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

THANK YOU!WWW.NORMANDEAU.COM