The role of flood wave superposition in the severity of large floods
<p>The severity of floods is shaped not only by event- and catchment-specific characteristics but also depends on the river network configuration. At the confluence of relevant tributaries with the main river, flood event characteristics may change depending on the magnitude and temporal match...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-04-01
|
| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/24/1633/2020/hess-24-1633-2020.pdf |
| Summary: | <p>The severity of floods is shaped not only by event- and catchment-specific characteristics but also depends on the river network
configuration. At the confluence of relevant tributaries with the main
river, flood event characteristics may change depending on the magnitude
and temporal match of flood waves. This superposition of flood
waves may potentially increase the flood severity downstream in the main
river. However, this aspect has not been analysed for a large set
of river confluences to date.</p>
<p>To fill this gap, the role of flood wave superposition in the flood
severity at downstream gauges is investigated in four large
river basins in Germany and Austria (the Elbe, the Danube, the Rhine and
the Weser). A novel methodological approach to analyse flood wave
superposition is presented and applied to mean daily discharge data from
37 triple points. A triple point consists of three gauges: one in the
tributary as well as one upstream and downstream of the confluence with the
main river respectively. At the triple points, differences and similarities in
flood wave characteristics between the main river and the tributary are
analysed in terms of the temporal match and the magnitudes of flood peaks.</p>
<p>At many of the confluences analysed, the tributary peaks consistently arrive
earlier than the main river peaks, although high variability in the
time lag is generally detected. No large differences in temporal matching are
detected for floods of different magnitudes. In the majority of
cases, the largest floods at the downstream gauge do not occur due to
perfect temporal match between the tributary and the main river. In terms of
spatial variability, the impact of flood wave superposition is
site-specific. Characteristic patterns of flood wave superposition are
detected for flood peaks in the Danube River, where peak discharges
largely increase due to inflow from alpine tributaries. Overall, we
conclude that the superposition of flood waves is not the driving
factor behind flood peak severity at the major confluences in Germany; however,
a few confluences show the potential for strong flood magnifications if a temporal shift in flood waves was to occur.</p> |
|---|---|
| ISSN: | 1027-5606 1607-7938 |