Attachment D - Tech Appendix G (Hydraulic Analysis) — San Marcos City Council, December 12, 2023

Appendix G
Hydraulics Analysis/Floodplain Study

HYDRAULIC ANALYSES
FOR

RESTAURANT ROW

July 27, 2023

Wayne W. Chang, MS, PE 46548, Exp. 6/30/2023
Chang
Civil Engineering ◦ Hydrology ◦ Hydraulics ◦ Sedimentation

P.O. Box 9496
Rancho Santa Fe, CA 92067
(858) 692-0760

TABLE OF CONTENTS

Introduction .....................................................................................................................................1 Hydraulic Analysis..........................................................................................................................2 Conclusion ......................................................................................................................................4 LOMR Determination Document ...................................................................................................5

APPENDIX
A. Draft MT-2 Forms (will finalize with CLOMR), HEC-RAS Effective, Existing Condition, and Proposed Conditions Results

MAP POCKET
Existing Condition HEC-RAS Work Map
Proposed Condition HEC-RAS Work Map
1 INTRODUCTION

The proposed Restaurant Row redevelopment proj ect will be located within Old California Restaurant Row in the city of San Marcos. The site is bounded by West San Marcos Boulevard to the south and Via Vera Cruz to the east (see th e Vicinity Map). Surrounding uses include Wells Fargo Bank, a Buffalo Wild Wings, and additional restaurants to the east as well as health service and commercial buildings to the north. An uno ccupied commercial site and a Regal Edwards cinema are to the west. Vacant land and commercial uses are south along the opposite side of West San Marcos Boulevard. Under existing conditi ons, the project area consists of commercial development with restaurants surrounded by a large parking lot. The site generally drains towards its center within the middle of th e large parking lot. Surface grates collect project runoff and convey the runoff to an existing 30-inch pipe th at runs west through s ite. This 30-inch pipe connects an upstream 36-inch by 60-inch elliptical pipe from Via Vera Cruz to an existing downstream concrete trapezoidal channel west of the site. San Marcos Creek is located approximately 1,000 feet south of the site and ultimately collects the project’s storm runoff.

The project proposes a mixed-use z one that incorporates retail storefronts, urban living, and community destinations in a vertical pedestrian -oriented setting. To maintain the pedestrian- oriented setting, the ground floor will be limited to retail and other active uses along the primary street frontage of Via Vera Cruz and West Sa n Marcos Boulevard. Re sidential units will

2 encompass the majority of the site, includi ng homes over commercial un its along the project frontage. Another project known as the Sears Site , under a different developer, is adjacent and west of this project. The Sears Site and this Restaurant Row project are designed in conjunction to provide a pedestrian paseo access between both sites. The pedestrian access is included throughout this project connecting to the Sears Site in orde r to provide pedestrian access from Buffalo Wild Wings to the Regal Edwards cinema . This pedestrian paseo corrid or also serves as a secure, illuminated access throughout the project site. A flood park is implemented in the existing floodway (see FEMA discussion belo w) with a variety of amenitie s tolerant of inundation. The proposed site will allow for opportunity to program special events for the community.

FEMA has mapped a 100-year fl oodplain, 500-year floodplain, and re gulatory floodway within the site. These are associated with the “North Split” from San Marcos Creek and contained on Flood Insurance Rate Map No. 06073C0793G. FEMA’s Letter of Map Revision Determination Document is attached after this report text and became effective March 7, 2013.

The project grading is being designed by Project Design Consultants (PDC). The project will fill areas north and south of the floodway to raise the proposed buildings above the 100-year floodplain elevations with required freeboa rd. Grading and encroachments will be minimized within the floodway. This report contains pr eliminary existing and proposed condition 100-y ear hydraulic analyses for entitlement of the redevelopment project.

HYDRAULIC ANALYSIS

The FEMA effective study was performed about a decade ago, so an updated 100-year HEC-RAS (latest version 6.3.1) floodplain analysis was performed for the North Split based on July 16, 2021 1-foot contour interval topographic mapping prepared for the project (NAVD 88). The HEC-RAS Work Map in the map pocket contains the topogra phic mapping and cross-sections as well as the proposed grading. The existing condition cross-sectio ns start just below the site and extend just upstream of the site. Cross-sections 3041.591 a nd 3496.377 are at the same locations as the effective cross-sections, but ba sed on the recent ma pping. Additional ex isting condition cross- sections (2910.673, 3196.821, 3348.291, 3614.247, and 3753.787) were added to allow a more detailed analysis of the site than the effective model. Do wnstream cross-section 2623.03 and upstream cross-section 3952.589 are at the effective locations and from the effective model for tie- in purposes. Cross-sections 3196.821 to 3753.787 are at the lower and upper ends of the project footprint. For proposed conditions, these two cross-sections as well as the intermediate ones were modified to reflect PDC’s grading plan.

The prior Sears site is just west of Restaurant Row. The Sears site is cu rrently being permitted.

The most recent grading was obtained and proposed condition cross-sections 2910.673 and 3041.591 reflect the grading.

The following describes the additional HEC-RAS input parameters and results. The FEMA 100- year flow rate of 2,136.96 cubic feet per second was used. The downstream starting floodplain and floodway water surface elevati ons at cross-section 2623.023 we re set at 528.57 and 528.92 feet NAVD 88, respectively, to tie in with the effec tive model. The effective model uses a roughness 3 coefficient of 0.020 throughout the study reach analyzed in this report. This is likely because the floodplain primarily contains paved surfaces as well as landscape islands, trees, and lighting (see Figure 1). Asphalt pavement has a roughness coeffi cient of 0.013 to 0.016 per the County of San Diego Hydraulic Design Manual. The effective combin ed roughness of the as phalt, scattered landscaping, lighting, and other improvements is 0.020. The existing condition model uses a roughness coefficient of 0.020 consistent with the effective model. The proposed conditions park area design is under development, but is currently proposed with a dog park (n=0.030), skate park (n=0.015), landscaping (0.030 for grass to 0.040 for plants), and playground (0.030). The park area is outlined on the proposed c ondition rational method work ma p. The proposed driveways and parking are modeled with n=0.020. The other porti ons of the proposed condi tions cross-sections use the same n=0.020 as existing conditions.

Figure 1. Existing Parking Lot within Restaurant Row

The effective, existing, and proposed condition 100-year resu lts are included in Appendix A and summarized in Table 1. The proposed condition elev ations are mos tly equal to or less than the existing condition elevations. The proposed condition 100-year water surface elevation is slightly higher than the existing condition elevation at cross-section 3348.291, but the proposed condition elevation is lower than the effective elevation. The water surface elevations match at the upstream tie-in at cross-section 3952.589.

4 FIRM
Station
River
Station
Dup. Effective
WSE, ft
Existing
WSE, ft
Proposed
WSE, ft
Prop. – Exist.

WSE, ft
Prop. – Effect.

