DISCOVERY STREET LEVEE SYSTEM
EMERGENCY RESPONSE PLAN
August 2026
Prepared by:
RICK
Water Resources Division
Prepared for:
City of San Marcos
DISCOVERY STREET LEVEE SYSTEM
EMERGENCY RESPONSE PLAN
Final Draft for FEMA LOMR / Levee Accreditation Support San Marcos Creek District - Phase 1
City of San Marcos, California
Prepared for Prepared by Date Status
City of San Marcos RICK August 2026 Final Draft
Document Contents
• 1. Plan Purpose and Regulatory Basis
• 2. Levee System and Interior Drainage Description
• 3. Roles and Responsibilities
• 4. Flood Warning, Monitoring, and Activation Trigg ers • 5. Emergency Response Actions
• 6. Interior Drainage Operations
• 7. Evacuation Coordination and Public Warning
• 8. Training, Inspection, Documentation, and Update s
• 9. FEMA Requirements Crosswalk
• 10. Source Go-Bys and Justification Matrix
• 11. References
1. Plan Purpose and Regulatory Basis
The purpose of this Emergency Response Plan (ERP) is to define monitoring, communication, inspection, and emergency-response procedures for the Discovery Street Levee System and associated interior drainage facilities along the south side of San Mar cos Creek between Via Vera Cruz and Bent Avenue.
The plan is intended to support FEMA levee accredit ation review for a Letter of Map Revision (LOMR) by addressing emergency preparedness and operation criteria for an accredited levee system.
This plan is organized to directly address the FEMA review comment requesting documentation of: (1) the flood warning system used to trigger emergency operations; (2) a formal plan of operation for closures and mechanized interior drainage features; (3) the responsible person by name or title; (4) public evacuation planning for communities within the levee system; and (5) official adoption by the community or responsible agency.
Regulatory / guidance source Requirement or guidance used in this plan 44 CFR 65.10(c)(2), Interior
drainage systems
Requires documentation of the flood warning system, formal operating actions and responsibility assignments, manual backup for automatic systems, and periodic inspection/testing of interior drainage systems associated with levees.
44 CFR 65.10(c), Operation
plans and criteria
Requires closure devices or mechanical drainage systems to be operated under an officially adopted operation manual and under the jurisdiction of a federal, state, or NFIP-participating community agency.
FEMA Guidance for Flood Risk
Analysis and Mapping: Levees,
Guidance Document 95
Provides FEMA mapping/accreditation procedures for levees and explains documentation expectations for accredited levee systems.
DHS/FEMA Emergency
Preparedness Guidelines for
Levees: A Guide for Owners and
Operators
Recommends emergency preparedness plan content including roles, communication protocols, warning triggers, feature maps, training, exercises, and flood-fighting preparation.
Cal OES Flood Preparedness
Guide for Levee Maintaining
Agencies
Provides California levee-maintaining-agency planning guidance using SEMS/ICS, local/operational-area coordination, flood-fight preparation, and documentation practices.
2. Levee System and Interior Drainage Description
The Discovery Street levee and drainage system are part of the San Marcos Creek District Phase 1 Project. A Technical Memorandum titled “San Marcos Creek District – Phase 1, Discovery Street Interior Drainage System Study” dated May 5 and prepared by Parsons summarizes the hydraulic improvements to Discovery Street between Via Vera Cruz and Bent Avenue. The Technical Memorandum (the memo) has been utilized for this Emergency Response Plan. The project includes a levee on the south side of San Marcos Creek between Bent Avenue and Via Vera C ruz and replacement/bridge improvements at Via Vera Cruz and Bent Avenue designed to convey the ultimate 100-year flood event.
Feature Description for ERP use
Watercourse San Marcos Creek, an east-to-west trending perennial watercourse entering the project area near SR-78 culverts and exiting under Discovery Street near San Marcos High School.
