Programme  Poster session 4  abstract 409

Assessment of flood damage risk for engineering structures in river floodplains

Author(s): Borris Gjunsburgs, Roberts Neilands, Elena Govsha
Water Engineering and Technology Department, Riga Technical University

Keyword(s): Flood, risk, engineering structures, scour

Article: abs409_article.doc
Poster: abs409_poster.jpg
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Session: Poster session 4
AbstractWater flow regime in rivers is

changing because of the climate, but it means that impact is not only on nature, economy, and urban infrastructure,

but also strongly influences the transport infrastructure – roads, bridges, dams, and also water supply system,

irrigation systems and canals. Frequency and intensity of flood events with high water levels and considerable

discharges becomes frequent and increases the load on engineering structures in rivers and possibility to be

The objective of this research is to study erosion processes developing during the multiple floods and

work out methods that allows estimating stability and safety of engineering structures in river floodplains.

methods and formulas do not take into account multiple floods impact on scour process near structures, floods

probability, floods duration and sequence, computing only equilibrium stage or temporal development of scour at the

flood peak.
In the present study, a differential equation of equilibrium of the bed sediment movement for clear

water was used and a new method for computing the scour development at engineering structures in river floodplain

during multiple floods was elaborated. The method was verified by experimental data.
A new method for

computing equilibrium stage of local scour at engineering structures in river floodplain was also developed.

two mentioned methods we propose to estimate possible damage of engineering structures caused by multiple

floods. The parameters of scour hole computed during multiple floods can be compared with its equilibrium

parameters by equations suggested, and the flood damage risk factor for engineering structures can be determined as

a ratio hs/hequil, where hs is a scour depth developed during/after multiple floods, and hequil is a equilibrium scour

depth. The closer current depth value of the scour hole is to the equilibrium value of the scour hole, the more is risk

factor and less is the stability of the structure. By risk factor we can estimate the current stability of the structure in

the period of maintenance or predict/compute it’s stability at the design stage.
For critical conditions, as flood

management measures, when the developed scour hole is close to the equilibrium conditions, emergency protection

measures (for example, riprap, rock riprap, sand/cement filled bags, etc.) should be fulfilled.
In this paper are

presented new method how to forecast and estimate floods impact on engineering structures in river floodplains.

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