How do soil conditions vary across urban vacant lots in Phoenix? How do they compare to previously mapped national soil survey data?What are the implications for stormwater retention and flooding prevention?

Vacant land in Phoenix comprises 6.5% of the total city area. This land could be a potential asset or a vulnerability, depending on the state of these vacant properties.

We focused here on soil properties, with the goal of understanding how these vacant lot soils might play a role in stormwater retention and prevent local flooding.

We selected 20 vacant lots which were all located in CAP PASS (Phoenix Area Social Survey) neighborhoods distributed throughout the Phoenix metropolitan area.

Single ring infiltrometerfor saturated

infiltration rate

Tension infiltrometerfor near-saturated

infiltration rate

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Sources: Esri, HERE, DeLorme, Intermap,increment P Corp., GEBCO, USGS, FAO, NPS,NRCAN, GeoBase, IGN, Kadaster NL,Ordnance Survey, Esri Japan, METI, Esri China(Hong Kong), swisstopo, MapmyIndia, ©OpenStreetMap contributors, and the GIS UserCommunity

0 10 205km

Vacant Lot Sampling Sites

2011 CAPLTER PASS Neighborhoods Field sampling of soilphysical characteristics

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Vacant Lot Sampling Sites

Hydrologic Soil Group (HSG)

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Comparison with NRCS spatial soil survey data

Spotlight on vulnerability related to vacancy & drainage

There is substantial variability in infiltration ratesin vacant lots across the region.

The two field infiltration methods do not alwaysagree, even in terms of relative trends.

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Neighborhood Poverty & Infiltration Rates

p=0.007R2=0.31

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HSG from NRCS soil survey

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Near Saturation Infiltration Rates by Vacant Lot Site

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Saturated Infiltration Rates by Vacant Lot Site

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There is mediocre agreement betweensoil survey data and measured field

infiltration, though observed infiltrationwas often better than predicted

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Sat. infiltration via soil survey (cm/hr)

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Predicted vs Observed Infiltration

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Hydrologic Soil Groups (HSGs) accordingto field data and soil survey

Observed infiltration rates

in these vacant lotswill influence whether

runoff is generatedin various storm events

Lower (worse) infiltration rateswere found in vacant lots

in more impoverishedneighborhoods

The SevenEleven PASSneighborhood in South Phoenix

has high vacancy, poorengineered drainage,and lowest observed

infiltration rates

Sites 9-11 in SevenEleven PASS neighborhood

range of observedinfiltration rates

runoffgenerated

precipinfiltrated

--Assess influence of demolition history on soil properties at these lots--Possible field evaluation of vacant lots in other UREx SRN cities--Incorporation of these findings into runoff modeling of vacant lots

--Infiltration rates were highly variable across vacant lots, and this has important implications for whether or not runoff is generated during storm events--Some of the lowest infiltration rates were in socially vulnerable neighborhoods--There are substantial discrepancies between these observations and NRCS soil survey data

CAP LTER under NSF grant no. DEB-1637590 for logistical and vehicle supportUREx SRN under NSF grant no. 1444755 for REU support of Shannon Newell

Stormwater Infiltration Patterns in Vacant Lots in the Phoenix Metro AreaLauren McPhillips1, Shannon Newell2, and Nancy Grimm1

1 Arizona State University, Tempe AZ 2 Northern Arizona University, Flagstaff AZ

Acknowledgements

Overview Sites & Methods

Results

Next Steps

Conclusions

Contact:Lauren.McPhillips@asu.eduTwitter: @laurenicium