The city engineer presented on challenges facing Miami Beach due to its low elevation as a barrier island. King tides in 2019 caused minor flooding in several areas. NOAA projects that annual flood days will increase significantly by 2030 and 2050 as sea levels continue to rise. The city's flood mitigation programs have helped avoid over 60 flood events and raised road elevations are directly correlated with reduced flooding. Before and after photos show examples of infrastructure projects that mitigated flooding.

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Commission Meeting
December 11th, 2019
Presented by:
Nelson Perez-Jacome P.E.
City Engineer

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Miami Beach: Challenges of a low elevation barrier island

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Low Elevation Seawalls / Limestone and Permeable Soils
MIAMI BEACH SEA LEVEL RISE
ADAPTATION CHALLENGES
1. Topography & Geology
2. Aging Infrastructure
3. High groundwater
4. Limited Data

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Sunny Day Flooding is already impacting us…
Indian Creek and 32nd Street

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NOAA Tide Water Elevations – King Tides 2019
Minor Flooding
Major Flooding
Moderate Flooding
Predicted
Tide 0.975’
NAVD
Verified
Tide 2.18’
NAVD
Virginia Key, Biscayne Bay

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2019 King Tides – Year in Review
• This year peak king tides were
experienced from September
26th through October 3rd.
• The stormwater system
functioned as expected but
higher than normal tides
caused minor flooding or
standing water in some areas.
• Most affected areas were:
Indian Creek, North Bay Road,
North Beach and Commerce
Street.

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Standing Water Reports King Tides
Sept 26th - Oct 3rd 2019
18 flood/standing water related
complaints were reported through
EGov and by Calls to the Public Works
Department Control Room
Crisis Track Reported Standing
Water at 140 Locations on Sep. 28th, 2019
• 82 - Green: Standing Water 0” – 3”
• 46 - Orange: Significant Standing Water 3” – 6”
• 12 - Yellow: Stormwater Flooding 6” – 12”

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King Tides September 26th to October 3rd 2019 in photos

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King Tides September 26th to October 3rd 2019 in photos

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NOAA reports the frequency and duration of floods due to
High Tides is increasing…
Median high tide floods per year (black bars) from 1920-2018
(national median).
The annual-median rise in coastal sea levels is also shown (blue line)
The characterization of the trends in annual HTF frequencies, with 42
locations now accelerating and 25 linearly increasing with time.
In 2018 the national median annual high tide floods (HTF) frequency reached 5 days, which tied the historical record of 2015

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NOAA Reports annual flood records are expected to be broken again next
year and for the years and decades to come…
Since 2000 our region has seen a 200 to 250% increase in high
tide related flood events.
If this trends continues our region will likely see an average of 7 to 15 days
of flooding by 2030 and 25 to 70 days by 2050. Miami Beach may see more
days of flooding due to its lower elevations.

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2019 SLR Projections – Sea Level will continue to rise
30-Year
Design
Horizon
2050
12” (1
FT)

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2015 vs. 2019 SLR Projections

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Our Program is Working…
Indian Creek and 27th Street

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Sunset Harbour
2.8 ft
Hurricane Irma
Sept 10 - 2017
2.3 ft
KING TIDES
Oct 5 -2017
1.7 ft
Old Crown
Road Elev.

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Avoided 60 Tidal Flooding Incidents
Due to Road Raising at Sunset Harbour
January 2017 – October 2019
July 2017 Jan 2018 July 2018 Jan 2019 Jul 2019
Water
Lever
in
Feet

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Miami Beach Tidal Gauges – King Tide 2019
• Miami Beach tidal gauges indicate a
maximum tidal level of 2.25 feet
NAVD on Oct. 1.
• This graph shows that we avoided
eight tidal flooding events due to
road raising in Sunset Harbour during
Sept. 26-Oct. 3.
• 2017: 17 events avoided
• 2018: 11 events avoided
• 2019: 32 events avoided
through October 2019

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Avoided flooding is directly correlated with higher elevations
1.27’ NAVD
1.80’ NAVD

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Flood Mitigation Results Purdy Ave and Dade Blvd
AFTER
BEFORE Tides: 1.27 ft NAVD 10/11/11 Tides: 1.88 ft NAVD 10/15/19

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Flood Mitigation Results Purdy Ave and 20th Street
BEFORE Tides: 1.27 ft NAVD 09/11/11 Tides: 1.88 ft NAVD 10/15/19
AFTER

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Flood Mitigation Results Purdy Ave - North of Dade Blvd
BEFORE Tides: 1.80 ft NAVD 10/29/12 Tides: 1.88 ft NAVD 10/15/19
AFTER

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Flood Mitigation Results Palm Island 316 South Coconut Ln
BEFORE AFTER Tides: 1.88 ft NAVD 10/15/19
Tides: 1.40 ft NAVD 10/17/12

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Flood Mitigation Results Palm Island 303 North Coconut Ln
AFTER
BEFORE Tides: 1.42 ft NAVD 10/17/12 Tides: 1.88 ft NAVD 10/15/19