Levee / flood protection
feature
Levee along the south side of San Marcos Creek between Bent Avenue and Via Vera Cruz, intended to protect public and private facilities from the 100-year San Marcos Creek floodplain.
Feature Description for ERP use
Bridge interfaces Via Vera Cruz bridge and Bent Avenue bridge are associated Phase 1 hydraulic improvements. Bridge openings should be inspected during flood events for debris, obstruction, scour, or damage that could affect conveyance.
Interior drainage system Series of inlets, headwalls, drainage pipes, and junction structures along Discovery Street routing onsite and offsite runoff by gravity flow to San Marcos Creek.
Interior drainage critical
locations
Upstream headwall/ditch locations H-5 and H-6 within or adjacent to LakeView Mobile Estates, identified in the memo as critical upstream hydraulic locations.
Mechanical systems /
closures
The memo describes a gravity system and explicitly states that it does not utilize a tide gate structure. No pump station, mechanical closure, or automatic control feature is identified in the reviewed memorandum. If such features exist in the as-built system, this plan must be revised to include operating instructions, manual backup, and annual testing.
2.1 Key Hydraulic Information from Technical Memorandum Item Value / finding Use in ERP
Ultimate 100-year
FEMA WSE at
proposed interior
outfall, Creek Sta.
50+67.637
534.23 ft NAVD88 Primary high-water trigger and exterior tailwater condition for field monitoring.
Ultimate 50-year
FEMA WSE at
proposed interior
outfall, Creek Sta.
50+67.637
533.46 ft NAVD88 Early action trigger / elevated tailwater monitoring threshold.
Coincidental-event
basis
Area ratio approximately
275; 25-year interior flow
used with 100-year San
Marcos Creek condition
per San Diego County
hydraulic guidance cited in
memo.
Supports ERP emphasis on simultaneous creek
tailwater and interior drainage monitoring.
Item Value / finding Use in ERP
H-5 HGL, 100-year
Creek / 25-year local
coincidental
condition
534.85 ft Field check point for maximum interior HGL in LakeView engineered ditch area.
H-6 HGL, 100-year
Creek / 25-year local
coincidental
condition
535.08 ft Field check point for maximum interior HGL in LakeView engineered ditch area.
Interim FEMA
backwater
conclusion
Interim 100-year WSE
531.55 ft; H-5 and H-6
upstream inverts 531.78 ft
and 532.54 ft; backwater
cannot reach private
properties in interim
condition.
Supports monitoring emphasis on ultimate
condition and private-property interface.
Ultimate FEMA
backwater
conclusion
At ultimate 100-year WSE
534.23 ft, backwater may
reach LakeView Mobile
Estates property if there is
no positive interior flow,
but is contained within
existing engineered
concrete ditches.
Supports ditch inspection, alerting, and public
notification trigger if water approaches top of
ditch/property elevations.
3. Roles and Responsibilities
Function Responsible title /
agency Primary responsibilities
Plan owner / levee
operator
City of San Marcos Public
Works Director or
designee
Maintain and implement this ERP; ensure
annual inspections, training, and updates;
coordinate with engineering, maintenance, and
emergency management staff.
Field operations lead Public Works Operations
Manager / Maintenance
Superintendent
Mobilize field crews; inspect levee, bridges,
storm drain outfall, inlets, headwalls, and
LakeView ditches; initiate debris removal and
flood-fighting actions when safe.
Function Responsible title /
agency Primary responsibilities
Emergency
management
coordination
City Emergency Services /
San Marcos Fire
Department / County
Operational Area
Coordinate emergency notifications, evacuation
warnings/orders, sheltering, public information,
and SEMS/ICS activation.
Engineering support City Engineer or retained
civil engineer
Provide technical evaluation of levee distress,
seepage, erosion, bridge scour, storm drain
backwater, and post-event condition
assessments.
Public information City Public Information
Officer
Issue public messaging in coordination with
emergency management and public safety
officials.
