HomeMy WebLinkAboutPA2023-0051_20230222_Coastal Hazards Analysis Report dated 2-08-2023
P M A C O N S U L T I N G , I N C .
CONSULTING STRUCTURAL ENGINEERS
28161 Casitas Ct. PH. (714) 717-7542
Laguna Niguel, CA 92677
e-mail: consulting@pma-bg.com
February 8, 2023
Stephen Wan
David R. Olson Architects
470 Wald
Irvine, CA 92618
COASTAL HAZARDS ANALYSIS REPORT
Edwin Haronian and Sharona Cohen; Applicant
413 Via Lido Soud
City of Newport Beach, County of Orange
PMA Job #51922
Dear Mr. Wan,
PMA Consulting, Inc. is pleased to provide this report regarding Coastal Hazards Analysis for
the proposed development at the subject site. The site is adjacent to Newport Bay; thus, it may be
subject to Coastal Hazards such as, flooding, wave runup and erosion. This study investigates the
potential for the aforementioned hazards to impact the proposed development on the site over the next
75 years and addresses compliance with Coastal Hazards Analysis Report requirements and standards
of NBMC Section 21.30.15.E.2.
STATEMENT OF THE PREPARER’S QUALIFICATIONS
Plamen Petrov, P.E., the preparer of the Coastal Hazards Analysis Report on this project, holds
a Master of Science in Structural Engineering from University of Architecture, Structural Engineering
& Geodesy of Sofia, Bulgaria, and is a Licensed Civil Engineer by the State of California Certificate
No. C66947. For the last 23 years of his professional career, he has been actively involved in the
design and entitlement of many Waterfront Developments such as custom homes, seawalls, piers,
platforms, floating docks and marinas. A great number of Coastal Hazards Analysis Reports prepared
by him have been reviewed and accepted/approved by California Coastal Commission.
All the above being said, Plamen Petrov, P.E. shall be considered a qualified preparer for the
Coastal Hazards Analysis Report on this project.
Requirements in Appendix A for Step 1:
Establish the project sea level rise range for the proposed project’s planning horizon (life
of project) using the current best available science.
The State of California Sea-Level Rise Guidance 2018 update developed by the Ocean
Protection Council in close coordination with Policy Advisory Committee with representation
from California Natural Resources Agency, the Governor’s Office of Planning and Research, and the
California Energy Commission provides a bold, science-based methodology for state and local
1
governments to analyze and assess the risks associated with sea-level rise, and to incorporate Sea-
Level Rise into their planning, permitting, and investment decisions, and it is considered the current
best available science.
As reflected in the clouded area of the enclosed Table 28, based upon direct interpolation
of the data for High emissions 2090 & 2100 and Low Risk Aversion, over the project’s planning
horizon of 75 years, the estimated Sea-Level Rise (SLR) for year 2098 shall be approximately
3.10’, which is the Sea- Level Rise for the proposed project. Based on the highest high tide of
+7.88’MLLW (7.70’NAVD88) recorded in the project area, the above established Sea-Level Rise
will account for bay water level of +10.80’NAVD88.
As of March 23, 2021, City Council of City of Newport Beach has adopted new standards
establishing a minimum top of bulkhead/seawall elevation based on 5-year increments, reflected
in Table 2 below from City of Newport Beach Waterfront Projects Guidelines and Standards
Harbor Design Criteria for Commercial and Residential Facilities 2021 Edition.
Requirements in Appendix A for Step 2:
Determine how physical impacts from sea level rise may constrain the project site,
including erosion, structural and geologic stability, flooding, and inundation.
According to the enclosed Architectural Building Sections A4.1, finished 1st floor
elevation of the proposed development is at +10.59’ NAVD88=+10.79’MLLW which follows the
Base Flood Elevation established for the area. Based on the SLR established in Step 1 above, 1st
floor of the proposed structure will remain above High Tide Sea level approximately until year
of 2093, based on Low Risk Aversion. As we well know, majority of the public streets in Newport
Bay area are currently at much lower elevations than the subject site and they will flood due to
SLR way before the development on this site becomes subject to flooding.
