What is Extremeabout Riverside County?

Arturo Diaz, P.E.Engineering Project Manager

Overview

Riverside County Rain Gauge Network Significant Storm Events

Riverside County Formed in 1893 Population: 2.2 million people (2010 census)

4th largest county in CA 11th largest county in U.S. 7,300 sq. miles 200 miles across.

Size Comparison

Riverside County continued.. The 7,300 sq miles include: River valleys, low deserts, and mountains Mediterranean climate in western portion Highest elevation: 10,843 ft (San Jacinto Peak)

Lowest elevation: -141 ft bsl (Oasis)

Riverside County Watersheds

Santa Ana River Region

Santa Margarita River Region

Whitewater Region (Colorado River)

You are here

Salton Sea

District Rain Gauge Network

68 (0.2 MM) Class I GaugesEngineering Quality Data

75 ALERT 1mm Radio TelemeteredRain Gauges (In co-op with CVWD)

District Rain Gauge Network

20 Cellular Telemetered GaugesReal Time Reporting

4 Heated 0.2mm Class I Rain Gauges (Higher Elevations)

Rainfall Analysis22 Wet Years39 Dry Years47 Normal Years

Rainfall AnalysisAVG = 4.1” AVG = 12.2” AVG = 25.7”

Thunderstorm EventHurricanes that form in the Pacific Ocean off the coast of Mexico sendperceptible moisture into the air which can lead to thunderstorms andflooding events hundreds of miles to the North.

A recent example of this was tropical storm Dolores which caused 2inches of rain to fall over the Moreno Valley area on July 18th-19th 2015.

Flash Flooding

Flash flooding occurred around the city of Moreno Valley as streets were quickly overwhelmed by stormflows. Rainfall intensities for the July 19th

event exceeded previous record maximums for the 10 minute through 2 hour storm durations.

kabcJohn Bender/ Press Enterprise

Storm Event Data

0.75” 10 minute 5,000+ year event

1.06” 15 minute 10,000+ year event

1.46” 30 minute 5,000+ year event

0

5

10

15

20

25

30

35

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

RainfallM

oder

ate

Historic Rainfall El Niño vs. Non-El Niño

Very

Str

ong

Wea

k

Mod

erat

e

Wea

k

Wea

k

Avg. Annual

5 strong El Niños – 1958 (25”), 1966 (14”), 1973 (15”), 1983 (24”), 1998 (25”)

QUESTIONS??