CDMP Progress Bulletin

Belize River Flood Assessment

Bulletin Date: October 1999

Belize is subject to significant flood hazards, including coastal surges associated with tropical storms and riverine flooding following heavy rains. In 1996, CDMP completed a coastal storm hazard assessment for Belize. The goal of this project is to provide the Government of Belize the capability to predict river water levels based on rainfall rates. This capability will allow the Belize Meteorology and Hydrology offices to create floodplain maps for the country and to provide a flood early warning system for emergency response. The flood hazard maps are being created through a flood hazard model integrated into a geographic information system (GIS).

The identification of flood-prone areas provides essential information for landowners, farmers, emergency planners and financial institutions in planning appropriate land use and locating investments.

The flood hazard model developed for the Belize River can be applied to river basins elsewhere in the country. Datasets required to run the model, such as land cover, river routing and rainfall estimates have been developed for the study area. This database can be updated with new information, as it becomes available.

Progress to date

The flood hazard assessment model for the Belize River is complete. A number of hydrologic models were tested before selecting a final model. The lack of spatially distributed rainfall data and the size and complexity of the basin caused instability in the traditional HEC model. Other models tested included a finite element model of the US Army Corps of Engineers and the University of Oklahoma, and a newer, fully distributed version, CAS2D, also developed by the USACOE. The CDMP organized a review by hydrology experts in both the United States and Belize of this model as applied in Belize. The model uses the Geographic Resource Analysis Support System (GRASS), which can run on IBM-compatible personal computers using Linux, a public-domain version of the UNIX operating system. GRASS is currently in use by the Belize Hydro-Met Service.

The flood model requires land cover, river routing and profile information and rainfall data. Land cover information was derived from satellite imagery provided by the Belize Land Information Unit. River route maps were created by combining information from maps provided by Belize with Digital Chart of the World base data. River profiles were provided by the Belize Meteorology and Hydrology office. Rainfall estimates were derived by combining existing rainfall gauge data with satellite-based rainfall estimates and model estimates for mountainous areas.

In September 1999, the results of the Belize River flood assessment were presented to the collaborating technical agencies in Belize.  Around forty representatives of public sector agencies and private sector interests participated in a half-day workshop.   The assessment methodology was presented and applications of the information and database were discussed with the participants.  The final report outlines the next steps that can be taken once high resolution digital elevation data is available for the Belize river basin.