D4 Garner State Park Pavilion Preservation Study Presented by Andy Johnston, PE, CPESC, CFM Halff Associates, Inc. Austin Mark Winford, RA, LEED AP Texas Parks and Wildlife Department, Austin Location Map 1
Civilian Conservation Corps (CCC) Focus of Work 2
Interrelated Items CCC Pavilion Structures FRIO RIVER CCC PAVILION HALL DANCE FLOOR TERRACE 3
Pavilion Dance Floor Pavilion Terrace 4
Pavilion Drainage FRIO RIVER Pavilion Drainage 5
Pavilion Dance Floor: Bird Bath Pavilion Digital Scan 6
Blue Shading Below a Given Elevation Elevation = 1391.80 Digital Scan Flooding Still Grades Toward River 1391.95 1392.05 1392.10 1392.15 7
Pavilion Dance Floor: Settlement Pavilion Dance Floor: Settlement 8
Dance Floor Edge Differences Interrelated Items Parking Lot 9
Parking Parking Digital Scan 10
Inlets/Pipes/Headwalls Inlets/Pipes/Headwalls 11
Inlets pipes wooden HW Erosion control on slopes. Embrace historical methods. Planter boxes for revegetation. Key = get veg back on the slopes. Green Gabion planter boxes 12
View from the River Vegetation Suites Red mulberry Desert willow Burrowbrush Lindheimer indigo Lindheimer senna Non-wet plant types. Frogfruit Knotgrass Switchgrass Common reed Black willow Arroyo willow Water primrose Smooth bidens Bushy bluestem Emory sedge Buttonbush Bald cypress Equally wet or non-wet plant types. Moderate stability rating Wet-footed plant types. Strong stability rating 13
Permeable parking spaces Porous pavement material 14
Slope Erosion cut through Slope Erosion behind wall CCC wall footing exposed 15
Hindrances foot traffic fencing Include vegetative fencing Hindrances foot traffic fencing Include vegetative fencing 16
Hindrances foot traffic (upstream) Create a stairway? Amenity? River access point? Blend in with rock toe stabilization? Controlled access point 17
Interrelated Items - Streambank Google Earth chronology (2012) Meander pattern. Changing sides in our reach. 18
Google Earth chronology (1995) USGS Gauge Uvalde 1997, June 22 100,000 cfs 2000, June 22 100,000 cfs 2002, July 2 189,000 cfs 2004, June 29 72,300 cfs 2007, July 21 74,100 cfs Google Earth chronology (2005) 19
Google Earth chronology (2008) Google Earth chronology (2012) 20
Stream has moved opposite bank CCC Original Plans 21
CCC Original Plans MAJOR GOAL: Do not loose any more streambank. CCC Original Plans MAJOR GOAL: Analyze the bank and wall for structural stability. 22
FEMA Floodplain Zone A 1967 Channel Improvements 23
1967 Channel Impingement 2005 Channel Work 24
Stream rock blocks (2005) downstream upstream Stream rock blocks 25
Stream rock blocks Stream rock blocks (footing) 26
Stream rock blocks (upstream) Stream steep bank 27
Riparian Zone values and functions Values (the things we want) Recreational value. Aesthetic beauty. Wildlife habitat. Forage. Aquatic habitat. Water quality. Water quantity. Functions (the things we can influence) Dissipate stream energy. Trap sediment. Stabilize banks. Reduce erosion. Store water. Sustain baseflow. Groundwater recharge. Creek Doctors What is the least amount of work that needs to be done to make things better? What things are still working fine? What is throwing the system out of balance? Each patient is different. Listen to unique needs. Holistic approach (park use, environmental, stabilization). Use natural channel design concepts. Recruit vegetation. Sustainable design. Potomology. The systematic study of the factors affecting river channels to provide the basis for predictions of the effects of proposed engineering works on channel characteristics. 28
Resist Alternatives Usually continuous, applied directly on the bank, or toe, or both, offers resistance to river or stream forces, some methods can self-adjust, others are rigid. Redirect Indirect, usually discontinuous techniques that redirect flow & energy of the river or stream away from the area of the eroding bank. Resistive (continuous) Natural features (rock outcroppings, blue clay, etc.) Loose Rock Riprap (filter stone layer, soil choked surface) Boulder Blankets (bank paving) Grouted Riprap Root Wads Log Revetment Trenchfill (setback revetment) Sack Revetments (RRap) Windrow Revetment Soil Cement Gabions Sheet pile Concrete Retaining walls (to include cellular confinement layers) LUNKERS Longitudinal Peaked Stone Toe Protection (LPSTP) Longitudinal Fill Stone Toe Protection (LFSTP) Self adjusting (sustainable). Foundation is critical. 29
Redirective (discontinuous) Impermeable Dikes, also called Spurs, Groins, Jetties including Stone-Filled Pile Dikes and Stone-Filled Dikes. Permeable Dikes (Pile Dikes, Palisades). Vane Dikes. Contraction Dikes, or Wingdams. "L" and "T" Head Dikes. Upstream & Downstream Angled Deflectors (Bank Barbs, Rock Vanes, Rock Vanes with J-Hooks). Bendway Weirs (many variations including L& T-Head Bendways). Engineered Log Jams. Kellner Jacks, Tripod Jacks, Tetrahedron Jacks Hard Points (also called transverse dikes, always normal to the flow. Kickers and Missouri River Kickers. Deflectors (also "wiggle" deflectors) and false point bars Stream scour pockets 30
Stream scour pockets Stream scour pockets 31
Stream scour pockets Enhance opportunities to trap sediment, recruit vegetation, dissipate energy, create a naturally armored toe, and help stabilize the upper slope (less steep). Large rock boulders (stable reach) 32
Armor toe + Harvest sediments Stream create sediment traps 33
Stream deposition - colonizers Stream stabilizers root wads 34
Stream remove/relocate point bar Slope and toe protection (plan view) 35
Riparian Zone values and functions Values (the things we want) Recreational value. Aesthetic beauty. Wildlife habitat. Forage. Aquatic habitat. Water quality. Water quantity. Functions (the things we can influence) Dissipate stream energy. Trap sediment. Stabilize banks. Reduce erosion. Store water. Sustain baseflow. Groundwater recharge. Interrelated Items 36
D4 Garner State Park Pavilion Preservation Study Presented by Andy Johnston, PE, CPESC, CFM Halff Associates, Inc. Austin Mark Winford, RA, LEED AP Texas Parks and Wildlife Department, Austin 37