ERDC/CHL TR-20-9 

Dredging Operations and Environmental Research (DOER) Program

Effect of Tropical Storms and Precipitation on 

Dredging Volumes: Houston-Galveston, TX, and 

Mayport, FL

Coastal and Hydraulics Laboratory 

Ashley E. Frey and Lauren A. Coe June 2020

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Dredging Operations and Environmental 

Research (DOER) Program 

ERDC/CHL TR-20-9 

June 2020 

Effect of Tropical Storms and Precipitation on 

Dredging Volumes: Houston-Galveston, TX, and 

Mayport, FL

Ashley E. Frey

Coastal and Hydraulics Laboratory

US Army Engineer Research and Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

Lauren A. Coe

US Army Corps of Engineers

Los Angeles District

911 Wilshire Blvd.

Los Angeles, CA 90017

Final report

Approved for public release; distribution is unlimited

Prepared for US Army Corps of Engineers

Washington, DC 20314-1000

Under Project Number 14-03; “Effect of Tropical Storms and Precipitation on 

Dredging Volumes; Houston-Galveston, TX, and Mayport, FL”
ERDC/CHL TR-20-9 ii

Abstract

This study characterizes infilling responses within dredged navigation 

channels to rainfall from tropical storms and hurricanes. This project 

created a web tool based on the methods described in this report. This 

report discusses the different analysis methods considered to relate storm 

and rainfall to dredging volumes at two pilot sites, Galveston, TX, and 

Mayport, FL. A comprehensive storm Impact Factor for hurricanes was 

developed to quantify the impact at a site based on proximity, duration, 

and wind speed. The methods vary based on the length and timing of 

periods of storms and rainfall prior to a dredge event. At Galveston, TX, 

when 2-year dredging volume totals were compared to hurricane activity 

occurring in the previous 2 years, the maximum dredging volume removed 

was higher after higher hurricane activity when compared to low activity 

periods. The average amount dredged was higher following periods of high 

hurricane activity. At Mayport, FL, dredging volumes were compared to 

hurricane activity occurring since the last dredging action took place. 

Similarly to Galveston, TX, the maximum dredging volume removed was 

higher after higher hurricane activity periods when compared to low 

activity periods. The average amount dredged was higher following 

periods of high hurricane activity.

DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. 

Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. 

All product names and trademarks cited are the property of their respective owners. The findings of this report are not to 

be construed as an official Department of the Army position unless so designated by other authorized documents.

DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.
ERDC/CHL TR-20-9 iii

Contents

Abstract.................................................................................................................................... ii

Figures and Tables...................................................................................................................v

Preface...................................................................................................................................viii

1 Introduction ......................................................................................................................1

1.1 Background........................................................................................................1

1.2 Objective.............................................................................................................2

1.3 Approach ............................................................................................................2

1.4 Galveston, TX .....................................................................................................3

1.5 Mayport, FL ........................................................................................................4

1.6 Report organization...........................................................................................6

2 Site Conditions .................................................................................................................7

2.1 Hurricanes and tropical storms ........................................................................7

2.1.1 Galveston, TX............................................................................................................... 7

2.1.2 Mayport, FL................................................................................................................ 10

2.2 Precipitation.................................................................................................... 12

2.2.1 Galveston, TX.............................................................................................................12

2.2.2 Mayport, FL................................................................................................................ 16

2.3 Dredging history.............................................................................................. 18

2.3.1 Galveston Harbor, TX ................................................................................................18

2.3.2 Mayport Basin, FL .....................................................................................................20

3 Storm and Precipitation Analysis.................................................................................22

3.1 Tropical storm and hurricane analysis .......................................................... 22

3.1.1 Hurricanes and infilling.............................................................................................22

3.1.2 Determination of Impact Factor...............................................................................22

3.2 Precipitation analysis ......................................................................................31

3.2.1 Galveston, TX.............................................................................................................31

3.2.2 Mayport, FL................................................................................................................ 34

3.3 Dredged volume comparison methods ......................................................... 35

3.3.1 Method 1 – Time between dredging events............................................................36

3.3.2 Method 2 – Set blocks of time .................................................................................40

3.4 Classification of years .................................................................................... 45

3.5 Methods discussion ........................................................................................47

4 Results and Discussion .................................................................................................49

4.1 Galveston Harbor, TX...................................................................................... 49

4.2 Mayport Basin, FL............................................................................................51

5 Conclusions ....................................................................................................................55
ERDC/CHL TR-20-9 iv

References.............................................................................................................................56

Appendix A: Additional Houston-Galveston, TX, Channels Dredging History ................57

Appendix B: Alternate Dredge Volume Comparison Methods, Galveston, TX...............64

Unit Conversion Factors.......................................................................................................75

Acronyms and Abbreviations...............................................................................................76

Report Documentation Page
ERDC/CHL TR-20-9 v

Figures and Tables

Figures

Figure 1. Houston-Galveston navigation channels and Galveston Harbor, TX......................4

Figure 2. US NS Mayport, FL, location near Jacksonville, FL...................................................5

Figure 3. Mayport Basin and Entrance Channel, FL. ................................................................6

Figure 4. Maximum wind speed of tropical storms and hurricanes between 1945

and 2013 within 150 miles of Galveston, TX.............................................................................8

Figure 5. Tracks of all hurricanes and tropical events within 150 miles 

of Galveston, TX, 1945–2013 (NOAA [2015a]).........................................................................9

Figure 6. Category 3, 4, and 5 hurricanes, and Hurricane Ike, affecting 

Galveston, TX, 1945–2013 (NOAA [2015a]). ............................................................................9

Figure 7. Maximum wind speed of tropical storms and hurricanes between 1954

and 2013 within 150 miles of Mayport, FL..............................................................................10

Figure 8. All hurricanes and tropical events within 150 miles of Mayport, FL, 

1954–013 (NOAA [2015a]). ......................................................................................................11

Figure 9. Category 3, 4, and 5 hurricanes affecting Mayport, FL, 1954-2013 

(NOAA [2015a])............................................................................................................................11

Figure 10. Locations of NOAA NCDC stations from which precipitation data near 

Galveston Harbor, TX, were obtained........................................................................................12

Figure 11. Annual precipitation at Galveston station from 1947 to 1998. .........................14

Figure 12. Average monthly rainfall at Galveston station. .....................................................14

Figure 13. Annual precipitation at Galveston Scholes Field station from 1946

to 2014..........................................................................................................................................15

Figure 14. Average monthly precipitation at Galveston Scholes Field station....................15

Figure 15. Location of rainfall station near Jacksonville, FL, used for Mayport, FL............16

Figure 16. Annual precipitation for Jacksonville, FL, station from 1948 to 2012, 

used for Mayport, FL....................................................................................................................17

Figure 17. Average monthly precipitation for Jacksonville, FL, station. ................................17

Figure 18. Channel locations in the Galveston Harbor, TX, area. .........................................18

Figure 19. Hurricane Jerry storm track, 15–16 October 1989.............................................23

Figure 20. Yearly precipitation totals, Galveston, TX, 1947–2014. ......................................32

Figure 21. Yearly precipitation totals, Mayport, FL, 1948–2014..........................................35

Figure 22. Actual versus average rainfall between dredging events, 

Galveston Harbor, TX, 1947–2012...........................................................................................38

Figure 23. Storm Impact Factors between dredging events, Galveston Harbor, TX, 

1947–2012..................................................................................................................................39

Figure 24. Rainfall and volume dredged over 2-year intervals, Galveston Harbor, 

TX, 1948–2013. ..........................................................................................................................40

