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Roy Petrakis

Roy Petrakis work for the Western Geographic Science Center and is located in Tucson, AZ.

I am a Geographer with the U.S. Geological Survey - Western Geographic Science Center in Tucson, AZ. I am a team member for both the Tribal Land Vegetation and Watershed Modeling and Aridland Water Harvesting Study teams. My research often addresses themes such as wildfire and fuel treatments, climate variability and drought, surface water, watershed management, land use/land cover, and riparian ecosystems, among others, using remote sensing and GIS applications and methodologies.

In my time with the USGS, I have published on topics including the use of fuel treatments in reducing wildland fire severity, mapping surface water trends on a national scale, and assessing riparian vegetation response to changing climate conditions to inform Tribal restoration priorities.

Professional Experience

  • 2020 – Current: Geographer, U.S. Geological Survey – Western Geographic Science Center

  • 2015 – 2020: Contractor, U.S. Geological Survey – Western Geographic Science Center

Education and Certifications

  • M.A. – 2015 – Geography – University of Arizona, School of Geography and Development

  • B.A. – 2011 – Geography – University of Arizona, School of Geography and Development

Science and Products

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Franklin Mountains near the Hueco Bolson

Mapping Riparian Vegetation Response to Climate Change on the San Carlos Apache Reservation and Upper Gila River Watershed to Inform Restoration Priorities: 1935 to Present

Riparian systems are critical to the human and ecological communities that interact with them. For the members of San Carlos Apache Tribe, this is particularly true, as riparian systems provide immense cultural and natural values such as ceremonial grounds and recreation areas. However, the riparian areas within the San Carlos Apache Reservation are at risk of degradation due to climate change and
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Climate Adaptation Science Centers
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Mapping Riparian Vegetation Response to Climate Change on the San Carlos Apache Reservation and Upper Gila River Watershed to Inform Restoration Priorities: 1935 to Present

Riparian systems are critical to the human and ecological communities that interact with them. For the members of San Carlos Apache Tribe, this is particularly true, as riparian systems provide immense cultural and natural values such as ceremonial grounds and recreation areas. However, the riparian areas within the San Carlos Apache Reservation are at risk of degradation due to climate change and
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Land Cover Point of Pines

Tribal Land Vegetation and Watershed Modeling

San Carlos Apache Reservation covers 1.8 million acres in east-central Arizona, and has diverse ecosystems and vegetation types that support a natural resource-based economy.
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Natural Hazards Mission Area, Land Change Science Program, Western Geographic Science Center
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Tribal Land Vegetation and Watershed Modeling

San Carlos Apache Reservation covers 1.8 million acres in east-central Arizona, and has diverse ecosystems and vegetation types that support a natural resource-based economy.
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Photograph of gabion dam in Nogales, Sonora

Aridland Water Harvesting Study

Most of western North America has been severely grazed by cattle, causing grasslands to deteriorate and desert scrub expansion. Climate in arid and semi-arid regions is often typified by short, intense rainfall events which contribute to short-term flooding and erosion. Associated arroyo cutting occurs when ephemeral creek beds are carved into the floodplain when erratic overland flow occurs; this...
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Land Change Science Program, Western Geographic Science Center
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Aridland Water Harvesting Study

Most of western North America has been severely grazed by cattle, causing grasslands to deteriorate and desert scrub expansion. Climate in arid and semi-arid regions is often typified by short, intense rainfall events which contribute to short-term flooding and erosion. Associated arroyo cutting occurs when ephemeral creek beds are carved into the floodplain when erratic overland flow occurs; this...
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Mapping Riparian Vegetation Response to Climate Change on the San Carlos Apache Reservation and Upper Gila River Watershed to Inform Restoration Priorities: 1935 to Present - Database of Riparian Floodplain Boundaries for the San Carlos and Gila Rivers

We developed this spatial database of historic and current floodplains to analyze trends in vegetation conditions, identify areas more at risk of degradation, and assess the relationship between riparian vegetation dynamics and climate conditions.Our study area is the riparian areas along the San Carlos River and Gila River within the San Carlos Apache Reservation and the Upper Gila River Level-4
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Western Geographic Science Center

Mapping Riparian Vegetation Response to Climate Change on the San Carlos Apache Reservation and Upper Gila River Watershed to Inform Restoration Priorities: 1935 to Present - Database of Trends in Vegetation Properties and Climate Adaptation Variables

We apply a research approach that can inform riparian restoration planning by developing products that show recent trends in vegetation conditions identifying areas potentially more at risk for degradation and the associated relationship between riparian vegetation dynamics and climate conditions. The vegetation is characterized using a series of remote sensing vegetation indices developing using
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Western Geographic Science Center

National Surface Water Maps using Daily MODIS Satellite Data for the Conterminous United States, 2003-2019

Members from the U.S. Geological Survey (USGS) Patterns in the Landscape - Analyses of Cause and Effect (PLACE) team are releasing monthly surface water maps for the conterminous United States (U.S.) from 2003 through 2019 as 250-meter resolution geoTIFF files. The maps were produced using the Dynamic Surface Water Extent (DSWE) algorithm applied to daily Moderate Resolution Imaging Spectroradiome
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Climate Research and Development Program, Western Geographic Science Center

