamics, the latter often caused by hydrodynamic changes. This paper offers practical ranges within which seagrasses can be expected to occur for these two main environmental factors: light availability and sediment deposition. With a few exceptions, comparatively little variation was found among species in light requirements for photosynthesis. Predicted compensation depths calculated from photosynthesis data correlated well with independently estimated maximum colonization depths. In contrast, considerable differences exist in architectural characteristics. Large shoot size or the capacity to elongate vertical stems enabled several species to raise their leaf canopy closer to the water surface and thus suffer less in turbid water. The latter also allows a response to siltation: sedimentation rates of 2-13 cm yr(-1) can probably be coped with, depending on the species. Observed horizontal rhizome elongation rates differed considerably among species: colonizing seagrasses expand horizontally at rates between 1 and 10 m yr(-1). The higher horizontal growth rates are probably sufficient to track the migration of sand waves and, thus, horizontally escape sedimentation. [KEYWORDS: Dutch wadden sea; zostera-marina l; cymodocea-nodosa; eelgrass; patterns; biomass; productivity; communities; beds; variability]

Designing Policy for Reducing the Off‐farm Effects of Soil Erosion Using Choice Experiments

Abstract: Soil erosion produces both on-site private costs and off-site social costs, such as desertification, rural depopulation, siltation of waterways and reductions in biodiversity. To design efficient policies, land use planners and decision makers need information on the relative weights of changes in these consequences, since policy alternatives, such as different management restrictions, will have varying impacts on these consequences of erosion. The research presented here uses the choice experiment method to evaluate these relative weights, using a case study in the Alto Genil and Guadajoz watersheds in southern Spain. We find that reductions in desertification, protection of water quality, protection of biodiversity, the area covered by the scheme, and the number of rural jobs safeguarded are all significant determinants of preferences over alternative policy designs.

Sedimentation of Prairie Wetlands

Abstract: Many wetlands in the prairie pothole region are embedded within an agricultural landscape where they are subject to varying degrees of siltation. Cultivation of wetland catchment areas has exacerbated soil erosion; wetlands in agricultural fields receive more sediment from upland areas than wetlands in grassland landscapes and hence are subject to premature filling (i.e., they have shorter topographic lives). Associated impacts from increased turbidity, sediment deposition, and increased surface water input likely have impaired natural wetland functions. Although trapping of sediments by wetlands is often cited as a water quality benefit, sediment input from agricultural fields has potential to completely fill wetlands and shorten their effective life-span. Thus, the value placed on wetlands to trap sediments is in conflict with maximizing the effective topographic life of wetlands. Herein, we provide an overview ofsedimentation, identify associated impacts on wetlands, and suggest remedial management strategies. We also highlight the need to evaluate the impact of agricultural practices on wetland functions from an interdisciplinary approach to facilitate development of best management practices that benefit both wetland and agricultural interests. The prairie pothole region (PPR) occurs in a topographic, hydrologic, and land use setting that exacerbates the accumulation and retention of sediments in wetlands. Sediment retention by wetlands is often described as a water quality benefit (e.g., Botto and Patrick 1978; Kuenzler 1990). However, excessive sediment input from erosion of agricultural soils has potential to severely impact PPR wetlands; sediment is the major pollutant of wetlands, lakes, rivers, and estuaries in the United States (Baker 1992; USEPA 1995). Wetlands in the PPR are embedded within an agricultural landscape where cultivation of wetland catchment areas (i.e., the area that contributes surface runoff to the wetland basin) has greatly altered surface runoff dynamics and hydrologic inputs to groundwater. Grasslands that once protected prairie soils from erosion and moderated surface runoff have been converted to cropland. Consequently, wetlands in agricultural fields receive