Evaluating Coastal Erosion Structures Lauren Hunt, Christopher Sample, Kathleen Sullivan December...
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Transcript of Evaluating Coastal Erosion Structures Lauren Hunt, Christopher Sample, Kathleen Sullivan December...
Evaluating Coastal
Erosion Structures
Lauren Hunt, Christopher Sample,
Kathleen Sullivan
December 16th, 2014
Project Sponsors: Jeff Carlson,Peter Morrison, and Mary WawroProject Advisors: Dominic Golding
Stanley Selkow
Overview
-What is Erosion
-Objectives/Goals
-What we did and how we did it
-Findings
-Conclusions and Recommendations
Defining coastal erosion is rather straightforward
Understanding coastal erosion is not as easy
What is Erosion?
Why is erosion an issue?
Threatens 300,000 homesDestroys 1,500 homes
In Nantucket 2 feet to 12 feet a
year
Sheep Pond Road Area5 houses lost10 Houses relocated
Limitations
-No universal rating scale
-Erosion rates from aerial photos and CZM transect lines
-Structures which have permits
-7 weeks of onsite visits
Objectives
Categorize Data
Variety of structures
and methods
Evaluated impacts and effectivenes
s
Breakdown of Opinions
Coastal erosion
practices and policies
Island stakeholders
Create Recommendation
s
Future Policies
Erosion control
strategies
Erosion Structures
•Seawalls•Groins•Geotextiles•Offshore Breakwaters
Hard
•Beach Nourishment•Vegetation•Sand Fencing•Jute Mesh and Bags
Soft
Site VisitsLocated Structures
-Aerial photographs-CZM database
Documented-Notes-Photographs
Post evaluation notes
Good •2 Points
Fair •1 Point
Poor •0 Points
Structure Test
Property Test
Beach Test
Total
Score 0-
6
5 or 6 •Effective
3 or 4 •Adequate
0 to 2 •Ineffective
Effectiveness Rating Scale
Structure•Integrity•Condition
Property•Scouring•Holding back land
Beach •Beach present in front of property
Types of Structure
FindingsTypes of Structures
Hard Soft
42%
58%
Location of Structures
Northwest SiasconsetSouth Harbor
69%17% 7%
7%
Effectiveness Rating Scores
5 to 6 3 to 4 0 to 2
50%44%
6%
Types of Structure
Findings
Effective Adequate Ineffective0
5
10
15
20
25
HardSoft
Num
ber
of
Str
uct
ure
s
Soft Structures
Pocomo Road Coskata Course Way
Now more likely to be permitted by
Conservation Commission
-Sand fencing -Jute mesh and bags
-Sand nourishment -Beach grass plantings
Stakeholder Perspectives
Natural Resources Department
Nantucket Coastal Conservancy
Josh Posner, President SBPF
John Merson, Baxter Road resident
ConclusionSoft structures may
-Decrease erosion
-Encourage accretion
-Require more maintenance
Hard structures may
-Protect land behind them
-Cause scouring
-Distant impacts
Recommendations
Continue to inspect structures
-function as expected-limit unauthorized
Update and maintain database
Maintain systematic photographic record
Recommendations
ConCom continue to work with homeowners
Develop systematic approach to evaluate effectiveness
Acknowledgments
A special thanks to:Jeff Carlson and all of the Natural Resources Department
Sheila Lucey the Harbor Master
Mary Wawro and Peter Morrison
Harvey Young and Young’s Bicycle Shop
Andrew Mckenna-Foster and the Maria Mitchell Association
And to all those that have taken the time to talk with us
Questions and Comments
-Created database of 72 structures
with 20 fields of information
-32 Effective structures, 36 adequate structures, 4 ineffective structures
-Recommend the town maintains database with all current and future structures
-No cookie cutter way to signify one structure is better than any other, effectiveness will vary by location due to outside impacts
-Recommend future evaluations of effectiveness