Watershed Pairing of Sub-Basins within Smith Canyon Watershed using a Hierarchical Clustering Approach

This data release contains data used in an upcoming associated publication currently in review. The overarching effects and benefits of land management decisions, such as through watershed restoration, are often not fully understood due to a lacking control within an experimental design. This can be addressed through the application of a paired watershed approach, allowing for comparison between
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Western Geographic Science Center

DSWEmod surface water map composites generated from daily MODIS images - California

USGS researchers with the Patterns in the Landscape ? Analyses of Cause and Effect (PLACE) project are releasing a collection of high-frequency surface water map composites derived from daily Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. Using Google Earth Engine, the team developed customized image processing steps and adapted the Dynamic Surface Water Extent (DSWE) to generate s
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Climate Research and Development Program, Western Geographic Science Center

Perceived Social Value of the Sonoita Creek Watershed using the Social Values for Ecosystem Services (SolVES) Tool, Arizona, U.S.A.

Mapping the spatial dynamics of perceived social value across the landscape can help develop a restoration economy that can support ecosystem services in the region. Many different methods have been used to map perceived social value. We used the Social Values for Ecosystem Services (SolVES) GIS tool, version 3.0, which uses social survey responses and various environmental variables to map social
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Western Geographic Science Center

Implementation of a Surface Water Extent Model using Cloud-Based Remote Sensing - Code and Maps

This data release comprises the raster data files and code necessary to perform all analyses presented in the associated publication. The 16 TIF raster data files are classified surface water maps created using the Dynamic Surface Water Extent (DSWE) model implemented in Google Earth Engine using published technical documents. The 16 tiles cover the country of Cambodia, a flood-prone country in So
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Western Geographic Science Center

Datasets for analyzing stream gage discharge and Landsat imagery integration in the greater Central Valley, California from 1984 to 2015

This data release comprises the data files and code necessary to perform all analyses presented in the associated publication. The *.csv data files are aggregations of water extent on the basis of the European Commission's Joint Research Centre (JRC) Monthly Water History database (v1.0) and the Dynamic Surface Water Extent (DSWE) algorithm. The shapefile dataset contains the study area 8-digit
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Western Geographic Science Center

Dataset for 2013 Creek Fire Research Points, Pre- and Post-Fire Data

The practice of fire suppression across the western United States over the past century has led to dense forests, and when coupled with drought has contributed to an increase in large and destructive wildfires. Forest management efforts aimed at reducing flammable fuels through various fuel treatments can help to restore frequent fire regimes and increase forest resilience. Our research examines h
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Western Geographic Science Center

Riparian vegetation response amid variable climate conditions across the Upper Gila River watershed: informing Tribal restoration priorities

Restoring degraded river systems is an enormous challenge, especially given the uncertainty in a time of climate change. Here, Roy Petrakis explains how restoration approaches informed by remote sensing and a climate adaptation framework increase the potential for overall success. He discusses research being done on the Gila River as a case study of how it might work.
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Roy Petrakis
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Western Geographic Science Center

Riparian vegetation response amid variable climate conditions across the Upper Gila River watershed: Informing Tribal restoration priorities

Riparian systems across the Southwest United States are extremely valuable for the human and ecological communities that engage with them. However, they have experienced substantial changes and stresses over the past century, including non-native vegetation expansion, vegetation die-offs, and increased fire activity. Vegetation management approaches, such as ecological restoration, may address som
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Roy Petrakis, Laura M. Norman, Barry R. Middleton
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Western Geographic Science Center

Analysis of surface water trends for the conterminous United States using MODIS satellite data, 2003–2019

Satellite imagery is commonly used to map surface water extents over time, but many approaches yield discontinuous records resulting from cloud obstruction or image archive gaps. We applied the Dynamic Surface Water Extent (DSWE) model to downscaled (250-m) daily Moderate Resolution Imaging Spectroradiometer (MODIS) data in Google Earth Engine to generate monthly surface water maps for the conterm
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Roy Petrakis, Christopher E. Soulard, Eric K. Waller, Jessica J. Walker
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Climate Research and Development Program, Western Geographic Science Center

DSWEmod - The production of high-frequency surface water map composites from daily MODIS images

Optical satellite imagery is commonly used for monitoring surface water dynamics, but clouds and cloud shadows present challenges in assembling complete water time series. To test whether the daily revisit rate of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery can reduce cloud obstruction and improve high-frequency surface water mapping, we compared map results derived fro
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Christopher E. Soulard, Eric Waller, Jessica J. Walker, Roy Petrakis, Britt Windsor Smith
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Climate Research and Development Program, Western Geographic Science Center

A shared vision for enhancing ecological resilience in the U.S. - Mexico borderlands: The Sky Island Restoration Collaborative

No abstract available.
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Laura M. Norman, Michele Girard, H. Ron Pulliam, Miguel L. Villarreal, Valer Austin Clark, Aaron D. Flesch, Roy Petrakis, Jeremiah Leibowitz, Deborah Tosline, Kurt Vaughn, Tess Wagner, Caleb Weaver, Trevor Hare, Jose Manuel Perez, Oscar E. Lopez Bujanda, Josiah T. Austin, Carianne Funicelli Campbell, James B. Callegary, Natalie R. Wilson, Jeff Conn, Tom Sisk, Gary L. Nabhan
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Western Geographic Science Center

Hierarchical clustering for paired watershed experiments: Case study in southeastern Arizona, U.S.A.