WSE, ft
3952.589 535.03 535.03 535.03 0.00 0.00
3753.787 532.74 532.71 -0.03
3614.247 532.15 531.57 -0.58
3496.377 532.21 531.38 531.02 -0.36 -1.19
3348.291 530.10 530.22 0.12
3196.821 530.26 530.13 -0.13
A 3041.591 529.75 529.71 529.38 -0.33 -0.37
2910.673 529.41 529.41 0.00
2623.023 528.57 528.57 528.57 0.00 0.00

Table 1. 100-Year HEC-RAS Water Surface Elevation (WSE) Results (NAVD 88)

A proposed condition 100-year fl oodway analysis was also perfo rmed. The results are included with the proposed condition floodpla in analysis in Appendix A, a nd show that the surcharge at cross-sections 2623.023 to 3952.589 is between 0 and 1 feet so me et FEMA requirements. The upstream effective and proposed condition floodw ay elevations at cross-section 3952.589 match and are 535.03 NAVD 88. The proposed condition floodway is plotted on the Proposed Condition HEC-RAS Work Map along with the effective fl oodway. The plotting shows that the proposed condition floodway is generally along or inside the effective floodway, so the proposed condition floodway will not impact floodway-related development potential on surrounding properties.

CONCLUSION

Existing and proposed condition 100-year HEC-RAS hydraulic analyses have been performed for entitlement of the Restaurant Row project. The proposed conditions reflect Project Design Consultants’ entitlement grading plans. The site design is intended to minimize floodway encroachments and results in minor changes to the existing condition 100-year water surface elevations. The proposed condition water surface el evations are generally lower than existing conditions. There is a minor increase in water surface elevations at cross-section 3348.291, but the proposed 100-year water surface el evation is lower than FEMA’s current effective elevation, so there is no impact on the effective floodplain. In addition, no insurable structures are affected.

Case No.: Page 1 of 5 Effective Date: March 7, 2013 Issue Date: October 23, 2012 LOMR-APP

12-09-1029P
Washington, D.C. 20472
Federal Emergency Management Agency

LETTER OF MAP REVISION

DETERMINATION DOCUMENT

COMMUNITY AND REVISION INFORMATION PROJECT DESCRIPTION

COMMUNITY
APPROXIMATE LATITUDE & LONGITUDE: 33.132, -117.193
SOURCE: USGS QUADRANGLE D A T U M : NAD 83
City of San Marcos
San Diego County
California
COMMUNITY NO.: 060296

BASIS OF REQUEST

IDENTIFIER

NO PROJECT HYDRAULIC ANALYSIS

FLOODWAY

NEW TOPOGRAPHIC DATA
San Marcos Creek

ANNOTATED MAPPING ENCLOSURES ANNOTATED STUDY ENCLOSURES DATE: May 16, 2012 NO.: 06073C0793G TYPE: FIRM*
DATE: May 16, 2012 NO.: 06073C0789G TYPE: FIRM*
DATE OF EFFECTIVE FLOOD INSURANCE STUDY REPORT: May 16, 2012 PROFILE(S): 392P, 393P, 394P and 398P
FLOODWAY DATA TABLE: 13
Enclosures reflect changes to flooding sources affected by this revision. * FIRM - Flood Insurance Rate Map; ** FBFM - Flood Boundary and Floodway Map; *** FHBM - Flood Hazard Boundary Map FLOODING SOURCE(S) & REVISED REACH(ES) See Page 2 for Additional Flooding Sources San Marcos Creek - from the upstream side of West Discovery Street to approximately 60 feet downstream of Twin Oaks Valley Road

SUMMARY OF REVISIONS
Revised Flooding Effective Flooding Flooding Source Increases Decreases San Marcos Creek Zone AE Zone AE YES YES
BFEs* BFEs YES YES
Floodway Floodway YES YES
Zone X (shaded) Zone X (shaded) YES YES
* BFEs - Base Flood Elevations

DETERMINATION
This document provides the determination from the Department of Homeland Security's Federal Emergency Management Agency (FEMA) regarding a request for a Letter of Map Revision (LOMR) for the area described above. Using the information submitted, we have determined that a revision to the flood hazards depicted in the Flood Insurance Study (FIS) report and/or National Flood Insurance Program (NFIP) map is warranted. This document revises the effective NFIP map, as indicated in the attached documentation. Please use the enclosed annotated map panels revised by this LOMR for floodplain management purposes and for all flood insurance policies and renewals in your community.

This determination is based on the flood data presently available. The enclosed documents provide additional information regar ding this determination. If you have any questions about this document, please contact the FEMA Map Information eXchange (FMIX) toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFI P is available on our website at http://www.fema.gov/business/nfip.
125360 PT202.02.BKR.12091029P.H17 102-I-A-C
Siamak Esfandiary, Ph.D., P.E., Program Specialist
Engineering Management Branch
Federal Insurance and Mitigation Administration
NEW PROFILE(S): 200P(a) and 565P

Case No.: Page 2 of 5 Effective Date: Issue Date: LOMR-APP12-09-1029P Washington, D.C. 20472
Issue Date: October 23, 2012 Effective Date: March 7, 2013 Federal Emergency Management Agency

LETTER OF MAP REVISION

DETERMINATION DOCUMENT (CONTINUED)

OTHER FLOODING SOURCES AFFECTED BY THIS REVISION

FLOODING SOURCE(S) & REVISED REACH(ES)
San Marcos Creek- Highway 78 Splitflow - from the San Marcos Creek confluence to the San Marcos Creek divergence Northern Split - from the Las Posas Creek (Lower) confluence to the San Marcos Creek Highway 78 Splitflow divergence Las Posas Creek (Lower) - from the San Marcos Creek confluence to the Northern Split confluence

SUMMARY OF REVISIONS
Flooding Source Effective Flooding Revised Flooding Increases Decreases San Marcos Creek- Highway 78 Splitflow Zone AE Zone AE YES YES Floodway Floodway YES YES
BFEs* BFEs YES YES
Northern Split Zone AO Zone AE YES YES
Zone AO Floodwa y YES NONE
Zone AE
BFEs
Floodway NONE YES
Las Posas Creek (Lower)
Zone AE Zone AE YES YES
Depths
BFEs
BFEs YES NONE
BFEs YES
Floodway

YES YES
* BFEs - Base Flood Elevations
This determination is based on the flood data presently available. The enclosed documents provide additional information regar ding this determination. If you have any questions about this document, please contact the FEMA Map Information eXchange (FMIX) toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFI P is available on our website at http://www.fema.gov/business/nfip.
125360 PT202.02.BKR.12091029P.H17 102-I-A-C
Siamak Esfandiary, Ph.D., P.E., Program Specialist
Engineering Management Branch
Federal Insurance and Mitigation Administration
Zone AE
Floodway
BFEs
Zone AE YES
YES
YES
YES
YES

Case No.: Page 3 of 5 Effective Date: Issue Date: LOMR-APP12-09-1029P Washington, D.C. 20472
Issue Date: October 23, 2012 Effective Date: March 7, 2013 Federal Emergency Management Agency

LETTER OF MAP REVISION

DETERMINATION DOCUMENT (CONTINUED)

COMMUNITY INFORMATION

APPLICABLE NFIP REGULATIONS/COMMUNITY OBLIGATION
We have made this determination pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (P.L. 93-234) and in accordance with the National Flood Insurance Act of 1968, as amended (Title XIII of the Housing and Urban Development Act of 1968, P.L. 90-448), 42 U.S.C. 4001-4128, and 44 CFR Part 65. Pursuant to Section 1361 of the National Flood Insurance Act of 1968, as amended, communities participating in the NFIP are required to adopt and enforce floodplain management regulations that meet or exceed NFIP criteria. These criteria, including adoption of the FIS report and FIRM, and the modifications made by this LOMR, are the minimum requirements for continued NFIP participation and do not supersede more stringent State/Commonwealth or local requirements to which the regulations apply.

