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Can precipitation intermittency predict flooding?
Ben Livneh1, Nels R Bjarke2, Parthkumar A Modi3
1Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, United States; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309, United States; Western Water Assessment, University of Colorado Boulder, Boulder, CO 80309, United States.
The Science of the Total Environment
|June 14, 2024
Summary
Flood risk is influenced by dry spells before storms. Extended dry periods significantly lower flood probabilities, especially in arid regions, highlighting the importance of precipitation intermittency for predicting future flood events.
Area of Science:
- Hydrology
- Climate Science
- Environmental Science
Background:
- Increasing extreme rainfall events are not consistently leading to higher flood magnitudes, presenting a challenge for flood risk assessment.
- Antecedent moisture conditions are hypothesized as a key factor, but the drivers of this pre-flood variability are understudied.
Purpose of the Study:
- To investigate the role of precipitation intermittency (dry spell length before a flood) in explaining flood variability.
- To assess the sensitivity of flood magnitude to dry spell duration across different climatic and soil conditions.
Main Methods:
- Analysis of flood data from 108 watersheds spanning from 1950 to 2022.
- Evaluation of precipitation intermittency as a predictor of flood magnitude, with a focus on arid/semi-arid regions and low soil field capacity basins.
Main Results:
- Flood magnitude is significantly sensitive to precipitation intermittency, particularly in arid regions (PET/P > 0.84) and basins with low soil field capacity (<0.31 m³/m³).
- Extended dry spells (>20 days) necessitate more intense storms to produce flooding, while shorter dry spells allow a broader range of storms to cause floods.
- Flood probability declines by approximately 0.5% per additional day of dry spell, with probabilities up to 30% lower after prolonged dry periods.
Conclusions:
- Precipitation intermittency is a critical factor in understanding current and predicting future flood risks.
- The findings emphasize the need to incorporate dry spell dynamics into hydrological models and flood management strategies.
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