Drivers of Sediment Mobilization


What effect do different landuse practices where have on sediment movement?

Once a more complete description of sediments is available (from measurements, models), it will be possible to examine specific issues more quantitatively. That said, from preliminary results the following can be said:

What are the impacts of changes in the practices of agricultural activities on local and regional water quality?

     The land use modeling showed that an increase in agriculture is likely to increase streamflow particularly in the SMV basin. An increase in streamflow increases sediment load especially during the heavy rain events, as evidenced by the TSS measurements conducted in Nov. 2013. Chemical evidence shows a strong anthropogenic influence, especially during storm events.

What is the effect of the increase in forest cover on the reduction in erosion potential and turbidity?

     Results from the modeling efforts show that forest cover decreases downstream streamflow. Increasing forest cover also reduces the amount of exposed soil susceptible to erosion since forest covers have deeper roots to stabilize soil and reduces the rainfall through the canopy layer.

What are the priority areas for intervention to reduce turbidity via implementation of practices friendly to use of soil?

     The priority areas will be dependent on local policies governing agriculture, but ideally, where there are currently low/short crops or exposed soil, a buffer zone should be created. Interspersing plants groundcover with agriculture has been shown to help with erosion in some areas.

How has the incorrect use of land in the regions of the headwaters of the Rio Santa Maria da Vitória impacted the accumulation of sediments in the bay of Vitoria? Is it possible to measure this impact?

     Landuse in SMV results in very high sediment loads, far beyond natural, especially during storms. This sediment ends up in the bay, which would result in sediment accumulation. Measuring the impact is feasible, but beyond the immediate scope of this project. The chemical tracers started here indicate unique terrestrial ‘biomarkers” relative to material of marine origin. A sediment-sampling program in the bay could show the terrestrial source material. Application of  a model such as SisBaHia could track sediment plumes from the river mouth through the bay.