We provide the floodway designation to your community as a tool to regulate floodplain development. Therefore, the floodway revision we have described in this letter, while acceptable to us, must also be acceptable to your community and adopted by appropriate community action, as specified in Paragraph 60.3(d) of the NFIP regulations.

COMMUNITY REMINDERS
We based this determination on the 1-percent-annual-chance flood discharges computed in the FIS for your community without considering subsequent changes in watershed characteristics that could increase flood discharges. Future development of projects upstream could cause increased flood discharges, which could cause increased flood hazards. A comprehensive restudy of your community’s flood hazards would consider the cumulative effects of development on flood discharges subsequent to the publication of the FIS report for your community and could, therefore, establish greater flood hazards in this area.

Your community must regulate all proposed floodplain development and ensure that permits required by Federal and/or State/Commonwealth law have been obtained. State/Commonwealth or community officials, based on knowledge of local conditions and in the interest of safety, may set higher standards for construction or may limit development in floodplain areas. If your State/Commonwealth or community has adopted more restrictive or comprehensive floodplain management criteria, those criteria take precedence over the minimum NFIP requirements.

We will not print and distribute this LOMR to primary users, such as local insurance agents or mortgage lenders; instead, the community will serve as a repository for the new data. We encourage you to disseminate the information in this LOMR by preparing a news release for publication in your community’s newspaper that describes the revision and explains how your community will provide the data and help interpret the NFIP maps. In that way, interested persons, such as property owners, insurance agents, and mortgage lenders, can benefit from the information.

Case No.: Page 4 of 5 Effective Date: Issue Date: LOMR-APP12-09-1029P Washington, D.C. 20472
Issue Date: October 23, 2012 Effective Date: March 7, 2013 Federal Emergency Management Agency

LETTER OF MAP REVISION

DETERMINATION DOCUMENT (CONTINUED)
We have designated a Consultation Coordination Officer (CCO) to assist your community. The CCO will be the primary liaison between your community and FEMA. For information regarding your CCO, please contact:

Ms. Sally M. Ziolkowski
Director, Mitigation Division
Federal Emergency Management Agency, Region IX
1111 Broadway Street, Suite 1200
Oakland, CA 94607-4052
(510) 627-7175

STATUS OF THE COMMUNITY NFIP MAPS
We will not physically revise and republish the FIRM and FIS report for your community to reflect the modifications made by this LOMR at this time. When changes to the previously cited FIRM panel(s) and FIS report warrant physical revision and republication in the future, we will incorporate the modifications made by this LOMR at that time.

Case No.: Page 5 of 5 Effective Date: Issue Date: LOMR-APP12-09-1029P Washington, D.C. 20472
Issue Date: October 23, 2012 Effective Date: March 7, 2013 Federal Emergency Management Agency

LETTER OF MAP REVISION

DETERMINATION DOCUMENT (CONTINUED)

PUBLIC NOTIFICATION OF REVISION
A notice of changes will be published in the Federal Register. This information also will be published in your local newspaper on or about the dates listed below and through FEMA’s Flood Hazard Mapping website at https://www.floodmaps.fema.gov/fhm/Scripts/bfe_main.asp.

LOCAL NEWSPAPER Name: The North County Times
Dates: October 31, 2012 and November 7, 2012

Within 90 days of the second publication in the local newspaper, a citizen may request that we reconsider this determination. Any request for reconsideration must be based on scientific or technical data. Therefore, this letter will be effective only after the 90-day appeal period has elapsed and we have resolved any appeals that we receive during this appeal period. Until this LOMR is effective, the revised flood hazard determination information presented in this LOMR may be changed.

CROSS SECTION DISTANCE WIDTH
(FEET)

SECTION
AREA
(SQUARE
FEET)
MEAN

VELOCITY
(FEET PER

SECOND)

REGULATORY WITHOUT

FLOODWAY
WITH

FLOODWAY INCREASE
Las Posas Creek
(Upper)
A 2,325 1 230 244 6.5 541.7 541.7 541.7 0.0
B 2,535 1 45 97 9.4 542.3 542.3 543.1 0.8
C 3,175 1 35 160 5.8 551.4 551.4 551.4 0.0
D 3,785 1 160 204 7.0 553.0 553.0 554.0 1.0
E 4,400 1 70 163 8.7 559.1 559.1 559.1 0.0
F 5,325 1 37 160 8.9 567.8 567.8 567.9 0.1
G 5,975 1 20 109 13.0 571.7 571.7 572.1 0.4
Las Posas Creek
(Lower)
A 1,045 2 319 1,574 1.6 521.3 521.3 521.4 0.1
B 1,625 2 513 1,853 1.3 521.4 521.4 521.6 0.2
1 Feet Above Linda Vista Drive `
2 Feet above Confluence with San Marcos Creek
T A B L E 13
FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD

WATER-SURFACE ELEVATION (FEET NAVD)

FLOODWAY DATA

LAS POSAS CREEK (UPPER) - LAS POSAS CREEK (LOWER) SAN DIEGO COUNTY, CA

AND INCORPORATED AREAS

FEDERAL EMERGENCY MANAGEMENT AGENCY

REVISED DATA

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

CROSS SECTION DISTANCE WIDTH
(FEET)

SECTION
AREA
(SQUARE
FEET)
MEAN

VELOCITY
(FEET PER

SECOND)

REGULATORY WITHOUT

FLOODWAY
WITH

FLOODWAY INCREASE
Lake San Marcos/
San Marcos Creek
ZU 1,440 1 220 4,212 3.8 503.3 503.3 503.3 0.0
ZV 3,710 1 320 4,183 4.0 503.5 503.5 503.5 0.0
ZW 5,270 1 388 5,060 3.5 503.7 503.7 503.7 0.0
ZX 6,840 1 275 4,162 4.2 505.4 505.4 505.5 0.1
ZY 7,730 1 400 2,399 5.8 510.9 510.9 510.9 0.0
ZZ 8,400 1 450 1,793 8.6 513.1 513.1 513.2 0.1
San Marcos Creek
A 2,110 2
572 3,143 4.7 518.7 518.7 518.8 0.1
B 3,268 2
162 1,035 10.9 521.1 521.1 521.6 0.5
C 5,015 2
435 1,618 7.0 528.4 528.4 528.7 0.3
D 6,863 2
480 2,301 4.9 537.0 537.0 538.0 1.0
E 8,144 2 427 1,967 5.0 542.0 542.0 542.4 0.4
F 9,283 2
422 1,758 5.4 546.5 546.5 547.1 0.6
G 10,326 2
413 1,913 4.9 551.7 551.7 552.0 0.3
H 12,173 2 290 1,993 6.3 565.7 565.7 565.8 0.1
I 13,541 2 285 2,270 5.5 567.8 567.8 568.3 0.5
J 14,920 2 245 2,079 2.5 574.8 574.8 574.8 0.0
K 15,657 2 220 1,043 4.2 576.5 576.5 576.5 0.0
L 16,782 2 175 1,164 4.9 589.6 589.6 589.6 0.0
M 18,222 2 130 436 10.1 596.5 596.5 596.6 0.1
N 19,614 2 227 681 6.5 610.1 610.1 610.6 0.5
O 20,585 2 103 630 7.0 619.7 619.7 620.7 1.0
P 21,225 2 181 760 5.8 624.3 624.3 625.3 1.0
1 Feet above San Marcos Dam `
2 Feet above Lake San Marcos
T A B L E 13
FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD

