Chris Sallese, Special Projects, Dannenbaum Engineering presentation at the FOR Annual meeting regarding progress reopening the mouth of the San Bernard

1. San Bernard River
Project Update
Presentation to
Friends of the River
September 19, 2015

2. Scope of work
Develop a RESTORE Act grant application to fund an ecosystem
restoration project on the San Bernard River
• Dredge the historical channel to restore river flow to the Gulf
• Evaluate potential structure solutions to avoid future channel
siltation/shoaling
• Develop a plan to use dredge material beneficially (beach and marsh
restoration)
• Obtain the necessary permits (Corps, GLO,….)
• Work with stakeholders to develop consensus on an actionable plan and
secure a RESTORE grant.

3. History

4. Bathymetry Change River Flow Data

5. Modeling Summary
• The mouth of the San Bernard River is influenced by the Brazos Delta which
continues to evolve.
• The littoral drift and associated tidal wave action will continue to move
material into the mouth
• Current river flow does not sustain a velocity to move sediment away from
the river mouth
• A one time structural project at the mouth of the river will not be feasible
without periodic maintenance
• Structural features will have impacts on sediment flow along the littoral
drift and could cause additional erosion to shoreline south of the jetty.

6. Management Alternatives
Team looked at six different management options:
• Option A - No Action
• Option B - Dredge re-opening, no stabilization;
• Option C - Dredge re-opening, stabilization with single jetty on east side;
• Option D - Dredge re-opening, stabilization with dual jetties on both sides;
• Option E - Dredge re-opening, stabilization with eastern weir jetty and
western typical jetty; and,
• Option F - Establish a channel to connect to Cedar Lakes to increase tidal
prism.

7. Channel Configurations
7 channel configurations were investigated:
• Rectangular channel with bottom elevation of MLT-10 ft, bottom width of 100 ft, and
extending 0 ft into Gulf
• Trapezoidal channel with bottom elevation of MLT -8.5 ft, bottom width of 100 ft, and
extending 1050 ft into the Gulf
• Trapezoidal channel with bottom elevation of MLT -10 ft, bottom width of 130 ft, and
extending 1300 ft into the Gulf
• Trapezoidal channel with bottom elevation of MLT -8.5 ft, bottom width of 150 ft, and
extending 1050 ft into the Gulf
• Trapezoidal channel with bottom elevation of MLT -8.5 ft, bottom width of 120 ft, and
extending 1050 ft into the Gulf
• Trapezoidal channel with bottom elevation of MLT -7 ft, bottom width of 160 ft, and
extending 900 ft into the Gulf
• Trapezoidal channel with bottom elevation of MLT -5 ft, bottom width of 240 ft, and
extending 600 ft into the Gulf

8. Alternative Configuration Results
Option and
Channel
config.
Configuration Est. Initial
dredge
volume
Est. maint.
Interval,chan
nel
(years)
Est. maint.
dredge volume,
channel
Est. time to
shoreline advance
past East jetty
(years)
Est. maint. dredge
volume, bypass
Note
A No action, natural
maintenance
None None None - None Mouth remains closed. No anticipated
benefit to circulation or velocity.
B4 Dredge re-opening,
no stabilization
123,000 cu. yd 2 <123,000 cu. yd
per 2 years1
- None Spit growth and uncertain navigability
toward end of maintenance cycle. 1Some
natural bypassing of westward-moving
littoral sediments.
C4 Dredge re-opening,
long (-8.5ft) jetty
stabilization, east
side only
123,000 cu.
yd
2 <29,000 cu. yd
per 2 years
2
or
122
352,000 cu. yd per 2
years, or 2,112,000 cu.
yd per 12 years2
Maintenance dredging of channel to
remove deposits of eastward moving
sediments. (Tidal flushing may lessen this
amount). East jetty will initially capture
westward sediments; 2If no mechanical
bypass dredging, time until jetty
impoundment: 10-15 years
C7 Dredge re-opening,
long (-5ft) jetty
stabilization, east
side only
94,000 cu. yd 2 14,000 cu. yd
per 2 years
2
or
43
<352,000 cu. yd per 2
years, or <704,000 cu. yd
per 4 years3
Maintenance dredging of channel to
remove deposits of eastward moving
sediments. (Tidal flushing may lessen this
amount). East jetty will initially capture
westward sediments; 3If no mechanical
bypass dredging, time until jetty
impoundment: 4-5 years. Short jetty
anticipated to allow some natural
bypassing of westward moving sediments,
reducing volume for mechanical bypass
dredging.

