Learn about Flood Factor and RCP Curves.
Environmental change and flood risk
The First Street Foundation Flood Model allows for the understanding of risk from multiple types of flood events by taking into account flooding that may be caused by fluvial (riverine), pluvial (rainfall), storm surge, and tidal sources. Each of these sources has been, and continues to be, impacted by changing environmental factors in a multitude of ways. In order to understand those changing environmental conditions, the modeling process has integrated those considerations directly into the production of future facing risk layers and statistics derived from those layers. These environmental factors are built into the model with guidance from the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathway (RCP) curves and the Coupled Model Intercomparison Project 5 (CMIP5) global climate model (GCM) ensemble.
About RCP curves
The RCP curves represent an agreed upon set of scenarios that can be used in the development of research focused on future environmental changes. The standard set of comparative curves are based on carbon concentrations into the future, with trajectories related to scenarios in which emissions are relatively uncontrolled (RCP 8.5) on the high end to a dramatic restriction on emissions (RCP 2.6) on the low end. In contrast, RCP curves 4.5 and 6.0 are thought of as more moderate, and potentially more realistic trajectories into the future.
IPCC Representative Concentration Pathways
The Flood Model uses the RCP 4.5 curve to project future emissions characteristics, and associated environmental change, out into the year 2050. More importantly, the RCP 4.5 and RCP 6.0 curves are relatively indistinguishable from one another through 2050, making our models representative of a moderate projection of environmental change into the future.
To add climate uncertainty to our models, a series of simulations using the RCP 4.5 expectations and information from the GCM ensemble were conducted to produce a distribution of expected environmental factor outcomes from highly unlikely to highly likely. To round out our presentation of environmental change, we draw risk from the 25th percentile (low), 50th percentile (middle), and 75th percentile (high) of the distribution. These three projections represent the most likely projection using the RCP 4.5 curve (middle) and more unlikely low and high projections out to 2050. By including the low, middle, and high projections on Flood Factor we are able to provide a more comprehensive set of expectations of flood risk into the future. The inclusion of these global climate models, forward-facing climate considerations, and high-resolution flood risk layers ultimately contribute to the uniqueness of the Flood Model in terms of coverage, precision, and climate adaptability.