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Geographic Information Systems and Modeling

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.

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Geographic Information Systems and Modeling

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  1. Geographic Information Systems and Modeling Andrew Mckenna-Foster

  2. Outline • What are Geographic Information Systems? • Modeling with GIS • Septic Suitability Model • Erosion Potential Model

  3. 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

  4. Modeling with GIS • Several input maps • Simulate factors that affect water quality • Septic suitability • Erosion potential

  5. Septic Suitability Model • What makes land suitable for septic systems? • Gentle slopes • Soil containing loam, sand, and gravel • Input maps: • Soil • Slope

  6. Soil Map • Digitized polygons of the 17 soil types in the watershed • Septic suitability description

  7. Septic Suitability of Soils

  8. 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

  9. Weighted Overlay 66% 34% Septic Suitability Suitable Soil Slope Moderate Unsuitable + =

  10. Septic Suitability Suitable Septic Suitability Results Moderate • 84% of watershed suitable • <1% unsuitable • Uses: • Guidance for proper system installation • Focus remediation efforts Unsuitable

  11. 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

  12. Slope and Soil Maps • Same slope map • The soils were ranked for erodibility on a 1 to 9 scale based on K values

  13. 1998 Land Use Map

  14. 1 Proximity Maps 2 3 4 5 8 6 • Lake proximity zones • 200 ft • 1,200 ft • Stream proximity zones • 200 ft 7 8 9 8 7 8 6 5

  15. Weighted Overlay Slope Soil Land Use Lake Proximity Stream Proximity 30% 20% 20% 30% 15% + = + + +

  16. Erosion Potential Erosion Potential Results Low Moderate • Northeast corner has high impact • Wetlands are light gray • Useful for focusing remediation and erosion control efforts High

  17. 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

  18. Buffer Strip and Septic Surveys: Results and RemediationElizabeth Turnbull

  19. Outline Shoreline Zoning Regulations Development Survey Buffer Strip Survey and Remediation - Septic Systems - Septic Remediation

  20. Maine’s Residential Shoreline Zoning Regulations • MAXIMUM: • Structure height • MINIMUM: • Setback • Shore frontage • Area (ft2) • Total area of impervious surface

  21. Development Assessment • 5 Farms • 2 Gas Stations • Car Wash • Car Repair Garage • Motel • 2 Sand and Gravel Pits 560 total houses • 203 shoreline • 357 non-shoreline • 142 seasonal • 418 year-round

  22. Buffer Strips

  23. Well- buffered property • full lakeshore coverage • plants cover the entire area between the lake and the house • thick, diverse vegetation • riprap Poorly buffered property • little vegetation • artificial beach • lawn mowed to shore • no deep root systems

  24. Results show a large quantity of poor and failing buffers

  25. Arrows indicate high concentrations of poor and failing buffer strips

  26. Avoid mowing to the shore Native species Duff layer Riprap Winding paths Any buffer is better than nothing Buffer Remediation

  27. Wastewater Disposal in Threemile Pond • Mostly septic systems • Common problems: • Too near the shore • Old • Grandfathered • Leaky

  28. 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? Septic Health

  29. Some Watershed Remediation TechniquesSarah Goodwin

  30. Overview of Selected Watershed Management • Sources • Road Survey • Agriculture • Household remediation

  31. 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

  32. Phosphorus Inputs All Inputs Cultural Inputs

  33. Road Survey • Importance of road maintenance, camp roads in particular • Assessed all roads in watershed

  34. Crowning and Grading • Smooth surface and a crown that rises 1/2 inch for each foot of road width • Remove berms • Grade when appropriate

  35. Ditches • Collect and store storm water • Trapezoidal or parabolic • Vegetation

  36. Water Diversions • Water bars • Culverts

  37. Road Assessment Results • 22 acres of camp roads • 74 acres of municipal or state roads • Camp roads in worst condition • Implications for Threemile Pond

  38. Problem Areas and Suggested Improvements Problem Areas

  39. Other Forms of Remediation • Agriculture • Household impacts

  40. Agriculture • Potential impacts • Limit excessive use of fertilizers • Contour cultivation • Stubble mulching • Minimizing tillage

  41. Other Remediation Techniques • Fertilizer use • Household products • Boat ramp

  42. 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

  43. Lake RemediationAubris Pfeiffer

  44. Overview of Remediation • Remediation of Threemile Pond • Review of nonapplicable remediation techniques • Recommendations • Implementation in Threemile Pond

  45. 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

  46. Challenges for Threemile Pond Remediation • Multiple Towns • Non-point Sources • Nature of a lake system • Cost/benefit analysis

  47. Application to Threemile Pond Important to consider: • Technique requirements • Costs/benefits • How it specifically applies to Threemile Pond and its demands

  48. Common Remediation Techniques • Dredging • Water removal techniques: • Hypolimnetic Withdrawal • Dilution • Drawdown

  49. Algicides Temporary, toxic, expensive Aquatic Plant Harvesting Not enough phosphorus in biomass Physical Liners Application is difficult & expensive, lake size Additional techniques

  50. Potential Techniques for Threemile Pond • Wetland Maintenance • Alum Treatment • Hypolimnetic Aeration • Biological control through fish stock manipulation

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