Figure 25. Storm Impact Factors and volume dredged over 2-year intervals, 

Galveston Harbor, TX, 1948–2013...........................................................................................41
ERDC/CHL TR-20-9 vi

Figure 26. Rainfall and volume dredged over 3-year intervals, Galveston Harbor, 

TX, 1948–2013. ..........................................................................................................................42

Figure 27. Storm Impact Factors and volume dredged over 3-year intervals, 

Galveston Harbor, TX, 1948–2013...........................................................................................43

Figure 28. Linear regression of cumulative dredging at Galveston, TX................................49

Figure 29. Linear regression of cumulative dredging at Mayport, FL...................................52

Figure B-1. Actual versus average rainfall between dredging events (6 months 

prior), Galveston, TX.....................................................................................................................66

Figure B-2. Storm Impact Factors between dredging events (6 months prior), 

Galveston, TX................................................................................................................................67

Figure B-3. Actual versus average rainfall between dredging events (1 year prior), 

Galveston, TX................................................................................................................................69

Figure B-4. Storm Impact Factors between dredging events (1 year prior), 

Galveston, TX................................................................................................................................70

Figure B-5. Rainfall and volume dredged over 5-year intervals, Galveston, TX...................71

Figure B-6. Storm Impact Factor and volume dredged over 5-year intervals, 

Galveston, TX................................................................................................................................72

Figure B-7. Rainfall and volume dredged over 6-year intervals, Galveston, TX. ..................73

Figure B-8. Storm Impact Factor and volume dredged over 6-year intervals, 

Galveston, TX................................................................................................................................74

Tables

Table 1. Galveston Harbor, TX, dredging volumes...................................................................19

Table 2. Mayport Turning Basin and Entrance Channel, FL, dredging volumes. ................21

Table 3. Time and maximum wind speed classified by distance from Galveston 

Entrance Channel for Hurricane Jerry.......................................................................................25

Table 4. Factors to determine storm impact. Left, distance (miles); middle, wind 

speed (mph); right, time (hr).......................................................................................................26

Table 5. Impact Factors, duration, and maximum and minimum wind speed for 

each tropical event, Galveston Harbor, TX................................................................................27

Table 6. Impact Factors, duration, and maximum and minimum wind speed for 

each tropical event, Mayport, FL................................................................................................28

Table 7. Rainfall and storm Impact Factors between dredging events, 

Galveston Harbor, TX, 1947–2010. ..........................................................................................37

Table 8. Total rainfall and storm Impact Factors for 2-year intervals, 

Galveston Harbor, TX, 1947–2012...........................................................................................44

Table 9. Two-year interval categorization based on storm Impact Factor, 

Galveston, TX, 1947–2012........................................................................................................46

Table 10. Classification of rainfall and storm Impact Factors, Mayport, FL, 1954–

2008..............................................................................................................................................47

Table 11. Cumulative volume and residuals from modeled dredging volume, 

Galveston Harbor, TX, 1947–2012...........................................................................................50
ERDC/CHL TR-20-9 vii

Table 12. Range of annual dredged volumes and average annual dredged 

volumes based on previous 2-year interval storm period level, Galveston Harbor, 

TX. ..................................................................................................................................................51

Table 13. Cumulative volume and residuals from modeled dredging volume, 

Mayport, FL, 1954–2010...........................................................................................................52

Table 14. Range of dredging volumes on annual and per-event basis for low and 

high storm periods, Mayport, FL................................................................................................53

Table 15. Deviation from average dredging volume on annual and per-event basis 

for low and high storm periods, Mayport, FL............................................................................54

Table A-1. Comprehensive dredging data for the Houston-Galveston navigation 

channels........................................................................................................................................57

Table A-2. Bolivar Roads Channel dredging quantities or history. ........................................58

Table A-3. Inner Bar Channel dredging.....................................................................................58

Table A-4. Outer Bar Channel dredging. ...................................................................................59

Table A-5. Entrance Channel dredging. ....................................................................................60

Table A-6. Extended Entrance Channel dredging....................................................................60

Table A-7. Anchorage Area dredging..........................................................................................61

Table A-8. GIWW – East dredging..............................................................................................61

Table A-9. GIWW – West dredging.............................................................................................62

Table A-10. Bolivar Roads to Redfish Reef dredging...............................................................63

Table B-1. Rainfall and storm Impact Factors between dredging events (6 months 

prior), Galveston, TX.....................................................................................................................65

Table B-2. Rainfall and storm Impact Factors between dredging events (1 year 

prior), Galveston, TX.....................................................................................................................68
ERDC/CHL TR-20-9 viii

Preface

This study was conducted for Headquarters, US Army Corps of Engineers 

(HQUSACE) as part of the Dredging Operations and Environmental 

Research (DOER) Program, Project Number 14-03, “Channel Infilling 

Analysis.” The DOER Program Manager was Dr. Todd Bridges. Mr. Jeffrey 

A. McKee was the HQUSACE Navigation Business Line Manager 

overseeing the DOER Program. 

The work was performed by the Coastal Engineering Branch, Navigation 

Division, and the Coastal Processes Branch, Flood and Storm Protection 

Division, US Army Engineer Research and Development Center, Coastal 

and Hydraulics Laboratory (ERDC-CHL). At the time of publication of this 

report, Lauren M. Dunkin was Chief, Coastal Engineering Branch; 

Mr. Charles E. Wiggins was the Technical Director, Navigation; Dr. 

Jacqueline S. Pettway was Chief, Navigation Division; Ms. Ashley Frey was 

Chief, Coastal Processes Branch; Dr. Cary Talbot was Chief, Flood and 

Storm Protection Division; and Mr. Mike Ott was the HQUSACE 

Navigation Business Line Manager overseeing the DOER Program. The 

Deputy Director of ERDC-CHL was Mr. Jeffrey R. Eckstein, and Dr. Ty V. 

Wamsley was the Director.

The Commander of ERDC was COL Teresa A. Schlosser, and the Director 

of ERDC was Dr. David W. Pittman.
ERDC/CHL TR-20-9 1

1 Introduction

As part of the “Evaluation of Dredging Requirements as a Function of 

Channel Infilling Processes” Research Task in the US Army Corps of 

Engineers (USACE) Dredging Operations and Environmental Research

Program, dredging records were analyzed to determine the impact of 

meteorological conditions on future dredging requirements. Research 

began in mid-Fiscal Year (FY)14 and concluded in FY17. This technical 

report describes the process and analysis for two sites: (1) Galveston 

Harbor, TX, and (2) Mayport Basin, FL (US Navy aircraft carrier basin at 

Naval Station (NS) Mayport, FL).

1.1 Background

The need for this research came from discussions with USACE dredging 

managers who are responsible for making decisions regarding nationwide 

channel maintenance. Generally, maintenance dredging of a channel 

occurs on a regular dredging cycle where the channel is dredged to a 

target-maintained depth suitable for navigation and then allowed to incur 

natural sediment deposition until the next dredging event. As the tidal 

hydraulics and long-shore sediment transport forcings acting in coastal 

entrance channels are very complex, dynamic, and highly localized, there 

is often a significant amount of uncertainty associated with the volumes of 

sediment that accrue between dredging events. This fact coupled with the 

USACE 2-year budget formulation cycle can make it difficult for dredging 

managers to accurately predict channel maintenance budgetary needs.

