Modeling large-scale fluvial erosion in geographic information systems
Geographic Information Systems and Modeling
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Transcript of Geographic Information Systems and Modeling
![Page 1: Geographic Information Systems and Modeling](https://reader035.fdocuments.in/reader035/viewer/2022062321/56812ac4550346895d8e974c/html5/thumbnails/1.jpg)
Geographic Information Systems and Modeling
Andrew Mckenna-Foster
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Outline
• What are Geographic Information Systems?
• Modeling with GIS
• Septic Suitability Model
• Erosion Potential Model
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Geographic Information Systems• Visualization of geographic
features and the corresponding physical attributes– Road map
– Land use type
– Soil map
– Contour map
• Modeling of natural processes using Arc GIS™ Spatial Analyst
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Modeling with GIS
• Several input maps
• Simulate factors that affect water quality
• Septic suitability
• Erosion potential
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Septic Suitability Model
• What makes land suitable for septic systems?– Gentle slopes– Soil containing loam, sand, and gravel
• Input maps:– Soil– Slope
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Soil Map
• Digitized polygons of the 17 soil types in the watershed
• Septic suitability description
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Septic Suitability of Soils
Soil series Septic suitability Septic rating
Marlow-stony Not Suitable 9
Lyman Not Suitable 9
Peru Not Suitable 9
Buxton Not Suitable 9
Marlow Moderate 5
Colton Suitable 1
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Slope Map
• Ranked for suitability on a 1 to 9 scale:– Steep slope = 9– Gentle slope = 1
• Range = 0o to 28o
• Created from digital elevation maps
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Weighted Overlay
=+
66%34%
Soil SlopeSuitable
Moderate
Unsuitable
Septic Suitability
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Septic Suitability Results
• 84% of watershed suitable
• <1% unsuitable• Uses:
– Guidance for proper system installation
– Focus remediation efforts
Septic Suitability
Suitable
Moderate
Unsuitable
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Erosion Potential Model• Displays
– Erodibility of land in watershed– Potential effect erosion has on water quality
• Accounts for proximity to the lakes and streams
• 5 Input maps– Soil– Slope– Land Use Type– Proximity to lakes– Proximity to streams
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Slope and Soil Maps
• Same slope map
• The soils were ranked for erodibility on a 1 to 9 scale based on K values
Soil series K value Erosion rating
Marlow-stony
0.2 4
Lyman 0.28 6
Peru 0.20-0.24 5
Buxton 0.32 6
Marlow 0.24 5
Colton 0.18 4
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Land Use Type Erosion Value
Wetlands 1
Mature Forest 1
Transitional Forest 3
Reverting Land 4
Pasture 7
Residential 8
Cleared Land 9
Crop Land 9
Commercial/Municipal 9
1998 Land Use Map
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Proximity Maps
8• Lake proximity
zones– 200 ft
– 1,200 ft
• Stream proximity zones– 200 ft
4
65
321
78
9
6
7
8
8
5
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Weighted OverlaySlope Soil Land Use
30% 20%
+ + +
20%
Lake Proximity Stream Proximity
30%
=+
15%
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Erosion Potential Results
• Northeast corner has high impact
• Wetlands are light gray
• Useful for focusing remediation and erosion control efforts
Erosion PotentialLow
Moderate
High
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Summary of GIS Models
• Septic suitability model– Functioning septic systems = better water quality– Guidance for proper septic placement and
installation
• Erosion potential model– Locates areas that contribute high erosion runoff– Focus remediation and control efforts for
maximum increase in water quality
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Buffer Strip and Septic Surveys: Results and Remediation
Elizabeth Turnbull
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- Shoreline Zoning Regulations
- Development Survey
- Buffer Strip Survey and Remediation
- Septic Systems
- Septic Remediation
Outline
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Maine’s Residential Shoreline Zoning
Regulations
• MAXIMUM:– Structure height
• MINIMUM: – Setback– Shore frontage– Area (ft2)– Total area of
impervious surface
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Development Assessment
560 total houses
• 203 shoreline
• 357 non-shoreline
• 142 seasonal
• 418 year-round
• 5 Farms
• 2 Gas Stations
• Car Wash
• Car Repair Garage
• Motel
• 2 Sand and Gravel Pits
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Poorly buffered property
• little vegetation
• artificial beach
• lawn mowed to shore
• no deep root systems
Well- buffered property
•full lakeshore coverage
•plants cover the entire area between the lake and the house
•thick, diverse vegetation
•riprap
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Results show a large quantity of poor and failing buffers
Buffer Strip Survey Results
44
58
38
64
0
10
20
30
40
50
60
70
Buffer Grade
Good
Fair
Poor
Fail
