Climate projections and risk and vulnerability assessment

Climate projections for Sør-Trøndelag and Trondheim

The annual precipitation in Sør-Trøndelag is estimated to increase by 20%, which will be observed in both intensity and frequency, throughout all seasons, but especially summer and fall. Figure 14 illustrates climate projections for precipitation in Trondheim for the next ten years using RPC 8.5. The darkest areas are expected to receive 189246 mm of precipitation over the next decade, while the lighter areas will receive 90058 mm. This may lead to problems with stormwater and flooding and increase erosion that may trigger quick clay landslides (Norsk Klimaservicesenter, 2022).

Risk and vulnerability assessment for Trondheim municipality 2012-2024 (RVA)

In our analysis we have only included the events relevant for our scenario which we base on extreme weather events that could lead to flooding and trigger quick clay landslides. (Trondheim Kommune, 2012)

River flooding in Nidelva

The report is based on extraordinary events and dangerous episodes with unusually high water levels in Nidelva and events likely to occur because of this. Flooding results from heavy precipitation due to heavy rain, snow melting or spring and storm surge which changes the riverbed and has potential for big material damages in dense areas like Bakklandet (ibid.) The maps illustrate the danger zone, and 10, 20, 50 and 100 year floods in Nidelva.

Flood paths

Flood paths show the runoff paths caused by high precipitation or snow melting. Stormwater damages due to heavy rain have occurred more often in recent years due to a combination of poor capacity, reduced drainage and clogged culverts, pipes, and stream runs. Risk associated with flood paths must be seen in association with topography and non-permeable surfaces. To enable safety and prevent damages it is important to maintain existing flood paths and establish new ones. (Trondheim

Flood paths in Bakklandet:

Quick clay landslides

A landslide can be defined as a collapse of a mass from a slope in the terrain. Quick clay landslides are almost always caused by a sudden soil liquefaction due to a combination of heavy rain, flooding and human activities. A quick clay landslide can result in flooding of masses in large areas. It is therefore suggested in the RVA that new buildings should only be constructed in areas considered to have a high probability of security and the stability in areas with marine alluvium must be documented. A quick clay landslide disaster in dense areas has a high risk of death, material damages and loss of livelihood. Three quick clay zones are in Bakklandet. (Trondheim Kommune, 2012)