The experience knowledge of long-time USACE dredging managers, 

coupled with uncertainty-driven conservatism in the submitted budgetary 

formulations, helps to minimize the instances where vessel draft 

restrictions are required due to severe shoaling and thus minimizes 

disruptions to waterborne commerce. However, due to limited outlays 

from the Harbor Maintenance Trust Fund, the USACE maintenance 

dredging program is budget constrained and therefore cannot afford to 

maintain full authorized channel dimensions at all deep-draft navigation 

projects. Additionally, many of the most experienced USACE district 

dredging managers have been retiring in recent years, mirroring trends 

across the federal government. This loss of institutional knowledge has 

exacerbated the need for improved predictive tools that provide USACE 

practitioners with a better understanding of channel infilling processes. 
ERDC/CHL TR-20-9 2

Additional site-specific information can be collected to better inform 

managers about how channel infilling processes respond to hurricane 

activity and precipitation totals between dredging events. A more 

comprehensive approach would include the evaluation of dredging records 

and meteorological forcing data so that locations and volumes within the 

channel can be predicted to achieve more efficient management of 

dredging.

1.2 Objective

The main objectives of this study are to (1) determine the effects of tropical 

storm activity and precipitation on future maintenance dredging 

requirements and (2) develop a generalized method that can be applied to 

different sites with the use of readily available data. An average dredging 

amount is typically used as a guideline for the request of funds because 

those requests may be made a significant time prior to when actual 

dredging takes place. This analysis should provide additional information 

about how a site has reacted to storms or rainfall in the past and inform 

managers on how similar conditions may impact dredging volumes in the 

future. This study analyzed channel infilling based on forcing data and 

historical dredging events. 

1.3 Approach

Two pilot sites were chosen to develop the analysis: (1) Galveston Harbor, 

TX, and (2) Mayport Basin, FL. Galveston and Mayport were selected 

since they both experience tropical events and precipitation and have a 

river input or bay system. After completing the analysis at these sites and 

applying the methodology at additional test sites, a more uniform method 

for predicting channel dredge volumes was developed that can be 

expanded to any other channel system in the country. 

Previous studies focusing on Galveston Island and the Houston Ship 

Channel, TX, and Mayport, FL, made analysis data readily available. 

Dredging data that had been processed and analyzed in support of those 

studies were applied to the infilling processes questions being 

investigated in this effort, which greatly reduced the amount of time 

needed to conduct this analysis. Additionally, the Houston-Galveston 

channel system consists of many interconnected channels within 

Galveston Bay and the Gulf Intracoastal Waterway (GIWW) and thus

provides a very complex case to test.
ERDC/CHL TR-20-9 3

1.4 Galveston, TX

Houston-Galveston refers to two connected channels, the Galveston 

Entrance Channel and the Houston Ship Channel, which combine to 

make up one of the busiest waterways in the world. The HoustonGalveston navigation channels are labeled in Figure 1. More than 60 

ships and 340 barge movements transit the Houston Ship Channel each 

day (Houston-Galveston Navigation Safety Advisory Committee 2011). 

The authorized project channel depth is 45 ft.1 (All depths in this 

document are referenced to mean lower low water.) The total distance 

from the Galveston Entrance Channel to the end of the Houston Ship 

Channel at Buffalo Bayou/Light-Draft Channel is approximately 

65 miles. From the GIWW to the end of the Galveston Extended Entrance 

Channel in the open waters of the Gulf of Mexico, the distance is 

16 miles. The distance between the Houston Main Turning Basin and the 

intersection with the GIWW is 49 miles. 

 

1 For a full list of the spelled-out forms of the units of measure used in this document, please refer to US 

Government Publishing Office Style Manual, 31st ed. (Washington, DC: US Government Publishing 

Office 2016), 248-52, https://www.govinfo.gov/content/pkg/GPO-STYLEMANUAL-2016/pdf/GPOSTYLEMANUAL-2016.pdf.
ERDC/CHL TR-20-9 4

Figure 1. Houston-Galveston navigation channels and Galveston Harbor, TX. 

Although the entire system is very complex and extends into the City of 

Houston, not all of the navigation channels are included in this dredging 

analysis. The focus of this analysis is to determine dredging based on 

storms and precipitation. Although some of the more inland channels may 

experience shoaling due to storm events, the effects of storms are more 

apparent nearer to the Gulf where the storms are more impactful. For that 

reason, this analysis only considered the Galveston Harbor; however, 

dredging for all Gulfward channels (the last mile of Bolivar Roads to 

Redfish Reef, Bolivar Roads, Inner Bar, Outer Bar, Entrance Channel, and 

Extended Entrance Channel) is presented in Appendix A. 

1.5 Mayport, FL

The Mayport, FL, Entrance Channel and NS Mayport Basin are located on 

the eastern coast of Florida just north of Jacksonville. The NS facilities are 

situated at the mouth of the St. Johns River as it meets the Atlantic Ocean. 

The entrance channel to the Basin extends approximately 4 miles offshore

into the Atlantic Ocean. Figure 2 shows a map of the greater Jacksonville 

area, and Figure 3 shows the region of focus at Mayport. 
ERDC/CHL TR-20-9 5

Mayport functioned well as a pilot site because much of the data record 

was long, the site undergoes frequent dredging, and the site experiences 

sedimentation from both river and coastal sources influenced by rainfall 

and tropical storms, respectively. Furthermore, the Mayport, FL, site was 

also the focus of a comprehensive shoaling study completed by the US 

Army Engineer Research and Development Center for the US Navy1, and 

therefore, the data were readily available.

Figure 2. US NS Mayport, FL, location near Jacksonville, FL. 

 

1 Thomas, R. T., and L. M. Dunkin. Unpublished manuscript. US Navy FCA Shoaling Study: Demonstration 

Project, Mayport, FL. Vicksburg, MS: US Army Engineer Research and Development Center.
ERDC/CHL TR-20-9 6

Figure 3. Mayport Basin and Entrance Channel, FL. 

1.6 Report organization

This report is organized into five chapters. Chapter 1 discusses the purpose 

of the research and the site locations. Chapter 2 describes the site 

conditions: tropical events, precipitation, and dredging history. Chapter 3 

discusses methodologies for the analysis of storms and precipitation, and 

the appropriateness of each method. Chapter 4 gives an estimate of 

dredging needs for future years. Summary and conclusions are presented 

in Chapter 5.
ERDC/CHL TR-20-9 7

2 Site Conditions

To make the methodology discussed in this report as widely applicable as 

possible, readily available and easily accessible datasets of historical 

rainfall and hurricanes were chosen to discern trends between dredging 

and varying site conditions.

2.1 Hurricanes and tropical storms

Hurricanes and tropical storms up to 150 miles from a chosen site are 

considered in this analysis. The distance of 150 miles was chosen to 

capture strong distant storm that have a wide radius of influence. For 

larger storms, hurricane force winds (>74 mph) can extend up to 150 miles 

from the storm center (NOAA 1999). Hurricane activity is reported to have 

influence on 1% probability extreme precipitation at a distance of up to 

230 miles (Barlow 2011). The storms range from minor tropical 

depressions to major hurricanes. The Saffir-Simpson Scale ranks 

hurricanes from 1 to 5 according to sustained wind speed and is commonly 

used as a tool to alert the public of potential damage for each category 

(NHC CPHC 2020). Wind speeds in this analysis can be considered a 

proxy for wave conditions and surge-induced currents that drive the 

movement of sediment in open waters. The maximum storm surge 

typically occurs near the radius of maximum winds (NOAA NHC 2020). 

