18_S-B LRGFCP Hydraulic Model Update Report 200807.pdf

Lower Rio Grande Flood Control Project

HEC-RAS Hydraulic Model Update and Validation (Penitas to River Mile 28 and Off-River Floodways in Texas and Mexico)

Book 1 of 1

Prepared For:

International Boundary and Water Commission United States and Mexico

United States Section

July 2008

Contract Number: IBM05D0001 Task Order Number: IBM06T0014

Prepared By:

Lower Rio Grande Flood Control Project (LRGFCP) 7/14/2008 i

For the Lower Rio Grande Flood Control Project (LRGFCP), Penitas to River Mile 28 and Off-River Floodways in Texas and Mexico

Book 1 of 1

Table of Contents

Description Page No.

A. Introduction

B. Purpose and Scope of the Study

C. Data Research, Site Inventory, and Site Survey

D. 2007 Hydraulic Model Update

E. Scour Analysis for the Hidalgo-Reynosa and Progreso Bridges

F. Rio Grande Unsteady State Model

G. Conclusions

H. References

I. Project Software

List of Tables

Table 1: Manning’s n Values

Table 2: Subcritical Flow Contraction and Expansion Coefficients

Table 3: Drag Coefficients for Various Pier Shapes

Table 4: Yarnell’s Pier Coefficient, K, for Various Pier Shapes

Table 5: Entrance Loss Coefficients ii

Table 6: Flow Assignments for the Rio Grande and the US Floodways and the

Mexico Floodway as Per Minute 238

Table 7: Hidalgo-Reynosa Southbound Bridge Scour Results

Table 8: Hidalgo-Reynosa Northbound Bridge Scour Results

Table 9: Progreso Bridge Scour Results

Table 10: Comparison of Rio Grande Historical Mean Daily Discharge Data 1967 and HEC-RAS Unsteady State Model

Table 11: Rio Grande US Levee Freeboard Encroachment and Overtopping

Summary Table

Table 12: Rio Grande Mexico Levee Freeboard Encroachment and Overtopping

Summary Table

Table 13: Arroyo Colorado Left Levee/High Bank Freeboard Encroachment and

Overtopping Summary Table

Table 14: Arroyo Colorado Right Levee/High Bank Freeboard Encroachment and

Overtopping Summary Table

Table 15: Main and North Floodways Left Levee Freeboard Encroachment and

Overtopping Summary Table

Table 16: Main and North Floodways Left Levee Freeboard Encroachment and

Overtopping Summary Table

Table 17: Mexico Floodway Left Levee Freeboard Encroachment and

Overtopping Summary Table

Table 18: Mexico Floodway Right Levee Freeboard Encroachment and

Overtopping Summary Table

Table 19: Rio Grande Levee Freeboard Table iii

Table 20: Arroyo Colorado Levee Freeboard Table

Table 21: Main and North Floodways Levee Freeboard Table

Table 22: Mexico Floodway Levee Freeboard Table

Figures

Figure 1: Hidalgo-Reynosa Southbound Bridge Scour Results Plot

Figure 2: Hidalgo-Reynosa Northbound Bridge Scour Results Plot

Figure 3: Progreso Bridge Scour Results Plot

Figure 4: HEC-RAS Plot of 1967 Beulah Hydrograph At Rio Grande City

Attachments

Attachment A, Aerial Mapping and Cross Section Layouts

Aerial Index (Rio Grande, Main, North, Arroyo Colorado, and Mexico

Floodways)

Aerial Maps Rio Grande

Aerial Maps Main Floodway

Aerial Maps North Floodway

Aerial Maps Arroyo Colorado Floodway

Aerial Maps Mexico Floodway

Report Indices

Project Model Summary Tables:

Index Contents

Rio Grande Steady State HEC_RAS Model Summary Table

Rio Grande Unsteady State HEC-RAS Model Summary Table iv

Arroyo Colorado Floodway Steady State HEC-RAS Model Summary

Table

Main & North Floodway Steady State HEC-RAS Model Summary Table

Mexico Floodway Steady State HEC-RAS Model Summary Table

Flow Assignments for the Rio Grande and Floodways:

Index Contents

Existing Floodway System

Rio Grande Steady State Model Data:

Index Contents

Rio Grande Steady State HEC-RAS Standard Table 1

Rio Grande Steady State HEC-RAS Standard Table 2

Rio Grande Steady State HEC-RAS Water Surface and Levee Profiles

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Southbound Bridge

Scour Graphic

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Southbound Bridge

Scour Table

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Southbound Scour

Detailed Report

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Northbound Bridge

Scour Graphic

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Northbound Bridge

Scour Table

Rio Grande Steady State HEC-RAS Hidalgo- Reynosa Northbound Scour

Detailed Report v

Rio Grande Steady State HEC-RAS Progreso Bridge Scour Graphic

Rio Grande Steady State HEC-RAS Progreso Bridge Scour Table

Rio Grande Steady State HEC-RAS Progreso Scour Detailed Report

Comparable Soils Data for Approximation of D50 & D90 Grain Sizes

Rio Grande Unsteady State Model Data:

Index Contents

Rio Grande and Floodways: Flood of September-October 1967 Discharge

Hydrographs Graphic Plot

Rio Grande City 1967 Hurricane Beulah Stage-Discharge-Time Graphic

Plot

Rio Grande City 1967 Hurricane Beulah Stage-Discharge-Time Ordinates

September Through October 1967 Rio Grande Gauge Flow Data Tables

Rio Grande Unsteady State Standard Table 1

Rio Grande Unsteady State Standard Table 2

Rio Grande Unsteady State Water Surface and Levee Profiles

Arroyo Colorado Floodway Steady State Model Data:

Index Contents

Arroyo Colorado Floodway Steady State Standard Table 1

Arroyo Colorado Floodway Steady State Standard Table 2

Arroyo Colorado Floodway Steady State Water Surface and Levee

Profiles

Main & North Floodways Steady State Model Data:

Index Contents vi

Main & North Floodways Steady State Standard Table 1

Main & North Floodways Steady State Standard Table 2

Main & North Floodways Steady State Water Surface and Levee Profiles

Mexico Floodway Steady State Model Data:

Index Contents

Mexico Floodway Steady State Standard Table 1

Mexico Floodway Steady State Standard Table 2

Mexico Floodway Steady State Water Surface and Levee Profiles

Report Appendices

Appendix A, Book 1 of 3, Lower Rio Grande

Table of Contents

Lower Rio Grande Existing HEC-RAS Input Data (Table 1)

