Increasing Regional Flood and Stormwater Resilience through Urban Forestry and Green Infrastructure in Houston, TX

1. Increasing Regional Flood and
Stormwater Resilience through
Urban Forestry and Green
Infrastructure in Houston, TX
Joshua DuBois
FW562/Winter 2019
Background image is creative commons image from MS one drive.

2. Objectives
Introduction:
-Definitions: What is an urban forest, ecosystem services, green infrastructure?
-Ecosystem Services from Urban forests are essential to Houston, TX region
Background:
-Houston, TX: Geographic and Demographic snapshot
-Historical storms
-How exactly can trees reduce effects from stormwater and flooding?
-Current state of the urban forest regionally in Houston?
-Current efforts to recognize and sustain the urban forest/green infrastructure.
Conclusion:
-Research paper direction
Image from https://medium.com/@allisgracee/the-social-use-of-green-infrastructure-
acd5eabb6ed0

3. Introduction
Definitions
Urban Forest:
Urban forests are defined by the US Forest Service as dynamic ecosystems that provide multiple, critical benefits
to any community that contains them. Urban forests are critical components of infrastructure that help to filter
air and water, mitigate stormwater, provide shade which helps to reduce energy and provide habitat for wildlife
and recreation opportunities.
Ecosystem Services:
Ecosystem services are the benefits people obtain from ecosystems. These include provisioning services such as
food, water, timber, and fiber; regulating services that affect climate, floods, disease, wastes, and water quality;
cultural services that provide recreational, aesthetic, and spiritual benefits; and supporting services such as soil
formation, photosynthesis, and nutrient cycling (Millennium Assessment 2005).
Green Infrastructure:
An interconnected network of natural areas and other open spaces that conserves natural ecosystem values and functions,
sustains clean air and water, and provides a wide array of benefits to people and wildlife (Benedict and McMahon, 2006),
OR more recently defined by the EPA as “Green infrastructure is a cost-effective, resilient approach to managing wet
weather impacts that provides many community benefits. While single-purpose gray stormwater infrastructure—
conventional piped drainage and water treatment systems—is designed to move urban stormwater away from the built
environment, green infrastructure reduces and treats stormwater at its source while delivering environmental, social, and
economic benefits.
Image from constructionecoservices.com

4. Ecosystem Services from Urban forests are essential to
Houston, TX region
Houston, TX
Located on the Gulf Coast, Houston, Texas, USA has been subject to major hurricanes and
stormwater events since before its founding in 1837.
One of the fastest growing cities in one of the fastest growing states in the U.S., Houston is
already the 4th largest metropolitan region in the US.
This rate of urban growth has enormous economic and environmental impacts especially in the
realm of stormwater management and these can be compounded by hurricanes and storm
events.
Green Infrastructure/Urban Forestry benefits
Green Infrastructure can help harness the power of nature in the urban environment to
capture “ecosystem services”.
Urban forests and street trees are components of a GI/ES approach.
UF’s provide multiple benefits not only in the form of stormwater mitigation, but also air
pollutant reduction, UHI reduction, providing habitat for wildlife, shading buildings to reduce
heating/cooling costs, crime reduction and increase spending in commercial districts and
increased home values…
Image from californiafiltrationspecialists.com

5. Houston, TX Geography
-Location on a coastal plain with
clay soils makes wetlands and
other permeable surfaces
essential to absorbing stormwater.
-Humid subtropical climate
-Average annual high/low temp of
78.3F/59.8F
-Average annual rainfall 45.28
inches
-Population of almost 7 million, 4th
largest metropolitan area in the
U.S.
Image from Houstonchronicle.com
Figure from worldatlas.com
Figure from usclimatedata.com

6. Historical Storms
Hurricanes and Flooding (National Weather
Service, NOAA).
1. 1900 Galveston Hurricane: deadliest disaster in
U.S. history, 8,000 estimated dead.
2. 1979 Tropical Storm Claudette: produced
continental U.S. record 24-hour rainfall total of 43
inches.
3. 2001 Tropical Storm Allison: Costliest storm in
U.S. history approx. $5 billion, 22 deaths.
4. 2008 Hurricane Ike: Greatest storm surge since
Hurricane Carla (Category 4) in 1961 was
estimated at 15-20 feet.
5. 2017 Hurricane Harvey: Slow moving storm
dumped torrential rains resulting in
unprecedented flooding in Houston and
surrounding areas. Category 4 hurricane with
sustained winds of 130 mph.
Image from cnbc.com

7. How exactly can trees reduce effects from
stormwater and flooding?
-Urban forests can help to reduce “peak flow”
which is the maximum rate of runoff during a
rainfall event.
-3 ways trees divert stormwater (interception,
stemflow, infiltration) NYC study (Elliot et al., 2018).
“By increasing lag time between initiation of rainfall
and peak runoff and reducing rainfall intensity,
urban forest systems may help stormwater control
measures reach their full capability to infiltrate and
store stormwater runoff. A tree canopy’s ability to
temporarily detain rainfall can be seen as a type of
flow control tool that could be used to meter runoff
volume, thus minimizing velocity to stormwater
infrastructure. This would reduce their incidences
of inundation” (Teague & Kuehler 2016). REWORK
-Trees and their associated tree pits, reduced runoff
from asphalt by as much as 62% (Armson et al.
2013).
Figure from Field, & Lichvar (2019).