Law enforcement /
traffic control
San Diego County Sheriff /
local law enforcement
Support evacuation, road closures, and access
control if directed by incident command.
3.1 Activation Authority
The Public Works Director, Emergency Manager, Incid ent Commander, or authorized designee may activate this ERP when any trigger in Section 4 is met. Activation may be partial (monitoring only), operational (field response), or emergency (incident command and public protective action coordination).
4. Flood Warning, Monitoring, and Activation Triggers
Because the interior drainage system is hydraulical ly controlled by San Marcos Creek tailwater and gravity drainage, flood warning should combine regi onal forecast information, local field observations , and project-specific water-surface elevations from Section 2.1 of this ERP. Final implementation should include a surveyed staff gage or equivalent referen ce at/near the interior system outfall and field-ch eck points at H-5 and H-6.
Trigger level Trigger condition Required actions
Level 0 - Normal /
readiness
No flood watch or heavy-rain
forecast affecting San Marcos
Creek; system in normal condition.
Maintain annual inspections and update
contact list. Confirm access to outfall,
levee patrol route, bridge crossings, and
LakeView ditch inspection points before
rainy season.
Level 1 - Flood
Watch /
preparedness
NWS forecast, local forecast, or
City/County alert indicates potential
significant rainfall or San Marcos
Creek rise; or field crews observe
Notify Public Works operations lead.
Review staffing and equipment. Inspect
bridge openings, inlets, headwalls, and
outfall when safe. Prepare to monitor
Trigger level Trigger condition Required actions
rising creek levels, debris
accumulation, or nuisance ponding.
outfall tailwater and H-5/H-6 ditch
locations.
Level 2 - High
Water / active
monitoring
Observed or forecast San Marcos
Creek water surface approaches
the 50-year/early action tailwater at
the Discovery outfall (approx.
533.46 ft NAVD88), or interior
drainage ditches show sustained
ponding/backwater.
Activate field monitoring. Patrol levee and
bridge interfaces. Check for debris,
erosion, seepage, blocked inlets, outfall
obstruction, and water in H-5/H-6 ditches.
Coordinate with emergency management
and document conditions with photos and
logs.
Level 3 -
Emergency
operations
Observed or forecast San Marcos
Creek water surface reaches or
exceeds the ultimate 100-year
tailwater at the outfall (approx.
534.23 ft NAVD88), or backwater
reaches LakeView ditch areas, or
observed levee distress, seepage,
sand boils, erosion, bridge
obstruction, roadway flooding, or
imminent overtopping occurs.
Activate incident coordination. Increase
patrol frequency. Notify City emergency
management, Fire, law enforcement, and
County Operational Area as appropriate.
Prepare public warning/evacuation
messaging for areas landward of the
levee. Conduct flood-fighting only where
safe and under qualified supervision.
Level 4 - Failure /
uncontrolled
flooding
Confirmed levee breach,
uncontrolled overtopping, structural
distress creating imminent failure
potential, or interior flooding
threatens occupied structures.
Public safety incident command leads
response. Issue evacuation
warnings/orders through appropriate
authorities. Close unsafe roads and
bridges. Maintain life safety priority; defer
engineering repairs until safe access is
available. Begin damage documentation
and recovery planning.
4.1 Monitoring Sources
• National Weather Service watches, warnings, and qu antitative precipitation forecasts for the San Marcos Creek watershed.
• County of San Diego Operational Area alerts and em ergency management notifications. • City field observations of San Marcos Creek water level, bridge debris, levee condition, storm drain outfall condition, and interior drainage ponding.
• USGS or other available stream/rain gage informati on for San Marcos Creek or nearby watershed indicators, if applicable and confirmed by the City.
• Project-specific surveyed staff gage or reference mark at the Discovery Street interior drainage outf all, recommended for final plan implementation.
