The Parkway, surely one of the most beautiful urban parks in the country precisely because it embraces one of the most beautiful and historically significant rivers in the country, needs preservation, protection, and strengthening.
We need public leadership who will stop this juggling of evacuation warnings, mandatory flood insurance, 100 or 200 year levees; instead. work to increase the height of Folsom Dam, and build the Auburn Dam on the American River that can offer a 500 year + level of protection.
From ARPPS perspective, we need to dam the river to ensure whatever level of run-off occurs in the entire American River watershed, year after year, can be captured and held in its reservoir to be used, as needed, during the normally dry spring and summer, to preserve the integrity of the Parkway.
In this decision- making process, the ongoing threat of pineapple-express storms, fueling flooding in 1986 and 1997, are a crucial factor.
A recent report presented at the 2005 symposium of the American River Watershed Institute www.arwi.us/ , A Long Term (50-yr[1948-1999]) Historical Perspective on the Meteorology and Hydrology of Flood-Generating Winter Storms in the American River Basin, by Michael D. Dettinger, Ph.D., Research hydrologist, U.S, Geological Survey, Scripps Institution of Oceanography, concludes:
"The long-term perspective taken here reveals that, historically, El Nino conditions have favored having more low-altitude precipitation (relative to the usual high0altitude orographic [influence of mountains on precipitation, airflow etc.] enhancement) that, falling most often as rain rather than snow, may tend to increase flood risks. Pineapple express patterns and the flood risks that they entail, on the contrary, appear to have been favored by near-neutral (non-El Nino) tropical conditions during El Nino-rich decades (warm phases of the Pacific Decadal Oscillation).
"Furthermore, this long-term perspective confirms our suspicion that the risks for flood generation in the American River basin are special in several ways. With its broad expanses of moderate-altitude terrain and its near equal mix of rainfed and snowmelt runoff, the basin is particularly sensitive to storm-by-storm variations in the amounts and distributions of rainfall. The orientation of the western slopes of the Sierra Nevada in the modulated year-to-year increases in orgraphic precipitation enhancement during La Nina winters, rivaled in the Sierra Nevada only by the southern ramparts of the range where topography may favor El Nino orographic enhancements. Pineapple express storms bring particularly warm and wet storms to the area and thus pose important flood risks. On long-term average, the American River has the dubious distinction of being situated beneath the margins of most intense precipitation associated with pineapple-express circulations and of being situated at the point in the Sierra Nevada and Cascades where pineapple-express circulations (on average) bring the warmest temperatures. (p. 72 [12]) http://www.arwi.us/precip/SymPro-2005-Dettinger-5.pdf
In addition to protecting us against flooding, we will then be able to provide year round integrity to our crown jewel, the American River Parkway; having the ability to draw the cold waters at the proper flow for the salmon run, and providing predictable and stable flows for optimal public recreation.