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FLOODING HAZARD
The primary hazard due to flooding from the ocean waters for this site, like majority of the
sites located adjacent to Newport Bay, would be due to long term Sea-Level Rise. The current water
levels in Newport Bay are reflected on the enclosed Datums for Newport Bay Entrance.
While Sea-Levels have been Rising for decades, higher rates of raise are forecast for the
coming century because of climate change – see enclosed table 28. Increases can be attributed to
warmer temperatures, which cause water to expand, as well more liquid mass caused by melting of ice
caps. Current estimates of future SLR generally fall in the range of 5.4-6.7 ft for the year 2100. Global
warming may impact flooding in other ways as well. Warmer water could intensify North Pacific
storms, bringing greater wind and wave energy to shoreline in winter and higher intensity precipitation.
The Newport Beach Peninsula portion of the Pacific Institute California Flood Risk Map is
shown herein as OE S Quadrangle. The dark blue colored areas show the areas where a 100-year Sea-
Level Rise of 55 inches is added to the existing FEMA coastal flood elevation shown in light blue.
Obviously, the entire Newport Bay area will be affected if sea level rises 55 inches by the year 2100.
If the sea level rises in the next several decades as currently estimated, regional measures
to mitigate the potential flooding hazard shall be taken. As determined in Step 2 above, 1st floor
elevation of the proposed structure will remain above High Tide Sea level approximately until
year of 2093. In the event that SLR prediction of 6.70’ (Medium High-Risk Aversion) for year of
2100 holds true, block walls can be built along site property lines to elevation of +14.4’NAVD88.
Thus, the proposed development shall not be a subject to Flooding over the economic life of the
structure.
WAVE RUNUP AND TSUNAMI
Wave runup is the uprush of water from wave action on a shore barrier intercepting Stillwater
level. On steeply sloped shorelines, the rush of water up the surface of the natural beach, including
dunes and bluffs, or the surface of a manmade structure, such as revetment or vertical
wall can result in flood elevations higher than those of the crest of wind-driven waves. See Wave
Runup Sketch & ACSE Diagram below.
Due to its location, this site is not a subject to typical ocean waves and the associated wave
runup. Bay generated waves that may arrive at this site are very small wind waves and boat wakes.
These types of waves are generally dampened by the moored vessels and dock systems located in front
of the site and have no significant energy and runup effect. Tsunami type waves that approach from
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the ocean shoreline will likely not reach the site for several reasons. There is no significant near field
source of a tsunami like the geologic conditions of some other places on Earth such as Japan, for
example. A far field tsunami reaching the ocean shoreline will likely not reach the site because of the
distance and developments between the shoreline and this site. A near or far field tsunami propagating
into Newport Bay proper would likely cause a seiche or standing wave on the order of 1.3 feet
traveling within the bay. At the highest anticipated tide in Newport Beach of +7.88’MLLW this shall
result in slight overtopping of the bulkhead/seawall. Due to its very infrequent occurrence – 500-
year recurrence interval – tsunami should not be considered a significant impact over the life of
the proposed structure -75 years.
EROSION HAZARD
Erosion refers to the wearing or washing away of coastal lands. Beach erosion is a chronic
problem along many open ocean shores of the United States. To meet the needs for comprehensive
analysis of shoreline movement, the United States Geological Survey has conducted analysis of
historical shoreline changes along open ocean sandy shores of the conterminous United States and has
produced an Open-File Report 2006-1219 entitled “National Assessment of Shoreline Change Part 3:
Historical Shoreline Change and Associated Coastal land Loss Along Sandy Shorelines of the
California Coast”. The report looks at survey data of the following periods: 1800s, 1920s-1930s, and
1950s-1970s, whereas the lidar shoreline is from 1998-2002. The report looks at both long-term and
short-term changes. According to the report, the average rate of long-term shoreline changes for the
State of California was 0.2±0.1 m/yr., and accretional trend. The average rate of short-term shoreline
change for the state was erosional; with an average rate of -0.2±0.4 m/yr. The beach footprint of this
site is stabilized and not subject to significant long-term erosion. Review and analysis of historical
aerial photographs and field measurements for seawall repairs in the area show no change in the
position of the shoreline over the last several decades. The future shoreline changes over the next 75
years are assumed to be the same as in the previous several decades.
