Using new high accuracy Light Detection and Ranging elevation data we generate coastal flooding maps for Norway.Thus far, we have mapped ∼80% of the coast, for which we currently have data of sufficient accuracy to perform our analysis.Although Norway is generally at low risk from sea-level rise largely owing to its steep topography, the maps presented here show that on local scales, many parts of the coast are potentially vulnerable to flooding. There is a considerable amount of infrastructure at risk along the relatively long and complicated coastline. Nationwide we identify a total area of 400 km 2 , 5 105,000 buildings, and 510 km of roads that are at risk of flooding from a 200 year storm-surge event at present. These numbers will increase to 610 km 2 , 137,000, and 1340 km with projected sea-level rise to 2090 (95th percentile of RCP8.5 as recommended in planning). We find that some of our results are likely biased high owing to erroneous mapping (at least for lower water levels close to the tidal datum which delineates the coastline). A comparison of control points from different terrain types indicates that the elevation model has a root mean square error of 0.26 m and is the largest source of uncertainty in 10 our mapping method. The coastal flooding maps and associated statistics are freely available, and alongside the development of coastal climate services, will help communicate the risks of sea-level rise and storm surge to stakeholders. This will in turn aid coastal management and climate adaption work in Norway.
Introduction 15Higher sea levels driven by anthropogenic climate change present a large challenge for many coastal communities. There are numerous negative consequences of sea-level rise, i.e., flooding, loss of life and land, damage and loss of buildings and infrastructure, increased erosion, saltwater intrusion, changing ecosystems, and reduced biodiversity (see e.g., Nicholls, 2010;Nicholls and Cazenave, 2010). The consequences of increasing sea level are large and many because the coastal zones are densely populated areas, have a large population growth, and are economically important.
20Compared to many other coastal nations, Norway is at relatively low physical vulnerability to accelerating sea-level rise (Aunan and Romstad, 2008). Norway has a very rugged coast with fjords, inlets, and many thousands of islands. The coastline 1 https://doi.is relatively long being around 103,000 km in length (Kartverket, 2019a) and is largely characterized by steep topography and an exposed bedrock that is resistant to erosion. An important component of sea-level change for Norway is vertical land motion (VLM) due to glacial isostatic adjustment. Regional differences in VLM essentially explain differences in observed sea-level 25 changes along the coast. Observations from Norway's tide gauge network show that relative sea level fell over the recent period 1984-2014 around Oslo and in the middle of Norway, where VLM is largest. Whereas other parts of the coast experienced a limited sea-level rise (Br...