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2. Today. Today's topic:Suitability modeling in GIS This week reminders in lab:Remember to complete any late labs by end of next weekThis week in lab: Work on your final projectRequired reading: Collins et al. 2001 (Land Use Suitability Analysis paper). 3. Review from Monday: Modeling in GIS.
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1. Suitability Modeling in GISRESM 440Wednesday October 20, 2010
2. 2 Today Todays topic:
Suitability modeling in GIS
This week reminders in lab:
Remember to complete any late labs by end of next week
This week in lab: Work on your final project
Required reading: Collins et al. 2001 (Land Use Suitability Analysis paper)
3. 3 Review from Monday: Modeling in GIS What is modeling? Attempting to simulate real-world processes in GIS
Static model: One point in time
Dynamic model: Several points in time
4. 4 Suitability modeling Suitability modeling: integration of multiple criteria and criteria weights to find best solution(s) to a spatial ranking question
Used to identify / rank locations for many purposes
Spatial decision support: Using GIS based models to aid in decision making
Used by:
Land managers (USFS, BLM, NPS, states, counties)
Municipalities and local governments (cities, towns etc.)
Many others
5. 5 Examples of suitability modeling/ranking Community/land use planning: (Example: Areas suitable for development)
Habitat suitability modeling (areas suitable for wildlife species)
Site selection (areas suitable for industrial park)
Vulnerability assessment (areas vulnerable to exotic species)
Other assessment or ranking (comparisons of areas for conservation)
6. 6 Goals of suitability modeling Identify best/worst locations
Provide supporting maps and information
Help review plans and compare alternatives
Identify areas where further study is needed (information gaps)
7. 7 History of suitability modeling (Collins et al.) Manual overlay of hand-drawn maps (early 1900s)
Inclusion of ecological inventory (human made, natural aspects) (1960s)
Computer mapping, map algebra overlays (late 60s, early 70s)
Multi-criteria evaluation and spatial decision support (1990s-today)
New directions: expert systems, complex spatial problem solving
8. 8 Process of suitability modeling Define the overall problem or goal
What are you ranking?
What is required result?
Develop flow chart or plan for analysis
Determine evaluation criteria and scoring within criteria
Determine weights for individual criteria
Calculate result (ranking or suitability)
Evaluate and present results
9. 9 Basic ideas behind suitability/ranking models
10. 10 Step: Criteria development Criterion: one element of a suitability model that can be represented by a spatial layer
Steps in criteria development:
Determine best criteria to represent your need
Obtain relevant GIS dataset(s)
Interpret data: Translate into mappable, quantifiable elements
Assign criterion scores/ranks
Normalize criterion scores across all criteria (same scale)
11. 11 Ranking/scoring within criteria Assigning values for criteria
Discrete: Good/bad, Yes/No, 0/1
Continuous: Criteria scores vary along a numeric scale
Generally higher values mean more suitable
Scores can be assigned incrementally (e.g. 0 to 10)
Scores can vary according to a user-defined relationship function
12. 12 Step: Weighting/combining multiple criteria Determining criteria weights:
How important is each criterion?
Expert knowledge
Solicit weights from stakeholders (surveys, meetings)
Determining method to combine criteria & weights
Additive linear model is most common (see previous slide)
Other models also can be used
GIS processes
Usually performed using cell-based raster overlay
Map each criteria, determine score, multiply by weight
Uses map algebra Grid overlays
13. 13 Additional considerations/limitations Practical limits/potential problems
Difficult to translate some criteria into meaningful scores
Subjectivity in assigning scores, criteria weights
Applying pixel-based results to the real world
Data limitations
Data not always equally available or of equal quality for all criteria
Highly susceptible to assumptions & limitations of individual map layers
14. 14 Examples of suitability models Land development suitability model:
Site selection model (Bolstad, pp 487-495)
Habitat suitability model:
Beaver
Introduced species vulnerability model:
Emerald Ash Borer
Watershed ranking model:
Conservation Success Index for Eastern Brook Trout
15. 15 Example 1. Site suitability example (Bolstad) Model: Suitability for site to build a home
Base layers: Elevation, soils, roads
16. 16 Example 1. GIS steps used Spatial Analyst menu: Surface Analysis (aspect, slope)
Spatial Analyst menu: Distance
ArcToolbox: Clip, Dissolve, Buffer tools
Spatial Analyst menu: Reclassify
Spatial Analyst menu: Convert features to raster
Spatial Analyst menu: Raster Calculator (to combine results)
17. 17 Example 2. Habitat Suitability Index (HSI) HSIs developed for hundreds of wildlife species
Some are applicable spatially, some are not
Aquatic and terrestrial species
Based on literature, field studies
Apply different spatial aspects of species biology:
Limiting resources for species
Food
Cover
18. 18 Example 2. HSI for beaver habitat Habitat layers:
Slope < 15%
Preferred land cover (forested wetland is best)
Proximity to water
Distance from roads/bridges
Assign numeric score to each layer
Final map indicates habitat suitability
19. 19 Example 3. Introduction of forest pest species GIS can be used to model / rank susceptibility to introduction of forest insect pests
Uses:
Identify areas with risk factors
Identify areas for future monitoring or prevention efforts
Example: Emerald Ash Borer
Introduced in Midwest
Severe economic damage
Specific to ash trees
Likely introduced in shipping materials from overseas
20. 20 Example 3. Emerald Ash Border (EAB) EAB introduction risk mapping (MN example)
Risk factors:
Sawmills
Campgrounds
Nurseries
Urban areas
Firewood dealers
Seasonal homes
Dont move firewood!
21. 21 Example 4. Conservation Success Index (CSI) Trout Unlimited
Ranks watersheds based on probability of success for supporting cold water fish species (trout)
Used to guide policies and priorities related to species conservation, based on best probability of success
22. 22 Example 4. CSI scoring framework example
23. 23 Example 4. Brook trout CSI Brook trout conservation potential model based on:
% of original range still occupied
Degree of flow modification
# Introduced species
Land use conversion potential
24. 24 Example 4. Brook trout CSI by watershed
25. 25 Advantages of suitability modeling in GIS Quantifiable, mappable results for sometimes abstract concepts
Ability to adjust models, see how results are affected (sensitivity analysis)
Process of assigning weights may increase awareness & promote consensus-building among stakeholders for given policy issue
Greater awareness of future data needs and gaps
26. 26 Summary Suitability Modeling
Criteria, weighting
Examples of application of suitability modeling
Limitations and advantages of this approach
Coming up next week:
Test review
Future directions in GIS
3D or virtual modeling