However, there is a rapid rate of SLR predicted in the next 75 years. If that prediction holds true, the
rapid SLR may accelerate shoreline erosion, but it shall not impact the structure on the subject lot over
its economic life.
CONCLUSION
In conclusion, flooding, wave runup and erosion will not significantly impact this
property over the proposed life of the development. Thus, need for a shoreline protective device
other than the above- mentioned site block walls is not anticipated over the economic life of the
proposed structure to protect it from flooding, wave runup and erosion.
The above conclusion was prepared based on the existing conditions, proposed drawings,
current projection of future Sea-Level Rise, and within the inherent limitations of this study, in
accordance with generally acceptable engineering principles and practices. We make no further
warranty, either expressed or implied.
PMA Consulting, Inc. appreciates the opportunity to work with you towards the successful
completion of your project. Should you have any questions regarding this report, please contact us.
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Respectfully submitted,
Plamen Petrov, P.E.
Principal
Enclosures:
Location Map
Aerial View
Topographic Survey
Architectural Sections A4.1
Table 28: Projected Sea-Level Rise (in feet) for Los Angeles 2098 Low Risk Aversion
Table 28: Projected Sea-Level Rise (in feet) for Los Angeles 2100 Low & Medium-High Risk Aversion
Datums for Newport Bay Entrance
Newport Beach OE S Quadrangle
5
6
7
8
9
Probabilistic Projections (in feet) (based on Kopp et al. 2014)
H++ scenario
(Sweet et al.
2017)
*Single
scenario
MEDIAN LIKELY RANGE 1-IN-20 CHANCE 1-IN-200 CHANCE
50% probability
sea-level rise meets
or exceeds…
66% probability
sea-level rise
is between…
5% probability
sea-level rise meets
or exceeds…
0.5% probability
sea-level rise meets
or exceeds…
Low
Risk
Aversion
Medium - High
Risk Aversion
Extreme
Risk Aversion
High emissions 2030 0.3 0.2 - 0.5 0.6 0.7 1.0
2040 0.5 0.4 - 0.7 0.9 1.2 1.7
2050 0.7 0.5 - 1.0 1.2 1.8 2.6
Low emissions 2060 0.8 0.5 - 1.1 1.4 2.2
High emissions 2060 1.0 0.7 - 1.3 1.7 2.5 3.7
Low emissions 2070 0.9 0.6 - 1.3 1.8 2.9
High emissions 2070 1.2 0.8 - 1.7 2.2 3.3 5.0
Low emissions 2080 1.0 0.6 - 1.6 2.1 3.6
High emissions 2080 1.5 1.0 - 2.2 2.8 4.3 6.4
Low emissions 2090 1.2 0.7 - 1.8 2.5 4.5
High emissions 2090 1.8 1.2 - 2.7 3.4 5.3 8.0
Low emissions 2100 1.3 0.7 - 2.1 3.0 5.4
High emissions 2100 2.2 1.3 - 3.2 4.1 6.7 9.9
Low emissions 2110* 1.4 0.9 - 2.2 3.1 6.0
High emissions 2110* 2.3 1.6 - 3.3 4.3 7.1 11.5
Low emissions 2120 1.5 0.9 - 2.5 3.6 7.1
High emissions 2120 2.7 1.8 - 3.8 5.0 8.3 13.8
Low emissions 2130 1.7 0.9 - 2.8 4.0 8.1
High emissions 2130 3.0 2.0 - 4.3 5.7 9.7 16.1
Low emissions 2140 1.8 0.9 - 3.0 4.5 9.2
High emissions 2140 3.3 2.2 - 4.9 6.5 11.1 18.7
Low emissions 2150 1.9 0.9 - 3.3 5.1 10.6
High emissions 2150 3.7 2.4 - 5.4 7.3 12.7 21.5
STATE OF CALIFORNIA SEA-LEVEL RISE GUIDANCE
APPENDIX 3: SEA-LEVEL RISE PROJECTIONS FOR ALL 12 TIDE GAUGES | 72
TABLE 28: Projected Sea-Level Rise (in feet) for Los Angeles
Probabilistic projections for the height of sea-level rise shown below, along with the
