Levee Relocation at Shanghai Bend

Feather River levee district #1

Chris L. Ball
Data Acquisition Geog 26
5/11/2000

Overview

California is home to the most elaborate river control system in the world. Part of maintaining this system requires relocating and replacing existing levees. The Feather River levee system at the Shanghai Bend site has recently been reconstructed. This area which was once orchards and farmland has seen significant growth as an urban expansion of South Yuba City.

The original levee was situated to follow the path of the river which changed during the flood of 1907 (Morton). The previous system at the Shanghai Bend site cut across with a nearly 90 degree turn, leaving a large section of the levee directly opposing the river flow.

The urbanization of this area motivated engineers to straighten out the levy system to facilitate river flow and provide a safer environment for local residents. The project was completed in October of 1999 by the Army Core of Engineers.

 

Flooding in the Yuba-Sutter area

The Yuba-Sutter area lies on a flood plain in the Sacramento Valley and has experienced four major floods in the past one hundred years.

The 1907 flood killed 4 people and prompted the building of the Oroville dam. The current levee system is based off the levees constructed at this time (Morton).

The flood of 1955 killed 38 people and caused over $20,500,000 of damage. The levee failure in the 1955 flood occurred near the Shanghai Bend site.

The 1986 flood initiated the proposal for the Yuba County Levee Restoration and Enhancement Project, which was enacted prior to the 1997 flood.

 

Shanghai Bend Site

The Shanghai Bend site is located near the section of the levee that failed in 1955. The levee was relocated at that time approximately 150 ft. to the west. A section of the levee further south, directly across Shanghai Bend was left curving a nearly 90 degree turn which impeded water flow. This section of the levee was removed and a straight section constructed in its place.

Levee Construction

"This is one of the problems with engineered flood control systems...They encourage development in the most flood-prone areas. People think they are completely protected by the flood control system, but in truth such systems are inherently unreliable. Damage from floods in this country has actually gone up despite our huge investment in flood-control infrastructure." ~Philip Williams, Civil Engineer(Pottinger)

Levees are constructed from earthen materials, sand, soil, and clay, but older levees were made with whatever materials were available. Often after a flood had subsided, levees were reconstructed with the left over debris. The result was poorly constructed sandy levees which are more prone to failure (Vogel).

Levees are broadly classified as either "Urban" or "Agricultural". The type of levee built is determined by its function and both types have different structural requirements (US A.C.E.).

The Shanghai Bend levees were built when this area was primarily agricultural, and were thus built with different parameters in mind. The encroaching urbanization has forced engineers to address these antiquated levees .

 

Levee Failure

Though overtopping of the levee is a concern, seepage through a levee is the primary cause of its failure. Tree roots, gophers, rain and the river flow itself deteorite the levee over time. In all four of the Yuba-Sutter floods levee failure was attributed to seepage. (Morton) Engineers pulled core samples from Feather River levees and found a layer of clay on top, which resists water flow, but found silty/sandy soil lower down which has a high porosity. These levees are more likely to fail in flood conditions due to their composition. (Vogel)

Slurry walls are vertical channels filled with SCB (Soil, Cement, Bentonite) that prevent seepage. (Morton) Bentonite is a clay which is derived from volcanic ash. Bentonite has the useful property of expanding several times its original volume when immersed in water (Klein 513).

The walls run down the center of the levee and older levees can be retrofitted with slurry walls. The Yuba County Levee Restoration and Enhancement Project initiated on January 24, 1997, proposed to rebuild 22 miles of levee, including retrofitting existing levees with slurry walls, in the Yuba City - Marysville area (Vogel).

 

Data Collection

I collected data along the levee at Shanghai Bend using a Garmin 12XL GPS receiver. The data was stored as waypoints and were averaged for 1 minute or until fluctuations ceased. The data was collected over a period of 3 days, and averaged +/- 15 feet (maximum deviation 0f +/- 38ft. on first day).

The waypoints were used to draw out the changes made to the levy in the past 93 years at the Shanghai Bend site.

The Digital Ortho Quarter Quad (DOQQ) was produced by the USGS in 1952, updated in 1973. This map does not show the current locations of the levees in this area.

 

Conclusion

 

The Shanghai Bend levee has been relocated and reconstructed to provide adequate protection for the residents of South Yuba City. The levee was rebuilt to meet urban levee standards and the park area itself has seen several landscaping improvements. The relocation should improve river flow and help prevent flooding in the area.

Resources

Klein, Cornelis; Hurlbut, C.S.; Manual of Mineralogy; John Wiley 1977

Dingman, S. L.; Physical Hydrology; Prentice Hall 1993

Pottinger, Lori, "California Flood Control System Springs Leaks",
World Rivers Review, Vol 12, #1, February 1997

Vogel, Nancy; "Ancient Levees Targeted", The Sacramento Bee - Floods of '97

Morton, R.C.; Safe Levee Homepage, http://www.escalera.com/safelevee

U.S. Army Corps of Engineers; Memphis District, General Levee Information
http://www.mvm.usace.army.mil/floodcontrol/Levees/levees.htm

DRG Exchange; http://216.36.33.21/~mgreger/GIS/exchange.htm

Equipment and Software

Garmin 12XL GPS recover
IXLA SuperPro Digital Camera
ArcView3.1