5. Emergency Response Actions
Phase Actions
Preparedness /
pre-season
Review ERP and contact list; inspect levee, bridge interfaces, outfall, inlets, headwalls, and LakeView ditches; confirm access routes; clear sediment/debris as needed; verify availability of barricades, pumps if used by City, sandbags, rock, plastic sheeting, lighting, radios, PPE, and traffic control devices.
Initial response Upon Level 1 activation, assign a field lead, initiate situation log, confirm forecast and field conditions, and inspect the Discovery outfall, H-5/H-6 ditch areas, Via Vera Cruz bridge, Bent Avenue bridge, Discovery Street drainage inlets, and levee slopes/crest.
High-water patrol During Level 2 or higher, patrol at intervals set by the field lead based on rate of rise, weather, daylight, access, and safety. Inspect for seepage, sand boils, sloughing, erosion, animal burrows, cracking, settlement, low spots, debris blockage, bridge scour, and storm drain backwater.
Flood fighting Use sandbags, temporary diversion, inlet clearing, erosion protection, and emergency pumping only when directed by the incident/field lead and only where safe. If a pump is used temporarily, document location, capacity, start/stop times, discharge point, and observed performance.
Public safety
coordination
If observed or forecast conditions could affect residences, mobile homes, Discovery Street, bridge approaches, or evacuation routes, notify emergency management and public safety officials immediately. Public warning or evacuation decisions remain with the appropriate emergency authority.
Post-event Inspect entire levee and drainage system after water recedes. Document high- water marks, erosion, sediment deposition, debris, blocked drains, damaged slopes or pavement, and ditch/backwater extent. Complete corrective maintenance and update this ERP based on lessons learned.
6. Interior Drainage Operations
The 2016 memorandum describes the Discovery Street system as a gravity interior drainage system discharging to San Marcos Creek. It does not descri be pumps, tide gates, flap gates, sluice gates, or other mechanized drainage features. Therefore, this draft ERP treats the operational plan as a monitoring, inspection, debris-removal, and emergency-response plan rather than a mechanical-closure operating procedure. If levee internal drainage sys tems are updated or changed to mechanical components, this section must be revised before adoption.
Condition Expected system behavior Operational response Normal rainfall / low
creek tailwater
Runoff captured by inlets and
headwalls and routed through
pipes/junction structures by gravity
to San Marcos Creek.
Maintain inlets, pipes, headwalls, and
outfall free of debris and sediment.
High San Marcos Creek
tailwater with positive
interior runoff
Interior HGL rises but modeled
trunk-line HGL/EGL remain
subsurface for the selected
design; H-5/H-6 ditches are the
critical locations for localized
impacts.
Monitor outfall tailwater and H-5/H-6
ditch water levels. Confirm drainage
remains within engineered ditches
and does not threaten residential
structures.
Ultimate 100-year creek
tailwater without
positive interior flow
Backwater from San Marcos
Creek can extend into the
LakeView Mobile Estates ditch
area under ultimate conditions, but
the memo states it remains
contained in existing engineered
concrete ditches.
Coordinate with emergency
management if backwater
approaches top of ditch, occupied
structures, or evacuation/access
routes. Document extent and high-
water marks.
Obstruction / blocked
inlet / bridge debris
Hydraulic performance may be
reduced, potentially increasing
interior ponding or localized
flooding.
Remove debris only if safe. Barricade
hazardous areas. Notify emergency
management if blockage threatens
structures or public access.
System distress or
unexpected flooding
Observed conditions exceed
assumptions in technical
memorandum.
Escalate to Level 3 or 4, notify City
Engineer/emergency management,
and consider evacuation coordination
if occupied structures may be
affected.
6.1 No-Mechanical-System Statement for FEMA Review
Based on the reviewed 2016 technical memorandum, the Discovery Street interior drainage system is a gravity drainage system and “does not utilize a tid e gate structure.” No mechanized pump station or automatic closure is identified in that memorandum. Therefore, the FEMA requirement for operation/testing of mechanized portions is address ed by documenting that none are identified in the available technical basis, while retaining inspecti on and response procedures for the gravity outlets, headwalls, inlets, and bridge/levee interfaces.