WATER-SURFACE ELEVATION (FEET NAVD)

FLOODWAY DATA

LAKE SAN MARCOS/SAN MARCOS CREEK -

SAN MARCOS CREEK

SAN DIEGO COUNTY, CA

AND INCORPORATED AREAS

FEDERAL EMERGENCY MANAGEMENT AGENCY

REVISED DATA

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

CROSS SECTION DISTANCE WIDTH
(FEET)

SECTION
AREA
(SQUARE
FEET)
MEAN

VELOCITY
(FEET PER

SECOND)

REGULATORY WITHOUT

FLOODWAY
WITH

FLOODWAY INCREASE
San Marcos Creek -
Highway 78 Split
Flow
A 2,651 1 138 265 7.9 552.8 552.8 552.8 0.0
B 3,470 1 216 452 8.2 556.5 556.5 556.5 0.0
C 4,440 1 168 433 8.6 562.3 562.3 562.3 0.0
Northern Split
A 1,248 2 100 438 4.9 529.8 529.8 530.7 0.9
B 2,480 2
155 289 7.4 536.6 536.6 536.6 0.0
C 3,660 2
230 333 6.4 545.0 545.0 545.0 0.0
1 Feet above Confluence with San Marcos Creek `
2 Feet above Confluence with Las Posas Creek (Lower)
T A B L E 13
FLOODING SOURCE FLOODWAY 1-PERCENT-ANNUAL-CHANCE FLOOD

WATER-SURFACE ELEVATION (FEET NAVD)

FLOODWAY DATA
SAN MARCOS CREEK-HIGHWAY 78 SPLIT FLOW -

NORTHERN SPLIT

SAN DIEGO COUNTY, CA

AND INCORPORATED AREAS

FEDERAL EMERGENCY MANAGEMENT AGENCY

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013
/206
B
A
PABLO
DR

ZONE AE
WEST

DISCOVERY
ST
1ST ST

S RANCHO SANTA FE RD

VIA BELLA
DONNA

LAMPASAS WAY

LAS CRUCES AVELONITA
WAY
VIA

JUANITA
LA

SIERRA DR

ZONE AE
(EL 519)

BOARDWALK
518

S PACIFIC ST

SECURITY
SAN
RUE
GRA
PL
PL
NDON
521
1ST ST

SAN DIEGO COUNTY

BEVERLY
AVE

KNIGHTSREALM

GRANADA
WAY
DE

MCMAHR RD
524
521

CITY OF SAN MARCOS

MARGIE PL
VALLE
519

LA NOCHE DR
San Marcos Creek

PROFILE BASELINE DISCOVERY ST

SAN DIEGO COUNTYZONE AE
528
529

LIMIT OF

FLOODWAY

LINDA VISTA DR

APPLEWILDE DRGINGER GLEN

CRESTVIEW
LILAC
CT

HONEYGLEN DR
C
A
B
16 1% ANNUAL CHANCE FLOOD DISCHARGE

CONTAINED IN CULVERT
CT

S LAS POSAS RD

VIA VERA
CRUZ
LAW ST
ZY

STONE DR
535
San Marcos Creek

REVISED
AREA
532
535

RYAN DR
Private Rd
B

CITY OF SAN MARCOS
ZZ
A
DX1196
525
Las Posas
Creek (Lower)
521
506

LA MIRADA DR
Private Rd
Private Rd
516 Private
Rd
513

COMMERCE ST
Private Rd
511
509
Private Rd
Private Rd
8 VIA VERA CRUZ
526
Private Rd
530

SAN DIEGO AQUEDUCT
0 TAMARISK
LN

LINDA VISTA DR
FLORA

SEVILLE

PORTOLA

RANCHO LOS VALLECITOS

DE SAN MARCOS LAND GRANT
VIA
NOTE: MAP AREA SHOWN ON THIS PANEL IS LOCATED
WITHIN TOWNSHIP 12 SOUTH, RANGE 3 WEST AND THE

RANCHO LOS VALLECITOS DE SAN MARCOS LAND GRANT

VALLECITOS

SAN DIEGO COUNTY

UNINCORPORATED AREAS
060284
17 LAKE SAN
MARCOS

S PACIFIC ST
527
Northern
Split
Private Rd
528

CITY OF SAN MARCOS
060296
DR

VIA LIDO

VIA LAS FLORES DRVIA
VIA

PALOMAR
519
Private
Rd

LA CASITA DR

LA CAMPANA

VIA ALTA VISTA
VIA
ROSA

LA COLUSA DR

VIA BELLAMARIA

VIA BELLAMONICA

DEBRAPL
519
Private
Rd
Private Rd

W SAN MARCOS BLVD
1995000 FT JOINS PANEL 0793
/78/65 /84/73/79/78/65/76 /32/70/76/79/79/68/32/73/78/83/85/82/65/78/67/69/32/80/82/79/71/82/65/77 /78/70/73/80
Federal Emergency Management Agency
Notice to User: The shown below should be used when placing map orders; the shown above should be used on insurance applications for the subject community.

Map Number
Community Number
/70/73/82/77
/70/76/79/79/68/32/73/78/83 /85/82/65 /78/67/69/32/82 /65 /84/69/32/77/65/80 /80 /65/78 /69/76 /32/32 /32/48/55/56/57/72
CONTAINS:

COMMUNITY NUMBER PANEL SUFFIX
/77/65 /80/32/78/85/77/66/69/82
/48 /54/48/55/51/67/48 /55/56/57/72
/77/65 /80/32/82/69/86 /73/83 /69/68
/77/65 /89 /32 /49/54 /44 /32/50/48/49/50
/80 /65/78 /69/76 /32/55/56/57/32/79/70/32/50/51/55/53
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)

SAN DIEGO COUNTY,

CALIFORNIA
SAN DIEGO COUNTY 060284 0789 H
SAN MARCOS, CITY OF 060296 0789 H
VISTA, CITY OF 060297 0789 H

AND INCORPORATED AREAS
MAP SCALE 1" = 500'
/50 /53 /48 /48 /53 /48 /48
/70 /69/69 /84
/49 /53 /48 /48 /49 /53 /48
/77/69 /84/69 /82/83
Legend
1% annual chance
(100− Year) Floodplain
1% annual chance
(100− Year) Floodway

