Soil Erosion and Tropical Land Management

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  • Created by: nicola
  • Created on: 24-04-11 12:07

Slope failure is more obvious than soil erosion - especially on cleared ground e.g. for agriculture 

Determined by: 

  • Climate/ climate change
  • Tectonic activity
  • Human activity - only factor that can be controlled through appropriate land use

However soil erosion is more problematic and is an on-going problem

The magnitude and frequency of climatic events and development determine the differences between developed and developing world slopes

  • More rainfall and increased intensity lead to higher erosion rates
  • Higher temps mean PET curves rise - growing season starts later and finishes earlier as less moisture availability
  • Increase frequency and magnitude of El Nino and La Nina oscillations give rise to more erratic weather conditions

Soil erosion has 2 phases: 

  • Detachment of particles
  • Transport of material downslope
    • Rain splash is important in both these phases

Issue of topsoil erosion vs replacement by weathering - hardly ever balances with amount of erosion caused by changes to vegetation, natural erosion and soil conservation

Issues of scale - local/plot vs catchment

  • Studies undertaken on coffee and coffee intercropped with other plants e.g. bananas
  • Used DEM to find soil type, geology, land use and topography
  • Found catchment scale measurements were higher than plot scale however much of the erosion was geomorphological from river banks
  • Therefore coffee doesn't cause large scale erosion

Rill Formation

Slopes have natural contours which become filled with water and attack the higher end of the slope

The weight causes material to be pushed down the slope - continuous process unless a defence is installed to manage this

Conditions for overland flow in the tropics:

  • Saturation
  • Infiltration excess - when intensity of storm is higher than the infiltration rate of water into the soil
  • Perched water table - upper layers are saturated with water but lower layers stay dry (usually when there is a hard impermeable iron pan within the soil)

Pipe flow - significant in gully erosion = occurs when there is a concentration of roots in the top soil which when rotten allow water to flow through the channels (common in arid areas)

Lowland streams - much less sediment carried than those from mountains e.g. in Amazon

Tropical Steeplands

High erosion rates occur with a change from natural to managed vegetation

Intensive agriculture is practised on hillsides e,g, in Jamaica

  • Intense erosion - 80 tonnes per hectare per annum on areas…

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