Lower Rio Grande Existing HEC-RAS Input Data (Table 2)

Existing HEC-RAS River Profile and Cross Section Plots

Existing HEC-RAS Errors, Warnings and Notes

New Cross Section Locations (Table 3)

New Cross Section Endpoints (Table 4)

Appendix A, Book 2 of 3, Main and North Floodways

Table of Contents

Main and North Floodways Existing HEC-RAS Input Data (Table 1)

Main and North Floodways Existing HEC-RAS Input Data (Table 2)

Existing HEC-RAS River Profile and Cross Section Plots

Existing HEC-RAS Errors, Warnings and Notes vii

New Cross Section Locations (Table 3)

New Cross Section Endpoints (Table 4)

Appendix A, Book 3 of 3, Arroyo Colorado

Table of Contents

Arroyo Colorado Existing HEC-RAS Input Data (Table 1)

Arroyo Colorado Existing HEC-RAS Input Data (Table 2)

Existing HEC-RAS River Profile and Cross Section Plots

Existing HEC-RAS Errors, Warnings and Notes

New Cross Section Locations (Table 3)

New Cross Section Endpoints (Table 4)

Appendix B, Book 1 of 1, Site Inventory

Table of Contents

Site Inventory Summary of Structure Crossings:

Site Inventory and Summary of Structures of the Rio Grande and

Floodways from Penitas to Brownsville

Mexico Floodway:

Highway 101 - Northbound

Highway 101 – Southbound

Highway 101 - Puente El Tigre

Old Highway 101 - Arroyo Del Tigre

Highway 101 - Agricultural Crossing

Highway 2 Libre Bridge over Cauce De Alivio

Highway 2 Libre Bridge over Vaso Palito Blanco - Puente El Regio

Rail Road Bridge viii

Highway 2 Toll Road

Rio Grande:

Veterans International Bridge

Gateway International Bridge – Northbound

Gateway International Bridge – Southbound

Brownsville & Matamoros Bridge Company

Los Indios Bridge

Progreso Bridge #1 - Vehicular and Pedestrian

Progreso Bridge #2 - Commercial Truck Traffic

Pharr-Reynosa

Hidalgo-Reynosa - Northbound Bridge & As-Built

Hidalgo-Reynosa - Southbound Bridge & As-Built

Arroyo Colorado:

Rail Road Bridge #1 - Port of Harlingen

Bridge #2 – Cemetery Road

FM 509 Bridge

Loop 499 – Ed Carey Drive Bridge

Business 77 – Sunshine Strip Bridge

Pedestrian Bridge #1 – Upstream of Bus 77, Downstream of RR

Business 77 Rail Road Bridge

Pedestrian Bridge #2 – Arroyo Park, Upstream of RR Bridge

Expressway 77 – Northbound Frontage Road

Expressway 77 – Main Lanes

Expressway 77 – Southbound Frontage Road ix

Bridge #9 – Dilworth Road

FM 800 Bridge

FM 506 Bridge

FM 2556

FM 491 Bridge

Bridge #14

North Floodway to Arroyo Colorado Culvert

North Floodway:

Old Alice Road Bridge

FM 1420 Bridge

FM 507 Bridge

FM 2629 Bridge

Bridge #5

Bridge #6

US 77 – Northbound Frontage Road Bridge

US 77 – Main Lanes

US 77 - Rail Road Bridge

FM 506 Bridge

FM 1425 Bridge

Highway 107 Bridge

Bridge #13

Bridge #14

Mile 12 North Bridge

FM 491 – Baseline Bridge x

Expressway 83 Bridge

Expressway 83 Rail Road Bridge

Business 83 Bridge

Bridge #20 – Llano Grande Country Club

Main Floodway:

FM 1015

Highway 88 Bridge

FM 493 Bridge

FM 907 Alamo Road

Bridge #27 - Stewart Road

“I” Road Bridge

US 281 – New Bridge

US 281 – Old Bridge

Bridge #29

Jackson Road Bridge

McColl Road Culvert

Bridge #32

10th Street Bridge

23rd Street (Spur 115) - Twin Bridges Main Lanes

23rd Street (Spur 115) – Frontage Road Culvert

Comparison of Existing HEC-RAS Model with 2007 Site Inventory:

Rio Grande Bridges

Arroyo Colorado Floodway Bridges

Main & North Floodway Bridges xi

Appendix C, Book 1 of 2, 2007 Survey and Hydrographic Data Collection

Report

Table of Contents

Survey Report

Cross Section Location and Survey Points Map

Cross Section Control Points

Survey ASCII Points File

Graphical Plots of Hydrographic Cross Sections

Appendix C, Book 2 of 2, 2007 Survey and Hydrographic Data Collection

Report

Table of Contents

Surveyor’s Field Notes

Location Photos at Cross Sections

Appendix D, Book 1 of 1, 2007 New HEC-RAS Cross Section Data

Table of Contents

Rio Grande:

New Cross Section Locations Table

HEC-RAS Profile Plot

New Cross Section Plots

Arroyo Colorado Floodway:

New Cross Section Locations Table

HEC-RAS Profile Plot

New Cross Section Plots

Main & North Floodways:

xii

New Cross Section Locations Table

HEC-RAS Profile Plot

New Cross Section Plots

Mexico Floodway:

New Cross Section Locations Table

HEC-RAS Profile Plot

New Cross Section Plots

The Main Floodway from 23rd Street

The Mexico Floodway from Hwy 101

The Rio Grande from the Los Indios Bridge

The Arroyo Colorado from Loop 499

Lower Rio Grande Flood Control Project Report

(Penitas to River Mile 28 and Off-River Floodways in Texas and Mexico)

A) Introduction

This report presents a validation and update for the Lower Rio Grande Flood Control Project’s (LRGFCP) existing 2003 Rio Grande, from Penitas to River Mile 28 and the 2003 North, Main, and Arroyo Colorado floodway hydraulic models. It also will address the provision of a new hydraulic model for the Mexico floodway. The following terms ‘2003 models’ represents the existing hydraulic model for the Rio Grande and the United States side floodways, and ‘2007 models’ which is the updated hydraulic model that includes the Rio Grande, the United States side floodways, and the Mexico floodway will be used throughout this report.