0.2% annual chance
(500− Year) Floodplain

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

/206
546
D
560
539
554
535
552
San Marcos Creek
Highway 78 Splitflow
537
543542 546
537
Northern Split
/80
/55/56
E
F
C
GRAND
AVE
G
H
I
568
568

LOWERY LNCHINABERRY
LN

BINGHAM
DR

ZONE AE
B
C
Culvert

LINDA VISTA DR
1% ANNUAL CHANCE FLOOD

DISCHARGE CONTAINED

IN CULVERT

KNOLL RD
VALLECITOS DE ORO Twin Oaks
Valley Creek

REVISED
AREA

BALDWIN LN

CITY OF SAN MARCOS
060296

WESTLAKE DR

PICO AVE

TWIN OAKS

VALLEY RD

ZONE AE
DX1195
JOY CT

RANCHO LOS VALLECITOS

DE SAN MARCOS

LAND GRANT

LOS VALLECITOS BLVD

JOHNSTON
LN

POSITIVEPL

LOCUST ST

ECHO LN

CHINABERRY
LN
550

TERRIER WAY

WINDRIDGE
CIR
VERA
Private Rd
Private Rd

HONEYGLEN DR

HAPPY HILL LN

COMMERCE ST

SHENANDOAH
AVE
LUPINE
DR

DISCOVERY ST
VIA
CRAVEN
RD

FOXHALL CT
SONOMA
ST

ZONE AE
Private
Rd
539

S BENT AVE
Private Rd
CRUZ

TRAVELERS WAY
Private
Rd

N ECHO LN

CRIBBAGE LN

PARK PL DAISY LN

BOARDWALK

MARANATHA
WAY
568
546 558
557
545
567
553
A
Private
Road

0.2% ANNUAL CHANCE

FLOOD DISCHARGE

CONTAINED IN CULVERT
544

LOS VALLECITOS BLVD
550
560
562 566
557
San Marcos
Creek
567
552
ZONE
AE
SHUBIN
LN
566
36 66
000m
N
36 67
000m
N
JOINS PANEL 0789
/78/65 /84/73/79/78/65 /76 /32/70 /76/79/79/68/32/73/78/83/85/82/65/78 /67/69/32/80/82 /79/71/82/65/77 /78/70/73/80
Federal Emergency Management Agency
Notice to User: The shown below should be used when placing map orders; the shown above should be used on insurance applications for the subject community.

Map Number
Community Number
/70/73/82/77
/70/76/79/79/68/32/73/78/83 /85/82/65 /78/67/69/32/82 /65 /84/69/32/77/65/80 /80 /65/78 /69/76 /32/32 /32/48/55/57/51/71
CONTAINS:

COMMUNITY NUMBER PANEL SUFFIX
/77/65 /80/32/78/85/77/66/69/82
/48 /54/48/55/51/67/48 /55/57/51/71
/77/65 /80/32/82/69/86 /73/83 /69/68
/77/65 /89 /32 /49/54 /44 /32/50/48/49/50
/80 /65/78 /69/76 /32/55/57/51/32/79/70/32/50/51/55/53
(SEE MAP INDEX FOR FIRM PANEL LAYOUT)

SAN DIEGO COUNTY,

CALIFORNIA
SAN MARCOS, CITY OF 060296 0793 G

0.2% annual chance
(500− Year) Floodplain

REVISED TO

REFLECT LOMR
EFFECTIVE:

March 7, 2013

APPENDIX A

DRAFT MT-2 FORMS

HEC-RAS EFFECTIVE,

EXISTING CONDITION, AND

PROPOSED CONDITION RESULTS

FEMA FORM FF-206-FY-21-100 (formerly 086-0-27)
(01/21)

Page 1 of 3 ends

OMB Control Number: 1660-0016
Expiration: 1/31/2024

DEPARTMENT OF HOMELAND SECURITY
Federal Emergency Management Agency

OVERVIEW & CONCURRENCE FORM

PAPERWORK BURDEN DISCLOSURE NOTICE

Public reporting burden for this form is estimated to average 1 hours per response. The burden estimate includes the time for r eviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submit ting the form.

You are not required to respond to this collection of information unless it displays a valid OMB control number. Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, Department of Homeland Security, Federal Emergency Management Agency, 500 C Street, SW, Washington, DC 20472 , Paperwork Reduction Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance Program. Please do not send your completed survey to the above address.

PRIVACY ACT STATEMENT

AUTHORITY: The National Flood Insurance Act of 1968, Public Law 90-448, as amended by the Flood Disaster Protection Act of 1973, Public Law 93-234.

PRINCIPAL PURPOSE(S): This information is being collected for the purpose of determining an applicant's eligibility to request changes to National Flood Insurance Program (NFIP) Flood Insurance Rate Maps (FIRM).

ROUTINE USE(S): The information on this form may be disclosed as generally permitted under 5 U.S.C § 552a(b) of the Privacy Act of 1974, as amended. This includes using this information as necessary and authorized by the routine uses published in DHS/FEMA/NFIP/LOM A-1 National Flood Insurance Program (NFIP); Letter of Map Amendment (LOMA) February 15, 2006, 71 FR 7990.

DISCLOSURE: The disclosure of information on this form is voluntary; however, failure to provide the information requested may delay or prevent FEMA from processing a determination regarding a requested change to a (NFIP) Flood Insurance Rate Maps (FIRM).

A. REQUESTED RESPONSE FROM DHS-FEMA
This request is for a (check one):

CLOMR: A letter from DHS-FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or proposed hydrology changes (See 44 CFR Ch. 1, Parts 60, 65 & 72). All CLOMRs require documentation of compliance with the Endangered Species Act. Refer to the Instructions for details.

LOMR: A letter from DHS-FEMA officially revising the current NFIP map to show the changes to floodplains, regulatory floodway or flood elevations. (See 44 CFR Ch. 1, Parts 60, 65 & 72).

B. OVERVIEW

1. The NFIP map panel(s) affected for all impacted communities is (are):

Community No. Community Name State Map No. Panel No. Effective Date

2. a. Flooding Source:
b. Types of Flooding: Riverine Coastal Shallow Flooding (e.g., Zones AO and AH) Alluvial Fan Lakes Other (Attach Description)

3. Project Name/Identifier:

4. FEMA zone designations (choices: A, AH, AO, A1-A30, A99, AE, AR, V, V1-V30, VE, B, C, D, X) a. Effective:
b. Revised:
060296 City of San Marcos CA 06073C 0789H 03/07/2013 Northern Split San Marcos Creek
Restaurant Row
AE, Shaded X
AE, Shaded X

FEMA FORM FF-206-FY-21-100 (formerly 086-0-27)
(01/21)

Page 2 of 3 ends

5. Basis for Request and Type of Revision:
a. The basis for this revision request is (check all that apply) Physical Change Improved Methodology/Data Regulatory Floodway Revision Base Map Changes Coastal Analysis Hydraulic Analysis Hydrologic Analysis Corrections Weir-Dam Changes Levee Certification Alluvial Fan Analysis Natural Changes New Topographic Data Other (Attach Description)
Note: A photograph and narrative description of the area of concern is not required, but is very helpful during review. b. The area of revision encompasses the following structures (check all that apply) Structures: Channelization Levee/Floodwall Bridge/Culvert Dam Fill Other (Attach Description)

6. Documentation of ESA compliance is submitted (required to initiate CLOMR review). Please refer to the instructions for more information.

