Geographic Information Systems and Modeling

Andrew Mckenna-Foster

Outline

• What are Geographic Information Systems?

• Modeling with GIS

• Septic Suitability Model

• Erosion Potential Model

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

Modeling with GIS

• Several input maps

• Simulate factors that affect water quality

• Septic suitability

• Erosion potential

Septic Suitability Model

• What makes land suitable for septic systems?– Gentle slopes– Soil containing loam, sand, and gravel

• Input maps:– Soil– Slope

Soil Map

• Digitized polygons of the 17 soil types in the watershed

• Septic suitability description

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

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

Weighted Overlay

=+

66%34%

Soil SlopeSuitable

Moderate

Unsuitable

Septic Suitability

Septic Suitability Results

• 84% of watershed suitable

• <1% unsuitable• Uses:

– Guidance for proper system installation

– Focus remediation efforts

Septic Suitability

Suitable

Moderate

Unsuitable

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

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

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

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

Weighted OverlaySlope Soil Land Use

30% 20%

+ + +

20%

Lake Proximity Stream Proximity

30%

=+

15%

Erosion Potential Results

• Northeast corner has high impact

• Wetlands are light gray

• Useful for focusing remediation and erosion control efforts

Erosion PotentialLow

Moderate

High

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

Buffer Strip and Septic Surveys: Results and Remediation

Elizabeth Turnbull

- Shoreline Zoning Regulations

- Development Survey

- Buffer Strip Survey and Remediation

- Septic Systems

- Septic Remediation

Outline

Maine’s Residential Shoreline Zoning

Regulations

• MAXIMUM:– Structure height

• MINIMUM: – Setback– Shore frontage– Area (ft2)– Total area of

impervious surface

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

Buffer Strips

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

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

•Arrows indicate high concentrations of poor and failing buffer strips

Buffer Remediation

• Avoid mowing to the shore• Native species• Duff layer• Riprap• Winding paths• Any buffer is better than nothing

Wastewater Disposal in Threemile Pond

• Mostly septic systems

• Common problems:– Too near the

shore– Old– Grandfathered– Leaky

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?

Some Watershed Remediation Techniques

Sarah Goodwin

Overview of Selected Watershed Management

• Sources

• Road Survey

• Agriculture

• Household remediation

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

All Inputs Cultural Inputs

Phosphorus Inputs

Road Survey

• Importance of road maintenance, camp roads in particular

• Assessed all roads in watershed

Crowning and Grading

• Smooth surface and a crown that rises 1/2 inch for each foot of road width

• Remove berms

• Grade when appropriate

Ditches

• Collect and store

storm water

• Trapezoidal or

parabolic

• Vegetation

Water Diversions

• Water bars

• Culverts

Road Assessment Results

• 22 acres of camp roads

• 74 acres of municipal or state roads

• Camp roads in worst condition

• Implications for Threemile Pond

Problem AreasProblem Areas and Suggested Improvements

Other Forms of Remediation

• Agriculture

• Household impacts

Agriculture

• Potential impacts

• Limit excessive use of fertilizers

• Contour cultivation

• Stubble mulching

• Minimizing tillage

Other Remediation Techniques

• Fertilizer use• Household products• Boat ramp

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

Lake Remediation

Aubris Pfeiffer

Overview of Remediation

• Remediation of Threemile Pond

• Review of nonapplicable remediation techniques

• Recommendations

• Implementation in Threemile Pond

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

Challenges for Threemile Pond Remediation

• Multiple Towns

• Non-point Sources

• Nature of a lake system

• Cost/benefit analysis

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.

Common Remediation Techniques

• Dredging

• Water removal techniques:

– Hypolimnetic Withdrawal

– Dilution

– Drawdown

Additional techniques• Algicides

– Temporary, toxic, expensive

• Aquatic Plant Harvesting– Not enough

phosphorus in biomass

• Physical Liners

– Application is difficult & expensive, lake size

Potential Techniques for Threemile Pond

• Wetland Maintenance

• Alum Treatment

• Hypolimnetic Aeration

• Biological control through fish stock manipulation

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

Ideal tool for determining alum treatment application

Bathymetry map Anoxic depth & alum treated area map

Hypolimnetic aeration

• Prevents anoxic/anaerobic conditions by aerating the hypolimnion

• Destratification vs. layer technique

QuickTime™ and aGIF decompressorare needed to see this picture.

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

Implementation in Threemile Pond

• Alum treatment, hypolimnetic aeration, and fish stock manipulation are promising

• Methods worth further consideration and study

• Consider implementation for improvement

Emily Arell

Future Predictions and

Recommendations for Threemile Pond

Historic Population Trends

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%

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

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

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

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

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

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

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

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

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

Threemile Pond

• Remediation means the preservation of:

– Environmental Health

– Economic Viability

– Cultural History

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

Questions