Mitigation of the Urban Heat Island Effect via NeighborWoods Tree

Program

Project Manager-Clancy Taylor

GIS Analyst/Web Designer-Will Johnston

GIS/Remote Sensing Analyst-Michael Amaral

GIS/Remote Sensing Analyst-Megan Branam

Outline

1.Introduction

2.Data

3.Methods

4.Results

5.Implications, Considerations, and Conclusions

Introduction

• Austin, Texas

• NeighborWoods Tree Planting Program

• Mitigation of Urban Heat Island Effect

• Effectiveness of Program

Urban Heat Island Effect

• Developed Areas are Hotter than Rural Areas

• Negative Impacts on City

• Mitigation of UHI Effect

Data

• The Austin Urban Forestry Department provided the NeighborWoods tree locations

• City of Austin provided base map information

• USGS Earth Explorer images from Landsat 4-5, 7, and 8.

Methods – Remote Sensing

• Extract the data

• Re-projected to Texas State Plane Central (4203)

• Convert digital numbers to Spectral Radiance

• Convert Spectral Radiance to at-satellite brightness temperature

• Convert to Celsius

Methods-GIS

• Determined how to group study areas & control areas (zip codes)• Chose top 10 zip codes with most trees/

top 10 least trees (majority of zip code within AE service area)

• Joined zip code shapefile with tree shapefile

• Calculated average surface temperature for each zip code

• Converted raster layer to point vector

• Did same process for all 20 zip codes per year for all 3 years

Methods-Statistical Analysis

• Wilcoxon Signed Rank Test

• Nonparametric Test

• Testing differences between mean temperatures

• 2002, 2009, 2014

• Mean Temperature per Zip Code

• 10 Zip Codes w/ Most Dense Tree Plantings

• 10 Zip Codes w/Least Dense Tree Plantings

Hypothesis Testing

• Null Hypothesis (H0): The median of differences between the temperature differences of the non-dense tree zip codes and the temperature differences of the dense zip codes is not statistically significant.

• Alternative Hypothesis (H1): The median of differences between the temperature differences of the non-dense tree zip codes and the temperature differences of the dense zip codes is statistically significant.

Methods – Tree Benefit Calculator

• Information gathered from the National Tree Benefit Calculator website

• Trees planted are 1 in. in diameter

• Trees grow 1 in. in diameter every year

• Trees from one year are multiplied many times

• Disregard 2002 year, no species information

Results– Remote Sensing

• Not real land surface temperature

• Light travels through the atmosphere, along with “noise”

• Cloud coverage

• Not the highest quality images

• For two images, the pixel size was 50 feet

• One image 100 foot pixel size

Results-GIS

• Base map

• Established study/ control areas

• Average surface temperatures per zip code

• Prepared data for statistical analysis

• Final maps

Results-Statistical Analysis

• Significant Temperature Differences

• 2002-2014; 2009-2014

• No Temperature Differences

• 2002-2009

Results– Tree Benefit Calculator

• Trees are awesome!

• Many assumptions involved

• Keep planting trees!

Considerations

• Health of Trees

• At Satellite Brightness Temperature

• Climatology

• Other Cooling or Mitigation Factors

Conclusions

• NeighborWoods-Urban Heat Island Mitigation

• Energy and CO₂ Savings and Reduction

• Neighborhood Level Temperature Reduction

• As Austin continues growing, so should NeighborWoods