C. REVIEW FEE
Has the review fee for the appropriate request category been included? Yes No, Attach Explanation
Fee amount: $
- Please see the DHS-FEMA Web site at http://www.fema.gov/forms-documents-and-software/flood- map-related-fees for Fee Amounts and Exemptions.

D. SIGNATURES

1. REQUESTOR'S SIGNATURE
All documents submitted in support of this request are correct to the best of my knowledge. I understand that any false statem ent may be punishable by fine or imprisonment under Title 18 of the United States Code, Section 1001.

Name: Company:

Mailing Address: Daytime Telephone: Fax No.:

E-mail Address:

Signature of Requestor (required):

Date:

2. COMMUNITY CONCURRENCE
As the community official responsible for floodplain management, I hereby acknowledge that we have received and reviewed this L etter of Map Revision (LOMR) or conditional LOMR request. Based upon the community's review, we find the completed or proposed project meets or is d esigned to meet all of the community floodplain management requirements, including the requirements for when fill is placed in the regulatory floodway, an d that all necessary Federal, State, and local permits have been, or in the case of a conditional LOMR, will be obtained. For Conditional LOMR requests, the applicant has documented Endangered Species Act (ESA) compliance to FEMA prior to FEMA's review of the Conditional LOMR application. For LOMR requests, I acknowledge that compliance with Sections 9 and 10 of the ESA has been achieved independently of FEMA's process. For actions authorized, funded , or being carried out by Federal or State agencies, documentation from the agency showing its compliance with Section 7(a)(2) of the ESA will be submitt ed. In addition, we have determined that the land and any existing or proposed structures to be removed from the SFHA are or will be reasonably safe fro m flooding as defined in 44CFR 65.2(c), and that we have available upon request by FEMA, all analyses and documentation used to make this determination.

Community Official's Name and Title:

Community Name: Mailing Address:

Daytime Telephone: Fax No.:

E-mail Address:

Community Official's Signature (required): Date:
6,500.00
Wayne W. Chang Chang Consultants
P.O. Box 9496
Rancho Santa Fe, CA 92067
(858) 692-0760 (858) 832-1402
[email protected]
9/22/2022
City of San Marcos
1 Civic Center Drive
San Marcos, CA 92067 (760) 744-1050

FEMA FORM FF-206-FY-21-100 (formerly 086-0-27)
(01/21)

Page 3 of 3 ends

3. CERTIFICATION BY REGISTERED PROFESSIONAL ENGINEER AND/OR LAND SURVEYOR This certification is to be signed and sealed by a licensed land surveyor, registered professional engineer, or architect autho rized by law to certify elevation information data, hydrologic and hydraulic analysis, and any other supporting information as per NFIP regulat ions paragraph

65.2(b) and as described in the MT-2 Forms Instructions. All documents submitted in support of this request are correct to the best of my knowledge. I understand that any false statement may be punishable by fine or imprisonment under Title 18 of the United States Code, Section 1001.

Certifier's Name: License No.: Expiration Date:

Company Name:

Telephone No.: Fax No.:

E-mail Address:

Mailing Address:

Signature: Date:

Ensure the forms that are appropriate to your revision request are included in your submittal.

Form Name and (Number)
Riverine Hydrology and Hydraulics Form (Form 2)
Riverine Structures Form (Form 3)
Coastal Analysis Form (Form 4)
Coastal Structures Form (Form 5)
Alluvial Fan Flooding Form (Form 6)
Required if …
New or revised discharges or water-
surface elevations
Channel is modified, addition/revision of
bridge/culverts, addition/revision of
levee/floodwall, addition/revision of dam
New or revised coastal elevations
Addition/revision of coastal structure
Flood control measures on alluvial fans
Seal (Optional)
Wayne W. Chang 46548 6/30/2023
Chang Consultants
(858) 692-0760 (858) 832-1402
[email protected]
P.O. Box 9496
Rancho Santa Fe, CA 92067
9/22/2022

FEMA FORM FF-206-FY-21-101 (formerly 086-0-27A)
(01/21)

Page 1 of 3 ends

OMB Control Number: 1660-0016
Expiration: 1/31/2024

DEPARTMENT OF HOMELAND SECURITY
Federal Emergency Management Agency
RIVERINE HYDROLOGY & HYDRAULICS FORM (FORM 2)

PAPERWORK BURDEN DISCLOSURE NOTICE

Public reporting burden for this form is estimated to average 3.5 hours per response. The burden estimate includes the time for reviewing instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submit ting the form.

PRIVACY ACT STATEMENT

AUTHORITY: The National Flood Insurance Act of 1968, Public Law 90-448, as amended by the Flood Disaster Protection Act of 1973, Public Law 93-234.

Flooding Source:

Note: Fill out one form for each flooding source studied A. HYDROLOGY

1. Reason for New Hydrologic Analysis (check all that apply):

Not revised (skip to section B) No existing analysis Improved data Alternative methodology Proposed Conditions (CLOMR) Changed physical condition of watershed

2. Comparison of Representative 1%-Annual-Chance Discharges Location Drainage Area (Sq. Mi.) Effective/FIS (cfs) Revised (cfs)

3. Methodology for New Hydrologic Analysis (check all that apply) Precipitation/Runoff Model J Specify Model: Duration: Rainfall Amount:

Statistical Analysis of Gage Records
Regional Regression Equations Other (please attach description) Please enclose all relevant models in digital format, maps, computations (including computation of parameters), and documentation to support the new analysis.

4. Review/Approval of Analysis
If your community requires a regional, state, or federal agency to review the hydrologic analysis, please attach evidence of approval/review.

5. Impacts of Sediment Transport on Hydrology
Is the hydrology for the revised flooding source(s) affected by sediment transport? Yes No If yes, then fill out Section F (Sediment Transport) of Form 3. If No, then attach your explanation.

4. HEC-RAS File Description**:

Northern Split San Marcos Creek

FEMA FORM FF-206-FY-21-101 (formerly 086-0-27A)
(01/21)

Page 2 of 3 ends

B. HYDRAULICS

1. Reach to be Revised
Description Cross Section Water-Surface Elevation (ft.) Effective Proposed/Revised
Downstream Limit*
Upstream Limit*
*Proposed/Revised elevations must tie-into the Effective elevations within 0.5 foot at the downstream and upstream limits of revision.

2. Hydraulic Method/Model Used:

Steady State Unsteady State One-Dimensional Two-Dimentional

3. Pre-Submittal Review of Hydraulic Models*
DHS-FEMA has developed two review programs, CHECK-2 and CHECK-RAS, to aid in the review of HEC-2 and HEC-RAS hydraulic models, respectively. We recommend that you review your HEC-2 and HEC-RAS models with CHECK-2 and CHECK-RAS.