2.1.1 Galveston, TX

All hurricanes and tropical storms that occurred between 1945 and 2013 

within 150 miles of the Galveston Entrance Channel were considered in 

this analysis. During that period, 50 storms impacted the HoustonGalveston area. Figure 4 shows all tropical events since 1945 with 

maximum wind speed within 150 miles of the Galveston Entrance 

Channel. While some of these storms may have been Category 5 

hurricanes at some point, only the wind speed within the 150 mile radius

circle is important for this analysis. During the time period considered in 

this analysis, there were 12 storms that had maximum winds of tropical 

depression strength within 150 miles of Galveston, twenty tropical storms, 

eleven Category 1 hurricanes, two Category 2 hurricanes, three Category 3 

Hurricanes, two Category 4 hurricanes, and no hurricanes that reached 

Category 5 strength within 150 miles of Galveston. The strongest storm 

was Hurricane Audrey, which reached a wind speed of 144 mph and is in 
ERDC/CHL TR-20-9 8

the middle of the range for Category 4 wind speeds. The other Category 4 

hurricane was an unnamed storm known as the 1949 Texas Hurricane. 

The other major hurricanes (classified as Category 3 or higher) were an 

unnamed storm known as the 1945 Texas Hurricane, Hurricane Alicia, and 

Hurricane Rita. Hurricane Ike made landfall on Galveston Island and 

produced a devastating storm surge; however, when considering only wind 

speed, it was classified as a Category 2 hurricane. Figure 4 shows the 

maximum wind speed of all hurricanes that were tracked within 150 miles 

of Galveston Harbor, TX, with those strongest storms labeled.

Figure 4. Maximum wind speed of tropical storms and hurricanes between 1945 and 

2013 within 150 miles of Galveston, TX. 

Figure 5 shows the tracks of all hurricanes and tropical events within 150 

miles of the Galveston Entrance Channel. Figure 6 shows only Category 3, 

4, and 5 hurricanes, and Hurricane Ike, which was only a Category 2 

hurricane but was a direct hit on Galveston, TX, and resulted in large-scale 

damage. The analysis of tropical events considered wind speed, duration, 

and distance from the Galveston Entrance Channel and will be described 

in more detail in Chapter 3.
ERDC/CHL TR-20-9 9

Figure 5. Tracks of all hurricanes and tropical events within 150 miles 

of Galveston, TX, 1945–2013 (NOAA [2015a]). 

Figure 6. Category 3, 4, and 5 hurricanes, and Hurricane Ike, affecting 

Galveston, TX, 1945–2013 (NOAA [2015a]). 
ERDC/CHL TR-20-9 10

2.1.2 Mayport, FL

All hurricanes and tropical storms that occurred between 1954 and 2013 

within 150 miles of the Mayport Entrance Channel were considered in this

analysis. During that time period, 70 storms impacted the Mayport, FL,

area. These storms ranged from minor tropical depressions to major 

hurricanes. Figure 7 shows the maximum wind speed of all tropical storms 

and hurricanes that were tracked within 150 miles of Mayport, FL, since 

1953, with those strongest storms labeled. While some of these storms may 

have been Category 5 hurricanes at some point, only the wind speed within 

the 150 mile (radius) circle is important for this analysis. Figure 8 shows 

the tracks of all hurricanes and tropical events within the radius of 

interest. During the time period considered in this analysis, there were just 

three storms that were Category 3 or higher (Figure 9). The strongest 

storm was Hurricane Gracie, which reached a wind speed of 138 mph. The 

other two Category 3 storms were Donna (1960) and Dora (1964).

Figure 7. Maximum wind speed of tropical storms and hurricanes between 1954 and 

2013 within 150 miles of Mayport, FL. 

Donna Dora

Gracie

0

20

40

60

80

100

120

140

160

1950 1960 1970 1980 1990 2000 2010 2020

Wind Speed, mph

Year

Named

Unnamed
ERDC/CHL TR-20-9 11

Figure 8. All hurricanes and tropical events within 150 miles of Mayport, FL, 

1954–013 (NOAA [2015a]). 

Figure 9. Category 3, 4, and 5 hurricanes affecting Mayport, FL, 1954-2013 

(NOAA [2015a]). 
ERDC/CHL TR-20-9 12

2.2 Precipitation

Precipitation data from the Galveston, TX, and Mayport, FL, regions were 

obtained from the NOAA National Climatic Data Center.

2.2.1 Galveston, TX

There were two stations used in the vicinity of the Galveston Bay system: 

(1) Galveston and (2) Galveston Scholes Field. Two other stations (Deer 

Park and Alvin) had insufficient data coverage. These locations are shown 

in Figure 10. (Note: Rainfall will be used synonymously with precipitation

for the remainder of this report.)

Figure 10. Locations of NOAA National Climatic Data Center stations from which 

precipitation data near Galveston Harbor, TX, were obtained. 

The Galveston station recorded rainfall from 1947 to 2008, but data from 

1999 to 2008 were so incomplete they were removed from the analysis. 

Galveston Scholes Field provided rainfall data from 1946 to 1962 and from 

1999 to 2014. Rainfall data were collected at Deer Park from 1946 until 

2010 while data were recorded at Alvin from 1946 to 2010. There were 

gaps within each dataset. These gaps lasted from 1 month to multiple 

years. The average monthly rainfall was calculated at each location based 
ERDC/CHL TR-20-9 13

on the data available. This monthly average was used when the data were 

unavailable and is noted by the red diamonds in Figure 11 and Figure 13. 

Figure 11 and Figure 12 show the annual precipitation from 1947 to 2008 

and the average monthly rainfall at the Galveston station, respectively. The 

only year that included a monthly average to replace an incomplete month 

of data was 1994. The three driest years were 1948, 1954, and 1956, which 

experienced 22 in. or less rainfall. The wettest year was 1998 when nearly 

67 in. of rain fell. More than 60 in. of rain also occurred in 1961, 1973, and 

1997. Monthly rainfall in Galveston during this time period ranged from 2 

to 6 in. The driest months were February, March, and April where less 

than 3 in. of rain fell, and the wettest months were June, August, and 

September where more than 4 in. occurred. The average rainfall in 

September was more than 5.5 in. 

Figure 13 and Figure 14 show annual precipitation and average monthly 

rainfall at the Galveston Scholes Field station, respectively. Average 

rainfall for specific months replaced incomplete data in 1948 and 1999. 

Rainfall was not available from 1964 to 1998. The driest years were 1954, 

2008, and 2011. Less than 15 in. of rain fell in 2008; however, 

approximately 6 weeks of rainfall data are missing following Hurricane 

Ike. Similar to the Galveston station data, the driest months occurred in 

the winter and early spring while September is the wettest month with an 

average of more than 5.5 in. of rain.
ERDC/CHL TR-20-9 14

Figure 11. Annual precipitation at Galveston station from 1947 to 1998. 

Figure 12. Average monthly rainfall at Galveston station. 
ERDC/CHL TR-20-9 15

Figure 13. Annual precipitation at Galveston Scholes Field station from 1946 

to 2014. 

Figure 14. Average monthly precipitation at Galveston Scholes Field station. 
ERDC/CHL TR-20-9 16

2.2.2 Mayport, FL 

Rainfall data from Jacksonville International Airport station (station ID 

084358) was used at Mayport, FL. The location of this station is shown in 

Figure 15. The data were comprised of annual and monthly rainfall 

summaries from 1948 to 2013. Based on this station’s records, the average 

annual rainfall for Jacksonville, FL, is approximately 50 in. per year. 

