3 minute read
The Best, Most Likely and Worst Case Approach
Continued: VULNERABILITY, CAPACITY ASSESSMENT (VCA) AND RISK REGISTER
Hazard Vulnerability
Advertisement
Flood hazard related to sea level rise and storm tide
Organizational
vulnerability
Institutional
vulnerability • no disaster management authority or official disasterresponse systems • inexperienced earlywarning systems for unexpected flooding • lack of expert response team • organizations and departments inexperienced with flooding • lack of planned evacuation routes in sea level rise flooding disaster scenarios • Active NGOs, e.g. CARE, Trondheim Red Cross, etc. • community organizations, e.g. Svartlamon housing association, Svartlamon resident association, etc. • Decentralized decisionmaking in Svartlamon • Late response to disaster causing more damage and casualties • inability to coordinate efficiently, which may delay rescue and other necessary support
• no disaster management authority • low awareness and commitment of local authorities to sea level rise disaster reduction • lack of legislation, plans and instructions for local and national flooding disaster management • Presence of assistance departments, e.g. fire department, police, etc. • good cooperation with international organizations and EU frame • abundant human resources for disaster response • abundant financial resources for preparedness • Absent systematic disaster management mechanism leads to lower capacity in disaster coping • may cause more economic loss and casualties
Capacity Potential Risk
The Best, Most Likely and Worst Case Approach
The contingency plan adopts the best/most likely/worstcase approach in scenario development. This part investigates into the historical flooding impacts in Trondheim based on the research project FloodProBE (2009). These historical flooding events provide good example of possible ranges of impacts in our different scales of scenarios.
Table 2: HISTORY OF FLOODING IN TRONDHEIM Heavy precipitation, large runoff and flood events
Time Characteristics of scenarios Return Interval Impacts
9- First 30-40 mm in 20 hours, 20- 10-30 year Damages on the roads and houses 10.12.1987 30 mm in the coming 6 hours;
and show on the ground equivalent to 20 mm.
3031.03.1997 95 mm rain and snow melting in two days 40-50 year About 100 houses flooded and some roads had to be stopped. One manhole cover was lift at one place due to high pressure in the sewers.
30.0105.02.1999 48 mm in 1 day on 04.02.1999 15-20 year The flood attacked the whole city. Flood warning on 30 January 1999. flooding in basements and on roads was registered in large parts of the city, caused million kroner of economic damages.
29.07.2007 Rain from midnight to 7-8.00 in the morning with variable intensity in the whole city 13.08.2007 Intensive rain in 1 hour 100 year 60 houses were flooded.
>100 year Over 100 houses were damaged by floods.
Hazard scenario
Best case 5m sea level rise, with normal storm surge Flooding in basements and on roads of low-lying area, causing economic loss, affecting mobility
Most likely case 5m sea level rise, with king tide and waves
Worst case 10m sea level rise, with 100-year storm tide and waves
Potential impacts
Flooding in basements and on roads, damaging caravans and part of aged houses, causing a lot of economic loss and a small number of people hurt, affecting normal life Flooding inundates the first floor of some low-lying houses, flooding in basements and on roads for higher elevation., causing great economic loss and some casualties, threatening people’s lives
King tide is the highest astronomical tides that predictably occur a few times each year. The 100-year storm tide is a severe, rarely occurring flood event, a combination of a high astronomical tide and storm surge. (Olympia Sea Level Rise Response Plan, 2019)
Figure 7 five-meter sea level rise with normal storm tide
Figure 8 five-meter sea level rise with king tide
Figure 9 ten-meter sea level rise with 100-year storm tide In the best case, the sea level rises 5 meters in 30 years, and the climate change leads to more often extreme weathers such as the storm surges causing coastal flooding in Trondheim.
In the most likely case, the sea level rises 5 meters in 15 years, and it becomes highly probable that the king tides of maximum 5 meters will strike the coasts of Trondheim.
In the worst case, the sea level rises 10 meters in 5 years, and it becomes highly probable that the 100-year storm tide higher than 5 meters will strike the coasts of Trondheim.
Figure 10 possible scene when storm waves strike the coast
Figure 11 possible scene after a 100-year storm tide strikes
