A Sediment Budget for

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A Sediment Budget for Two Reaches of Alameda
Creek (1900s through 2006)
Paul Bigelow, Sarah Pearce, Lester McKee, and
Alicia Gilbreath
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Study Questions

• Are the study reaches supplying a major source of
  sediment to the flood control channel?
• What are the dominant processes, and what are the
  rates of erosion and amount of storage?
• What proportion of total sediment load at Niles
  is derived from the study reaches?
• How has the channel changed through time?

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Alameda CreekWatershed
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Area BehindDams
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Study Area
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Brief Watershed History

• Pre-1900 channel ditching, groundwater wells,
  small dams
• 1900 Ditching and draining of Tulare Lake
• 1911 ADLL incision rate of 6 in/yr

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1925 Calaveras Dam, gravel mining 1950s Four
largest flood events on record 1964 San Antonio
Dam 1968 Del Valle Dam 1970s Flood Control
Channel construction 1980s to 2000s Flood
Control Channel dredging
Oblique view of Pleasanton and Dublin (looking
west) during the 1955 flood
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Historical Flow Changes
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Arroyo De La Laguna
Lower Subreach
Upper Subreach
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Arroyo De La Laguna
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Arroyo De La Laguna
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Alameda Creek
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Sediment Budget Methods

• Incision bed elevation surveys 1959, 1971, 2007
• Bank Erosion Bar Storage field surveys and
  air photo analysis
• Cross Section Surveys historical and current
• Flood Plain Storage field surveys
• Only subset of data collected for Alameda Creek
  Reach
• (little incision, 90 of drainage area above
  dams)

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Compare Reaches w/ Watershed
Verona Gage Welch Gage Study Reaches Ungaged
Tribs Niles Gage?

• Balance the Budget
• Estimate Yield at Gages (rating curves)
• Estimate Yield for Ungaged tributaries (reservoir
  sedimentation rate)
• Compare Reaches w/ Niles Gage

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Sediment Budget Periods

• 1901 1959
• 1959 1971
• 1971 1993
• 1993 2006

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ResultsLong Profiles

• Arroyo De La Laguna
• Bed Elevation
• 1901 1959

4.5 m ave total incision depth 6 10 cm/yr
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1959 to 1971 Bed Elevation
1-2 m incision depth 7 15 cm/yr
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1971 to 2007 Bed Elevation
0.5 0.8 m incision 2 6 cm/yr
0.75 m aggradation
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Incision Pattern Over TimeIncision Migrating
Upstream
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Further Upstream
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Bank Erosion Bar Storage Aerial Photograph
Analysis

• Assessed entire study reach
• Focused on four locations
• Four time periods
• Quantified bank erosion and bar storage

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1939 Photo
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1950 Photo
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1966 Photo
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1993 Photo
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2005 Photo
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Bank erosion (metric tonnes/yr)
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Channel Cross Sections
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Channel Cross Sections
5-6 m
5-6 m
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Flood Plain Storage
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Sediment Budget by Process - ADLL
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Alameda Creek Reach
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Overall Watershed Comparisonfor Recent Period
(1994 2006)
Within 5
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Study Reaches Comparison to Niles Gage
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Study Area Sediment Yield Comparison to Regional
Values
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Sediment Budget Take Home Points

• Sediment budget has adjusted over several periods
  of land use alteration and disturbance from
  floods
• Budget dominated by incision in earlier periods,
  now adjusting through bank erosion
• ADLL sediment yield is high for a short reach
  (0.25 of total stream network length)
• But ADLL comprises a small portion of watershed
  sediment yield (6 of total yield)

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Future Channel Evolution

• Channel Evolution Models

• Process-based classification
• Describe channel form as it responds to a
  disturbance
• Shows typical channel adjustments to return a
  balance of sediment transport capacity

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Future Response of ADLL

• Conceptual Scenarios

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Next Steps - Recommendations

• Monitor future channel adjustment in ADLL, and
  continue to stabilize the reach
• Given management changes on Alameda Creek,
  monitor future channel response for sediment
  supply increase
• Conduct a phased watershed sediment budget
• Phase 1 Quantitatively (on public lands) and
  qualitatively (on private lands) assess feasibly
  manageable sediment
• Phase 2 (if needed) Quantitative evaluation of
  manageable sediment on private lands
• Conduct numerical modeling to understand sediment
  routing to and deposition within the Flood
  Control Channel