The Main floodway begins at Bankers Weir just south of McAllen, Texas on the United States side of the Rio Grande. This floodway continues eastward to the City of Mercedes, Texas. At this location the Main floodway splits and forms the Arroyo Colorado and the North floodway. The North floodway continues northward to just north of La Villa, Texas where it then turns eastward and continues to the Laguna Madre. The Arroyo Colorado continues eastward from Mercedes, Texas to just south of Harlingen, Texas where it turns northeasterly and then continues through Harlingen, Texas and Arroyo City, Texas. It then terminates at the Laguna Madre.

This study also entailed creating a working hydraulic model for the Mexico floodway. The Mexico floodway begins with headwater at the Retamal Weir just southeast of the Rio Grande, and then continues east to Vaso Del Culebron which in turn drains under Old Highway 2. At this location an adjacent channel parallel to the floodway breaks to the southwest and continues to Vaso Palito Blanco. The Mexico floodway turns southeast and continues from Old Highway 2 and is called Cauce De Alivio. The Mexico floodway hydraulic model terminates just southeast of Highway 180 and northwest of the

Gulf of Mexico. It should be noted that Highway 180 is also referred to as Highway 101. Mapping of the Rio Grande and the aforementioned floodways is provided in Attachment A, ‘Aerial Mapping and Cross Section Layouts’ and Report Index, ‘Existing Floodway System’.

The North Floodway from US 77

Aerial of Banker’s Weir and Anzalduas Dam

Aerial of Retamal Dam and Retamal Weir

Similar studies were conducted in 1992 and 2003 with respective reports entitled ‘Status of Conveying Capacity of the Lower Rio Grande Flood Control Project’ and ‘Hydraulic Model of the Rio Grande and Floodways within the Lower Rio Grande Flood Control Project’. The latter 2003 study updated and provided additional accuracy to the 1992 report. Since the 2003 study:

� Construction of new or modifications to existing bridge crossings across the Rio Grande and floodways have occurred.

� Land use and vegetative cover within or adjacent to the river and floodway areas have experienced moderate changes.

� Current topographic information, such as 2006 light detection and ranging (lidar) data and 2007 field survey information, has been obtained.

It should be noted that the ‘2003 models’ were based on Texas State Plain, South, 1929 datum. The 2006 LIDAR data is referenced to Texas State Plain, South, NAD 83, NAVD 88. The IBWC converted the ‘2003 models’, for use in this study, to Texas State Plain, South, NAD 83, NAVD 88. The vertical conversion varied throughout the project but generally was .36 feet lower than the prior 1929 vertical datum.

B) Purpose and Scope of the Study

The United States International Boundary and Water Commission (USIBWC) developed a Hydrologic Engineering Center – River Analysis System (HEC-RAS) hydraulic model for the Lower Rio Grande Flood Control Project (LRGFCP) in June 2003. The USIBWC has been using the ‘2003 model’ to provide planning and design for the LRGFCP.

The primary goal of this study is to:

� Update and verify the existing ‘2003 steady state model’ with respect to roughness coefficients, expansion and contraction coefficients, ineffective flow areas, blocked obstructions, reach lengths, bank locations, river geometry, and structure geometry.

� Evaluate existing cross section spacing and incorporate new surveyed cross sections to provide more accurate modeling of flow.

� Provide a new hydraulic model for the Mexico floodway using 2006 lidar data.

� Provide an unsteady state model for the Rio Grande from Rio Grande City, Texas to River

Mile 28 which utilizes the 1967 Beulah hydrograph recorded at Rio Grande City, Texas.

� Provide an analysis of scour potential at the Hidalgo-Reynosa and Progreso bridge crossings over the Rio Grande.

� Evaluate levee freeboard with respect to the requirement of two (2) feet along the floodway levees and three (3) feet along the Rio Grande levees.

C. Data Research, Site Inventory, and Site Survey

The ‘2003 models’ for the Rio Grande and the Main, North and Arroyo Colorado floodways were reviewed with respect to roughness coefficients, reach lengths, expansion and contraction coefficients, bank stations and bridge widths. This information was tabulated in Appendix A, Books 1, 2, and 3, Tables 1 and 2. Each model’s ‘Summary of Errors, Warning and Notes’ is also included. Profile plots which include water surfaces and river mile stationing, and cross section plots are also included. Book 1 of 3 corresponds to the Rio Grande, Book 2 of 3 the North and Main floodways, and Book 3 of 3 the Arroyo Colorado floodway. Blocked obstructions used in the ‘2003 model’ were not tabulated however they were checked using aerial photography. Blocked obstructions, in general, are used to represent obstructions within the channel cross section which reduces conveyance area. The ‘2003 models’ incorporated these in the floodway areas to represent obstructions such as urban area development within the floodplain and they were found to be fairly accurate. Within the Rio Grande, blocked obstructions were used to remove depressed areas that were lower than the banks of the Rio Grande. This was also found to be acceptable since many of the ponds, cultivated or furrowed areas, and resacas adjacent to the Rio Grande’s left and right banks retain water.

The following tables were used to evaluate the ‘2003 models’ and to develop the hydraulic coefficients for use in the updated‘2007 models’. These tables can also be found in the ‘HEC- RAS River Analysis System Reference Manual’, November 2006, United States Army Corps of Engineers, Hydrologic Engineering Center.

TABLE 1

Manning’s ‘n’ Value Type of Channel and Description Minimum Normal Maximum A. Natural Streams

1. Main Channels

a. Clean, Straight, full, no rifts or deep pools 0.025 0.030 0.033

b. Same as above, but more stones and weeds 0.030 0.035 0.040

c. Clean, winding, some pools and shoals 0.033 0.040 0.045

d. Same as above, but some weeds and stones 0.035 0.045 0.050

e. Same as above, lower stages, more ineffective slopes and sections 0.040 0.048 0.055

TABLE 1 (CONT’D.)

