Flooding and the El Niño‐Southern Oscillation phenomenon along the Pacific coast of Costa Rica

摘要

The rivers of western Costa Rica are prone to considerable interannual variability in flooding, which in the most severe years can lead to loss of life, property and national infra-structure. Flood generating processes are exclusively rainfall driven, but are complex in both their spatial and temporal distribution due to the variety of oceanic and continental influences which impinge on the region, and to the various natures and timings of their responses to the El Niño-Southern Oscillation (ENSO) phenomenon. Annual floods and partial duration series derived from daily discharge records from four basins within the Pacific watershed are analysed using a series of standard probability distributions and parameters estimated by means of L-moments. The observed temporal and spatial patterns of flood events are consistent with the documented meteorological processes and also exhibit marked changes in behaviour between the two extreme phases of the ENSO phenomenon. Particularly noticeable in this regard are; the variable length of the short dry season, the , which is related to the strength of the northeast trades, and interrupts the rainy season; the number of floods in the period immediately following the , which is positively associated with the number of tropical storms in the Caribbean basin; and the number of cold fronts emanating from North America during the boreal winter. Copyright © 1999 John Wiley & Sons, Ltd.