4. HEC-RAS File Description**:

Models Submitted Natural Run Floodway Run Datum
Duplicate Effective Model* File Name: Plan Name: File Name: Plan Name:

Corrected Effective Model* File Name: Plan Name: File Name: Plan Name:

Existing or Pre-Project
Conditions Model File Name: Plan Name: File Name: Plan Name:

Revised or Post-Project
Conditions Model
File Name: Plan Name: File Name: Plan Name:

Other - (attach description) File Name: Plan Name: File Name: Plan Name:
* For details, refer to the corresponding section of the instructions. **See instructions for information about modeling other then HEC-RAS. Digital Models Submitted? (Required) C. MAPPING REQUIREMENTS
A certified topographic work map must be submitted showing the following information (where applicable): the boundaries of the effective, existing, and proposed conditions 1%-annual-chance floodplain (for approximate Zone A revisions) or the boundaries of the 1%- a nd 0.2%- annual-chance floodplains and regulatory floodway (for detailed Zone AE, AO, and AH revisions); location and alignment of all c ross sections with stationing control indicated; stream, road, and other alignments (e.g., dams, levees, etc.); current community easements a nd boundaries; boundaries of the requester's property; certification of a registered professional engineer registered in the subject State; lo cation and description of reference marks; and the referenced vertical datum (NGVD, NAVD, etc.).

Digital Mapping (GIS/CADD) Data Submitted (preferred) Topographic Information:

Source: Date:

Vertical Datum: Spatial Projection:

Accuracy:

Note that the boundaries of the existing or proposed conditions floodplains and regulatory floodway to be shown on the revised FIRM and/or FBFM must tie-in with the effective floodplain and regulatory floodway boundaries. Please attach a copy of the effective FIRM and/or FBFM , at the same scale as the original, annotated to show the boundaries of the revised 1%-and 0.2%-annual-chance floodplains and re gulatory floodway that tie-in with the boundaries of the effective 1%-and 0.2%-annual-chance floodplain and regulatory floodway at the u pstream and downstream limits of the area on revision.

Annotated FIRM and/or FBFM (Required)
480' u/s S. Las Posas Rd 2623.023 528.27 528.27
d/s side Via Vera Cruz 3952.589 535.05 535.03
HEC-RAS v6.2
1655San_Marcos_C Dup Eff MP 655San_Marcos_Cr e Dup Eff Floodway NAVD 88

N/A N/A N/A N/A N/A
655San_Marcos_Cre Exist Cond RR N/A N/A NAVD 88
655San_Marcos_CrePC2023-0728FPFW 655San_Marcos_CrePC2023-0728FPFW NAVD 88

N/A N/A N/A N/A N/A
Project Design Consultants 7/16/2021
NAVD 88 NAD 83
1-foot contour interval
Note: File Name below is 1655San_Marcos_Creek.prj.

FEMA FORM FF-206-FY-21-101 (formerly 086-0-27A)
(01/21)

Page 3 of 3 ends

D. COMMON REGULATORY REQUIREMENTS*

1. For LOMR/CLOMR requests, do Base Flood Elevations (BFEs) or Special Flood Hazard Areas (SFHAs) increase compared to the effective BFEs? Yes No
If Yes, please attach proof of property owner notification. Examples of property owner notifications can be found in the MT-2 Form 2 Instructions.

2. For CLOMR requests, if either of the following is true, please submit evidence of compliance with Section 65.12 of the NFIP regulations:
The proposed project encroaches upon a regulatory floodway and would result in increases above 0.00 foot compared to pre-project conditions.

The proposed project encroaches upon a SFHA with or without BFEs established and would result in increases above 1.00 foot compared to pre-project conditions.

3. Does the request involve the placement or proposed placement of fill? Yes No
If Yes, the community must be able to certify that the area to be removed from the special flood hazard area, to include any structures or proposed structures, meets all of the standards of the local floodplain ordinances, and is reasonably safe from flooding in accordance with the NFIP regulations set forth at 44 CFR 60.3(A)(3), 65.5(a)(4), and 65.6(a)(14). Please see the M T-2 instructions for more information.

4. Does the request involve the placement or proposed placement of fill? Yes No If Yes, attach evidence of regulatory floodway revision notification . As per Paragraph 65.7(b)(1) of the NFIP Regulations, notification is required for requests involving revisions to the regulatory floodway Elements and examples of regulatory floodw ay revision notification can be found in the MT-2 Form 2 Instructions.

5. For CLOMR requests, please submit documentation to FEMA and the community to show that you have complied with Sections 9 and 10 of the Endangered Species Act (ESA). For actions authorized, funded, or being carried out by Federal or State agencies, please submit documentation from the agency showing its compliance with Section 7(a)(2) of the ESA. Please see the MT-2 instructions for more detail.

For LOMR requests, is the regulatory
floodway being revised? N/A, not a LOMR.

HEC-RAS Plan: Existing FPFW River: Northern Split Reach: Split 0.2 Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)
Split 0.2 3952.589 100-YR FP 2136.96 532.30 535.03 535.03 536.10 0.004304 8.46 260.81 121.00 0.99 Split 0.2 3952.589 100-YR FW 2136.96 532.30 535.03 535.03 536.10 0.004304 8.46 260.81 121.00 0.99 Split 0.2 3496.377 100-YR FP 2136.96 529.93 532.21 532.21 533.00 0.003971 7.64 316.83 372.50 0.93 Split 0.2 3496.377 100-YR FW 2136.96 529.93 532.22 532.22 533.00 0.003933 7.62 318.52 204.14 0.93 Split 0.2 3041.591 100-YR FP 2136.96 522.30 529.75 529.00 530.26 0.001072 6.49 437.06 204.87 0.54 Split 0.2 3041.591 100-YR FW 2136.96 522.30 530.71 528.91 531.11 0.000599 5.52 438.21 100.00 0.42 Split 0.2 2623.023 100-YR FP 2136.96 520.30 528.57 528.57 529.60 0.002062 9.75 310.55 126.92 0.73 Split 0.2 2623.023 100-YR FW 2136.96 520.30 528.92 528.92 530.53 0.002556 11.31 234.98 68.57 0.82 Effective 100-Year Floodplain and Floodway
0 200 400 600 800 1000 1200
532
534
536
538
540
542
544
546
Existing FP/FW
RS = 3952.589
Station (ft)
Elevation (ft)
Legend
WS 100-YR FP
WS 100-YR FW
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
0 200 400 600 800
528
530
532
534
536
538
540
542
544
Existing FP/FW
RS = 3496.377
Station (ft)
Elevation (ft)
Legend
WS 100-YR FW
WS 100-YR FP
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
545
Existing FP/FW
RS = 3041.591
Station (ft)
Elevation (ft)
Legend
WS 100-YR FW
WS 100-YR FP
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
Existing FP/FW
RS = 2623.023
Station (ft)
Elevation (ft)
Legend
WS 100-YR FW
WS 100-YR FP
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02

