El Nino-La Nina Implications on Flood Hazard Mitigation
Phoenix, AZ. Area
World Environmental and Water Resources Congress 2007: Restoring our Natural Habitat
Proceedings of the World Environmental and Water Resources Congress 2007 Tampa, Florida, USA,
ABSTRACT
Richard H. French1 and Jeff Irvin2
1
Department of Civil and Environmental Engineering, University of Texas at San Antonio, 6900 N.
Loop 1604, San Antonio, TX 78249-0668; email: richard.french@utsa.edu
2
URS Corp., 9400 Amberglen Blvd, Austin, TX, 78729; email: jeff_irvin@urscorp.com
In a previous investigation, five maximum annual winter period daily depths of
precipitation series from gaging stations on the U.S. Department of Energy's Nevada
Test Site were examined from the viewpoint of the effects of El Nino - La Nina
events on the series. This analysis demonstrated at the five precipitation gages
considered, with periods of record ranging from 33 to 45 years, that there were
actually two data series; one series associated with El Nino periods and a second
series with La Nina events and neutral periods. That is, the precipitation data series
contained a mixed population. This has critical implications from both the viewpoints
of flood hazard identification and mitigation when rainfall-runoff modeling is used and
environmental restoration. In this paper, annual maximum (winter and summer)
depths of precipitation are analyzed for five long-term gaging stations in the Phoenix,
AZ area.
©2007 ASCE
http://dx.doi.org/10.1061/40927(243)27
Permalink:
No Adverse Impact Floodplain Management
World Environmental and Water Resources Congress 2007: Restoring our Natural Habitat
Proceedings of the World Environmental and Water Resources Congress 2007 Tampa, Florida, USA,
The central message that ASFPM is trying to communicate is that we continue to
cause flood damages and these flood damages have not been communicated
effectively. This is in part due to the floodplain management community as a whole
spending too much time debating issues of individual standards while not stepping
back and evaluating the broad impact of the range of management approaches
throughout the watershed. Current management systems to reduce flood losses are
costly and often allow development that fails to evaluate or mitigate adverse impacts
on other properties, both now and in the future. No Adverse Impact is an approach
that will lead to reduced flood losses throughout the nation while promoting and
rewarding strong management and mitigation actions at the local level.
©2007 ASCE
http://dx.doi.org/10.1061/40927(243)28
Incorporating Climate Change and Variability into
Bulletin 17B LP3 Model
World Environmental and Water Resources Congress 2007: Restoring our Natural Habitat
Proceedings of the World Environmental and Water Resources Congress 2007 Tampa, Florida, USA,
The current techniques for flood frequency analysis presented in Bulletin 17B assume annual maximum
floods are stationary, meaning that the distribution of flood flows is not significantly affected by climatic
trends or long-term cycles (i.e. decadal variations). Observed trends in stream flows raise concern as to
whether or not this assumption is valid. This paper considers how the Bulletin 17B framework might be
modified to account for nonstationarity in flood records due to climate variability. In order to improve
estimates/forecasts obtained using the LP3 model, the effects of climate variability may be incorporated
into updated estimates of the mean, standard deviation, and perhaps the skew by regressing the LP3
parameters on climatic indices describing the Pacific Decadal Oscillation and Northern Atlantic Oscillation.
The effects of climatic cycles occurring over a shorter time frame, such as El Niño, are averaged into
estimates made using the procedures of Bulletin 17B. However, the effects of El Niño are likely to affect
the magnitude of annual maximum stream flows, and thus would impact flood risk in a given year. El Niño
effects are incorporated into forecasts by regressing the LP3 parameters on sea surface temperatures.
©2007 ASCE
Permalink: http://dx.doi.org/10.1061/40927(243)69