PowerPoint Presentation · flood volume in Power and Kinney Street watersheds ... o Chaparral St.
15
5/25/2017 1 © 2016 HDR, Inc., all rights reserved. City of Corpus Christi Downtown 2D Mapping Effort Brandon Hilbrich, PE, CFM Jake Fisher, PE, CFM Curtis Beitel, PE, CFM Project Background Information Modeling Approach Model Development Results Next Steps Overview © 2016 HDR, Inc., all rights reserved. Project Background Information
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Transcript of PowerPoint Presentation · flood volume in Power and Kinney Street watersheds ... o Chaparral St.
5/25/2017
1
© 2016 HDR, Inc., all rights reserved.
City of Corpus Christi
Downtown 2D Mapping Effort
Brandon Hilbrich, PE, CFM
Jake Fisher, PE, CFM
Curtis Beitel, PE, CFM
Project Background Information
Modeling Approach
Model Development
Results
Next Steps
Overview
© 2016 HDR, Inc., all rights reserved.
Project Background Information
5/25/2017
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Background
Corpus Christi has participated in
NFIP since 1973
Previous Effective FIRMo July 1985
o Protected area as Zone B
Background
FEMA started FIS update in 2007
FEMA requested certification from City
in March 2012o “Earthen levee on west side” (Salt Flats)
o “Small floodwall on northeast corner”
Draft FIRM in July 2012o Protected area as Zone AO w/ (Depth 3 FT) &
(Depth 2 FT)
o Bay Zone VE (EL 15)
o Surge = 8.4’
Background
FEMA’s Levee Analysis & Mapping Procedures (LAMP)o Proposed Approach in December 2011
o Final Approach in July 2013
FEMA Initiated Nueces County LAMP Pilot Studyo Initial Documentation
o Salt Flats Levee & Museum Floodwall
Local Levee Partner Team (LLPT) Meetingso On site and Monthly status calls
Submittals to FEMA
Review LAMP documents
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Background
FEMA and City agreed to show protected
area as a “Seclusion Area”o Allows Preliminary Nueces County FIRMs to
become Effective
Once LAMP Pilot Study is complete,
FEMA will update the FIRM map
Purpose
Downtown Flood Protection Systemo Two Storm Water Pump Stations
o Complex storm drain network
o Variable tailwater
Solution = 1D/2D XP-SWMM Model
Better understanding of the current level of
protection.o Existing Levee and Flood Protection Wall Impacts
o Pump Station Effectiveness
Identify proposed improvements to the
Downtown areao Improvements to existing flood protection system
o New drainage infrastructure
Downtown Flood Protection System
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Study Area
Two Major Watersheds of Inner Harbor Basino Salt Flats Watershed
• 2.5 sq mi
• 81% Urbanized
o Downtown Watershed
• 1.5 sq mi
• 84% Urbanized
13.9 miles of storm drain system
1.6 miles of open channel
Downtown area protected by 3.0 miles flood
protection wall
o Downtown Elevation: 2 to 7 feet
o Flood Protection Wall (top elevation): 12 to 14 feet
© 2016 HDR, Inc., all rights reserved.
Project Approach
Update hydrology using latest available data
Include Seawall Overflow analysis for current future (50-year and 100-
year) sea level rise conditions
Develop existing conditions XPSWMM 2014.1 1D/2D model
Identify 20 structures within Seclusion Area for finished floor survey
Develop, model, and evaluate impacts of 4 concept level CIP projects
Scope of Work
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Conform to City of Corpus Christi Drainage Design Manual and FEMA
Mapping Standards
Storm surge defined based on USACE sea level rise guidance
Model Design Criteria
Existing Conditions Analysis
o 9 Annual Chance Event (ACE) conditions
o 24-hour storm duration
Proposed Conditions Analysis
o 1% ACE under current sea level
o 4 concept level CIP projects
© 2016 HDR, Inc., all rights reserved.
