Determining Hydrological Controls on Flood Frequency

Study comparing data from hundreds of U.S. catchments could improve flood prediction.

Image courtesy of the Federal Emergency Management Agency/Andrea Booher
Aerial view of homes inundated with water following a 2011 flood in Minot, N.D. Researchers have compared data from hundreds of catchment sites in the United States to better understand the relationship between annual water balance and flood frequency.

The Science

Flooding is a major natural hazard with significant societal, economic, hydrological, and ecological consequences. Researchers have revealed the connections between flood frequency and measures of mean annual water balance.

The Impact

By attributing regional variations of flood frequency to quantitative measures of aridity and moisture transport in the climate, this research provides the basis for delineating hydrological regions, which may help improve flood estimation and prediction.


To improve flood frequency estimates, researchers led by Department of Energy (DOE) scientists at Pacific Northwest National Laboratory conducted a study providing insights on the connections between flood frequency and measures of mean annual water balance. This water balance was expressed in terms of two controlling measures: (1) the climatic aridity index (AI), which is a measure of the competition between evaporation and precipitation, and (2) base flow index (BFI), which is a measure of total annual runoff partitioning into surface and subsurface components.  Researchers performed the study using data from several hundred catchments across the continental United States. Their results showed that AI has a first-order control on the shape of the flood frequency curve in terms of the mean and variability of the annual maximum floods. While the mean annual flood discharge decreases with increasing aridity, variability increases. In contrast, BFI was found to exert a second-order control on flood frequency. Higher BFI, meaning higher contributions of subsurface flow to total streamflow, leads to a decrease of the mean annual (specific) flood discharge and vice versa. Developing further insights into the connection between annual water balance and flood frequency will be another step toward gaining a comprehensive, holistic understanding of hydrologic variability and similarity at the catchment scale.


Hong-Yi Li
Pacific Northwest National Laboratory


This research was funded by the Regional and Global Climate Modeling and Earth System Modeling programs of the Office of Biological and Environmental Research within DOE’s Office of Science.

Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RLO 1830.


Guo, J., et al. “Links between flood frequency and annual water balance behaviors: A basis for similarity and regionalization.” Water Resour. Res. 50 (2), 937–953 (2014). [DOI:10.1002/2013WR014374].

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Program: BER , CESD

Performer: DOE Laboratory