7. Evacuation Coordination and Public Warning
This ERP does not independently order evacuations. It establishes when the levee operator should notify emergency management and public safety officials so that protective actions can be implemented under the City/County emergency management system.
Evacuation planning
element ERP provision
Area of concern Areas landward/south of the Discovery Street levee and interior drainage system, including LakeView Mobile Estates ditch interface and adjacent public/private facilities protected by the levee. Final evacuation limits should be confirmed by City emergency management using current parcel, roadway, and inundation information.
Evacuation triggers Level 3 or Level 4 activation; backwater or interior ponding approaching occupied structures; levee seepage/sand boils/erosion or imminent overtopping; bridge or road closure affecting access; or direction by incident command.
Public warning channels AlertSanDiego / County emergency alert systems, City public information channels, law enforcement/fire notification, reverse 911/WEA if authorized, door-to-door notification where required, and accessible messaging for mobile home park residents. Confirm final channels with City/County OES.
Evacuation routes Use routes designated by incident command based on current road/bridge conditions. Potential local routes include Discovery Street, Via Vera Cruz, Bent Avenue, and connecting arterials, subject to closure status and field conditions.
Special populations Coordinate with mobile home park management and public safety officials for residents requiring additional notification or evacuation assistance.
7.1 Sample Public Warning Message Templates
Condition Draft message
High water advisory San Marcos Creek is rising near Discovery Street. City crews are monitoring the levee and drainage system. Avoid the creek, drainage ditches, and closed roads. Monitor official City and County emergency information.
Evacuation warning Flooding or levee/drainage-system concerns may affect the Discovery Street area. Prepare to evacuate if directed. Gather essential items,
Condition Draft message
medications, pets, and important documents. Follow instructions from public safety officials.
Evacuation order Evacuate the affected Discovery Street / LakeView area now as directed by public safety officials. Use designated routes and avoid flooded roads, San Marcos Creek, and drainage channels.
8. Training, Inspection, Documentation, and Updates
Program element Minimum procedure
Annual pre-season review Review ERP, contact list, access routes, flood-warning sources, and field inspection locations before the rainy season.
Annual inspection Inspect levee, bridge interfaces, outfall, inlets, headwalls, pipes as accessible, and LakeView ditch interface at least once per year and after significant storm events.
Training / tabletop exercise Conduct annual tabletop or field exercise covering activation triggers, inspection assignments, communication, public warning coordination, and documentation.
Mechanized features If later confirmed, operate/test pumps, gates, or automatic systems at least annually and document manual backup procedures.
Logs and documentation Maintain logs of forecasts, field observations, water levels, photos, public notifications, maintenance actions, pump use if any, and post- event findings.
Plan updates Update after any significant event, physical modification, change in responsible personnel, new as-built information, or FEMA/City review comment.
9. FEMA Requirements Crosswalk
FEMA reviewer item / 44
CFR element
Where addressed in
ERP Justification
Flood warning system used to
trigger emergency operation
activities
Sections 4 and 4.1 Uses NWS/County/City monitoring plus project-specific hydraulic elevations from
the technical memorandum.
Recommends a surveyed staff gage at
the outfall to convert model WSEs into
practical field triggers.
Formal plan of operation for
closures and mechanized
portions of interior drainage
system
Sections 5 and 6 The memo describes a gravity drainage
system and states no tide gate is used;
no pumps/mechanical systems were
identified. The plan therefore provides
formal inspection/response procedures
and flags need for revision if as-built
mechanical features exist.
Person by name or title
responsible for emergency
operation activities
Section 3 Assigns roles by title: Public Works
Director, Operations
Manager/Maintenance Superintendent,
Emergency Services, City Engineer, PIO,
law enforcement. Names can be added
for adopted version.