8. How exactly can trees
reduce effects from
stormwater and flooding?
-“Numerous studies have found that GSI systems can
absorb 50–90 percent of rainfall on site. Several studies
have also found that GSI can trap 45–99 percent of the
solid particles that are contained in stormwater” (Metzger
2017).
-Tree transpiration was the primary output from a
bioswale—accounting for 46-72% of the systems outputs
(Berland et al. 2017).
-“As part of new urban tree canopy goals in cities, the
planting and regrowth of urban forests and woodlands in
riparian areas can serve as active sites for stormwater
management and nutrient retention” (Kaushal et al. 2012,
p. 427). These can often be areas able to support multi use
greenway trails.
Figure from of treecanopybmp.org

9. State of the regional urban forest in Houston
Land Classification and UTC percentage
-As of 2015 Houston contains 33.3 million trees,
of which 19.2 million are on private property
-18.4% Urban Tree Canopy composed of 63
different species
-Stormwater reduction is estimated at 173 million
cubic feet/year valued at $7.8 million annually.
-Land use classification: Residential is the
dominant land class >30% containing almost 30%
of trees five inches and larger in diameter. Note
figure to the right—Yellow is residential.
-Tree size and type i.e. diversity can important for
many reasons. In stormwater control some
species are better at transpiring larger volumes of
water. Importantly, large trees provide greater
ecosystem services benefits.
“Between 1992 and 2010, according to research
by Texas A&M, nearly 25,000 acres of wetlands
were lost to development around Houston; they
would have stored nearly 4 billion gallons of
stormwater” (Kotkin 2017). Harvey dumped an
estimated 15 trillion gallons of rainwater.
Image from of HGAC Regional Data Lab

10. Current efforts that benefit the urban forest/green
infrastructure
Bayou Greenways 2020
-Will total 150 miles of trails when complete
-Provides access to 3,000 acres of greenspace
-Creating a connected network of parks and trails along
Houston’s major waterways
-Creates opportunities for alternate transportation routes,
increased public health, potential new planting space for more
urban trees
Benefits
Combined $90 million each year in projected city-wide annual
benefits*:
Public Health Value
$50 million in physical and mental health benefits (e.g.
recreation use value)
Environmental/Flood control
$10 million in environmental health benefits (e.g. enhanced
bicycle use, flood/runoff reduction and enhanced water quality)
Economic
$30 million in economic health benefits (e.g. enhanced property
values and company talent relocation and retention)
Image and benefit values from Houston Parks Board 2019. Accessed from
http://houstonparksboard.org/Bayou_Greenways_2020_fact_sheet_1.6.16.pdf

11. Building support for UF and
Greenways
Education and Outreach
-”Given the growing strength of the scientific case for the public health benefits of
urban trees, it makes sense to link health sector goals and funding with those of
urban forestry agencies” (Nature Conservancy 2017).
-By tying public health outcomes to urban forestry/greenway parks can build on a
broad range of users beneficiaries.
-Educating the public on the multiple benefits of urban forestry and greenways
-Outreach should target the general public as well as large landholders including
hospitals and school and other institutions or individuals. (itreetools.org).
-Outreach should include successful examples that highlight the ecosystem
services, popularity and multiple benefits of the UF and greenways. Cities like
Atlanta, Singapore can be used as blueprints.
-Giving stormwater engineers and other professionals a basis for including urban
forest systems in stormwater management projects should be part of an
education/outreach strategy (Teague and Kuehler, 2016).
Image from Houston Parks Board.

12. Building support for UF and
Greenways
Regional multidisciplinary planning
-Multidisciplinary, Regional approach will be necessary for comprehensive, coordinated
approach. Municipal government silos need to be broken down to “facilitate various
agencies working together towards effective and efficient policies” (Nature Conservancy
2017).
-By removing so called “silos,” communication and cooperation towards the same goals
can be accomplished and possibly increase the scope of projects .
-These examples can and should be applied to Houston area municipalities, federal and
state agencies and NGO’s, including City of Houston, Houston Parks Board, Harris County
Flood Control District and Trees for Houston, Texas State Forestry and others.
-By using ES as a framework, planners and managers can more clearly optimize benefits
by communicating related stormwater management methods, such as urban forests,
green roofs, urban river corridor restoration, within the same conceptual framework and
vision (Everard and Moggridge, 2012).
-Pool siloed budgets to lower management costs (T.K. BenDor et al. 2018).
Image from Houston Chronicle.

