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Strategies Addressing Hydromodification in Channels Through Unstable Terrains. John Gartner Barry Hecht Shawn Chartrand Edward Ballman, P.E. BALANCE HYDROLOGICS, INC. NOTE: First half of presentation is in: “Gartner GSA talk hydromodification 5-1-05 part 1.pdf. - PowerPoint PPT Presentation
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Strategies Addressing Hydromodification in Channels
Through Unstable Terrains
John GartnerBarry Hecht
Shawn ChartrandEdward Ballman, P.E.
BALANCE HYDROLOGICS, INC.
NOTE: First half of presentation is in: “Gartner GSA talk hydromodification 5-1-05 part 1.pdf
• Bank Failure
• Knickpoint
• Earthflow
Stream walks Sediment Point Sources
Incising tributaries
Custom modeling with HEC-HMS for middle watershed
Modeling middle reach effects
Solutions
1. ……………………….2. ……………………….3. ……………………….4. ……………………….5. ……………………….6. ……………………….
1. Headwater Detention (slight) 2. Reduce Peaks
Feb 25 2004 Storm
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Date
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cfs
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Measured Flow
Existing Condtion Modeled Flow
Proposed Condition Modeled Flow
Inc Rainfall
3. Detention (hyper)
Measured bankful
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Hours after start of storm
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Measured Bankful
4. Avoid Most Vulnerable Channels
5. Improved Grazing Management
6. Strategic Channel Stabilization
Photo courtesy of LSA Associates
Summary
• Hydromodification is a vital issue in the urbanizing West, especially in areas with geologic or geomorphic disturbance.
• Solutions are often best approached from geologic perspective:– Recognizing the one-time nature of channel adjustment – Based on intensive field work in disturbed landscapes.
• Value of baseline data – flow, sediment, channels.
• Solutions should spring from watershed perspective and work with site conditions.
Interdisciplinary effort and review
Thompson Creek, San Jose
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Hour of day (March 14-15, 2003)
Un
it F
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Upstream, non-urbanized station (TCEM)
Downstream, urbanized station (TCQR)
Note that the flow axis is logarithmic
Unit flow means that flow has been scaled by watershed area for each
stream gage location.
Watershed Area:TCQR = 17.4 sq.mi.TCEM = 2.3 sq.mi.