Rainfall precipitation in this study must be considered carefully so that the 

effects of storm-related rainfall and monthly rainfall are not double

counted as a factor in dredging events in the following time period.

Rainfall peaks in the month of September at the height of hurricane 

season. Figure 16 shows the annual precipitation rate at the site from 1948 

to 2012. Figure 17 shows the average monthly rainfall for Jacksonville, FL.

Figure 15. Location of rainfall station near Jacksonville, FL, used for Mayport, FL. 
ERDC/CHL TR-20-9 17

Figure 16. Annual precipitation for Jacksonville, FL, station from 1948 to 

2012, used for Mayport, FL. 

Figure 17. Average monthly precipitation for Jacksonville, FL, station. 
ERDC/CHL TR-20-9 18

2.3 Dredging history

2.3.1 Galveston Harbor, TX

To support this study, the USACE Galveston District (SWG) provided a 

record of all historical dredging events within the District up until early 

2014. Each entry includes dredging start and completion dates, the project 

name, a project key, project ID, channel ID, reach ID, stationing 

information, and estimated and actual dredged volumes. However, the 

channels of interest are not subdivided further than Houston Ship Channel 

or Houston-Galveston Navigation Channels. Therefore, it became necessary 

to subdivide each channel based on stationing information. The authorized 

depth of the Extended Entrance Channel, Entrance Channel, Outer Bar 

Channel, Inner Bar Channel, Galveston Harbor Channel, Bolivar Roads 

Channel, Texas City Channel, Bolivar Roads to Redfish Reef, Redfish Reef to 

Beacon 76, and Beacon 76 to Morgan's Point is 46 ft. SWG reports Morgan's 

Point to Carpenter Bayou has a maintenance depth of 46.5 ft. Between 

Carpenter Bayou and Green's Bayou, the authorized depth decreases from 

46.5 to 41.5 ft. Green's Bayou to Sims Bayou is 41.5 ft. Sims Bayou to the 

Main Turning Basin and Buffalo Bayou depths are 37.5 ft. The GIWW is 

maintained at 13 ft. Figure 18 shows the channel locations.

Figure 18. Channel locations in the Galveston Harbor, TX, area. 

A thorough analysis would include all of the Houston-Galveston channels 

considered together. However, in many cases, dredging begins in one 

channel and moves to the next immediately following completion. The first 

12 events took place in Galveston Harbor while many of the later events 

encompass multiple channels (Table A-1, Appendix A). Due to the 
ERDC/CHL TR-20-9 19

complexity of including all channels, Galveston Harbor was selected to test 

the method. Galveston Harbor has a long dredging history and has a fairly 

small footprint so that the approximate area where dredging occurred is 

well known. The complete dredging history for Galveston Harbor is 

presented in Table 1, and the dredging history for the remaining Galveston 

area channels can be found in the Appendix A.

Table 1. Galveston Harbor, TX, 

dredging volumes. 

Dredging Contract 

End Date 

Volume Dredged, 

yd3 

6/25/1947 6,082,994

1/9/1950 5,004,824

10/23/1951 3,212,051

4/24/1953 2,894,868

8/21/1955 3,902,472

6/15/1958 2,149,535

12/11/1960 4,032,000

7/23/1962 5,376,500

5/29/1964 1,777,693

7/20/1965 3,640,080

11/21/1966 4,842,983

6/2/1969 4,312,942

10/28/1972 4,055,450

6/1/1974 3,482,921

3/20/1976 4,993,000

4/12/1982 6,022,633

8/31/1982 2,262,062

10/7/1985 4,301,050

10/17/1986 1,266,653

9/30/1989 4,038,896

6/18/1994 5,162,753

4/6/1998 5,400,565

7/9/2000 3,818,488

8/3/2003 819,428

10/15/2005 998,152

8/31/2006 2,822,400
ERDC/CHL TR-20-9 20

Dredging Contract 

End Date 

Volume Dredged, 

yd3 

12/31/2007 2,956,986

7/31/2009 2,448,267

12/31/2009 969,085

3/31/2010 899,667

4/30/2012 2,084,922

The Galveston Harbor Channel connects to the Bolivar Roads Channel. It 

extends almost to the GIWW and is 4.4 miles long. Dredging records for 

Galveston Harbor are the most comprehensive of any channel in the 

Houst0n-Galveston Navigation System; more than 100M yd3 have been 

dredged since 1947, as shown in Table 1. Usually between 1 and 6M yd3 are 

dredged per event. On average, 3.3M yd3 are dredged every 2.2 years. The 

average shoaling rate of Galveston Harbor is 1.5M yd3/year, which is the 

highest shoaling rate of any channel in the lower portion of the HoustonGalveston Navigation Channels. 

2.3.2 Mayport Basin, FL

Dredging records for NS Mayport Turning Basin and Entrance Channel 

date back to 1954, 12 years after the NS was commissioned in 1942. At the 

time of commissioning in 1942, the entrance channel was deepened to 

42 ft to provide maintenance and refueling of submarines. In 1953, the 

arrival of the Midway carrier class of ships led to a deepening of the basin 

from the original 29 ft depth to 40 ft. In 1959, the basin was deepened an 

additional 2 ft to 42 ft. Table 2 lists both the maintenance and new work 

dredging history at NS Mayport Turning Basin and Entrance Channel.
ERDC/CHL TR-20-9 21

Table 2. Mayport Turning Basin and 

Entrance Channel, FL, 

dredging volumes. 

Dredging 

Contract End 

Date 

Volume Dredged, 

yd3 

(*indicates new 

work dredging) 

1/6/1954 346,312

8/1/1956 897,777

10/19/1959 1,411,640

9/1/1961 1,373,350*

10/20/1962 559,092

1/1/1964 289,050

3/1/1965 1,962,067

12/1/1966 868,479

3/10/1969 716,858

9/1/1969 441,323

8/4/1972 570,972

3/25/1974 547,565

2/1/1975 736,084

3/1/1978 1,789,701

10/24/1978 173,558

7/5/1979 47,148

3/1/1982 1,793,031

8/19/1983 81,363

11/19/1983 48,000

8/24/1984 223,000

6/1/1985 1,280,151

1/1/1990 1,600,135

5/29/1993 27,680

5/21/1994 1,230,507

1/29/1997 1,099,371

3/27/2000 1,097,800

10/22/2001 174,832

4/24/2003 1,289,138

1/1/2005 1,069,754

5/19/2008 629,034

1/30/2010 174,941

4/16/2012 4,552,000*
ERDC/CHL TR-20-9 22

3 Storm and Precipitation Analysis

3.1 Tropical storm and hurricane analysis

3.1.1 Hurricanes and infilling

Tropical storms and hurricanes have the potential to bring increased 

sediment deposition into coastal inlets, harbors, and channels. Winddriven storm surge can bring about coastal and inland flooding and 

sediment deposition. If this occurs in a maintained navigation channel, 

dredging will be needed to bring the channel back to pre-storm conditions.

The category of the storm, which is based solely on wind speed, cannot 

alone be used to predict how the storm will impact a site in terms of 

flooding or sediment deposition. A study comparing the impacts of 

Hurricane Wilma and Hurricane Andrew by Smith et al. (2007) 

demonstrated that a Category 3 storm like Hurricane Wilma could be 

more damaging than a Category 5 storm like Hurricane Andrew. While 

Hurricane Wilma was only a Category 3, the vastness of its wind field led 

to storm surges of 15 ft, three times that of Hurricane Andrew and a total 

area of deposition of 110 square miles, 2.5 times the area affected by 

Hurricane Andrew depositions (Smith et al. 2007). It is important that, 

when attempting to quantify a storm’s impact on a site, other storm 

characteristics are considered in addition to category.

