Soil Properties

  • Soil texture is important for anticipating infiltration and storage of water and is determined by the diameter of the soil particles.
  • Clay has the smallest soil particle diameter, followed by silt, and then sand with the largest particles.
  • Sandy soil allows water to infiltrate and drain more quickly than clay soil.
  • Clay soil can hold a larger volume of water than sandy soil, but runoff during intense rainfall is more likely with clay due to its lower infiltration rate. Clay also stays saturated longer than sand.
  • Depth to impermeable layers such as bedrock or a fragipan can influence how much water the soil layer can hold and how quickly it will saturate.
    • Shallow soils typically saturate more quickly.
  • Surface characteristics are very important for determining the potential for rapid surface runoff.
    • Urbanization – impermeable and compacted surfaces increase the amount and speed of runoff
    • Deforestation and forest fires – removal of vegetation and burning of the soil can increase the amount and speed of runoff as well as the sediment loading in the runoff, especially in sloped areas due to the loss of vegetation and the decrease in infiltration