Parts of Santa Catarina state in Brazil are particularly prone to flooding. The World Bank asked us to produce flood hazard maps and flood risk loss analysis to help achieve a better understanding of the potential flood hazard and identify ways to reduce flood risk.
Santa Catarina in Southern Brazil covers almost 100,000km2 with over 6 million people and 15 major cities. Rapid urban expansion has seen development in vulnerable areas with a high potential for devastating floods.
The Itajaí Basin, in particular, is prone to frequent, severe flooding. In November 2008, major flooding from heavy rainfall affected around 60 towns and over 1.5 million people. At least 135 people were killed, with over 78,700 forced to evacuate homes, 27,400 people left homeless, 7,154 homes destroyed and 186,000 left without electricity for weeks.
The area was flooded again in September 2011 when six people died and almost half a million people were affected. Recent flood events in 2013, 2014 and 2015 showed that flooding was becoming a serious and persistent hazard in Santa Catarina state.
We produced a comprehensive flood risk assessment and catastrophic loss model to identify high-risk locations, including a state-wide high-precision flood map. We then used this within a catastrophe model to establish worst-case scenarios. We simulated 10,000 years of realistic synthetic flooding events using a stochastic process driven by rainfall data and a covariance correlation matrix.
Using this event catalogue and our own Flowroute-i™ technology, we modelled loss estimations for an exposure portfolio which contained all the building assets for the state. We also produced catastrophic loss estimations for historic flooding events. This helped to provide validation for our results and allowed us to estimate loss for various scenarios. We created the map and conducted the bulk of the analysis work within a tight, four-month timeframe.
We also visited Brazil to present our findings to representative of the Santa Catarina state government and The World Bank. We followed this with a visit to the Secretariat of Sustainable Development where we discussed the findings in further detail along with effective strategies for communicating them to stakeholders.
The study formed the basis of our Brazil FloodCAT™ product, the most comprehensive and accurate catastrophe model available for Brazil. It showed where the potential fluvial flood hazard is greatest and where it poses the greatest risk to life. It’s also being used to quantify possible financial losses to the building stock across the entire state. The data generated through this work is superior to anything already available to the state government. It will enable them to make effective improvements to flood risk management both now and in the future.
In November 2008, major flooding from heavy rainfall affected around 60 towns and over 1.5 million people in Santa Caterina state.