flood wall

{{Short description|Wall for flooding prevention}}

{{distinguish|Floodwall (art installation)}}

{{More citations needed|date=January 2023}}

File:Zruč nad Sázavou, Ostrovský potok, u Vlašimské ulice.jpg, Czech Republic]]

File:Floodwall in Sunbury, Pennsylvania.JPG]]

File:NewOrleansFloodGate1.jpg French Market (1986)]]

A floodwall is a freestanding, permanent, engineered structure designed to prevent encroachment of floodwaters.{{Cite web |date=2016-10-24 |title=Floodwalls |url=https://www.geo.fu-berlin.de/en/v/iwrm/Implementation/technical_measures/Flood-protection-measures/structural_measures/Floodwalls/index.html |access-date=2023-01-22 |website=www.geo.fu-berlin.de |language=en}} Floodwalls are mainly used on locations where space is scarce, such as cities or where building levees or dikes (dykes) would interfere with other interests, such as existing buildings, historical architecture or commercial use of embankments.{{Clarify|reason=commercial use of embankments?|date=January 2023}}

Floodwalls are nowadays mainly constructed from pre-fabricated concrete elements. Floodwalls often have coupures, which are large openings to provide passage of traffic except during periods of flooding, when they are closed. As a floodwalls mostly consist of relatively short elements compared to dikes, the connections between the elements are critical to prevent the failure of the floodwall.

The substantial costs of floodwalls can be justified by the value of commercial property thus protected from damage caused by flooding.

Floodwalls are sometimes bad for ecosystems.{{Cite journal |last1=Serra-Llobet |first1=Anna |last2=Jähnig |first2=Sonja C. |last3=Geist |first3=Juergen |last4=Kondolf |first4=G. Mathias |last5=Damm |first5=Christian |last6=Scholz |first6=Mathias |last7=Lund |first7=Jay |last8=Opperman |first8=Jeff J. |last9=Yarnell |first9=Sarah M. |last10=Pawley |first10=Anitra |last11=Shader |first11=Eileen |last12=Cain |first12=John |last13=Zingraff-Hamed |first13=Aude |last14=Grantham |first14=Theodore E. |last15=Eisenstein |first15=William |date=2022 |title=Restoring Rivers and Floodplains for Habitat and Flood Risk Reduction: Experiences in Multi-Benefit Floodplain Management From California and Germany |journal=Frontiers in Environmental Science |volume=9 |doi=10.3389/fenvs.2021.778568 |issn=2296-665X |doi-access=free }} Floodwalls are almost always built in cities.