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•Arrows indicate high concentrations of poor and failing buffer strips
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Buffer Remediation
• Avoid mowing to the shore• Native species• Duff layer• Riprap• Winding paths• Any buffer is better than nothing
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Wastewater Disposal in Threemile Pond
• Mostly septic systems
• Common problems:– Too near the
shore– Old– Grandfathered– Leaky
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Septic Health
• Compost- No Disposal
• Conserve water- spread out use
• Pump regularly
• Replace when expanding and winterizing
• Avoid dumping bleach or antibacterial substances
• Avoid driving on leach field
• Native plants
• Low phosphate detergents and soaps
• New development?
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Some Watershed Remediation Techniques
Sarah Goodwin
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Overview of Selected Watershed Management
• Sources
• Road Survey
• Agriculture
• Household remediation
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Phosphorus Budget
• Determines the sources of phosphorus within the watershed
• Starts with estimations and is adapted to findings
• Determines the amount of phosphorus that each land type contributes
• Influenced by area of each land use type
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All Inputs Cultural Inputs
Phosphorus Inputs
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Road Survey
• Importance of road maintenance, camp roads in particular
• Assessed all roads in watershed
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Crowning and Grading
• Smooth surface and a crown that rises 1/2 inch for each foot of road width
• Remove berms
• Grade when appropriate
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Ditches
• Collect and store
storm water
• Trapezoidal or
parabolic
• Vegetation
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Water Diversions
• Water bars
• Culverts
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Road Assessment Results
• 22 acres of camp roads
• 74 acres of municipal or state roads
• Camp roads in worst condition
• Implications for Threemile Pond
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Problem AreasProblem Areas and Suggested Improvements
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Other Forms of Remediation
• Agriculture
• Household impacts
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Agriculture
• Potential impacts
• Limit excessive use of fertilizers
• Contour cultivation
• Stubble mulching
• Minimizing tillage
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Other Remediation Techniques
• Fertilizer use• Household products• Boat ramp
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Some Watershed Remediation Techniques
• Maintain integrity of roads
• Practice agriculture techniques that minimize phosphorus entering lakes
• Be aware of household impacts
• Importance of managing a watershed before looking to in lake remediation techniques
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Lake Remediation
Aubris Pfeiffer
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Overview of Remediation
• Remediation of Threemile Pond
• Review of nonapplicable remediation techniques
• Recommendations
• Implementation in Threemile Pond
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Definition of Lake Remediation
“the manipulation of a lake ecosystem to effect an in-lake improvement in degraded or
undesirable conditions”
~Dunst, et al. 1974
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Challenges for Threemile Pond Remediation
• Multiple Towns
• Non-point Sources
• Nature of a lake system
• Cost/benefit analysis
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Application to Threemile Pond
Important to consider:
• Technique requirements
• Costs/benefits
• How it specifically applies to Threemile Pond and its demands
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
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Common Remediation Techniques
• Dredging
• Water removal techniques:
– Hypolimnetic Withdrawal
– Dilution
– Drawdown
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Additional techniques• Algicides
– Temporary, toxic, expensive
• Aquatic Plant Harvesting– Not enough
phosphorus in biomass
• Physical Liners
– Application is difficult & expensive, lake size
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Potential Techniques for Threemile Pond
• Wetland Maintenance
• Alum Treatment
• Hypolimnetic Aeration
• Biological control through fish stock manipulation
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ALUM TREATMENT
• Chemically inactivates phosphorus• Learn from previous treatment
– Inadequate application
– Buffering agent
• More advanced technology– GPS and GIS to map areas of lake for specific
application
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Ideal tool for determining alum treatment application
Bathymetry map Anoxic depth & alum treated area map
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Hypolimnetic aeration
• Prevents anoxic/anaerobic conditions by aerating the hypolimnion
• Destratification vs. layer technique
QuickTime™ and aGIF decompressorare needed to see this picture.
