FastFlood Docs

Infiltration rate

Homogeneous rainfall

Infiltration is provides as a constant rate (millimeters per hour). You can directly download infiltration rates using the SOILGRIDS soil property dataset from ISRIC. We use their global prediction of soil texture and organic matter in combination with the pedotransfer functions from Saxton et al. (2006) to estimate saturated hydraulic conductivity. In reality, the initial moisture content of the soil, determined by precipitation in the weeks before, is another important factor, so keep in mind that calibration is required for correct hydrological behavior. Alternatively, you can load your own infiltration values as a map. These can also be deduced based on soil types, or directly based on measurements. Some example values area Land cover determines Mannings Surface roughness coefficient. Typical values for this are (in mm/hour)

  1. Sand – 210
  2. Loamy sand – 61.1
  3. Samdy loam – 25.9
  4. Loam – 13.2
  5. Silt loam – 6.8
  6. Sandy clay loam – 4.3
  7. Clay loam – 2.3
  8. Silty clay loam – 1.5
  9. Sily clay – 0.9
  10. Clay – 0.6

The USGS tool SPAW hydrology contains the pedotransfer functions from Saxton et al. (2006) and can also be used to predict these values for any texture.