3.1.2 Determination of Impact Factor

Before determining an Impact Factor for each tropical event, it was 

necessary to develop a list of all tropical events within a 150 mile radius of 

the location of interest and download the track for each event. The 

Historical Hurricane Tracks (NOAA 2015a) is an ideal resource allowing 

users to select a point on the map and specify a distance from the point to 

refine their search. These NOAA data provide a time stamp, exact location, 

and wind speed for several points along the storm’s track.

For Galveston Harbor, the point selected to develop the 150 mile radius 

was centrally located within the Inner Bar Channel. There were 103 storms 

that passed within 150 miles of the Inner Bar Channel between 1851 and 

2013. The first recorded dredging event occurred in December 1943, so the 

time period from 1942 to 2013 was used for the Galveston Harbor analysis. 

Storms occurring 1 year prior to the initiation of dredging and later have a 

potential impact on volumes. Fifty storm tracks occurred within 150 miles 
ERDC/CHL TR-20-9 23

of the Inner Bar Channel during that time period. This list of storms was 

cross-checked with the list of all hurricane positions in the Atlantic and 

Gulf. The storm track information was used to determine the maximum 

wind speed and time spent within each radius within different radii from 

the chosen location. 

There were 70 storms that passed within 150 miles of the Mayport 

Entrance Channel between 1953 and 2013. This time period was chosen 

because the dredging record begins in 1954. This list of storms was crosschecked with the list of all hurricane positions in the Atlantic and Gulf. 

The storm track information was used to determine the maximum wind 

speed and time spent within each radius within different radii from the 

chosen location.

To further describe the calculations, an example is provided. Hurricane 

Jerry made landfall on 15 October 1989 on Galveston Island. The 

hurricane track information is shown in Figure 19. The location of the 

center of circulation was recorded five times within the 150 mile radius. 

Based on the date and time, it is possible to calculate the amount of time 

the center of circulation was located within each concentric circle 

(Figure 19), representing a different radial distance from the site. 

Figure 19. Hurricane Jerry storm track, 15–16 October 1989. 
ERDC/CHL TR-20-9 24

According to NOAA location data, Hurricane Jerry spent a total of 19.96 hr

within 150 miles of the Galveston Entrance Channel. This total can be 

broken down further by time. For example, the eye was located within 

100 miles of the Galveston Entrance Channel for 13.27 hr of those 

19.96 hr. Hurricane Jerry’s center of circulation was located within 

75 miles for 10.09 hr, 50 miles for 6.51 hr, and within 25 miles for 2.58 hr. 

Because each recorded location also gives the wind speed, a similar 

calculation was completed to determine the maximum and minimum wind 

speed reported within each circle. When the storm eye was located 

between 100 and 150 miles (the biggest ring around the Galveston 

Entrance Channel), the maximum wind speed was 74.8 mph. This wind 

speed was recorded on 15 October 1989 at 1:00 pm. The minimum wind 

speed within the ring was calculated based on the wind speeds recorded on 

16 October 1989 at 1:00 am and 7:00 am, the time-stamped data points on 

either side of this ring. 

A linear decrease in wind speed was assumed, so the wind speed north of 

Houston at 150 miles from the Galveston Entrance Channel was calculated 

as 31.43 mph. The maximum wind speed within the 75- to 100-mile

distance ring occurred between 1:00 and 4:00 pm on 15 October 1989. The 

location of the maximum wind reported in that ring is at 75 miles to the 

south of the Galveston Entrance Channel, and the maximum wind was 

78.32 mph. The minimum wind speed of 38.01 mph occurred between 

1:00 and 7:00 am on 16 October 1989 at a distance of 100 miles from the 

Galveston Entrance Channel. 

The same process was used to determine the maximum and minimum 

wind speeds within each ring, and the results are shown in Table 3. Note 

that duration is the time within each circle (for example, duration within 

150 miles means total time within 150 miles of the Galveston Entrance 

Channel and will therefore be the highest duration entry) while 150 miles 

for maximum and minimum wind speed refers to the ring (for example, 

150 miles means the maximum and minimum wind speed between 100 

and 150 miles away from the Galveston Entrance Channel). The maximum 

wind was 86.3 mph, which occurred less than 25 miles away from the 

Galveston Entrance Channel. The minimum wind speed was 31.43 mph,

which occurred 150 miles away.
ERDC/CHL TR-20-9 25

Table 3. Time and maximum wind speed classified by distance from Galveston Entrance 

Channel for Hurricane Jerry. 

Distance from Entrance Channel, 

miles Duration, hr* Maximum Wind, mph Minimum Wind, mph 

25 2.58 86.3 70.3

50 6.51 86.3 56.5

75 10.09 82.2 44.4

100 13.27 78.3 38.0

150 19.96 74.8 31.4

* Duration is time inside each circle.

The wind speed in each circle and the duration of the storm’s center 

within each circle were used to calculate the Impact Factor for storms. 

These factors are somewhat arbitrary in that they have no meaning other 

than to classify storms as weak, average, or strong. When the amount of 

time a storm’s eye was located within a ring increased to the next time 

bin, the factor increased by 0.1. When a storm had wind speeds under 

74 mph, the factor increased by 0.15 each time the wind speed increased 

to the next speed bin. Once the storm reached hurricane winds speeds, 

the Impact Factor increased by 0.25 each time the wind speed increased 

to the next speed bin. When the storm was nearer to the site, the distance 

factor was lower.

Winds speeds lower than 39 mph (the threshold for a tropical storm) have 

been removed from consideration. Additionally, tropical storms with 

winds speeds of 39–50 mph were only included in calculation of the 

Impact Factor when the wind speed was within 50 miles of the site. Wind 

speeds between 50 and 60 mph were included in the calculation within 

75 miles while wind speeds between 60 and 73 mph were included within 

100 miles of the location of interest. Modifying the wind speed factors only 

decreased the Impact Factor of weaker storms that stall near the site. 

Lower wind speeds were removed based on distance away from the site 

because maximum winds of tropical storm force speed did not have much 

impact beyond a certain distance. These bins and their assigned values for 

distance, wind speed, and duration are shown in Table 4.
ERDC/CHL TR-20-9 26

Table 4. Factors to determine storm impact. Left, distance (miles); middle, wind 

speed (mph); right, time (hr). 

