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Stormwater Strategies


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  • 1. “English + Associates, Architects” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
  • 2. LID + Resilient Design on the Texas Gulf Coast
  • 3. Course Description The presentation centers around a case study of a new library building recently construction approximately 1500 feet (less than 1/3 mile) from Galveston Bay, in a sensitive ecosystem area also subject to storm surges associated with periodic Hurricanes. The presentation includes a review of the varied ecosystems present along the nearby Texas Gulf Coast, focusing on responsible design in those areas already containing significant development, and therefore unlikely candidates for large- scale ecosystem preservation. The presentation will review the initial site ecosystem assessment, development of LID and resilient design strategies in the early design phases, and a more detailed description of the systems ultimately incorporated in the site and building design. These include re-constructed wetlands, bioswales, underground detention and retention filtration methods, and native and adaptive plant selection, as well as building envelope resilient elements. Metrics associated with run-off rate reduction and storm water filtration will also be provided.
  • 4. Learning Objectives 1. Attendees will be able to understand the various ecosystems present on the Texas Gulf Coast, and the importance of these systems in protecting the health of the local natural environment. 2. Attendees will be exposed to various design strategies that mimic or respond to coastal ecosystems in order to create resilient sites and buildings. 3. Attendees will be able to identify potential plant selections for both LID and salt water inundation environments. 4. Attendees will be able to identify the basic construction elements of swales, bio-swales, wetlands, underground detention/retention, and filtration systems. At the end of this program, participants will be able to:
  • 5. Texas Ecosystems
  • 6. Coastal Prairies Coastal Prairie Coastal Marsh
  • 7. What is a Coastal Prairie • Tall grass and shrubs instead of trees. • Hard clay layer under the topsoil. • Abundant amount of rainfall. After enough rainfall the coastal prairie will turn in to a coastal marsh. • Warm, moist, tropic al air masses. Definition of Wetland: “Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.”
  • 8. Plant & Animal Species Gayfeather Black-eyed Susan Little Bluestem Indiangrass Ibis Red Tailed Hawk DragonflyButterfly
  • 9. Ecological Services Food Plant and animal species Textiles and dyes Medicine Migration Destination Filtration of local and federal waters Buffer from storm surges Plants supply oxygen
  • 10. Dangers to Coastal Prairies Pre-settlement there were 9 million acres of coastal prairies with 6.5 million of them in Texas. Today less than 1% survive giving Texas only 65,000 acres left. Overgrazing Extinction There are less than 100 Attwater Greater Prairie Chickens left in the wild and is only found in coastal prairies. Invasion of Exotic Plants The Macartney Rose and Chinese Tallow Tree are two of the most problematic invaders. People/Development Encroachment
  • 11. Restoration and Preservation of Coastal Prairies 1. Preparation by herbicide, solarization, or tillage 2. Planting by haying, seeding, so dding, or transplanting 3. Management by mowing, irrigation, gr azing, and fire
  • 12. Sensitive Ecosystems Trinity Bay Galveston Bay East Bay Gulf of Mexico
  • 13. Region Project Site
  • 14. Meador Library Case Study Site
  • 15. Developed Site Amenities Previously Cleared Wetland/Coastal Praire Naturalized Stream Vegetation Local Wildlife
  • 16. Recreating Natural Amenities Use native salt water resilient plants [Halophytes] Recreate wetland environment Maximize green space
  • 17. Storm Surge Considerations Code Minimum Height: 12’6 Presumed Worse Case: 17’ Category 4 Model Storm: 13’
  • 18. Site Hydrology 1 2 3 4 4 4 5 6 1. Building 2. Constructed Wetland 3. Terraced Swale 4. Vegetated Bioswale 5. Subsurface Retention/Detention 6. Outflow to Drainage
  • 19. Constructed Wetland Outflow Water level Root flow Nitrification, den itrification, adsor ption, absorptio n, ion exchange Gravel, sub strate, san d Water flow Impermeable layer Inflow
  • 20. Terraced Grassy Swale
  • 21. Bioswale with Retention/Detention Basin
  • 22. Plant Material for Bioswales Blue Flag Iris Wax mallow Butterfly Iris Dwarf Katie Ruellia Deep-rooted, native, salt water resistant plants are important factors to consider when picking the plant material for a bioswale in a coastal prairie. Cordgrass Gulf Coast Muhly
  • 23. Design the Site with LID •Total site area-218,150sf (or approx. 5 acres) Building footprint-21,125sf Developed footprint-55,900sf Open space-141,125sf •The site post developed runoff rate is less than the Pre-developed Run off rate for the 2-year 24hr event. •The site is designed as a series of overflows to slow the run off rate dramatically from the pre-developed rate. •The site as designed is capable of storing 10,300cf/storm event (or 77,049 gallons) within the combination of raintank, bioswales, and rain garden and the amount of detention is 25,720 cf. •Amount of water stored onsite and used for irrigation during the July design case – 77,123gals captured during the month allowing for a 109% reduction in potable water use for the month of July. •Over 80% of the suspended solids are removed from over 90% of the storm runoff •Plant type was designed to be native drought tolerant plants. The plants also were to be able to withstand the salt environment and handle sustained wet conditions during the storm events.
  • 24. Materials •Building envelope designed for high wind loads •Roof is rated for 190mph storm •Building structure is rated for 120mph •Coiling storm doors are rated for 140mph •Curtainwall system is rated for 130mph •Limited glazing not protected by shutters •Non shuttered glazing is large missile impact laminated double insulated semi reflective Low-E glazing •Minimal use of wood and other nondurable materials •Minimized cantilevers, fins, and overhangs
  • 25. Shutter System Illustration
  • 26. What Our Client Asked For • Code Minimum • Withstand forces similar to Hurricane Ike without damage • Meet current needs of library plus be able to expand with technology • Warm and inviting to community What They Didn’t Ask For • Highly sensitive to local environment • LEED [Did ask for further along in the process] • Take advantage of natural systems beyond local regulatory requirements for the site design
  • 27. Kathleen English This concludes The American Institute of Architects Continuing Education Systems Course