Climate and human impacts on hydrological processes and flood risk in
southern Louisiana
Abstract
Satellite observations of coastal Louisiana indicate an overall land
loss over recent decades, which could be attributed to climate- and
human-induced factors, including sea level rise (SLR). Climate-induced
hydrological change (CHC) has impacted the way flood control structures
are used, altering the spatiotemporal water distribution. Based on
“what-if” scenarios, we determine relative impacts of SLR and CHC on
increased flood risk over southern Louisiana and examine the role of
water management via flood control structures in mitigating flood risk
over the region. Our findings show that CHC has increased flood risk
over the past 28 years. The number of affected people increases as
extreme hydrological events become more exceptional. Water management
reduces flood risk to urban areas and croplands, especially during
exceptional hydrological events. For example, currently (i.e., 2016-2020
period), CHC-induced flooding puts an additional 73km2
of cropland under flood risk at least half of the time (median flood
event) and 65km2 once a year (annual flood event),
when compared to a past period (1993-1997). A ten- to twenty-fold
increase relative to SLR-induced flooding. CHC also increases population
vulnerability in southern Louisiana to flooding; additional 9900
residents currently live under flood risk at least half of the time, and
that number increases to 27,400 for annual flood events. Residents
vulnerable to SLR-induced flooding is lower (6000 and 3300 residents,
respectively). Conclusions are that CHC is a major factor that should be
accounted for flood resilience and that water management interventions
can mitigate risks to human life and activities.