HEC-RAS Plan: Exist Cond RR River: Northern Split Reach: Split 0.2 Profile: 100-year Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)
Split 0.2 3952.589 100-year 2136.96 532.30 535.03 535.03 536.10 0.004324 8.47 260.45 121.00 0.99 Split 0.2 3753.787 100-year 2136.96 529.94 532.74 532.74 533.47 0.003528 7.57 340.40 238.99 0.89 Split 0.2 3614.247 100-year 2136.96 529.10 532.15 532.15 532.91 0.003419 8.20 341.95 231.30 0.90 Split 0.2 3496.377 100-year 2136.96 528.19 531.38 531.38 532.05 0.002839 7.84 376.74 305.64 0.83 Split 0.2 3348.291 100-year 2136.96 527.04 530.10 529.80 530.53 0.002543 7.04 476.48 424.50 0.77 Split 0.2 3196.821 100-year 2136.96 526.15 530.26 530.33 0.000235 2.71 1033.44 436.49 0.25 Split 0.2 3041.591 100-year 2136.96 521.50 529.71 530.22 0.001004 7.36 476.22 301.48 0.52 Split 0.2 2910.673 100-year 2136.96 520.63 529.41 528.87 530.06 0.001128 7.78 399.95 202.98 0.53 Split 0.2 2623.023 100-year 2136.96 520.30 528.57 528.54 529.60 0.002053 9.73 311.08 126.96 0.73 Existing Condition 100-Year Floodplain
0 200 400 600 800 1000 1200
532
534
536
538
540
542
544
546
Existing Condition Restaurant Row
RS = 3952.589
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Ineff
Bank Sta
.02 .02 .02
0 200 400 600 800
528
530
532
534
536
538
540
542
544
Existing Condition Restaurant Row
RS = 3753.787
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800
528
530
532
534
536
538
540
542
544
Existing Condition Restaurant Row
RS = 3614.247
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800 1000
528
530
532
534
536
538
540
542
544
Existing Condition Restaurant Row
RS = 3496.377
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800 1000
526
528
530
532
534
536
538
540
542
Existing Condition Restaurant Row
RS = 3348.291
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800 1000 1200
524
526
528
530
532
534
536
538
540
542
Existing Condition Restaurant Row
RS = 3196.821
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
545
Existing Condition Restaurant Row
RS = 3041.591
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Ineff
Bank Sta
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
545
Existing Condition Restaurant Row
RS = 2910.673
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Bank Sta
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
Existing Condition Restaurant Row
RS = 2623.023
Station (ft)
Elevation (ft)
Legend
WS 100-year
Ground
Ineff
Bank Sta
.02 .02 .02

HEC-RAS Plan: PC 2023-0728 FPFW River: Northern Split Reach: Split 0.2 Reach River Sta Profile W.S. Elev Prof Delta WS E.G. Elev Top Wdth Act Q Left Q Channel Q Right Enc Sta L Ch Sta L Ch Sta R Enc Sta R (ft) (ft) (ft) (ft) (cfs) (cfs) (cfs) (ft) (ft) (ft) (ft) Split 0.2 3952.589 100-year FP 535.03 536.10 121.00 53.12 1914.28 169.56 321.84 420.74 Split 0.2 3952.589 100-year FW 535.03 0.00 536.10 121.00 53.12 1914.28 169.56 310.00 321.84 420.74 431.00 Split 0.2 3753.787 100-year FP 532.71 533.67 175.01 7.35 1889.69 239.92 103.85 198.41 Split 0.2 3753.787 100-year FW 532.71 0.01 533.66 156.56 3.17 1875.84 257.95 100.44 103.85 198.41 257.00 Split 0.2 3614.247 100-year FP 531.57 532.41 169.63 9.22 2013.84 113.90 139.23 265.59 Split 0.2 3614.247 100-year FW 532.17 0.60 532.63 169.63 11.43 1921.03 204.50 135.07 139.23 265.59 304.70 Split 0.2 3496.377 100-year FP 531.02 531.85 176.75 28.30 1540.84 567.82 245.76 333.49 Split 0.2 3496.377 100-year FW 531.02 0.00 532.21 109.80 33.07 1797.65 306.24 237.20 245.76 333.49 347.00 Split 0.2 3348.291 100-year FP 530.22 530.68 230.69 4.51 2048.35 84.10 384.20 520.30 Split 0.2 3348.291 100-year FW 531.12 0.90 531.37 171.14 9.93 2026.31 100.72 375.99 384.20 520.30 547.13 Split 0.2 3196.821 100-year FP 530.13 530.57 168.92 194.53 1714.56 227.87 430.81 509.77 Split 0.2 3196.821 100-year FW 531.02 0.88 531.32 139.50 212.75 1754.16 170.05 398.14 430.81 509.77 537.64 Split 0.2 3041.591 100-year FP 529.38 530.36 164.40 404.67 1347.84 384.46 228.05 252.09 Split 0.2 3041.591 100-year FW 530.36 0.98 531.19 72.22 527.19 1376.14 233.63 192.82 228.05 252.09 265.04 Split 0.2 2910.673 100-year FP 529.41 530.06 202.98 41.41 1253.82 841.73 319.33 343.61 Split 0.2 2910.673 100-year FW 530.42 1.00 530.99 86.10 130.83 1279.23 726.91 293.93 319.33 343.61 432.40 Split 0.2 2623.023 100-year FP 528.57 529.60 126.96 0.71 1284.82 851.42 157.60 181.58 Split 0.2 2623.023 100-year FW 528.92 0.35 530.53 68.57 4.34 1586.73 545.89 153.78 157.60 181.58 383.00 Proposed Condition 100-Year Floodplain and Floodway
0 200 400 600 800 1000 1200
532
534
536
538
540
542
544
546
Prop Cond 2023-0728 FPFW
RS = 3952.589
Station (ft)
Elevation (ft)
Legend
WS 100-year FP
WS 100-year FW
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
0 100 200 300 400 500 600 700 800
530
532
534
536
538
540
542
544
Prop Cond 2023-0728 FPFW
RS = 3753.787
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .
0 4
.015 .02
0 200 400 600 800
528
530
532
534
536
538
540
542
544
Prop Cond 2023-0728 FPFW
RS = 3614.247
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .
0 4
.03 .015 .
0 2
.015 .02
0 200 400 600 800 1000
528
530
532
534
536
538
540
542
544
Prop Cond 2023-0728 FPFW
RS = 3496.377
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .04 .03 .
0 2
.015 .02
0 200 400 600 800 1000
526
528
530
532
534
536
538
540
542
Prop Cond 2023-0728 FPFW
RS = 3348.291
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .
0 4
.013 .015 .
0 2
.
0 4
.
0 2
.04
0 200 400 600 800 1000 1200
526
528
530
532
534
536
538
540
542
Prop Cond 2023-0728 FPFW
RS = 3196.821
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .03 .015 .04 .02
0 200 400 600 800 1000
520
525
530
535
540
545
Prop Cond 2023-0728 FPFW
RS = 3041.591
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
545
Prop Cond 2023-0728 FPFW
RS = 2910.673
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Bank Sta
Encroachment
.02 .02 .02
0 200 400 600 800 1000
520
525
530
535
540
Prop Cond 2023-0728 FPFW
RS = 2623.023
Station (ft)
Elevation (ft)
Legend
WS 100-year FW
WS 100-year FP
Ground
Ineff
Bank Sta
Encroachment
.02 .02 .02
3041.591
3496.377
3952.589
2910.673
3196.821
3348.291
3614.247
3753.787
2623.023

San Marcos City CouncilDecember 12, 2023

San Marcos City Council
December 12, 2023