TYBEE ISLAND DUNE RESTORATION 2018 15 FEBRUARY 2018 PRESENTED BY: THOMAS ANGELL, ASLA - VERDANT ENTERPRISES, LLC - AGENT ALAN ROBERTSON - CITY OF TYBEE ISLAND BEACH TASK FORCE - CITY OF TYBEE ISLAND TABLE OF CONTENTS: PAGE 2 - PROPOSAL FOR IMPROVED SHORELINE PROTECTION PAGE 3 - DEFINITION OF SCOPE, IMPACT AREA & JUSTIFICATION PAGE 4 - EXISTING CONDITIONS - HURRICANE DAMAGE PAGE 5 - EXISTING CONDITIONS - 16TH STREET WASHOUT PAGE 6 - EXISTING CONDITIONS - VEHICULAR ACCESS PAGE 7 - EXISTING CONDITIONS - PEDESTRIAN PROMENADE PAGE 8 - DESIGN SOLUTION - DUNE RESTORATION PLAN PAGE 9 - DESIGN SOLUTION - BEACH - BERM - PEDESTRIAN PROMENADE INTERFACE PAGE 10 - DESIGN SOLUTION - VEHICULAR ACCESS PAGE 11 - DESIGN SOLUTION - SAND RETENTION STRUCTURES PAGE 12 - DESIGN SOLUTION - PEDESTRIAN PROMENADE PAGE 13 - DESIGN SOLUTION- PEDESTRIAN PROMENADE STORMWATER PAGE 14 - SUMMARY
PROPOSAL FOR IMPROVED SHORELINE PROTECTION We are requesting authorization to restore the dune fjeld from immediately south of 15 ½ Street extending approximately 1800 linear feet to immediately south of 19th Street, including closing vehicular access at 18th Street, adding subsurface stabilization at 19th Street to support access of Public Safety and Department of Public Works vehicles, and enhance the landscaping on the landward side of the impact area. In its duty to promote beach preservation and the prevention of shoreline erosion, the Beach Task Force examined each of the City’s 27 public beach access points. As part of the assessment, the access points were evaluated based on Type of crossover (Pedestrian or Vehicular), Condition of the crossover, whether it was Critical to emergency access or heavy pedestrian traffjc during season, its Flooding potential, and if we could readily Dam the access point in the event of a major weather event. Private crossovers were not evaluated at this time but should be included at a future date. In summary, the condition of our dune system is good but has been seriously weakened by both Hurricanes Matthew and Irma. There are several points at which dunes should be improved. Most importantly, there are fjve vehicle access points that weaken the dune system dramatically because they are relatively large and “at grade”. During Hurricanes Matthew and Irma the City realized signifjcant fmood events at these vehicle access points, specifjcally 19th, 18th, Center, 3rd, and 2nd Streets. For purposes of this request for a Letter of Permission, we are limiting the impact area to the South end of the shoreline. TYBEE ISLAND DUNE RESTORATION 2018 As we consider our recommendation we are mindful of City emergency vehicle access (fjre,police, lifeguard), adequate public access (number and locations), ADA access (height, degree of slope, and wheelchair accessibility) requirements, GADNR Shoreline Protection and Coastal Marshlands Protection requirements, and Public Works access. We also considered our recommendation in the context of the broader City Public Works Plan for appropriate storm water management, the City Emergency Management Plan for evacuation during a major storm event, and the City budget. This recommendation from the Beach Task Force was approved by the City Council at their September 28, 2017 meeting. PAGE 2 OF 14
DEFINITION OF SCOPE, IMPACT AREA & JUSTIFICATION SILVER AVENUE 18 TH PLACE 17 TH PLACE IZLAR AVENUE ATLANTIC AVENUE 19 TH STREET 18 TH STREET 17 TH STREET 16 TH STREET 15 TH STREET Ts CHU TERRACE 15 TH 1/2 STREET CROSSOVER TYBEE ISLAND DUNE RESTORATION 2018 We propose to use the current 18th Street crossover to bring sand onto the beach, placing it from approximately just south of the 15 ½ Street crossover to 19th Street. We estimate using dump trucks and front end loaders to place the sand along the length of the project, extending approximately 75’ seaward from the most seaward point of the DNR jurisdiction line. The outlined area denotes the approximate loss of the seaward dune fjeld from Oct. 2016 (date of Google Earth image). The length is approximately 1800 linear feet extending from just south of the Pier at 16th Street to approximately 30 yards south of 19th Street and varying from 30’ to 50’ in width. The height of the dunes varies from approximately 1’ to 6’. APPROXIMATE SPA JURISDICTION LINE N APPROXIMATE PROJECT LIMIT: +/- 492,285 SF ( ≈11 ACRES) APPROXIMATE PERVIOUS SURFACE (BEACH & DUNES): 340,930 SF (≈7.5 ACRES, 68% OF TOTAL AREA) SCALE: 1"=200' APPROXIMATE IMPERVIOUS SURFACE (PARKING LOT & PAVILION): 151,355 SF (≈3.5 ACRES, 32% OF TOTAL AREA) 0 100 200 400 PAGE 3 OF 14 0 100 200 400
