Effects of forest fires on headwater streamflow and the habitat suitability for benthic macroinvertebrates

We modelled hydrological, hydraulic and habitat suitability changes in a Mediterranean catchment after a wildfire. Gauged pre/post-fire hourly discharges were used to assess actual pre/post-fire hydrological conditions. To remove the weather variability effect, daily pre/post-fire discharges were simulated under the same weather conditions. An eco-hydraulic model was employed to calculate flow velocities, water depths and macroinvertebrate habitat suitability at various discharges across a 165 m long reach. The fire increased the magnitude and frequency of peak velocities and depths by 6.5-475%. Increased post-fire rainfall exacerbated hydrological-hydraulic extremes. However, the short duration of post-fire extremes led to small impacts on the habitat suitability for macroinvertebrates, which were stressed for a maximum 18.4% of the time after the fire (350 days in five years). In small Mediterranean-climate headwaters, after wildfires, less frequent streamflow becomes more frequent, high and of short duration. Macroinvertebrates largely resist such short-term, low-magnitude hydrological-hydraulic changes.

Automated summary

This study modeled the changes in hydrology, hydraulics and habitat suitability in a Mediterranean catchment after a wildfire. The results showed that the wildfire increased the peak velocities and depths, and post-fire rainfall worsened hydro-hydraulic extremes. However, these extreme conditions had minimal impact on the habitat suitability for macroinvertebrates.