Manning’s ‘n’ Values Type of Channel and Description Minimum Normal Maximum

f. Same a “d” but more stones 0.045 0.050 0.060

g. Sluggish reaches, weedy, deep pools 0.050 0.070 0.080

h. Very weedy reaches, deep pools, or floodways with heavy stands of timber and brush 0.070 0.100 0.150

2. Floodplains

a. Pasture no brush

1. Short grass 0.025 0.030 0.035

2. High grass 0.030 0.035 0.050

b. Cultivated areas

1. No Crop 0.020 0.030 0.040

2. Mature row crops 0.025 0.035 0.0.45

3. Mature field crops 0.030 0.040 0.050

c. Brush

1. Scattered brush, heavy weeds 0.035 0.050 0.070

2. Light brush and trees, in winter 0.035 0.050 0.060

3. light brush and trees, in summer 0.040 0.060 0.080

4. Medium to dense brush, in winter 0.045 0.070 0.110

5. Medium to dense brush, in summer 0.070 0.100 0.160

d. Trees

1. Cleared land with tree stumps, no sprouts 0.030 0.040 0.050

2. Same a above, but heavy sprouts 0.050 0.060 0.080

3. Heavy stand of timber, few down trees, little undergrowth, flow below branches 0.080 0.100 0.120

4. Same as above, but with flow into branches 0.100 0.120 0.160

5. Dense willows, summer, straight 0.110 0.150 0.200

Type of Channel and Description Minimum Normal Maximum

B. Lined or Built-Up Channels

1. Concrete

a. Trowel finish 0.011 0.013

b. Float, with gravel bottom 0.013 0.015 0.015

c. Finished, with gravel bottom 0.015 0.017 0.016

d. Unfinished 0.014 0.017 0.020

e. Gunite, good section 0.016 0.019 0.020

f. Gunite, wavy section 0.018 0.022 0.023

g. On good excavated rock 0.017 0.020 0.025

h. On irregular excavated rock 0.022 0.027

2. Concrete bottom float finished with sides of:

a. Dressed stone in mortar 0.015 0.017 0.020

b. Random stone in mortar 0.017 0.020 0.024

c. Cement rubble masonry, plastered 0.016 0.020 0.024

d. Cement rubble masonry 0.020 0.025 0.030

e. Dry rubble on riprap 0.020 0.030 0.035

3. Gravel bottom with sides of :

a. Formed concrete 0.017 0.020 0.025

b. Random stone in mortar 0.020 0.023 0.026

c. Dry rubble on riprap 0.023 0.033 0.036

4. Brick

a. Glazed 0.011 0.013 0.015

b. In cement mortar 0.012 0.015 0.018

5. Metal

a. Smooth steel surfaces 0.011 0.012 0.014

b. Corrugated metal 0.021 0.025 0.030

6. Asphalt

a. Smooth 0.013 0.013

b. Rough 0.016 0.016

7. Vegetal lining 0.030 0.050

Type of Channel and Description Minimum Normal Maximum

C. Excavated or Dredged Channels

1. Earth, straight and uniform

a. Clean, recently completed 0.016 0.018 0.020

b. Clean, after weathering 0.018 0.022 0.025

c. Gravel, uniform section, clean 0.022 0.025 0.300

d. With short grass, few weeds 0.022 0.027 0.330

2. Earth, winding and sluggish

a. No vegetation 0.023 0.025 0.030

b. Grass, some weeds 0.025 0.030 0.033

c. Dense weeds or aquatic plants in deep channels 0.030 0.035 0.400

d. Earth bottom and rubble side 0.028 0.030 0.035

e. Stony bottom and weedy banks 0.025 0.035 0.040

f. Cobble bottom and clean sides 0.030 0.040 0.050

3. Dragline-excavated or dredged

a. No Vegetation 0.025 0.028 0.033

b. Light brush on banks 0.035 0.050 0.060

4. Rock cuts

a. Smooth and uniform 0.025 0.035 0.040

b. Jagged and irregular 0.035 0.040 0.050

5. Channels not maintained, weeds and brush

a. Clean bottom, brush on sides 0.040 0.050 0.080

b. Same as above, highest stage of flow 0.045 0.070 0.110

c. Dense weeds, high as flow depth 0.050 0.080 0.120

d. Dense brush, high stage 0.080 0.100 0.140

TABLE 2

Subcritical Flow Contraction and Expansion Coefficients

Description Contraction Expansion No transition loss computed 0.0 0.0 Gradual transitions 0.1 0.3 Typical Bridge sections 0.3 0.5 Abrupt transitions 0.6 0.8

TABLE 3

Drag Coefficients for Various Pier Shapes

Pier Shape Drag Coefficient CD

Circular Pier 1.20 Elongated Piers with Semi-circular ends 1.33 Elliptical piers with 2:1 length to width 0.60 Elliptical piers with 4:1 length to width 0.32 Elliptical piers with 8:1 length to width 0.29 Square nose piers 2.00 Triangular nose with 30 degree angle 1.00 Triangular nose with 60 degree angle 1.39 Triangular nose with 90 degree angle 1.60 Triangular nose with 120 degree angle 1.72

TABLE 4

Yarnell’s Pier Coefficient, K, for Various Pier Shapes

Pier Shape Yarnell K Coefficient

Semi-circular nose and tail 0.90 Twin-cylinder piers with connecting diaphragm 0.95 Twin-cylinder piers without diaphragm 1.05 90 degree triangular nose and tail 1.05 Square nose and tail 1.25 Ten pile trestle bent 2.50

Pipe Culverts

Coefficient, ken

Concrete Pipe Projecting from Fill (no headwall) Socket end of pipe 0.2 Square cut end of pipe 0.5

Concrete Pipe with Headwall or Headwall and Wingwalls Socket end of pipe (grooved end) 0.2 Square cut end of pipe 0.5 Rounded entrance, with rounding radius=1/12 of diameter 0.2

Concrete Pipe Mitered to conform to fill slope 0.7 End section conformed to fill slope 0.5 Beveled edged, 33.7 or 45 degree bevels 0.2 Side slope tapered inlet 0.2

Corrugated Metal Pipe or Pipe-Arch Projected from fill (no headwall) 0.9 Headwall or headwall and wingwalls square edge 0.5 Mitered to conform to fill slope End section conformed to fill slope 0.7 End section conformed to fill slope 0.5 Beveled edges, 33.7 or 45 degree bevels 0.2 Side slope tapered inlet 0.2

TABLE 5

Entrance Loss Coefficients

Reinforced Concrete Box Culverts Coefficient, ken

Headwall Parallel to Embankment (no wingwalls):

Square-edged on three edges 0.5 Three edges rounded to radius of 1/12 barrel dimension 0.2

Wingwalls at 30 to 75 degrees to Barrel Square-edge at crown 0.4 Top corner rounded to radius of 1/12 barrel dimension 0.2

Wingwalls at 10 to 25 degrees to Barrel Square-edge at crown 0.5

Wingwalls parallel (extension of sides) Square-edged at crown 0.7

Side or slope tapered inlet 0.2

TABLE 5 (CONT’D)