H++ scenario (depicted in blue in the far right column), as seen in the Rising Seas
Report. The H++ projection is a single scenario and does not have an associated
likelihood of occurrence as do the probabilistic projections. Probabilistic projections
are with respect to a baseline of the year 2000, or more specifically the average
relative sea level over 1991 - 2009. High emissions represents RCP 8.5; low emissions
represents RCP 2.6. Recommended projections for use in low, medium-high and
extreme risk aversion decisions are outlined in blue boxes below.
*Most of the available climate model experiments do not extend beyond 2100. The resulting
reduction in model availability causes a small dip in projections between 2100 and 2110, as well as
a shift in uncertainty estimates (see Kopp et al. 2014). Use of 2110 projections should be done with
caution and with acknowledgement of increased uncertainty around these projections.
10
Probabilistic Projections (in feet) (based on Kopp et al. 2014)
H++ scenario
(Sweet et al.
2017)
*Single
scenario
MEDIAN LIKELY RANGE 1-IN-20 CHANCE 1-IN-200 CHANCE
50% probability
sea-level rise meets
or exceeds…
66% probability
sea-level rise
is between…
5% probability
sea-level rise meets
or exceeds…
0.5% probability
sea-level rise meets
or exceeds…
Low
Risk
Aversion
Medium - High
Risk Aversion
Extreme
Risk Aversion
High emissions 2030 0.3 0.2 - 0.5 0.6 0.7 1.0
2040 0.5 0.4 - 0.7 0.9 1.2 1.7
2050 0.7 0.5 - 1.0 1.2 1.8 2.6
Low emissions 2060 0.8 0.5 - 1.1 1.4 2.2
High emissions 2060 1.0 0.7 - 1.3 1.7 2.5 3.7
Low emissions 2070 0.9 0.6 - 1.3 1.8 2.9
High emissions 2070 1.2 0.8 - 1.7 2.2 3.3 5.0
Low emissions 2080 1.0 0.6 - 1.6 2.1 3.6
High emissions 2080 1.5 1.0 - 2.2 2.8 4.3 6.4
Low emissions 2090 1.2 0.7 - 1.8 2.5 4.5
High emissions 2090 1.8 1.2 - 2.7 3.4 5.3 8.0
Low emissions 2100 1.3 0.7 - 2.1 3.0 5.4
High emissions 2100 2.2 1.3 - 3.2 4.1 6.7 9.9
Low emissions 2110* 1.4 0.9 - 2.2 3.1 6.0
High emissions 2110* 2.3 1.6 - 3.3 4.3 7.1 11.5
Low emissions 2120 1.5 0.9 - 2.5 3.6 7.1
High emissions 2120 2.7 1.8 - 3.8 5.0 8.3 13.8
Low emissions 2130 1.7 0.9 - 2.8 4.0 8.1
High emissions 2130 3.0 2.0 - 4.3 5.7 9.7 16.1
Low emissions 2140 1.8 0.9 - 3.0 4.5 9.2
High emissions 2140 3.3 2.2 - 4.9 6.5 11.1 18.7
Low emissions 2150 1.9 0.9 - 3.3 5.1 10.6
High emissions 2150 3.7 2.4 - 5.4 7.3 12.7 21.5
STATE OF CALIFORNIA SEA-LEVEL RISE GUIDANCE
APPENDIX 3: SEA-LEVEL RISE PROJECTIONS FOR ALL 12 TIDE GAUGES | 72
TABLE 28: Projected Sea-Level Rise (in feet) for Los Angeles
Probabilistic projections for the height of sea-level rise shown below, along with the
H++ scenario (depicted in blue in the far right column), as seen in the Rising Seas
Report. The H++ projection is a single scenario and does not have an associated
likelihood of occurrence as do the probabilistic projections. Probabilistic projections
are with respect to a baseline of the year 2000, or more specifically the average
relative sea level over 1991 - 2009. High emissions represents RCP 8.5; low emissions
represents RCP 2.6. Recommended projections for use in low, medium-high and
extreme risk aversion decisions are outlined in blue boxes below.
