Flood timescales: Understanding the interplay of climate and catchment processes through comparative hydrology

Abstract

[1] We analyze the controls on flood duration based on the concept of comparative hydrology. Rather than modeling a single catchment in detail, we compare catchments with contrasting characteristics in order to understand the controls in a holistic way. We analyze the hydrographs of 9223 maximum annual flood events in 396 Austrian catchments ranging from 5 to $10,000 km 2 as a function of climatic controls such as storm type (synoptic and convective storms, rain-on-snow, snowmelt), and catchment controls such as soils, soil moisture, geology, and land form. The ratio of the flood volume and the flood peak is used as a measure of the flood duration or flood timescale. The results indicate that, spatially, the median flood timescales range from 16 h in the hilly catchments, where convective storms prevail, to 104 h in the lowland catchments where substantial inundation into the floodplain occurs. The range is even larger for different flood types, from 7 h for flash floods in the hilly catchments to 200 h for snowmelt floods in an Alpine area with deeply weathered rocks and deep soils. The results also indicate that the catchment area is not the most important control on the flood timescales. For the range of catchments considered here, climate is very important through storm type and antecedent soil moisture, and geology is very important through soil characteristics. The concept of comparative hydrology is also used to interpret the interplay of the processes controlling the flood duration at timescales from hours to millennia. It is argued that the flood timescale is a rich fingerprint of the hydrological processes in a catchment because it integrates a range of climate and catchment characteristics by a time parameter.

A regional comparative analysis of empirical and theoretical flood peak-volume relationships

“…The average number of flood events is at the similar level in the two regions on the West (~392 and ~399), while the lowest average can be found in the Mühlviertel + Waldviertel region (~289). These differences are related to the spatial distribution of the typical time scales of floods that have been defined by Gaál et al (2012) as the ratio of flood volume and peak flow and are presented in the Table 1. The medians of mean flood time scales for the whole region are about 26, 10 and 36 hrs for synoptic, flash and snowmelt floods, respectively.…”

“…There is a wide variety of flood generation mechanisms across Austria due to different hydrological, climatological and geological settings (e.g., Gaál et al, 2012;Parajka et al, 2010) which also challenge the analysis of flood peak-volume relationships. In order to reduce this complexity, here, as in Szolgay et al (2015Szolgay et al ( , 2016, we restricted our analysis to a geographically limited area, namely to the Northern Lowlands region of Austria (Fig.…”

“…The shorter the flood time scales, the larger the number of independent events that can be identified. The differences in the flood time scales are related to differences in both climate and catchment response characteristics (Gaál et al, 2012).…”

“…Gaál et al (2012) therefore analysed the ratio of flood volumes and peaks (termed as flood time scale) based on the concept of comparative hydrology and compared catchments with contrasting characteristics in a regional context in Austria in order to understand the hydrologic and climatic controls on this ratio in a holistic way. The results described the roles of climate (through the type of precipitation generated), together with the attributes of the environment and flow generation processes (through antecedent soil moisture and soil characteristics) on the magnitude of flood time scales.…”

The Impact of the Variability of Precipitation and Temperatures on the Efficiency of a Conceptual Rainfall-Runoff Model

“…1), which cover a wide range of physiographic conditions (different areas, elevations, slopes, and geology) and hydroclimatic conditions (different precipitation and air temperatures) (Gaál et al, 2012). The data were available for the 1981-2010 period and consisted of the daily precipitation, air temperature, potential evapotranspiration, and streamflow.…”