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Pajaro River

Introduction

(Switch out for NorCal) Central Coast (California)

History

The Pajaro River has a recurring history of flooding. The towns of Pajaro and Watsonville were built on the river’s natural floodplain. Before the Army Corps of Engineers built the levees, flooding devastated homes, businesses, and agriculture. Since the $748,000 levees were constructed in 1949, there have been several instances of flooding from severe weather events and failed levees. In 1963, the USACE (United States Army Corps of Engineers) acknowledged poor planning in levee design, and congress authorized re-construction of the flood control system, however no funds were provided from the federal government.

Timeline of floods

1890 A severe flood was enhanced when a rail bridge’s pilings by the mouth of the river allowed for debris to accumulate and cease discharge to the ocean. As a result, the floods were remembered as the “Highest yet known” for the next 50 years.

1894 Flooding near the city of Watsonville, California.

1907 Major flooding region wide.

1911, 1914, 1915, 1916, 1922, 1927, 1931, 1933, 1937 Each year experienced overflow near the city of Watsonville.

1938

Levee Construction- 1949 Army Corps of Engineers construction.

1955

1963 Overflow near the city of Watsonville.

1982 Flooding of agricultural land at Llagas Creek at the Pajaro River bordering Santa Clara and San Benito Counties. Floodwaters at the confluence of Pajaro River and Carnadero Creek flooded agricultural lands in Santa Clara and San Benito counties. The Pajaro River inundated part of Watsonville and adjacent agricultural land. High stages in the Pajaro River blocked Watsonville drainage.

1983 Flooding in agricultural lands at the confluence of Pajaro River and Carnadero Creek.

1986 Significant flooding on the Pajaro River in February.

March 1995 All residences and businesses damaged 2,500 evacuations

Damage to 3,280 acres of agricultural crops along the Pajaro River were estimated at $67 million, and urban damages in Pajaro estimated at $28 million. Two persons drowned

1997

1998  Town of Pajaro evacuated. The levee along the Pajaro River was breached in several places, and a Presidential disaster was declared.

Geology

The San Andreas Fault line crosses the Pajaro River at the Pajaro Gap near Aromas, California and California State Route 129. The Salinian Block rests above the Pacific Plate which slips north along the San Andres Fault. It is made up of granitic material, and marine sediments.

The Pajaro River has a history of changing its course due to the San Andreas fault slippage between the Pacific plate and the North American Plate. At another time it flowed into the Elkhorn Slough in Moss Landing, California then into the Pacific Ocean, but today it joins with Corralitos Creek to discharge into the Pacific at a slightly more north location.

The 1989 Loma Prieta earthquake in the Santa Cruz Mountains deformed the Pajaro levee system.

Other faults within the watershed are the Zayante fault, Sargent Fault, and Calaveras fault.

A.R. Wilson Granite Rock quarry is located by the Pajaro gap adjacent to the river in San Benito county.

Geography

Due to the geology in the area, the geomorphology of the watershed is unique. The river begins at Diablo range in the east. In the south, from the Gabilan mountains flows another tributary northward. From the north, tributaries flow from the Santa Cruz mountains southward to meet with the Pajaro.

Climate

Climate in the region is Mediterranean. Watsonville annual high temps reach 68°F and lows of 47°F. The average temperature is around 57°F and average precipitation in the form of rainfall is about 23.5 inches.

Certain tributaries frequently run dry due to a lack of rainfall in the summer.

Watershed

-More background on tributaries origins

-Seawater intrusion in Pajaro Valley groundwater, due to agriculture overdrawing groundwater from watershed

Ecology

Four species are listed as threatened or endangered under the federal ESA that are present or for which suitable habitat exists in or adjacent to the Pajaro River. Steelhead trout, the California red-legged frog, the tidewater goby, and the snowy plover, which nests at the Pajaro river mouth at Zumdowski State Beach at the Pacific Ocean.

There are six species listed as threatened or California species of special concern (SSC) under the CESA that regularly occur and/or breed near or in the Pajaro River. Western pond turtles, Pallid bat, Burrowing owls, San Francisco Dusky-footed Woodrat, Least Bell’s vireo, and the Yellow-breasted chat.

-Invasive species?

Water Quality

The river is heavily polluted by people dumping illegally. One cleanup in 2015 revealed over 1,000 tires, five boats, two trucks, and tons of trash.

High toxicity levels in the river are a result from agriculture in the watershed. During low flows, organophosphate pesticides have been detected in the river, and organochlorine pesticides have been detected post-high surface runoff events. Toxaphene, DDT, and Diazinon have also been detected at concentrations unhealthy to local aquatic species.

Improvements

The Pajaro River Watershed Integrated Regional Water Management Plan (IRWMP) is a movement by the Pajaro Valley Water Management Agency (PVWMA), San Benito County Water District (SBCWD), and Santa Clara Valley Water District (SCVWD) to join together in order to create and benefit the watershed as a whole.

The Pajaro River Bench Excavation Project which was approved in 2012 will remove excess sediment and vegetation from the bench in order to better allow flow through the levees to improve flood protection. Approximately 336,000 cubic yards will be removed. The project begins at Murphy’s crossing, and extends 7.5 miles westward to the Pacific Ocean ending before highway 1.

'How can you help? Volunteer!'

http://www.cheerupyourcreek.org/

http://saveourshores.org/volunteer/beach-river-cleanups/

http://www.americanrivers.org/take-action/cleanup/

http://cityofwatsonville.org/city-of-watsonville/coastal-clean-up