land use / land cover change in the phoenix metropolitan area 1984 - 2011 lori krider & melinda...

Land Use / Land Cover Change in the Phoenix Metropolitan Area

1984 - 2011Lori Krider & Melinda Kernik

1984 2011

Introduction

• Why Phoenix?o One of 10 fastest growing cities from 1990 -

2000 (Perry & Mackun, 2001)o Arid regions with high population are water

stressedo Water use is reflected by how the land is

used and managedo How is the landscape changing and how

does this effect water use?

Objective

• Use remote sensing software to assess land use / land cover change in Phoenix from 1984 – 2011o Expect to see dramatic changes due to rapid

population growth Increase in urban and suburban areas (sprawl) Increase in cultivated areas on edges of

metropolitan area Decrease in natural vegetation 

Objective

• Study Areao Phoenix-Mesa

Metropolitan Area South-central

Arizona 16,200 km2

Phoenix, Mesa, Tempe, Chandler, Gilbert, Scottsdale, Glendale, Sun City, Peoria, and Avondale

Google Maps

Preparation

• Tools: ERDAS IMAGINE 2011, USGS GLOVIS, ArcGIS 10, Google MapsTM and Google EarthTM

• Materials: Landsat TM images from 1984 and 2011 (two from each year, 30 m res., 7 bands, June), 2006 NLCD

• Pre-classification processingo Stack bands, mosaic and crop images for each yearo View NLCDo Unsupervised classification (5, 6 & 7 classes)

Analysis• Supervised classification

o Anderson Hierarchical Classification (levels 1 and 2) Altered, unaltered, developed and water

Altered  Human-assisted: healthy and stressed crops, golf

courses Uncultivated: fields not reflecting in IR Unaltered Natural: upland and scrub/shrub (not in IR) Hydrophillic vegetation: depressional vegetation often

associated with water (in IR) Water: lakes, rivers and large golf course water hazards Developed suburban (dwellings)

& urban/roads (commercial/industrial)

Analysis

• Training Areaso 15 - 45o Why?

Errors in first run with less training areas Combination of smaller category classes (i.e. healthy

crop + stressed crop) Reduce confusion and capture variety

• Change Detectiono Thematic: 1984 -> 2011o Difference 

to identify areas of significant change and overall patterns 

10, 20, and 30% thresholds

Post-classification• Accuracy Assessment

o stratified randomo same mosaics as reference

added Google MapsTM for 2011o switched "trainers"o 140 reference points (20 per class)

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1984 2011

Purple: Change to SuburbanLight Blue: Change to Urban

Thematic Change

Detection

1984

2011

Purple = changed to SuburbanBlue = changed to Urban

Green = more than 20% increase in NIRBlue = more than 20% decrease in NIR

Thematic Change Detection

1984 2011Limitations!

Accuracy Assessment

For future classifications:

• Clip to the smallest possible boundaries– More ontological classes = more classification

confusion

• Complications using 30m resolution images for reference data and the same image.

• Use this technique, to generate water infrastructure policy for Phoenix …probably not

References

1. Perry, M. J. & P. J. Mackun. Population Change and Distribution 1990 - 2000: Census 2000 Brief. April 2011. United States Census Bureau. 12 Nov. 2011. <http://www.census.gov/prod/2011pubs/c2kbr01-2.pdf>.