*Most of the available climate model experiments do not extend beyond 2100. The resulting
reduction in model availability causes a small dip in projections between 2100 and 2110, as well as
a shift in uncertainty estimates (see Kopp et al. 2014). Use of 2110 projections should be done with
caution and with acknowledgement of increased uncertainty around these projections.
11
12
13
Newport BeachNewport Beach
Costa MesaCosta MesaCosta MesaCosta MesaHuntington BeachHuntington Beach
¬«1
¬«55
¬«1
¬«55
117°52’30"W
117°52’30"W
117°55’0"W
117°55’0"W
117°57’30"W
117°57’30"W
118°0’0"W
118°0’0"W
33°37’30"N
33°37’30"N
33°35’0"N
33°35’0"N
33°32’30"N
33°32’30"N
33°30’0"N
33°30’0"N
407000mE
407000mE
08
08
09
09
410
410
11
11
12
12
13
13
14
14
15
15
16
16
17
17
18
18
419000mE
419000mE
3707
000
m
N
3707
000
m
N
08 08
09 09
3710 3710
11 11
12 12
13 13
14 14
15 15
16 16
17 17
18 18
19 19
3720 3720
3721
000
m
N
3721
000
m
N
This information is being made available for informational purposes only. Users of this informationagree by their use to hold blameless the State of California, and its respective officers, employees,
agents, contractors, and subcontractors for any liability associated with its use in any form. This work
shall not be used to assess actual coastal hazards, insurance requirements, or property values
and specifically shall not be used in lieu of Flood Insurance Studies and Flood Insurance Rate Maps issued by the Federal Emergency Management Agency (FEMA).
Data Sources: US Geological Survey, Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal ServicesCenter (CSC), Scripps Institution
of Oceanography, Phillip WIlliams and Associates, Inc. (PWA), US Department of Agriculture (USDA), California Coastal Commission, and National Aeronautics and Space Administration (NASA). Imagery from ESRI and i-cubed.
Created by the Pacific Institute, Oakland, California, 2009.
California Flood Risk: Sea Level Rise
00.511.520.25
Miles
01230.5
Kilometers
1:
2:
3:
4:
5:
6:
7:
8:
Seal Beach
Newport Beach
Tustin
not printed
Laguna Beach
not printed
not printed
not printed867
1 2 3
54
§¨¦
£¤
")
¬«
Interstate
US Highway
State Highway
County Highway
Grid coordinates:
UTM Zone 11N meters
Adjoining Quadrangles:
Map extents match USGS 7.5 minute topographic maps
Project funded by the California Energy Commission’s Public Interest Energy Research Program, CalTrans,and the California Ocean Protection Council
Newport Beach OE S Quadrangle
NAD83 GCS degrees
Coastal Zone Boundary
Current Coastal Base Flood
(approximate 100-year flood extent)
Sea Level Rise Scenario Coastal Base Flood + 1.4 meters (55 inches)
Landward Limit of Erosion High Hazard Zone in 2100
14