Plans for public evacuation
covering communities within
the levee system
Section 7 Provides evacuation coordination triggers,
affected area description, potential routes,
public-warning channels, and special-
population coordination. Final routing
must be confirmed by City emergency
management.
Documentation showing plan
has been officially adopted
Cover page and Section
8 / adoption placeholder
Adoption language and
resolution/approval documentation must
be added by the City or responsible
levee-maintaining agency prior to final
submittal.
Applicable federal, state, and
local laws/regulations
Sections 1, 3, 7, 8, 11 References FEMA levee accreditation criteria, California SEMS/ICS planning
framework, and City/County emergency-
management coordination.
10. Source Go-Bys and Justification Matrix
Source / go-by How it was used Reasonable adaptation for Discovery Street
44 CFR 65.10(c)(2) Interior
Drainage Systems
Core organization for flood
warning, formal operations,
responsible titles, manual
backup/mechanical testing, and
inspections.
Discovery system appears gravity-
only; therefore the plan
documents monitoring/inspection
and requires revision if
mechanical features are
confirmed.
44 CFR 65.10(c) Operation
Plans and Criteria
Used to state that levee
operations must be under an
appropriate agency and that
adopted operation documentation
is needed.
Responsible City titles and
adoption placeholder included.
FEMA Guidance for Flood
Risk Analysis and
Mapping: Levees
(Guidance Document 95)
Used as FEMA
mapping/accreditation context and
to align plan terminology with
accredited levee review.
ERP structured to respond directly
to FEMA review comment
language.
DHS/FEMA Emergency
Preparedness Guidelines
for Levees
Used for plan elements: project-
feature mapping, activation
authority, communication
protocols, supplies, training,
exercises, patrols, flood-fighting
actions, and public outreach.
Converted broad national
guidance into a small local
levee/gravity-drainage plan.
Cal OES Flood
Preparedness Guide for
Levee Maintaining
Agencies
Used for California SEMS/ICS,
levee-maintaining agency
responsibilities, local/operational-
area coordination, flood-fight
preparedness, and
documentation.
Plan assigns local field and
emergency-management roles
and relies on City/County
Operational Area coordination.
Discovery Street Interior
Drainage System Study
(Parsons, May 5, 2016)
Used for project facts, water-
surface elevations, drainage
operation, H-5/H-6 critical
locations, backwater behavior,
and no-tide-gate statement.
ERP trigger elevations and
inspection locations are tied
directly to the hydraulic memo
rather than generic thresholds.
11. References
• 44 CFR 65.10, Mapping of Areas Protected by Levee Systems, Electronic Code of Federal Regulations / Legal Information Institute. Accessed June 2026.
• FEMA, Guidance for Flood Risk Analysis and Mapping : Levees, Guidance Document 95, November 2019. • DHS/FEMA, Emergency Preparedness Guidelines for Le vees: A Guide for Owners and Operators, 2018 FEMA edition / 2012 USACE public-domain edition.
• California Governor's Office of Emergency Services , Flood Preparedness Guide for Levee Maintaining Agencies, Flood Emergency Action Team guidance.
• Parsons, San Marcos Creek District - Phase 1, Disc overy Street Interior Drainage System Study, Techni cal Memorandum, May 5, 2016.
• Fuscoe Engineering, Drainage Study, San Marcos Cre ek District Phase 1, November 2015, included as Attachment F to the Parsons memorandum.
Appendix A - Adoption / Approval Record Placeholder
Attach City Council resolution, Public Works Direct or approval memorandum, agency board action, or other official adoption/acceptance documentation he re. FEMA review comment item (v) should not be considered complete until adoption documentation is included or the FEMA reviewer accepts a schedule/commitment for adoption prior to accreditation.
Appendix B - Field Inspection Log Template
Date/time Inspector Location Observed condition Action taken Photo/file reference