Entrance Loss Coefficients

Concrete Culverts

Coefficient, ken

Extended wingwalls 0 degrees 0.5 45 degree wingwalls 0.3 Straight headwall 0.4

Aerial photography, site visits, land use maps, and vegetation mapping, were employed to confirm roughness coefficients used in the existing ‘2003 models’ for the Rio Grande and associated US side floodways. The ‘2003 models’ cross section lines and aerial photography of the project area were geo-referenced and superimposed together into one map as a visual aid of vegetative cover and land use at a particular cross section location. Land use mapping and vegetative mapping were obtained from prior studies for Hidalgo County and Cameron County, and an Environmental Impact Statement (EIS) prepared by the International Boundary and Water Commission, United States and Mexico, United States Section, ‘Alternative Vegetative Management Practices for the Lower Rio Grande Flood Control Project’, Cameron, Hidalgo, and Willacy Counties, Volumes I, II, & III, December 2003. The project area is referred to as being regionally located in ‘South Texas Brush Country’. This region, prior to development contains areas of short and tall brush and scrub. Vegetation types include agriculture, sabal, grassland, thorn and scrub. Land use is primarily agricultural cropland and pasture with secondary areas being forestland, citrus and rangeland. There are pockets of urbanization outside the levees such as McAllen, Reynosa, Progreso, Hidalgo, Mercedes, Harlingen, and Brownsville.

The roughness coefficients (n values) input into the ‘2003 models’ had been entered to vary with horizontal distance across the cross section and depicted changes in vegetative cover and/or land use. Spot site visits and the aerial photography confirmed that the coefficients used in the ‘2003 models’ depicted forestland with values between .08 and 0.2, tall and short brush areas with values between .06 and .08, and earthen areas with values between .02 and 04. These values are within the ranges listed in Table 1, ‘Manning’s (n) Values’ and were found to be acceptable.

The ‘2003 models’ were also reviewed, as mentioned earlier, for expansion and contraction coefficients and ineffective flow areas. The expansion and contraction coefficients were 0.1 and

0.3 at river cross sections and 0.2 and 0.5 at structure crossings. These values agree with those in Table 2, ‘Subcritical Flow Expansion and Contraction Coefficients’. There were no areas designated for ineffective flow along the Rio Grande, since they are usually employed at bridge crossings and the crossings along the Rio Grande are generally from levee to levee. Locations, in the ‘2003 models’, designated for ineffective flow along the floodways were appropriately placed at bridge crossings that encroach in the floodway and restrict the conveyance of flow.

A site inventory was performed to collect additional data. The specific tasks were to:

� Retrieve actual field measurements of all of the bridge and culvert crossings of the Rio Grande, and the North, Main, Arroyo Colorado, and Mexico floodways.

� Take site photographs for use in evaluating hydraulic parameters, such as cross section roughness coefficients, additional modeling of structures, and comparing field built to the ‘2003 models’ bridge or culvert geometries.

Prior to entering the field a summary of the structures known to cross the Rio Grande and the floodways on both the United States side and the Mexico side was prepared. Identification badges were obtained from the IBWC for those individuals traveling to the Mexico side to inventory the bridge and culvert crossings over the Mexico floodway. A checklist was prepared prior to going to the field which identified specific measurements and notes which were to be documented such as bridge width, pier shape, embankment slope, bridge skew, pier width etc.

The summary of crossings can be found in Appendix B, Book 1 of 1, ‘Site Inventory’, ‘Site Inventory Summary of Structure Crossings’. The completed checklists along with photographs of the crossings can also be found in Appendix B, Book 1 of 1, ‘Site Inventory’.

Discrepancies found between the ‘2003 models’ were minor and usually consisted of piers being grouped rather than modeled individually. It was found that generally the pier groups would obstruct the same area as the individual piers. The ‘2003 models’ used the energy equation for low flow conditions. The energy equation treats the bridge opening as a natural river section and the area of the piers are subtracted out of the cross sectional area. This in turn increases the wetted perimeter where the water is in contact with the bridge. Since the ‘2003 models’ grouping of piers at several locations did approximate the same area as the combined total of individual piers, we did not see any benefit to revising those locations. From past projects, where this had been done, negligible changes to the water surface were reported. It would however be necessary if we were considering scour potential. Other discrepancies were structures not being included in the model such as FM 509 crossing the Arroyo Colorado. The bridges at Hidalgo- Reynosa and Progreso had many discrepancies and therefore were re-modeled as part of this study. The bridge crossing FM 509 was also incorporated into the 2007 Arroyo Colorado model.

The structures crossing the Mexico floodway were all modeled as part of the new 2007 Mexico HEC-RAS model. A table documenting discrepancies between the ‘2003 models’ and the site inventory can be found in Appendix B, Book 1 of 1, ‘Site Inventory’, ‘Comparison of Existing HEC-RAS Model with 2007 Site Inventory’.

In addition, to the site inventory, a field survey using global positioning system (GPS) was performed to:

� Establish horizontal and vertical control based on Texas State Plain Grid, Texas South Zone, NAD 83 and NAVD 88 datum along the levees encompassing both sides of the Rio Grande and the North, Main, and Arroyo Colorado floodways

� Establish geographic coordinates for seventy-one (71) new cross section locations on both the United States side and the Mexico side of the Rio Grande. Surveyed locations at each cross section were to identify the horizontal and vertical coordinates of the toes of the levees, the top of levees, and also be staked with an iron rod on each top of the levee.

� Take bathymetric sections and establish geographic coordinates of the channel flowline at each of the seventy-one (71) cross sections on the Rio Grande extending from the left bank on the United States side to the right bank on the Mexico side of the Rio Grande for seventy-one (71) cross section locations. Sounding data was to be taken every three to five seconds.

� Establish geographic coordinates for nineteen (19) new cross section locations along the Main and North floodways and eleven (11) along the Arroyo Colorado floodway. Surveyed locations at each cross section were to identify the horizontal and vertical coordinates of the toes of the levees, the top of levees, and also be staked with an iron rod and cap on each top of the levee.

� Provide a three dimensional (3-D) .dxf file (AutoCAD) of the surveyed locations along each new cross section line (left levee, right levee, and channel).

Prior to executing the surveyor to the field a review was performed of the ‘2003 models’ reach lengths and summaries of errors, warnings, and notes. As mentioned previously, these are included in Appendix A, Books 1 of 3, 2 of 3, and 3 of 3, ‘Existing, Errors, Warnings and Notes’ for the Rio Grande and the floodways on the United States side. The warning messages which establish the need for additional cross sections are:

� The conveyance ratio, which is the upstream conveyance divided by the downstream conveyance, is low.

