Abstract
Floods are among the most damaging of natural disasters, and flood events are expected to increase in magnitude and frequency with the effects of climate change and changes in land use. As a consequence, much focus has been placed on the engineering of structural flood mitigation measures in rivers. Traditional flood protection measures, such as levees and dredging of the river channel, threaten floodplains and river ecosystems, but during the last decade, sustainable reconciliation of freshwater ecosystems has increased. However, we still find many areas where these traditional measures are proposed, and it is challenging to find tools for evaluation of different measures and quantification of the possible impacts. In this paper, we focus on the river Lærdal in Norway to (i) present the dilemma between traditional flood measures and maintaining river ecosystems and (ii) quantify the efficiency and impact of different solutions based on 2D hydraulic models, remote sensing data, economics, and landscape metrics. Our results show that flood measures may be in serious conflict with environmental protection and legislation to preserve biodiversity and key nature types.
Highlights
River flooding is one of the most damaging of natural disasters, causing potentially significant disruption to critical services such as energy, water provision, infrastructure, and transport
The results indicate that floods of 920 m3 /s inundate an area of 2,130,393 m2, and the construction of the wall would in the habitat simulations
Traditional flood measures such as dredging the riverbed and embankments are usually seen as flood protection measures, but it has been shown that its capacity to carry floods is limited and it can have direct and indirect consequences for ecosystems [50,51]
Summary
River flooding is one of the most damaging of natural disasters, causing potentially significant disruption to critical services such as energy, water provision, infrastructure, and transport. River flooding can have detrimental effects on the life and health of the local population and disrupt society by hampering transport of goods and persons [1,2]. Flood damage comprises a third of the economic losses inflicted by natural hazards worldwide, and between 1980 and 2018, the global direct economic losses due to floods exceeded. Future flood risks are likely to increase due to two factors: climate change [5] and land use modifications [6]. Climate change will affect the water cycle substantially by generating more intense local rainfalls, storm surges will be more frequent and severe [7]
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