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Biological Control: Fish Stock Manipulation
• Decrease planktivorous fish– Discontinue stocking of
alewives
• Increase piscivorous fish– Continue/Increase
stocking of brown trout
– Stock small & large mouth bass
Inexpensive and less ecologically damaging
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Implementation in Threemile Pond
• Alum treatment, hypolimnetic aeration, and fish stock manipulation are promising
• Methods worth further consideration and study
• Consider implementation for improvement
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Emily Arell
Future Predictions and
Recommendations for Threemile Pond
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Historic Population Trends
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Future Population Trends
TownPopulation
in 2000
Projected Population
in 2020
Percent Increase
China 4,106 5,500 34%
Vassalboro 4,047 4,800 18%
Windsor 2,204 2,800 27%
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Historic and Future Development Trends
• Agriculture will continue to decline
• Demand for housing and development will
continue to rise
– Shoreline property
– Subdividing of existing lots
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Prediction of Land Use Changes by 2040
• Cleared land• Transitional forest• Residential• Municipal
• Cropland• Pasture• Mature forest• Reverting• Wetlands
• Increase• Increase• Increase• Increase
• Decrease• Decrease• Decrease• Decrease• Decrease
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Watershed Management• Maintenance of septic systems
• Create Buffer strips
• Follow shoreline zoning regulations
• Maintain integrity of roads
• Practice agriculture techniques that minimize
phosphorus entering lakes
• Be aware of household impacts
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In-lake Remediation Techniques
• External phosphorus loading must be addressed prior
to in-lake treatment for successful remediation
• Possible Techniques for Threemile Pond:
1) Biological control through fish stock manipulation
2) Alum treatment
3) Hypolimnetic aeration
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Threemile Pond Remediation Summary
• Assess lakes individually
• Small changes can have a BIG effect
• Address as many problems as possible
• Establish a balance – Social– Economic– Environmental
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Water Quality Monitoring• Water monitoring throughout summer-Characterization
sites: 1, 2, 3
– Transparency: bi-weekly
– Dissolved Oxygen: bi-weekly
– Phosphorus: test surface and
epicore monthly
• Community volunteers
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Community Awareness and Education• Work closely with the China
Region Lakes Alliance and Threemile Pond Association
• Distribute fact sheets and brochures
• Provide information in town offices and schools
• Involve local schools in monitoring Threemile Pond
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Grants and Funding
• Maine DEP website
– Non-point source Water Pollution
Control Grants
– Non-governmental funding sources
– Watershed Protection Grant
• Maine Natural Resource Protection Act
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General Summary• The primary problem in Threemile Pond is cultural
eutrophication
– Remediation must consider all sources of phosphorus runoff
• Water quality will improve with:
– Reduction of external phosphorus loading
– Reduction of sediment release of phosphorus
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Threemile Pond
• Remediation means the preservation of:
– Environmental Health
– Economic Viability
– Cultural History
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Special Acknowledgments• Roy Bouchard
• Dave Halliwell
• Rebecca Manthy
• Jenna Richardson
• Nate Sylvester
• Dan Dubord
•George Gunning
• Bill Woodward
•Russell Cole
•Dave Firmage
•Dan Tierney
The staff at the China Town OfficeThe staff at the Vassalboro Town OfficeThe staff at the Windsor Town Office
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Questions