In December, 2010, the flood of record occurred in the Panama Canal Watershed. The investigators have been working in Panama for approximately 10 years studying the hydrometeorology, hydrology, in-stream wood transport and fate and landslides, and assisting the Panama Canal Authority in setting up a real-time weather and flood forecast system. This extreme event, with a return period thought to be between 100 and 200 years, provides an excellent opportunity to create a database of hydrometeorological, hydrological, and geomorphic features associated with this flood, as well as carbon cycling by large woody debris in a tropical mountainous watershed during an extreme event. Our project consists of field collection campaign, atmospheric simulations, and database creation components. Field studies will document landslides, large woody debris accumulations, high water marks, and geomorphic changes within the 414 sq. km old-growth upper Rio Chagres watershed. The Weather Research and Forecasting (WRF) atmospheric model will simulate the storms that caused the floods. Rain gage data provided by the Panama Canal Authority will be used in conjunction with the WRF model output to generated ground-truthed space-time rainfall series.
Collaborations with the Smithsonian Tropical Research Institute (STRI) and Technological University of Panama will assist in assembling data from disparate sources not readily available. The U.S. Bureau of Reclamation is a collaborator, as they have an interest in understanding the performance of the Madden Dam, which they designed in the 1920's. During the flood of December, 2010, the Madden dam was pushed to the limits of its design, even though it was originally designed to pass a 10,000-year flood. We will explore whether land-use changes in the watershed are responsible for this change in flood frequency. The long-term historical dataset owing to the existence of the Panama Canal, in addition to the existing hydrological and hydrometorological network will make this one of the best documented extreme flood events in any tropical mountainous watershed to date. The short-term, intensive once-off field campaign will also complement project EAR-1045166 that started on May 1, 2011.
Rainfall over the Panama Canal watershed (3,300 km2) supports the operation of the 80km-long fresh-water canal between the Atlantic and Pacific Oceans. More than 13,000 vessels use the Canal every year, representing commercial transportation activities of approximately 5% of the world trade. During the period of 7-9 December 2010, an unprecedented rain event, which was almost twice in magnitude of the maximum previously recorded event over the watershed, caused a 17-hour closure of the Panama Canal; one of the very few closures of the Canal due to weather conditions since its opening in 1914. The objective of our project was to collect, archive, and disseminate data from this extremely rare event to enable improved modeling for risk analysis, canal engineering and operations. Our data collection activities were performed in collaboration with the Panama Canal Authority (PCA) in Panama, and collaborators from the University of Wyoming through collaborative project EAR-1123498. The PCA has provided rainfall, streamflow, and Lake Alajuela water level data. We used the Weather Research Forecasting (WRF) model to simulate the meteorology of this event and to interpolate the observed rainfall data in the mountainous terrain of the Panama Canal watershed. The WRF rainfall output has been provided to our colleagues at the University of Wyoming for use in hydrologic flow studies and for public dissemination for other studies. Initial statistical analysis of this extreme rainfall event was also performed to identify the ability of standard techniques of extreme event analysis to provide useful prediction information to water managers. Our data collection activities included field work in Panama performed by our collaborators at the University of Wyoming. We conducted video surveys by helicopter to document the number and locations of landslides, as well as the number of logs stored in the river channel and discharged to Lake Alajuela. Landslides were categorized according to whether or not they reached the Chagres River. Data from water level sensors previously deployed in the upper Chagres watershed were obtained for comparison with other events since 2005. Satellite images were obtained and used to estimate the large-scale distribution of landslides. Watershed processes in the tropics are poorly understood compared to those in temperate climates. The Upper Rio Chagres has a long history of data collection due to Panama Canal operations, and offers a unique setting to study an old-growth watershed that is 98% undisturbed. For this reason our data collection activities to document this rare event are of broad interest to the tropical hydrology research community, water managers, risk analysts, and engineers. We are creating an on-line database of the flood, and are communicating our findings to PCA, the Technological University of Panama, and the Smithsonian Tropical Research Institute in Panama. We have produced three scientific papers that are currently for consideration for publication in scientific journals. The research project has engaged two scientists (one hydrologist and one meteorologist) from at the Hydrologic Research Center. Both are co-authors on two of the submitted papers. More details on our results are included in the final report for collaborative project EAR-1123498.