� The velocity head has changed by more than the allowable, which is set at a default value of one-half (0.5) foot.

� The energy loss is greater than one (1.0) foot.

A table was prepared for the Rio Grande and each floodway on the United States side which tabulated these messages by each of their existing cross sections. Existing distances between cross sections for the channel and the left and right over banks were also included as well as expansion and contraction coefficients. New cross sections were inserted at the locations experiencing numerous warnings and also those with extremely long distances between upstream and downstream sections. This table can be found in Appendix A, Books 1 of 3, 2 of 3, and 3 of 3, Table 3, ‘New Cross Section Locations’. The USGS maps, provided by the IBWC, of the Rio Grande and the Main, North and Arroyo Colorado floodways were geo-referenced and the existing and new cross section locations were superimposed on them. These maps can be found in Appendix C, Book 1 of 2, 2007 Survey and Hydrographic Data Collection Report, ‘Cross Section Location and Survey Control Points Map’. To assist the surveyor in finding these locations in the field, due to poor access and line of sight at many locations, the applicable tile of or tiles of lidar data were converted to shape files and brought into ArcMap along with the geo-referenced maps of new cross section locations. The coordinate end points, of the cross section or left and right levees were tabulated. These coordinates were used as an aid by the surveyor to establish where the levees or cross section endpoints were to be surveyed. The surveyor established these sites using handheld global positioning system locators. A visual determination would be made by the surveyor at the site, as to the accuracy of the coordinates provided. These tabulated coordinate end points can be found in Appendix A, Books 1 of 3, 2 of 3, and 3 of 3, Table 4, ‘New Cross Section Endpoints’.

The complete survey report can be found in Appendix C, Book 1 of 2, ‘2007 Survey and Hydrographic Data Collection Report’. Also included in Appendix C, Books 1 of 2 and 2 of 2 are:

� ASCII point list � Control points � Graphical plots of hydrographic cross sections of the Rio Grande � Surveyor’s field notes � Location photos at the individual cross sections

Aerial mapping which includes existing and proposed cross section locations, and corresponding lidar tile index number can be found in Attachment A, ‘Aerial Mapping and Cross Section Layouts’. It should be noted that site visits, aerial photography, and the location photos at each new cross section assisted in determining roughness coefficients in the ‘2007 model’.

D. 2007 Hydraulic Model Update

The ‘2003’ models’ incorporated design flows which were based on the 1970 agreement between the United States and Mexico known as Minute No. 238. In September 1967 the Rio Grande at Rio Grande City recorded a flood flow of 220,000 cubic feet per second (cfs) resulting from Hurricane Beulah. Minute 238 is an agreement to construct improvements to the Lower Rio Grande Flood Control Project (LRGFCP) based on a design flood of 250,000 cfs at Rio Grande City. The flow of 105,000 cfs diverted into the Main floodway is distributed as 84,000 cfs to the North floodway and 21,000 cfs to the Arroyo Colorado. The following table summarizes the flow assignments for the Rio Grande and both the United States floodways and the Mexico floodway.

TABLE 6

Flow Assignments For The Rio Grande And The United States Floodways And The Mexico Floodway As Per Minute 238

LOCATION CFS

Rio Grande at Rio Grande City 250,000

Storage Reduction between Rio Grande City and Penitas 15,000

Rio Grande at Penitas 235,000

Diversion to US Main Floodway 105,000

Rio Grande at Hidalgo Reynosa 130,000

Storage Reduction Between Hidalgo-Reynosa and Retamal Dam 5,000

Diversion to Mexico Floodway 105,000

Rio Grande at Brownsville-Matamoros 20,000

These same flow assignments remain unchanged and are included in the update to the ‘2007 models’. Report Index, Flow Assignments for the Rio Grande and Floodways’ contains a map detailing these locations. This map was taken from a study by the USACE entitled, United States Army Corps of Engineers, Galveston District, ‘Feasibility Report, Cameron County, Texas’, Volumes 1 and 2, 1990.

As mentioned earlier, the original ‘2003 models’ were adjusted from 1929 datum to NAD 83 and NAVD 88 datum. The first HEC-RAS plan is the original ‘2003 models’ with 1929 datum adjustment. The converted model became a second plan in the HEC-RAS ‘2007 model’ update and would be used for comparison purposes. The third HEC-RAS plan would incorporate the new cross sections and remodeling or addition of bridge or culvert crossing data into the 2007 NAD 83 NAVD 88 HEC-RAS plan. Report Index, ‘Project Model Summary Tables’, summarizes each of the three plans and lists:

� Plan file name and file extension � Geometry file name and file extension � Flow file name and file extension � Brief description of coordinate datum and modifications made to the model

The 2006 Lidar data, provided by the IBWC, was referenced or projected to NAD 83, NAVD 88, Texas State Plain Grid, South Zone. In order to complete each cross section it would necessary to fill in the voids along each of the cross sections with lidar coordinate point data where there was survey work was not done. These locations were:

� From one thousand feet outside of each of the left and right levees to the outside toe of each levee � From the inside toe of each left and right levee to the left and right river channel’s or floodway pilot channel’s left and right banks

The lidar data was converted to shape files and brought into ArcMap v. 9.2. Using 3D analyst, tin files were created from the lidar information. Due to limitations in the file size that the software can accommodate the river and floodways were segmented into sections. A .dxf (AutoCAD) file of the cross section locations along with aerial photography served as the back drop for extracting cross sections from the tin files created in ArcMap v. 9.2. Using HEC- GeoRAS v. 4.1.1, the cross sections and stream profiles for the river and floodways were re-drawn and exported to HEC-RAS v. 4.0. The extracted sections required point filtering, since the exported points numbered between two thousand (2000) and six thousands points (6000) and the HEC-RAS program will not accept over five hundred (500) points at any one cross section.

The target number of points at each cross section was set at four hundred and ninety (490) in order to allow for ineffective flow areas, levees and/or blocked obstructions which also count towards the five hundred (500) point maximum total in the cross section. Extracted points in the area of survey such as the levees and channels were deleted and replaced with the surveyed points. Each individual downstream section of river or floodway was processed in the same way and exported to its individual HEC-RAS model and appended to the previous processed section to complete each model.

