Intersecting Near-Real Time Fluvial and Pluvial Inundation Estimates
with Sociodemographic Vulnerability to Quantify a Household Flood Impact
Index
Abstract
Increased interest in combining compound flood hazards and social
vulnerability has driven recent advances in flood impact mapping.
However, current methods to estimate event specific compound flooding at
the household level require high performance computing resources
frequently not available to local stakeholders. Government and
non-government agencies currently lack methods to repeatedly and rapidly
create flood impact maps that incorporate local variability of both
hazards and social vulnerability. We address this gap by developing a
methodology to estimate a flood impact index at the household level in
near-real time, utilizing high resolution elevation data to approximate
event specific inundation from both pluvial and fluvial sources in
conjunction with a social vulnerability index. Our analysis uses the
2015 Memorial Day flood in Austin, Texas as a case study and proof of
concept for our methodology. We show that 37% of the Census Block
Groups in the study area experience flooding from only pluvial sources
and are not identified in local or national flood hazard maps as being
at risk. Furthermore, averaging hazard estimates to cartographic
boundaries masks household variability, with 60% of the Census Block
Groups in the study area having a coefficient of variation around the
mean flood depth exceeding 50%. Comparing our pluvial flooding
estimates to a 2D physics-based model, we classify household impact
accurately for 92% of households. Our methodology can be used as a tool
to create household compound flood impact maps to provide
computationally efficient information to local stakeholders.