Model Development
Available Data
GIS Data
o1-ft Contours and DEM (2011)
oSSURGO Soils for Nueces County
(2008)
oCity of Corpus Christi Landuse (2016)
oCity of Corpus Christ Downtown Building Planimetrics (2012)
oCity of Corpus Christ Storm Drain
Network Data (2016)
Concurrent Project
o S. Staples St. Improvements (2015) under construction
Record Drawings
oStorm Drain Systems (1938-2011)
oSalt Flats Channel (2009-2011)
oPower St. & Kinney St. Pump Stations (1948 & 2008)
oSeawall Improvements (2002-2004)
Pump Station Operations
Previous Studies
oCity-Wide Storm Water Master Plan
(On-going)
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Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
5/25/2017
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Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
5/25/2017
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Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
Blucher Arroyo
Coliseum
Furman
Kinney Street
Port Area
Power Street
Salt Flats
Major Drainage Systems
SWMP Inner Harbor Basin subdivided
into 136 subbasins
o Major SD > 30 inch
o Minor SD > 24 inch outfalls directly to
Corpus Christi Bay along Seawall
o Major SD Junctions
o Open channels throughout system
Delineated using 2011 1-ft LiDAR data
Hydraulic systems defined using City
network dataset, LiDAR, and as-builts
o Size, length, material
o Inverts, spill crests
Assumptions
o SD not inlet controlled
o Does not include entire SD network (manholes,
bends, and lateral systems)
1D Model Hydrology & Hydraulics
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1D Components linked to
2D Surface
Rainfall runoff, wave
overtopping, and storm
surge
o Overland areas
o Undefined open channels
2D Model Application
Update figure w.
overland flow image w.
velocity vectors
Input Data
o 2011 LiDAR DEM
o Breaklines
o 2D Landuse Roughness
One grid extents for entire model (30’ cell)
2D Model Data
Calculated RSLR for nearest NOAA station
o 50-year = +1.3 feet
o 100-year = +3.0 feet
Used peak WSELs from FEMA FIS (2012);
Applied RSLR to peak WSELs for future
conditions
Determined peak overtopping flow per foot of
Seawall
Storm surge stage and Overtopping flow
hydrographs used in model as boundary
conditions
Seawall Overtopping Analysis
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Tailwater – Storm Surge
Initial Depth Consideration
o Sea Level Condition
o Backflow Prevention
o Initial pump station depths
Wave Overtopping Flow
Levee Gates closed
System Boundary Conditions
Photo of SFL gate on Broadway St.
© 2016 HDR, Inc., all rights reserved.
Results
10% and 1% ACE
inundation depths mapped for entire study area
Overland flow transfer between watersheds
Local system inefficiencies
Existing Conditions
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Max WSELs (CSL conditions) determined
for all storm events within Seclusion Area
System assessment summarized by
specified Zones
Source of flooding for 1% ACE identified
Existing Conditions
Wave overtopping accounts for ≤10%
flood volume in Power and Kinney Street
watersheds
Depths increased by 0.5’ – 2’ along
Shoreline Blvd
Increases less than 0.5’ in Downtown low
areas
Existing Conditions
XPSWMM 1% ACE inundation mapping compared to FEMA
LAMP FLO-2D results developed in September 2015
FEMA LAMP Study Comparison
5/25/2017
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FEMA LAMP Study Comparison
Workshop held with City
to discuss existing
conditions
20 Buildings selected for
finished floor survey
Design constraints set
based on priority area
identified by City
Design Constraints
Evaluated 4 scenarios
o Existing Blucher-Arroyo System failure and improvements
o Proposed Hughes St. Pump Station (Design completed)
o Two additional project improvement scenarios to meet Design
Constraints
Simulated for 1% ACE under current sea level conditions only
Cost Estimates not developed for improvement options
Proposed Improvements
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Oct. 2002 Event
Road failure 10’ wide
Rainfall data not available
1% ACE Results
o 70 min. surcharge duration
o Peak flow = 85 cfs
o Flood depth near 1’ in area
o Did not impact Downtown
system near Power St.
Pump Station
Blucher-Arroyo System Failure
System Breach
Location
Blucher-Arroyo System Failure
System Breach
Location
Blucher-Arroyo System Failure
5/25/2017
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Acquired 2009 Design
Plans
SD Improvements
o N. Mesquite St.
o Hughes St.
o Chaparral St.
Relieve Salt Flats ditch
New pump station
Hughes St. Pump Station
1-9’x6’ (in)
2-6’x5’ (in)
2-8’x6’ (out)1-48” (in)
Hughes Street Pump Station
Option 1 Improvements
2-6’x3’ (in)
1-36”
Channel Improvements
Salt Flats Lift Station
Upsize to 48” RCP along
Lawrence St.
Results:
o Max 0.7’ flood depth reduction
o Flooding eliminated at
Education Service Center Region 2 (Bldg No. 5)
o Localized benefit
Option 2 Improvements
1-48”
5/25/2017
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City of Corpus Christ to provide existing conditions floodplain mapping to
FEMA for consideration in mapping the Seclusion Area.
Use holistic model to evaluate CIP projects selected for the recent City Bond
program.
Moving Forward
Contact Information
Curtis Beitel, PE, CFM
D 817.333.2817 M 817.521.5761
Brandon Hilbrich, PE, CFM
D 210.841.2835 M 361.275.4017
Jake Fisher, PE, CFM
D 972.960.4489
Questions
Questions?