9. Alternatives
Option and
Channel
config.
Configuration Est. Initial
dredge volume
Est. maint.
Interval,chan
nel
(years)
Est. maint.
dredge volume,
channel
Est. time to
shoreline advance
past East jetty
(years)
Est. maint. dredge
volume, bypass
Note
D4 Dredge re-opening,
long jetties (-8.5ft)
123,000 cu. yd 12 limited 2
or
124
352,000 cu. yd per 2
years, or 2,112,000 cu. yd
per 12 years4
Extends navigable life between maintenance
events; greater effect on littoral sediment
movement; East jetty will initially capture
westward sediments;4If no mechanical
bypass dredging, time until jetty
impoundment: 10-15 years
D7 Dredge re-opening,
short (-5 ft) jetty to
promote bypassing
94,000 cu. yd 2 <14,000 cu. yd
per 2 years
2
or
45
<352,000 cu. yd per 2
years, or <704,000 cu. yd
per 4 years5
Short jetties allow some natural bypassing
of westward moving sediments, reducing
volume for mechanical bypass dredging.
Short jetties may also allow sediment
deposits from tidal inflows inside channel –
thus requiring channel maintenance. 5If no
mechanical bypass dredging, time until jetty
impoundment: 4-5 years.
DW4 Dredge re-opening,
long jetty with east
side weir to capture
westward sediment
123,000 cu. yd 2 limited 2 352,000 cu. yd per 2
years6
Extends navigable life between maintenance
events; lessens effect on littoral sediment
movement. 6Deposition of littoral sediments
in deposition zone on the inner side of the
weir jetty needs to be dredged every two
years to free up capacity.
CW4 Dredge re-opening,
long jetty east side
only with weir to
capture westward
sediment, no west
jetty
123,000 cu. yd 2 29,000 cu. yd per
2 years
2 352,000 cu. yd per 2
years6
Extends navigable life between maintenance
events; lessens effect on littoral sediment
movement. 6Deposition of littoral sediments
in deposition zone on the inner side of the
weir jetty needs to be dredged every two
years to free up capacity.

10. Modeling Recommendations
Four structural alternatives are selected to be further evaluated by the larger
project team:
• D4 – Double (east side and west side) jetties extending to -8.5 MLT
• D7 – Double (east side and west side) jetties extending to -5 MLT
• C4 – Single east side jetty extending to -8.5 MLT
• C7 – Single east side jetty extending to -5 feet MLT

11. Recommendations

12. Potential Dredge Channel Configurations

13. Recommended Jetty Alignments
We focused our efforts on D4 which has the highest probability of resolving the
siltation/shoaling issue.

14. Complete Land and Bathometric Surveys

15. Courses of Action
Constructions costs: Three Structural Jetty and the dredge only option:
• COA #1- Rock Jetty
• Classic TX Coastal jetty system with a rock subbase and granite stone cover
• Cost- $86.2M
• COA#2- Hybrid Material Jetty
• Jetty with a rock subbase and articulated concrete matt cover
• Cost- $60.9M
• COA #3- Sheet pile Jetty
• Sheet Pile wall system consisting of driven sheets
• Cost- $27.8M
• COA #4- Dredge Only
• Cost- $6.0M

16. Dredging
• COA #1
• Construction- 600,000 cu yds
• Operations and Maintenance - 352,000 cu. yd per 2 years, or 2,112,000 cu. yd per 12 years
• Remove sediment behind the Jetty to slow eventual bypass and end of jetty shoaling
• COA #2
• Construction- 480,000 cu yds
• Operations and Maintenance - 352,000 cu. yd per 2 years, or 2,112,000 cu. yd per 12 years
• Remove sediment behind the Jetty to slow eventual bypass
• COA #3
• Construction- 450,000 cu yds
• Operations and Maintenance -352,000 cu. yd per 2 years, or 2,112,000 cu. yd per 12 years
• Remove sediment behind the Jetty to slow eventual bypass
• COA #4 (dredging only)-
• Open the channel- 400,000 cy yds
• Operations and Maintenance (2-3 yrs)- Dredge 125,000 cu yds ($2.5M)

17. Conclusions
• A structural solution is very expensive
• Revenue would need to be budgeted for the short and long term operations and
maintenance requirements
• The Dannenbaum-Berg/Oliver team is working with USACE on a permit for
dredging
• The County and Dannenbaum continue to socialize the project with TCEQ and the
GLO for RESTORE funding
• A grant application will be completed as soon as TCEQ finalizes the process

18. Section 7001 Study
• Commissioner Payne and Linder have meet with Congressman Weber and USACE
to discuss the Corps taking over the future maintenance dredging
• USACE has no existing authority….the project in 2009 was a one time exception
related to navigational safety
• Brazoria County has submitted a request for a USACE funded study under the
authority outlined in WRRDA 2014, Section 7001 to review the resiliency of the
GIWW and seek potential sources of material to stabilize the waterway banks.

19. Questions