EXISTING CONDITIONS - HURRICANE DAMAGE STORM SURGE BREACHING UNSTABILIZED DUNES HURRICANE IRMA STORM SURGE TYBEE ISLAND DUNE RESTORATION 2018 SAND WASHOUT AT 18TH STREET VEHICULAR ACCESS HURRICANE IRMA STORM SURGE STORM SURGE AT TYBRISA CIRCLE (16TH STREET WASHOUT UNSTABILIZED DUNE STORM SURGE DEGRADATION PAGE 4 OF 14
EXISTING CONDITIONS - 16 TH STREET WASHOUT The section between the Marine Science Center and 18th Street represent the most oft used and populous area of Tybee Island. During Hurricanes Matthew and Irma, this area experienced a massive washout and complete destruction of the constructed dune system, exposing and damaging local businesses crucial to Tybee Island’s tourist economy. SILVER AVENUE IZLAR AVENUE 17 TH PLACE Ts CHU TERRACE 17 TH STREET 16 TH STREET N 500’ TYBEE ISLAND DUNE RESTORATION 2018 PAGE 5 OF 14
EXISTING CONDITIONS - VEHICULAR ACCESS 18 TH PLACE 17 TH PLACE 18 TH STREET Ts CHU TERRACE 17 TH STREET STRAND TYBEE ISLAND DUNE RESTORATION 2018 N 500’ The 18th Street access is currently used by emergency vehicle access but in doing so, they are going against traffjc on the Strand to reach the Beach Emergency Station on the Tybrisa Circle, creating a diffjcult and dangerous situation. This access also begins at a choke point for traffjc as vehicles come off the Strand going out 18th and vehicles also come in 18th. The dune fjeld has been severely eroded from Hurricanes Matthew and Irma. By closing 18th we remove one of the three most critical fmooding points realized during Storms Matthew and Irma and provide adequate and more effective emergency vehicle and DPW vehicle access to and from the beach. Of particular note is that sand is most effective in preventing storm surge fmooding when part of an entrenched dune system. It is vital that we build an integral dune system, with a combination of engineered dunes, restoring dunes, and adding improved dune fencing. PAGE 6 OF 14
EXISTING CONDITIONS - PEDESTRIAN PROMENADE CLUTTERED SIDEWALK - UNSIGHTLY BACK OF DUNES - POOR SIGNAGE - NO SHOWER OR FOOT WASH The existing concrete collector walk from the parking area to the beach access points is lacking in aes - thetics and functionality. The street furnishing such as benches, waste receptacles, lights and parking meters are randomly placed and in confmict with the pedestrian use of the promenade. The continuous sand-fence is unsightly and the quality of the back dune vegetation is variable. The 10’-30’ swathe of bare sand between the back of existing dunes and the walk is bare and under utilized. There is a great opportunity to upgrade both the usability and aesthetics of this area with hardscape and planting im - provements. Storm water infjltration can also be improved. The use, enjoyment, services and orientation of both visitors and residents can also be enhanced by an integrated design. OBSTRUCTED AND DATED PROMENADE TYBEE ISLAND DUNE RESTORATION 2018 WEAK LANDSCAPE/SAND STABILIZATION AT PAVILION ENTRANCE 17 TH PLACE IZLAR AVE 18 TH STREET 17 TH STREET SILVER AVE 16 TH STREET Ts CHU TER N 500’ WEAK AND DAMAGED SIGNAGE WITH INADEQUATE WASHING FACILITIES PAGE 7 OF 14
DESIGN SOLUTION - DUNE RESTORATION PLAN SILVER AVENUE IZLAR AVENUE ATLANTIC AVENUE 19 TH STREET 18 TH PLACE 18 TH STREET 17 TH PLACE 17 TH STREET 16 TH STREET Ts CHU TERRACE 1 3 2 1 SCALE: 1"=200' 0 100 200 400 DUNE RESTORATION & MAINTENANCE: EQUIPMENT: 2 TYBEE ISLAND DUNE RESTORATION 2018 DUNE 1: 43,475 SF @ 8’ AVERAGE HEIGHT = +/- 22,000 TONS (+/-11,000 CUYDS) OF SAND - BULLDOZERS - DUMP TRUCKS DUNE 2: 27,870 SF @ 6’ AVERAGE HEIGHT = +/- 10,000 TONS (+/- 5,000 CUYDS) OF SAND - BACKHOE LOADER - SKID-STEER LOADER DUNE 3: 1,500 SF @ 4’ AVERAGE HEIGHT = +/- 8,000 TONS (+/- 4,000 CUYDS) OF SAND - CEMENT TRUCKS (CROSSOVER) - HAND SHOVELS SAND RETENTION SYSTEM: +/- 3,800 LF - RUBBER TIRE LOADERS - VIBRATORY SMOOTH DRUM ROLLER PLANTING AND IRRIGATION (SAND STABILIZATION): +/- 190,000 SF SUBSURFACE STABILIZATION (VEHICULAR ACCESS): (1) PERMASHIELD SYSTEM - 6’ HT x 70 LF CROSSOVER DUNE: 84’ DEEP x 70’ WIDE @ 7’ MAX HEIGHT = 158 TONS (78 CUYDS) OF SAND 3 PAGE 8 OF 14 0 100 200 400
DESIGN SOLUTION - BEACH - BERM - PEDESTRIAN PROMENADE INTERFACE *HEIGHTS & LOCATIONS VARY RESTORED DUNE - 6’ - 8’ HT* ANGLE OF REPOSE: 30°-34° ≈ 1.5:1 BUFFER ZONE: *NEW RESTORED DUNE - 50’-75’ WIDTH PROTECTIVE PEDESTRIAN EXISTING BEACH EXISTING EXISTING PARKING AVERAGE ANGLE OF REPOSE: 30°-34° PLANTING LOUNGE SIDEWALK LOT STABILIZED WITH NATIVE, XEROPHYTIC, SALT TOLERANT SPECIES & SAND PADS- RETENTION +/- 10’x10’ STRUCTURES TYBEE ISLAND DUNE RESTORATION 2018 http://travel.home.sndimg.com/content/dam/images/travel/fullset/2014/05/06/dd/top-10-southern-california-beaches-venice-beach.rend.hgtvcom.1280.720.suffjx/1491584248480.jpeg PAGE 9 OF 14
Recommend
More recommend