Watershed studies are often onerous due to a lack of data available to portray baseline conditions with which to compare results of monitoring environmental effects. A paired-watershed approach is often adopted to simulate baseline conditions in an adjacent watershed that can be comparable but assumes there is a quantifiable relationship between the control and treated watersheds. Finding suitably
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Roy Petrakis, Laura M. Norman, Kurt Vaughn, Richard Pritzlaff, Caleb Weaver, Audrey J Rader, H. Ronald Pulliam
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Western Geographic Science Center

Mapping perceived social values to support a respondent-defined restoration economy: Case study in southeastern Arizona, USA

Investment in conservation and ecological restoration depends on various socioeconomic factors and the social license for these activities. Our study demonstrates a method for targeting management of ecosystem services based on social values, identified by respondents through a collection of social survey data. We applied the Social Values for Ecosystem Services (SolVES) geographic information sys
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Roy Petrakis, Laura M. Norman, Oliver Lysaght, Benson C. Sherrouse, Darius J. Semmens, Kenneth J. Bagstad, Richard Pritzlaff
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Geosciences and Environmental Change Science Center, Western Geographic Science Center

Implementation of a surface water extent model in Cambodia using cloud-based remote sensing

Mapping surface water over time provides the spatially explicit information essential for hydroclimatic research focused on droughts and flooding. Hazard risk assessments and water management planning also rely on accurate, long-term measurements describing hydrologic fluctuations. Stream gages are a common measurement tool used to better understand flow and inundation dynamics, but gage networks
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Christopher E. Soulard, Jessica J. Walker, Roy E. Petrakis
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Climate Research and Development Program, Land Change Science Program, Western Geographic Science Center

Integrating stream gage data and Landsat imagery to complete time-series of surface water extents in Central Valley, California

Accurate monitoring of surface water location and extent is critical for the management of diverse water resource phenomena. The multi-decadal archive of Landsat satellite imagery is punctuated by missing data due to cloud cover during acquisition times, hindering the assembly of a continuous time series of inundation dynamics. This study investigated whether streamflow volume measurements could b
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Jessica J. Walker, Christopher E. Soulard, Roy E. Petrakis
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Climate Research and Development Program, Land Change Science Program, Western Geographic Science Center

Evaluating and monitoring forest fuel treatments using remote sensing applications in Arizona, U.S.A.

The practice of fire suppression across the western United States over the past century has led to dense forests, and when coupled with drought has contributed to an increase in large and destructive wildfires. Forest management efforts aimed at reducing flammable fuels through various fuel treatments can help to restore frequent fire regimes and increase forest resilience. Our research examines h
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Roy Petrakis, Miguel L. Villarreal, Zhuoting Wu, Robert Hetzler, Barry R. Middleton, Laura M. Norman
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Western Geographic Science Center, Wildland Fire Science

Historical analysis of riparian vegetation change in response to shifting management objectives on the Middle Rio Grande

Riparian ecosystems are valuable to the ecological and human communities that depend on them. Over the past century, they have been subject to shifting management practices to maximize human use and ecosystem services, creating a complex relationship between water policy, management, and the natural ecosystem. This has necessitated research on the spatial and temporal dynamics of riparian vegetati
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Roy Petrakis, Willem J.D. van Leeuwen, Miguel L. Villarreal, Paul Tashjian, Regina Dello Russo, Christopher A. Scott
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Western Geographic Science Center

Vegetative response to water availability on the San Carlos Apache Reservation

On the San Carlos Apache Reservation in east-central Arizona, U.S.A., vegetation types such as ponderosa pine forests, pinyon-juniper woodlands, and grasslands have significant ecological, cultural, and economic value for the Tribe. This value extends beyond the tribal lands and across the Western United States. Vegetation across the Southwestern United States is susceptible to drought conditions
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Roy Petrakis, Zhuoting Wu, Jason McVay, Barry R. Middleton, Dennis G. Dye, John M. Vogel
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Western Geographic Science Center

DSWE_GEE v1.0.0

Code for implementation of the Dynamic Surface Water Extent algorithm in Google Earth Engine. Multiple scripts allow the creation of single-scene or composited Dynamic Surface Water Extent (DSWE) images from Landsat and MODIS data. All code is written for use in the JavaScript API.
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Western Geographic Science Center
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Integrating stream gage data and Landsat imagery to complete surface water records

This article is part of the Spring 2020 issue of the Earth Science Matters Newsletter. 

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