13. Conclusion
Making connections
-The contributions and benefits of UF and GI are sustainable, measurable and
substantial and can be maximized through deliberative, coordinated and integrated
planning approaches.
-Newer green infrastructure and ecosystem services based approaches need to be
integrated into current urban planning initiatives.
-By tying the multiple benefits of the UF/GI to end user outcomes such as public health,
increased, new and broad support of UF/GI can be realized.
-Building support and recognition will require education and outreach efforts aimed not
only policy and decision makers but the general public as well.
-Cities should use a multidisciplinary approach that freely shares information across
departments and even other municipalities. Discarding a siloed approach can improve
efficiency, effectiveness and scale of projects due to lowered costs and shared resources.
Areas to explore
-Link the benefits of UF/Greenways to Public Health to increase stakeholders and
support
-Identify possible public health stakeholders, i.e. health insurance providers, public
agencies, etc.
-Highlight sustainable projects already in place/progress in Houston region
-Identify gaps in connectivity of regional trail network and explore the multiple benefits
of increased connectivity
-Link these benefits to UF/GI and stormwater mitigation as a major benefit and
synergistic relationship
-Lastly more specifically define policy makers, local, state and federal agencies that can
work together in a multidisciplinary fashion across organizations to maximize
expenditures and possibly increase scope of projects.
Image from curbed.com

14. References
• Armson, D., Stringer, P., Ennos, A.R. (2013). The effect of street trees and amenity grass on urban surface water runoff in Manchester, UK. Urban Forestry & Urban Greening, 12, 282-286.
http://dx.doi.org/10.1016/j.ufug.2013.04.001
• BenDor, T. K., Shandas, V., Miles, B., Belt, K., Olander, L. (2018). Ecosystem services and U.S. stormwater planning: An approach for improving urban stormwater decisions. Environmental Science
and Policy, 88, 92-103. https://doi.org/10.1016/j.envsci.2018.06.006
• Berland, A., Shiflett, S.A., Shuster, W.D., Garmestani, A.S., Goddard, H.C., Herrmann, D.L., and Hopton, M.E. (2017). The role of trees in urban stormwater management. Landscape and Urban
Planning, 162, 167-177. http://www.sciencedirect.com/science/article/pii/S0169204617300464.
• Elliot, R.M., Adkins, E.R., Culligan, P.J., Palmer, M.I. (2018). Stormwater infiltration capacity of street tree pits: Quantifying the influence of different design and management strategies in New York
City. Ecological Engineering, 111, 157-166. https://doi.org/10.1016/j.ecoleng.2017.12.003
• Everard, M., Moggridge, H.L. (2012). Rediscovering the value of urban rivers. Urban
• Ecosystems, 15(2), 293–314.
• Field, J., Lichvar, R. (2007, September). Review and Synopsis of Natural and Human Controls on Fluvial Channel Processes in the Arid West. Retrieved from:
https://www.researchgate.net/publication/267241434_Review_and_Synopsis_of_Natural_and_Human_Controls_on_Fluvial_Channel_Processes_in_the_Arid_West
• Houstonparksboard.org. Bayou Greenways 2020, n.d. Web. 1 Feb 2019. Retrieved from: http://houstonparksboard.org/bayou-greenways-2020/
• Kaushal, S.S., Belt, K.T. (2012). The urban watershed continuum: evolving spatial and temporal dimensions. Urban Ecosystems, 15, 409-435. DOI 10.1007/s11252-012-0226-7
• Kotkin, J., Gattis, T. (2017, December 15). Doing Houston Wrong. NewGeography. Retrieved from: http://www.newgeography.com/content/005826-doing-houston-wrong.
• Metzger, L. (2017, February 15). Green Stormwater Infrastructure Can Improve Houston’s Water Quality. Environment Texas. Retrieved from: https://environmenttexas.org/news/txe/green-
stormwater-infrastructure-can-improve-houston%E2%80%99s-water-quality
• Miller, R.W., Hauer, R.J., Werner, L. P. (2015). Urban Forestry Planning and Managing Urban Greenspaces. Long Grove, IL: Waveland Press, Inc.
• Teague, A., Kuehler, E. (2016, October 5). Give Me the Numbers. Forestnetwork. Retrieved from: https://foresternetwork.com/stormwater-magazine/sw-water/sw-stormwater/give-me-the-
numbers/
• The Nature Conservancy. (2017). How Cities Can Harness the Public Health Benefits of Urban Trees. Retrieved from:
https://www.nature.org/content/dam/tnc/nature/en/documents/Public_Health_Benefits_Urban_Trees_FINAL.pdf.
• USclimatedata.com. (2019). Retrieved February 1, 2019 from: https://www.usclimatedata.com/climate/houston/texas/united-states/ustx0617
• U.S. Forest Service. (2016). The Sustainable Urban Forest. Retrieved from: http://www.itreetools.org/resources/content/Sustainable_Urban_Forest_Guide_14Nov2016.pdf
• U.S. Forest Service. (2015). Houston’s Urban Forest. Retrieved from: https://www.srs.fs.usda.gov/pubs/rb/rb_srs211.pdf
• Weather.gov. Tropical Cyclone Climatology for SE TX, n.d. Web. 1 Feb 2019. Retrieved from: https://www.weather.gov/hgx/hurricanes_climatology