Orestimba Creek Feasibility Study - Stanislaus County

Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012
1.0 Introduction
1.1 Purpose and Scope
The purpose of this report is to present the results of the economic analysis performed for the
Feasibility Study of the Orestimba Creek Project. The report documents the existing condition
within the study area and proposed alternative plans to improve flood risk management, and
designate the National Economic Development (NED) Plan for purposes of estimating federal
interest for Orestimba Creek. The report presents findings related to flood risk, potential flood
damages and potential flood damage reduction benefits.
1.2 Study Area
The study area is located in the southwestern portion of Stanislaus County, in what is referred to
as the Newman Division by the U.S. Census Bureau (see, Figure 1). Orestimba Creek stretches
approximately 7.5 within the study after having left the foothills of the Diablo Mountain Range.
It is estimated that in the 500-year flood event the floodplain would encompass approximately
20,000 acres, including the City of Newman (see Figure 2-1). The City of Newman is the home
of approximately 12,321 residents (2010 Census data). Newman is home to the world’s first
school bus company and along with the surrounding area, it is home to some of California’s most
efficient and important agricultural industries. Tomato and vegetable processing, cheese
manufacturing, and turkey hatching are examples of some of the agricultural industries located in
the area. The area is acknowledged for crop diversity and productivity, which can be accredited
to a combination of exceptional factors such as, soil quality, air quality, climate, and water
supply.
1.3 History of Flooding
The city of Newman has experienced 14 floods in the past 58 years (1954, 1955, 1957-1959,
1963, 1968, 1969, 1978, 1980, 1983, 1986, 1995 and 1998). The major floods occurred in 6 out
of the last 14 flooding events (1955, 1958, 1963, 1980, 1983, 1995 and 1998). These floods
occurred along Orestimba Creek and affected both rural and urban land uses. The frequency of
flooding in and around Newman is similar that which occurs on an average cycle of between 4 to
5 years. These flooding events have affected the same general areas each time except when there
was a levee failure or similar occurrence that changed the location of flooding and the type of
land uses that were adversely affected. The following flooding summary descriptions focus on
the seven largest major flooding events.
In 1955, floodwaters inundated agricultural, residential, and commercial properties; caused
breaks in the DMC; washed out public streets and culverts; inundated and closed public streets in
many areas; and washed out the Southern Pacific Railroad ballast and ties.
The April 1958 flood damaged agricultural lands and public facilities in the Orestimba Creek
basin. Some residents were forced to evacuate their homes. Subsequently, in the 1959 flood,
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