The Mexico floodway model was processed in the same way with the exception that its model was generated completely from the 2006 lidar data. The ‘2007 Mexico floodway model’ contains one hundred and seventeen (117) cross sections. This floodway begins at the Retamal Weir which is a gravel elevated dike with vehicle access along the top. It connects the Retamal Dam and the Retamal Dike to the Culebron Canal. The new Highway 2, toll road, splits this floodway in half however there are bridge openings along the highway that allow flow to interchange from both sides. Where Highway 2 turns to the south and crosses the Culebron Canal the bridge opening is a restriction and was modeled as pier blocks with a lid. A portion of the flow downstream of the Retamal Weir and upstream of this Highway 2 bridge turns northward, due to this restriction, towards the Rio Grande and flows along the west and north side of Highway 2. The remaining portion of flow travels under the Highway 2, bridge at the Culebron Canal and flows along the south side of the highway. The floodway extends from here to a pond area known as Vaso Del Culebron; then narrows downstream at the Nacionales de Mexico railroad bridge; then narrows even more to about two thousand (2000) feet wide at the Old Highway 2 bridge crossing; and finally extends as the floodway, Cauce De Alivio, to Highway 183 or Old Highway 101 and the Gulf of Mexico.

As mentioned earlier, the roughness coefficients used in the ‘2007 model’ were based on site visits, site photos, land and vegetation maps, and aerial photography. Blocked obstructions were used in areas such as depressions or areas of ponding with no outlet. Depressed areas which did have an outlet such as to the Rio Grande were modeled as ineffective flow areas.

Appendix D, Book 1 of 1, ‘2007 New Cross Section Data,’ contains profile plots of the water surfaces and bank elevations, and the new 2007 cross section plots for the Rio Grande, the Main, North, Arroyo Colorado, and the Mexico floodway. The three water surface profiles in the profile plot, with exception of the Mexico floodway which is a new model, are the ‘2003 model’ water surface profile, the 2003 water surface profile adjusted to NAVD 88 vertical datum, and the ‘2007 model’ update. Report Indices for the ‘Rio Grande, and the Main, North, Arroyo Colorado, and the Mexico Floodways Steady State Model Data’, contain HEC-RAS Standard Tables 1 & 2 comparing all three HEC-RAS plans, and a profile plot with all three plans’ water surface elevations for comparison purposes. The profile plot also includes the left and right levee elevations.

E. Scour Analysis for the Hidalgo-Reynosa and Progreso Bridges

General

A scour analysis was prepared for each of the Hidalgo-Reynosa’s northbound and southbound bridges, and the Progreso bridges. The information from these analyses will identify the scour potential at each of these bridge locations which cross the Rio Grande. The hydraulic models in this report utilized the USACE Hydrologic Engineering Center, ‘River Analysis System’ (HEC- RAS), computer program, Version 4.0, which employs the equations from HEC-18 to calculate scour potential. The Federal Highway Administration’s Hydraulic Engineering Circular, HEC- 18, ‘Evaluating Scour at Bridges’, evaluates several types of scour: contraction scour, local scour at the piers, and local scour at the abutments. Determination of long term scour or

Downstream Face of Southbound Hidalgo-Reynosa Bridge seasonal scour known as aggradation and degradation requires long term field and stream monitoring and was not included in this evaluation.

These two bridge crossings which were previously modeled in the 2003 HEC-RAS model were compared to the 2007 site inventory and as-built drawings which can be found in Appendix B, ‘Site Inventory’. Discrepancies between the two sources of information are tabulated in Appendix B, ‘Comparison of Existing (2003) HEC-RAS Model with 2007 Site Inventory’.

The existing bridge geometry that was used in the 2003 HEC-RAS model was revised by compiling and incorporating the information from the as-built plans and the 2007 site inventory.

The new 2007 HEC-RAS hydraulic model provides the updated river geometry and hydraulic components. This revised model includes field investigation of Manning’s roughness coefficients (n values), expansion and contraction coefficients, ineffective flow areas, blocked obstructions and the addition of new surveyed cross sections. The scour potential was calculated with respect to the constrictions and obstructions created by each bridge crossing’s abutments and piers. The geo-technical information required for this analysis consists of a sieve analysis that correlates soil composition with respect to the percent passing of an individual soil grain size. Geo-technical explorations, soil sampling and testing were not included in the scope of this project however recent data had been collected at several proposed downstream bridge locations within the lower Rio Grande area. It was decided to review and use soils data similar to those locations downstream of the Hidalgo-Reynosa bridges that would be characteristic of the soils at both the Hidalgo-Reynosa and Progresso locations. This study obtained and reviewed both the Veteran’s bridge, located in Brownsville, Texas, and the Donna-Rio Bravo bridge, located in Donna, Texas, soils reports. The d50 and d90 grain sizes selected for use in this analysis are respectively 0.10 mm and 0.19 mm and are comparable to those found in the geo-technical report, ‘Geotechnical Exploration Final Report, Donna-Rio Bravo International Border Crossing- Alternative G’, February 18, 2003. A copy of this report can be found in the report index Rio Grande Steady State Model Data. The Rio Grande design flood flows were used in the analysis.

Hidalgo-Reynosa Bridges

Southbound

The Hidalgo-Reynosa southbound bridge is approximately 525 feet long with four (4) bents.

The bridge spans from the US levee to the Mexico levee with the low chord at 107.74 feet. The piers are groups of cylinders with a diameter of four (4) feet. In the original IBWC model the length of the bridge was 532 feet with four (4) piers with a diameter of 4.5 feet. Due to discrepancies with the site inventory the bridge geometry was updated using field measured data and the 1964 as-built plans. A copy of the as-builts can be found in Appendix B,’Rio Grande Site Inventory’.

The total scour calculated is based on the flow in the Rio Grande (125,000 cfs), a water surface elevation of 111.23 feet, and a channel velocity of 8.04 fps. The maximum total scour is 19.71 feet, based on the worst condition. Individual total scour calculations were preformed for each pier location based on pier diameter, depth of water, and velocity, and these results can be found in Table 7 of this report.

TABLE 7

Hidalgo-Reynosa Southbound Bridge Scour Results (RS 156.915) (Design Flood Flow)

Abutment/ Bent No

Abutment Scour (feet)

Pier Scour (feet)

Contraction Scour (feet)

Total Scour (feet)

Abutment 1 4.49 0.00 5.10 9.58 Bent 2 0.00 3.98 5.10 9.08 Bent 3 0.00 11.87 7.28 19.16 Bent 4 0.00 12.43 7.28 19.71 Bent 5 0.00 3.64 0.00 3.64

Abutment 6 25.15 0.00 0.00 25.15

FIGURE 1

Hidalgo-Reynosa Southbound Bridge Scour Results Plot (RS 156.915)

0 100 200 300 400 500 600

Bridge Scour RS = 156.915

Station (ft)

E le va tio n (f t)

Legend

WS PF 1

Ground

Bank Sta

Contr Scour

Total Scour

Northbound

The Hidalgo-Reynosa northbound bridge is approximately 855.7 feet long with eight (8) bents.

