Using Mixed Methods to Understand Floods in Tropical Coastal Catchments

Authors: Shannon Jones*, University of Denver
Topics: Water Resources and Hydrology, Geomorphology, Latin America
Keywords: coastal flooding, mixed methods, Nicaragua, hydrology, Latin America
Session Type: Virtual Guided Poster
Day: 4/7/2021
Start / End Time: 3:05 PM / 4:20 PM
Room: Virtual 54
Presentation File: No File Uploaded

Extreme floods are becoming more frequent and severe, particularly along coasts. They often cause significant economic damage and loss of life, creating great need to estimate extreme flood risk. However, quantifying the magnitude, timing, and duration of these events across the entire catchment is challenging, particularly in data-limited regions. In the tropics, hydrometeorological monitoring networks are often insufficient and the lack of flood data can lead to high uncertainty in flood modeling and mapping. Yet hydrologic modelling is a main tool used for water resource management and policy decisions. This study uses quantitative paleohydrology and qualitative interview methods to reconstruct the timing, duration, and magnitude of an extreme flood event from Tropical Storm Nate within an ungauged tropical coastal catchment in Ostional, Nicaragua. I demonstrate indirect data sources can be used to reconstruct flood events to improve knowledge of flooding in data-limited regions. I measured debris lines to estimate peak flood stage and used the competent depth method to estimate minimum critical discharge. To determine the timing and duration of rainfall and flood discharge and magnitude, I conducted 32 structured household interviews in three villages within the Ostional catchment. Results show that peak flood stage is commensurate for both qualitative responses and paleoproxy estimates. Additionally, 91% of the respondents never experienced a similar or worse flood. I plan to compare the study results to a rainfall-runoff model to validate modelled outputs and to mangrove sediment records to assess the recurrence interval of extreme floods in this region.

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