Post on 18-Jan-2016
transcript
EFFECTIVENESS OF TIME OF YEAR RESTRICTIONS
BY MARCIA BOWEN AND KIMBERLY PAYNE NORMANDEAU ASSOCIATES INC.
BENEFITS OF DREDGE WINDOWS
•Avoid impacts to vulnerable species•Easy to administer• Predictable: Aids scheduling
TYPICAL DREDGE WINDOWS
Species J F M A M J J A S O N D
Source: Massachusetts DMF 2011
THE CHALLENGE OF DREDGE WINDOWS
•How to balance the need to dredge with the mandate to protect natural resources?•Are dredge windows effective?• Is there new information on dredging impacts?•What is acceptable risk?
OVERARCHING QUESTIONS
•What are known impacts?•Are laboratory studies representative? •What do field studies tell us?•How can we improve the process?
TODAY’S TALK
•Examine a few major impacting factors– Suspended sediments– Sedimentation– Sound– Impingement
•Review results from field studies • Success stories•Where do we go from here?
TURBIDITY/TSS EFFECTS
• Potential effects: Interference w/feeding, respiration, migration; delayed hatching, growth; mortality.• Literature results: Can be harmful to certain species/lifestages at high levels for long periods based on lab studies.
RESPONSES OF ESTUARINE FISH EGGS AND LARVAE TO SUSPENDED SEDIMENTS
Source: Wilber and Clarke 2001
RESPONSES OF ESTUARINE FISH ADULTS TO SUSPENDED SEDIMENTS
Source: Wilber and Clarke 2001
DREDGE MONITORING RESULTS, WELL FLUSHED TIDAL RIVER
0.0 10.0 20.0 30.0 40.0 50.0 60.00
5
10
15
20
25
30
35
40Dredge
Post Dredge
Predredge
TSS, mg/L
Turb
idit
y, N
TU
RESPONSES OF ESTUARINE FISH EGGS AND LARVAE TO SUSPENDED SEDIMENTS
With Results
Source: Wilber and Clarke 2001
RESPONSES OF ESTUARINE FISH ADULTS TO SUSPENDED SEDIMENTS
With Results
Source: Wilber and Clarke 2001
EXTENT OF IMPACTS IS IMPORTANT
Max NTU=21-26
Source: Normandeau 1999
TURBIDITY/TSS CHALLENGE: ONE SIZE DOES NOT FIT ALL
•Changes in turbidity/TSS highly dependent on many factors– Size/shape of water body– Flow– Sediment type– Type of dredge– Duration and frequency
SEDIMENTATION
•Effects dependent on:– Sediment characteristics– Water flow and depth– Project duration vs. hatching time
•Biggest concern: species with demersal, adhesive eggs; SAV.
SEDIMENTATION
•Current work on winter flounder is a good approach:– combines modeling results, laboratory
testing, and surveys for timing/location of spawning
• TOY is reasoned and protective
SOUND
•Effects differ among species.• Impact criteria developed for endangered salmonids on West Coast.•Can dredging sounds have adverse effects?
EXAMPLE OF PEAK SOUND PRESSURE
Expressed as dB per Pascal
Source: Buehler 2009
TYPICAL PEAK DREDGE SOUNDS
peak criterion
PEAK SOUND -CUTTER & HYDRAULIC
Cutter
CutterCutterCutter
CutterCutterCutter
TSHD
TSHD
160
165
170
175
180
185
190
195
200
soun
d pr
essu
re
Source: MALS 2011
peak criterion
CONCLUSIONS
• Peak sound from dredging ,110- 185, < peak impact criterion, 206• No data on SEL (sound exposure levels, which are cumulative)• TOY restrictions should consider
– Species present – Characteristics of water body– Ambient sound
ENTRAINMENT/IMPINGEMENT: TOY WORK!
• Sea turtle deaths reduced by:– Good biological data– Good info. on specific dredge effects– Equipment modification– Time of year restrictions
ANNUAL TURTLE TAKES
Protective measures
implemented including TOY
Courtesy: Dickerson 2009
INITIATIVES
•Massachusetts Division of Marine Fisheries– Verify species/lifestage presence– Identify most sensitive species/lifestages– Adapt TOY for location, duration, and
type of dredging
-Municipal Maintenance Hydraulic Dredging on Cape Cod and the Islands
IN CONCLUSION….
• TOY can be effective if…….– Based on sound data– Developed collaboratively– With consensus on acceptable risk
DATA NEEDS
•Baseline species data• Dredge monitoring data•Burning questions:
– Dredging effects on demersal fish eggs– Interference with migration?– Effects on shellfish settlement?– Techniques and equipment to reduce
impacts
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