The bridge spans from the US levee to the Mexico levee with the low chord at 109.84 feet. The piers are group of cylinders with a diameter of 16.42 feet and eight (8) feet. In the original IBWC model the length of the bridge was 813.9 feet with eight (8) piers with a diameter of 8.2 feet and five (5) feet. Due to discrepancies with the site inventory the bridge geometry was updated using field measured data and the 1986 as-built plans. A copy of the as-builts can be found in Appendix B ‘Rio Grande Site Inventory’.

The total scour calculated is based on the flow in the Rio Grande (125,000 cfs), a water surface elevation of 110.83 feet, and a channel velocity of 7.67 fps. The maximum total scour of 26.48 feet, was calculated based on the worst condition. Individual total scour calculations were preformed for each pier location based on pier diameter, depth of water, and velocity, and these results can be found in Table 8 of this report.

Downstream face of Northbound Hidalgo-Reynosa Bridge

TABLE 8

Hidalgo-Reynosa Northbound Bridge Scour Results (RS 156.855)

Abutment/ Bent No

Abutment Scour

(ft)

Pier Scour

(ft)

Contraction Scour

(ft)

Total Scour

(ft) Abutment 1 N/A N/A N/A N/A

Bent 2 0.00 5.78 6.26 12.04 Bent 3 0.00 12.91 6.26 19.17 Bent 4 0.00 17.46 0.00 17.46 Bent 5 0.00 26.48 0.00 26.48 Bent 6 0.00 26.44 0.00 26.44 Bent 7 0.00 15.70 0.00 15.70 Bent 8 0.00 6.87 8.10 14.97 Bent 9 0.00 5.74 8.10 13.84

Abutment 10 N/A N/A N/A N/A

FIGURE 2

Hidalgo-Reynosa Northbound Bridge Scour Results Plot (RS 156.855)

0 200 400 600 800 1000

Bridge Scour RS = 156.855

Station (f t)

E le va tio n (f

t) Legend

WS PF 1

Ground

Bank Sta

Progreso Bridge

The Progreso bridge is actually two bridges built next to each other, but were modeled as one bridge for the purpose of this study. The upstream bridge is the toll bridge for both pedestrian and vehicular traffic, and the downstream bridge is for commercial traffic only. The bridge spans from the US levee to the Mexico levee with a length of 622 feet and a low chord of 79.54 feet. The piers are a group of cylinders with diameters of three (3) feet and four (4) feet. In the original IBWC model the length of the bridge was 633 feet with ten (10) piers having diameters of 1.25 feet for seven (7) piers, four (4) feet, and thirteen (13) feet for two (2) piers. Due to discrepancies between the site inventory and the ‘2003 model’, the bridge geometry was updated using field measured data.

The total scour calculated is based on the flow in the Rio Grande (20,000 cfs), a water surface elevation of 77.54 feet, and a channel velocity of 2.72 fps. The maximum total scour of 9.03 feet, was calculated based on the worst condition. Individual total scour calculations were preformed for each pier location based on pier diameter, depth of water, and velocity, and these results can be found in Table 9 of this report.

Downstream face of Progreso Bridge

TABLE 9

Progreso Bridge Scour Results (RS 120.605)

Abutment/

Bent No Abutment

Scour (ft)

Pier Scour

(ft)

Contraction Scour

(ft)

Total Scour

(ft) Abutment 1 N/A N/A N/A N/A

Bent 2 0.00 1.51 0.00 1.51 Bent 3 0.00 1.57 0.00 1.57 Bent 4 0.00 1.48 0.00 1.48 Bent 5 0.00 1.54 0.00 1.54 Bent 6 0.00 7.24 1.79 9.03 Bent 7 0.00 6.47 1.79 8.26 Bent 8 0.00 2.94 1.79 4.72 Bent 9 0.00 2.30 1.79 4.08

Bent 10 0.00 1.89 0.00 1.89 Bent 11 0.00 1.66 0.00 1.66

Abutment 12 N/A N/A N/A N/A

FIGURE 3

Progreso Bridge Scour Results Plot (RS 120.605)

0 100 200 300 400 500 600 700

Bridge Scour RS = 120.605

Station (f t)

E le va tio n (f t)

Legend

WS PF 1

Ground

Bank Sta

A copy of the detailed HEC-RAS scour reports can be found in the Report Index, ‘Rio Grande Steady State Model Data’.

F. Rio Grande Unsteady State Model

From August 18, through August 30, 1967 intense rainfall occurred on the entire Rio Grande watershed below Falcon Dam. The Rio San Juan watershed was the heavy contributor of storm water runoff. On September 19 to September 26 extreme heavy rains occurred again over the Rio Grande watershed from Laredo to the Gulf of Mexico. The Rio Grande reached a crest of 220,000 cubic feet per second at midnight, September 22, at the Fort Ringgold gauging station at Rio Grande City, Texas. In part, the already heavily saturated area from the August rains contributed to this high peak flow. The peak flow at the headwaters of the floodway systems was 216,000 cfs and the residual after the diversions was less than 16,000 cfs. This information was obtained from the International Boundary and Water Commission, United States and Mexico, Water Bulletin Number 37, ‘Flow of the Rio Grande and Related Data’ New Mexico to the Gulf of Mexico, 1967. Report Index, ‘Rio Grande Unsteady State Model Data’, contains a graphic stage-discharge-time plot of the hurricane Beulah hydrograph at Rio Grande City and a discharge-time plot of the watershed hydrographs contributing to this peak flow. Figure 4 below is the 2007 Unsteady State Model’s inflow hydrograph. The ordinates of the Beulah hydrograph, which were obtained from the IBWC Water Bulletin 37, were tabulated for stage, time, and discharge and can also be found in Report Index, ‘Rio Grande Unsteady State Model Data’.

FIGURE 4

HEC-RAS Plot of 1967 Beulah Hydrograph At Rio Grande City

0 2 4 6 8 10 12 14 16

50000

100000

150000

200000

250000

River: RIVER-1 Reach: Reach-2 RS: 238.6

Simulation Time (days)

F lo w cf s)

Legend

Flow

Q Min + Mul tipl ier

Histor…