Doctoral Dissertation Research: The Effects of Watershed Dynamics and Flood Hydrology on Mangrove Sedimentation in Tropical Coastal Catchments

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Coastal watersheds are increasingly at risk from major floods due to increased sea-level rise and human modification of the landscape. However, more localized flood research and modelling is needed, particularly in regions that lack information on local storm impacts and streamflow. Recent literature has focused on coastal flooding from sea-level rise, with much less attention to upstream contributions of channel flow or localized differences in flooding within the watershed.

Often areas that lack sufficient flood information are where extreme floods are likely to be more severe and devastating to local communities. Traditionally, flood management has heavily relied on instrumental and modelling methods and has excluded valuable information on the duration and extent of flooding from locals affected by these events. This investigation advances integrated methods for characterizing the extent of flooding in watersheds.

Research on this topic helps to inform management decisions pertaining to local flood risks and ecosystem management.

This doctoral dissertation project investigates extreme floods in a representative data-limited coastal watershed by using household surveys and preserved evidence of flooding in the landscape to create a graphical representation of the most recent extreme flood event. These data are also used in a locally calibrated rainfall-runoff model to estimate the timing and intensity of extreme floods.

The findings of this investigation help to establish baseline estimates on the relationship between rainfall and runoff. An additional objective of this research is to understand how more recent land-use changes affect coastal flooding, which is assessed by analyzing satellite imagery to highlight major changes in the channel, coastline, and watershed drainage area.

To determine how often extreme floods occur on longer timescales, the investigators are extracting sediment cores from coastal mangroves and analyzing for evidence of flood deposits. Combined, these methods provide a robust assessment of past extreme floods and highlight the importance of using multiple data sources and local information to improve flood planning and management.

Furthermore, these methods help to reduce uncertainty in flood modelling and provide an improved understanding of flooding in any data-limited region around the world.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.