Distance, 

miles Factor Wind, mph Factor Time, hr Factor 

25 1 39-50 0.5 57 to 60 2

50 1.5 50-60 0.65 54 to 57 1.9

75 1.75 60-73 0.8 51 to 54 1.8

100 2 73-80 1 48 to 51 1.7

150 4 80-90 1.25 45 to 48 1.6

90-100 1.5 42 to 45 1.5

100-110 1.75 39 to 42 1.4

110-120 2 36 to 39 1.3

120-130 2.25 33 to 36 1.2

130-140 2.5 30 to 33 1.1

140-150 2.75 27 to 30 1

150+ 3 24 to 27 0.9

21 to 24 0.8

18 to 21 0.7

15 to 18 0.6

12 to 15 0.5

9 to 12 0.4

6 to 9 0.3

3 to 6 0.2

0 to 3 0.1

The initial equation used to determine the Impact Factor of each storm is 

WW1 × TT1

DD1

+

WW2 × TT2

DD2

+

WW3 × TT3

DD3

+

WW4 × TT4

DD4

+

WW5 × TT5

DD5

= IF

where W is the factor for wind, T is the factor for time, D is the factor for 

distance, and IF is the Impact Factor. The subscripts refer to the distance 

from the site. Subscript 1 is 100 to 150 miles away, subscript 2 represents 

the factors for a distance of 75 to 100 miles away, subscript 3 is a distance 

of 50 to 75 miles away, subscript 4 is a distance of 25 to 50 miles away, and 

subscript 5 represents the factors inside a distance of 25 miles. D1 is 4, D2

is 2, D3 is 1.75, D4 is 1.5, and the factor representing D5 is 1. It is also 

important to note that the method to determine the Impact Factor was 

completed through ArcGIS, spreadsheets, and calculations. Future 

development efforts will automate the procedures employed here for any 

user-specified location.
ERDC/CHL TR-20-9 27

The Impact Factors for all storms within the Galveston, TX, area and the 

Mayport, FL, area are shown in Table 5 and Table 6, respectively. The 

overall maximum and minimum wind speeds observed and total duration 

within the 150 mile radius are illustrated. 

Table 5. Impact Factors, duration, and maximum and minimum wind 

speed for each tropical event, Galveston Harbor, TX. 

Name Year 

Impact 

Factor 

Total 

Time, 

hr 

Maximum 

Wind, 

mph 

Minimum 

Wind, 

mph 

Unnamed Jul-45 0 19 40 40

Unnamed Aug-45 0.34 30 112 45

Unnamed Jun-46 0 16 35 23

Unnamed Aug-47 0.6 46 81 35

Unnamed Oct-49 0.73 20 132 61

Barbara Jul-54 0 20 36 29

Unnamed Aug-55 0 12 46 40

Audrey Jun-57 0.5 14 144 67

Bertha Aug-57 0 23 69 29

Debra Jul-59 0.97 58 86 37

Cindy Sep-63 0.77 62 81 29

Abby Aug-64 0.11 23 63 33

Felice Sep-70 0.2 16 69 35

Unnamed Jul-71 0 20 29 26

Fern Sep-71 0.35 25 87 68

Edith Sep-71 0.4 13 98 83

Delia Sep-73 0.26 47 69 39

Unnamed Sep-73 0 41 35 35

Unnamed Jul-74 0 13 35 29

Unnamed Aug-74 0 11 34 29

Carmen Aug-74 0 20 40 29

Unnamed Jun-77 0 15 29 29

Debra Aug-78 0.07 20 58 33

Claudette Jul-79 0.11 60 52 33

Elena Sep-79 0 27 40 29

Unnamed Jul-80 0 40 35 29

Danielle Sep-80 0.12 22 56 44

Unnamed Jun-81 0 11 34 29

Chris Sep-82 0.18 28 63 45

Alicia Aug-83 1.18 44 115 44

Danny Aug-85 0.13 9 92 83

Juan Oct-85 0.09 7 86 86
ERDC/CHL TR-20-9 28

Name Year 

Impact 

Factor 

Total 

Time, 

hr 

Maximum 

Wind, 

mph 

Minimum 

Wind, 

mph 

Bonnie Jun-86 0.5 26 86 38

Unnamed Aug-87 0.12 22 46 37

Allison Jun-89 0 116 52 23

Chantal Aug-89 0.37 22 81 40

Jerry Aug-89 0.32 20 86 31

Dean Jul-95 0.1 29 46 23

Frances Sep-98 0 5 36 35

Unnamed Sep-00 0 16 35 29

Allison Jun-01 0.1 105 58 17

Bertha Aug-02 0 26 29 23

Fay Sep-02 0 42 58 35

Claudette Jul-03 0.22 17 92 69

Grace Aug-03 0.12 17 40 30

Ivan Sep-04 0 13 48 29

Rita Sep-05 0.34 17 122 62

Humberto Sep-07 0.55 31 92 32

Eduard Aug-08 0.2 21 63 33

Ike Sep-08 0.9 19 109 73

Table 6. Impact Factors, duration, and maximum and minimum wind speed 

for each tropical event, Mayport, FL. 

