Flood frequency analysis using mean daily flows vs. instantaneous peak flows

Abstract

Abstract. In many cases flood frequency analysis needs to be carried out on mean daily flow (MDF) series without any available information on the instantaneous peak flow (IPF). We analyze the error of using MDFs instead of IPFs for flood quantile estimation on a German dataset and assess spatial patterns and factors that influence the deviation of MDF floods from their IPF counterparts. The main dependence could be found for catchment area but also gauge elevation appeared to have some influence. Based on the findings we propose simple linear models to correct both MDF flood peaks of individual flood events and overall MDF flood statistics. Key predictor in the models is the event-based ratio of flood peak and flood volume obtained directly from the daily flow records. This correction approach requires a minimum of data input, is easily applied, valid for the entire study area and successfully estimates IPF peaks and flood statistics. The models perform particularly well in smaller catchments, where other IPF estimation methods fall short. Still, the limit of the approach is reached for catchment sizes below 100 km2, where the hydrograph information from the daily series is no longer capable of approximating instantaneous flood dynamics.

Unveiling Torrential Flood Dynamics: A Comprehensive Study of Spatio-Temporal Patterns in the Šumadija Region, Serbia

“…The distribution of recorded events per month in the Šumadija region (Figure 3) indicates that the majority of recorded torrential floods occurred in a warmer part of the year-in May and June (74 or 21.5% each), then in July (47 or 13.7%), and March (40 or 11.6%) and April (33 or 9.6%) in a colder part of the year. Consequently, most fatalities are recorded in May (19), July (18), and June (5) in several dozen flood events. This output is explained by the rainfall regime of the temperate continental climate in this part of Serbia, where the major and the highest intensity rainfall episodes occur in May and June, while the sudden snow melt occurs alone or combined with intense rainfall in early spring happens in March and April or even in February.…”

“…The annual distribution of recorded events allows us to distinguish the peak years based on the number of documented events (Figure 4), and these are 1999 (38), 2014 (18), 1981 ( 16), and 1986 (16). In terms of the death toll, the peak years are 1999 (18 deaths) and 1969 (3), while 1986 and 1994 each record 1 flood death, respectively.…”

“…In terms of the death toll, the peak years are 1999 (18 deaths) and 1969 (3), while 1986 and 1994 each record 1 flood death, respectively. The annual average of registered torrential flood events is 6.3 if only the years with recorded events are taken The annual distribution of recorded events allows us to distinguish the peak years based on the number of documented events (Figure 4), and these are 1999 (38), 2014 (18), 1981 (16), and 1986 (16). In terms of the death toll, the peak years are 1999 (18 deaths) and 1969 (3), while 1986 and 1994 each record 1 flood death, respectively.…”

“…Flood Frequency Analysis (FFA) emerges as a crucial tool in this context, facilitating the assessment and mitigation of flood risk by offering insights into the frequency and severity of flood events, pivotal for infrastructure planning and risk management strategies [17]. To ensure a precise evaluation of flood dynamics and magnitude, a considerable volume of accurately recorded peak flows is imperative for robust FFA outcomes [18]. FFA, a statistical method frequently employed to estimate flood magnitude within a designated return period, finds extensive application in studies related to water resource management [19].…”

Simulating instantaneous peak streamflow in unguaged basins in the Northeast United States

“…These streamflow estimates are traditionally based on a certain statistical recurrence interval, like a 25or 100-year return period, which represent the likelihood for a flood of that degree to occur any given year. Return period design flows should typically be based on measurements of instantaneous peak streamflow (Bartens & Haberlandt, 2021). Often, these data are relatively scarce, missing entirely, or not exactly what are intended (e.g., only be mean daily flows).…”