HomeMy WebLinkAboutPA2022-0306_200230119_Coastal Hazards report dated 10-31-22WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
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October 31st, 2022
KPI Architect & Planning 17752 Mitchell N. Suite ‘C’ Irvine, CA 92614
RE: COASTAL HAZARDS ANALYSIS REPORT FOR COASTAL
DEVELOPMENT PERMIT
Mr. Jeff Logan; Applicant 2286 Channel Road City of Newport Beach, County of Orange
WSA Job #7543
Dear Mr. Logan,
William Simpson & Associates 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
Masoud Jafari, S.E., the preparer of this report, holding a Bachelor of Science Degree in Structural Engineering from Tehran, Iran, is a Licensed Civil Engineer - Certificate No. C43673 - and Structural Engineer - Certificate No. S3812 - by the State of California. He joined the company
in 1987 and is now partly the owner, serving as the principal in charge of the company. He has
been actively involved in the design and entitlement of waterfront developments such as custom homes, seawalls, piers, platforms, floating docks and marinas for over 30 years.All the above being said, Masoud Jafari, S.E. shall be considered a qualified preparer for the Coastal Hazard Report on this project.
PA2022-0306
WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
2
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 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 Medium-High Risk Aversion,
over the project’s planning horizon of 75 years, the estimated Sea-Level Rise (SLR) for year
2095 shall be 6.00’, 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 +13.70’NAVD88.
As it has been requested on previous projects by the City of Newport Beach Planning
Department, we have enclosed Table 28 with interpolated data for High emissions 2090 &
2100 and Low Risk Aversion. Based on that interpolation, the estimated SLR for year 2095
shall be approximately 2.95’, which is much smaller than the governing estimated SLR for
Medium-High Risk Aversion
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 section 1.12 & Topographic Plan, top of 1st
floor slab elevation of the proposed development is at +12.15’ NAVD88=+12.33’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 2075. 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.
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.
PA2022-0306
WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
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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 below High Tide sea level
approximately until year of 2075. Utilizing Flashing and Waterproofing up to +13.7’
NAVD88, as reflected on the enclosed detail, and sandbags or other methods deployed at
doors openings shall keep the building protected from flooding until year of 2095. In the
event that SLR prediction of 6.00’ for year of 2095 holds true, the existing wall has been
designed and detailed to accommodate raise to top of wall elevation of +13.7’NAVD88, as
reflected on the enclosed S-1 thru S-2.
Per the current City of Newport Beach Waterfront Projects Guidelines and
Standards. The existing shore protection shall be increased to the City minimum elevation
of +10.9 feet NAVD88 as part of the proposed development. (See attached sheet S-2, Detail
K)
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.
PA2022-0306
WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
4
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 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
PA2022-0306
WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
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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. The existing seawall/bulkhead is
required to protect the proposed structures on the lot, the adjacent properties, public
facilities and infrastructure; thus, it can’t be removed. Removal of the seawall/bulkhead will
result in erosion and undermining the foundations of the structures and site walls at the
subject site and both adjacent sites. Once the existing seawall/bulkhead is
repaired/reinforced in compliance with the enclosed drawings S-1 and S-2, need for a new
shoreline protective devise shall not anticipated over the economic life of the proposed
development to protect it from flooding, wave runup or erosion. If found not adequate for
the actual sea level rise over the next 75 years, the existing seawall/bulkhead assembly allows
to be increased in height to+13.7’NAVD88, without further seaward encroachment. If during
this period the seawall/bulkhead displays any sign of distress that requires immediate
attention, due to some unforeseen catastrophic or disastrous events, it should be repaired or
replaced at that time accordingly, without seaward encroachment from its current location.
Per the current City of Newport Beach Waterfront Projects Guidelines and
Standards. The existing shore protection shall be increased to the City minimum elevation
of +10.9 feet NAVD88 as part of the proposed development.( See attached sheet S-2, Detail
K)
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.
William Simpson & Associates 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.
Respectfully submitted, Masoud Jafari, Principal
PA2022-0306
WILLIAM SIMPSON & ASSOCIATES, INC.
CONSULTING STRUCTURAL ENGINEERS
23 ORCHARD, SUITE 250 PH. (949) 206-9929
LAKE FOREST, CA 92630 FAX (949) 206-9955
www.wsase.com e-mail: Tmail@wsase.comT
6
Enclosures
Page #
Location Map 7 Aerial View 8
Table 28: Projected Sea- Level Rise ( in Feet) For Los Angeles 9-10
Topographic Survey 11
Architectural Section 12 Waterproofing Detail 13
Datums for Newport Bay Entrance 14-16
Newport Beach OE S Quadrangle 17
Preliminary Helical Anchor Design 18-19
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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.
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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.
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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
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