Anderson Bridge 1926	Loma Linda 1969	Redlands 1998

San Timoteo Creek - Flooding History

Documentation of flooding within the San Timoteo Creek has existed since the 1820's. Floods have been recorded in 1825, 1833, 1840, 1850, 1859, 1862, 1867, 1884, 1889, 1891, 1916, 1926, 1935, 1938, 1939, 1969, and 1998.

The flood of 1862, deposited approximately 6 feet of sediment on the Loma Linda floodplain. The flood of 1969, damaged or destroyed 400 homes, 300 vehicles, five bridges, and one school. El Nino' related flood damages of 1998, included a primary Southern Pacific Railroad line south of Redlands.

San Timoteo Creek Project

Current Authorized Project - Upstream of Barton Road

San Timoteo Creek

Sediment Basins and Trasition Structure

Purpose:

San Timoteo Creek is tributary to Santa Ana River, and recommended flood improvements have been authorized for construction as part of Santa Ana River Mainstem including Santiago Creek. The purpose of the improvements is to control the sediment generated in San Timoteo Creek and provide 100-year flood conveyance to existing improved channel. The improvement will protect the floodplain in the communities of Loma Linda, Redlands, and portion of San Bernardino County.

Introduction:

The Los Angeles District, U.S. Army Corps of Engineers completed Design Memorandum # 7 " Santa Ana River Mainstem Project including Santiago Creek – Basis for Design, San Timoteo Creek, Channel, and Sediment Control Sturcture" in April 1993. The report was prepared in coordination with the San Bernardino County Flood Control District and other local groups.

The design memorandum only covers the portion of San Timoteo Creek from 400 feet upstream of Barton Road to 4,700 feet upstream of San Timoteo Canyon Road (referred to as Reach 3B). The remaining reaches (Reaches 1,2, and 3A) have already been constructed.

Study of potential flood control measures for San Timoteo Creek in San Bernardino County was initially authorized by public Law 738,74^th Congress, June 22, 1936.

The Energy and Water Development Act of 1988 authorized San Timoteo Creek for construction as a Feature of the Santa Ana River Mainstem project

Scope of Studies:

San Timoteo Creek is tributary of the Santa Ana River and drains portion of San Bernardino and Riverside Counties. The existing creek is partially improved for a reach of 3.4 miles through the cities of Loma Linda and Colton and the county of San Bernardino before it confluence with the Santa Ana River in San Bernardino County. Upstream, the existing creek has the capacity to protect the surrounding community from approximately a 20-year frequency flood. The recommended plan would provide 100-year level of protection (19,000cfs).

Project Location and Description of Drainage Area:

The San Timoteo Creek basin drains about 125 square miles of water shed from San Bernardino Mountains to its confluence with Santa Ana River. Elevations range from a high of 8,707 feet above the sea level at Wilshire Peak to a low of 980 feet at creek confluence with Santa Ana River. Slopes range approximately 800 feet per mile on the lowere reaches of San Timoteo Creek. The average slope for the basin is approximately 250 feet per mile measured along the longest watercourse.

Modified Reach 3B Plan:

The Corps of Engineers and San Bernardino Flood Control District, conducted a series of workshops from September 1998 to January 1999. The purpose of workshop meetings was to gather input and identify public concerns on the Modified Reach 3B Plan. The project goals/objectives would consist of the following:

a. - Same level of flood protection as the authorized plan.
b. - Sediment management with shallow basins
c. - Basin control structures.
d. - Gently sloping and meandering sides in basins and along the channel.
e. - Habitat restoration/enhancement.
f. - Revegetation of slopes and perimeter areas of sedimentation basins.
g. - Provisions for pedestrian, bicyclist, and equestrian paths.
h. - Fencing only as required for safety and to preclude wehicular accesses.
i. - Water conservation, preservation, or enhancement
j. - Provision for wildlife movement.
k. - Consideration for feasibility of utilizing earth material from basin excavation to be place ina manner to stabilize existing natural stream banks between the upstream end of the modified plan and Alessandro Road.
l. - To the maximum extent practical, minimize impact to existing residential, farm, and.
m. - Consideration of alternatives for bank protection within the sedimentation basins.
n. - Look at extending the project upstream.

Modified Plan 3B consist of following:

Total length of the project is 13,700 feet (2.6 miles).
The number of drop structure is 17.
Average depth of the basins is 8.5 to 12 feet.
Average channel depth downstream of San Timoteo Canyon road is 12 feet.
Average total depth downstream of San Timoteo Canyon road is 21 feet.
Average total depth downstream of Beaumont Avenue is 24 feet.
Acres of riparian/wetland habitat to the maximum extent.
Total real estate required is 98 acres.
Total project cost is about $34 million (without mitigation)
Distance upstream to Alessandro is about 6,000 feet.
Upstream mitigation may provide some bank protection.

Project Elements:

Drainage Area 125 sq. miles
100-year peak discharge 19,000 cfs.
Parapet wall on existing channels 1200 ft.
Trapezoidal concrete transition 1400 feet.
Sediment basins 11,600 feet.
Inlet 700 feet.

Board of Supervisors Resolution

On April 14, 1998, San Bernardino County Board of Supervisors passed a resolution supporting the modified plan as described above. The Board requested the Corps of Engineers to initiate engineering analysis and project development, which include the following:

Basin control structure softened the appearance.
Gently sloping and meandering sides in the basins and along the channel.
Revegetation of the slopes and perimeter areas of sediment basins.
Provision for pedestrian, bicyclist, and equestrian path.
Fencing as only required for safety and to prevent vehicular access.
Water conservation, preservation, and enhancement.

To maximum extent practical, minimization of impacts to existing residential, farm and historic structures, citrus groves, and wells.

Consideration of using earth material form basin excavation to be placed to stabilize existing natural stream banks between the upstream end of the modified plan and Alessandro road.

It is a pleasure to provide you with this latest update of our efforts on your behalf to provide adequate flood protection in your area. If you have any additional questions, regarding this information please contact the Federal Projects Section fo the Flood Control District at (909) 387-2571.

For Project Information Contact:

Jim Borcuk, Chief - Federal Projects and Flood Control Engineering
(909)387-7962