Name Date 

Impact 

Factor 

Total 

time, 

hr 

Maximum 

Wind, 

mph 

Minimum 

Wind, 

mph 

UNNAMED 1953 

1 Aug. 1953 0.00 13 52 31

UNNAMED 1953 

2 Sep. 1953 0.00 8 50 29

FLORENCE Sep. 1953 0.00 8 53 42

UNNAMED 1957 Jun. 1957 0.00 7 40 40

UNNAMED 1959 Jun. 1959 0.00 2 36 35

GRACIE Sep. 1959 0.13 3 138 131

BRENDA 1960 Jul. 1960 0.00 13 52 35

DONNA Sep. 1960 0.38 12 115 104

ALMA 1962 Aug. 1962 0.00 4 40 29

GINNY 1963 Oct. 1963 0.25 21 101 75

UNNAMED 1964 Jun. 1964 0.00 39 35 35

CLEO Aug. 1964 0.29 33 68 37

DORA Sep. 1964 1.14 35 115 79

HILDA Oct. 1964 0.00 3 40 40
ERDC/CHL TR-20-9 29

Name Date 

Impact 

Factor 

Total 

time, 

hr 

Maximum 

Wind, 

mph 

Minimum 

Wind, 

mph 

ALMA 1966 Jun. 1966 0.00 15 66 46

ABBY Jun. 1968 0.29 31 57 47

BRENDA 1968 Jun. 1968 0.00 21 29 29

DOLLY Aug. 1968 0.00 10 31 29

UNNAMED Aug. 1968 0.00 33 29 29

GLADYS Oct. 1968 0.41 18 86 81

GERDA Sep. 1969 0.00 11 48 34

JENNY Oct. 1969 0.00 29 35 29

ALMA 1970 May. 1970 0.00 17 29 29

DAWN Sept. 1972 0.00 28 35 35

UNNAMED 1973 

1 Jun. 1973 0.00 6 26 26

UNNAMED 1973 

2 Sept. 1973 0.00 20 29 29

HALLIE Oct. 1975 0.00 27 35 35

DOTTIE Aug. 1976 0.00 14 52 41

UNNAMED 1979 

1 Jun. 1979 0.00 13 35 35

UNNAMED 1979 

2 Jul. 1979 0.00 8 35 35

DAVID Aug. 1979 0.62 19 98 80

UNNAMED 1980 

1 Jul. 1980 0.00 26 29 23

UNNAMED 1980 

2 Nov. 1980 0.00 8 25 23

UNNAMED 1981 Jul. 1981 0.00 13 35 30

DENNIS Aug. 1981 0.07 17 50 40

UNNAMED 1984 Jun. 1984 0.00 21 35 30

DIANA Sept. 1984 0.38 33 86 63

ISIDORE Sept. 1984 0.29 26 52 52

BOB Jul. 1985 0.18 18 74 62

ISABEL Oct. 1985 0.00 55 50 29

KATE Nov.1985 0.08 6 75 75

UNNAMED 1987 Aug. 1987 0.00 18 17 17

CHRIS Aug. 1988 0.08 9 49 44

UNNAMED 1988 Aug. 1988 0.00 15 35 35

KEITH Nov. 1988 0.00 4 46 46

MARCO Oct. 1990 0.00 10 34 23

ANA Jul. 1991 0.00 31 29 23

EARL Sept. 1992 0.00 9 35 23
ERDC/CHL TR-20-9 30

Name Date 

Impact 

Factor 

Total 

time, 

hr 

Maximum 

Wind, 

mph 

Minimum 

Wind, 

mph 

GORDON 1994 Nov. 1994 0.00 9 26 23

ALLISON Jun. 1995 0.00 3 50 44

JERRY Aug. 1995 0.00 17 32 27

JOSEPHINE Oct. 1996 0.00 5 65 52

GEORGES Oct. 1998 0.00 9 29 28

FLOYD Sept. 1999 0.05 3 115 109

IRENE Oct. 1999 0.15 15 75 75

GORDON 2000 Sept. 2000 0.00 15 58 29

GABRIELLE Sept. 2001 0.00 20 47 46

EDOUARD Sept. 2002 0.00 48 48 23

KYLE Oct. 2002 0.03 17 40 35

UNNAMED 2003 Jul. 2003 0.00 23 24 24

HENRI Sept. 2003 0.00 6 35 29

BONNIE Aug. 2004 0.00 6 34 29

CHARLEY Aug. 2004 0.28 9 86 78

JEANNE Sept. 2004 0.00 12 58 43

TAMMY Oct. 2005 0.13 17 52 38

ALBERTO 2006 Jun. 2006 0.00 10 42 37

ERNESTO Aug. 2006 0.07 13 66 45

BARRY Jun. 2007 0.00 18 46 35

FAY Aug. 2008 0.26 53 60 46

ALBERTO 2012 May. 2012 0.00 21 46 46

BERYL May. 2012 0.28 60 69 29

DEBBY Jun. 2012 0.00 15 40 35

ANDREA Jun. 2013 0.00 8 58 46

At Galveston, TX, Alicia had the highest Impact Factor. Alicia’s area of 

maximum winds traveled directly through Galveston metropolitan area,

and water levels at Galveston Island were as high as 12 ft (National 

Research Council 1984). At Mayport, FL, the storm with the highest 

associated Impact Factor was Hurricane Dora, which is often cited as the 

most powerful and damaging hurricane to hit the Jacksonville area in 

recorded history (Doehring et al. 1994). Dora made landfall 10 September 

1964 and brought 125 mph winds and a 12 ft storm surge. Tide levels in 

St. John’s River were pushed up to 5 ft above normal conditions, and high 

tides at the beaches were up to 7 ft above normal (Kerr 2010).
ERDC/CHL TR-20-9 31

One drawback of using 150 miles as the maximum radius is that some 

strong storms potentially are not included in the analysis. For example, 

Hurricane Carla made landfall on the northeast part of Matagorda Island, 

TX. The nearest Hurricane Carla’s center of circulation came to the 

Galveston Entrance Channel was 155 miles; therefore, it was not included 

in the analysis. However, Hurricane Carla was the most intense hurricane 

to make landfall on the Texas coast in the twentieth century (NOAA 

2015b) and had a diameter of hurricane-force winds of 300 miles. The 

average hurricane-force winds are felt in a 100 mile diameter. Due to the 

size and intensity of Hurricane Carla, a 10 ft storm surge was recorded in 

Galveston. Even though Hurricane Carla’s eye was very far from 

Galveston, it still had a significant impact on the Houston-Galveston area. 

While this method generates no Impact Factor associated with Hurricane 

Carla, it was important to consider it in the analysis. In cases such as 

these, the Impact Factor can be estimated based on known storm surges, 

and additional information about the storm and its relative strength 

compared to other storms for which an Impact Factor was calculated.

3.2 Precipitation analysis

3.2.1 Galveston, TX

Since no station provided a full record from 1947 to present, both the 

Galveston station and the Galveston Scholes Field station (Figure 10) were 

used for the analysis. Except for 2 months in 1994, the Galveston station 

had a complete record of rainfall from 1947 to 1999. Beginning in 1999, 

rainfall records at the Galveston station became intermittent. Rainfall at 

the Galveston Scholes Field station was collected from June 1999 to 

present. Several months of data were not available after Hurricane Ike, so 

these months were excluded from the analysis.

Rainfall totals for years 1947–2014 for Galveston, TX, are shown in Figure 

20. Based on historical data between 1947 and 2014, the average annual 

rainfall was calculated as 41.38 in. A year with 25% greater precipitation, 

51.73 in. or more, was considered a wetter year. A drier year in which 25% 

less precipitation fell was classified as less than 31.04 in. of rainfall per 

year. Note that several months of rainfall data were missing in 1994 and 

2008; therefore, the totals are much less than average. When calculating 

the average, it was assumed that the months with missing rainfall totals 

had average amounts of precipitation.
ERDC/CHL TR-20-9 32

Figure 20. Yearly precipitation totals, Galveston, TX, 1947–2014. 

Twelve years had annual precipitation greater than 51.73 in. Those years 

were 1961, 1966, 1973, 1979, 1983, 1991, 1992, 1995, 1997, 1998, 2001, and 

2002. The year with the highest precipitation was 1998 when 66.66 in. of 

rain fell. For the rainy years, it was important to determine whether most 

of the precipitation occurred during a handful of events or if the year was 

consistently wet. The first rainy year was 1961 when the precipitation total 

was 63.97 in. Nearly 65% of the rain during that year occurred during 

June, September, and November. A significant rain event occurred in each 

of those months. On 18 June 1961, 10.44 in. of rain fell. The total 

precipitation between 10 and 12 September 1961 was 15.26 in., while 

7.58 in. of rain fell on 13 November 1961. The rain in September 1961 

coincides with Hurricane Carla, but the other two events were purely rain 

and thunderstorms and not a named storm. 

There were no storm events in 1966, but heavy amounts of precipitation 

fell in May and September 1966. Rain was distributed throughout each 

month, but no significant rainfall event was noted. In 1973, more than 

10 in. of rain fell in April and August. The highest single-day rainfall total 

was 8 in. on 24 March 1973. Other than a rainfall total of 6.9 in. on 16–17 

April 1973, there were no significant rain events during the year. In 1979, 
ERDC/CHL TR-20-9 33

more than 17 in. of rain was recorded in July. More than 14 in. of this rain 

can be attributed to Tropical Storm Claudette. In 1983, the only significant 

amount of rainfall (6.28 in.) occurred on 18 August during Hurricane 

Alicia. While 1991 and 1992 were wetter than average years, there were no 

single or multi-day storms that produced more than 5 in. of rain. Most of 

the months were wetter than average due to El Niño. 

Although rain was distributed fairly evenly throughout 1995, two events 

(one in early October and one in the middle of December) produced more 

than 6 in. of rain. Neither was associated with a named storm. The two 

wettest years on record were 1997 and 1998. Rainfall totals in March 1997, 

June 1998, and September 1998 were in excess of 10 in. In 1997, 6.7 in. of 

rain fell from 1 to 3 October, and 7.82 in. fell on 17–18 December. Nearly 

12 in. of rain fell on 28–29 June 1998. Almost 10 in. of rain was recorded 

on 10–11 September 1998 while 5.09 in. fell on 4–6 October 1998. The 10–

11 September 1998 event was the only rain associated with a named storm 

(Frances). In 2001, 5.59 in. of rain was recorded on 9 June, and 12.1 in. of 

rain fell between 28 August and 1 September. The rain event in June 2001 

was associated with Tropical Storm Allison. Finally, more than 11 in. of 

rain fell in September and October 2002, but no extreme single or multiday rainfall events occurred. 

Nine years (1948, 1954, 1956, 1963, 1978, 1994, 2005, 2008, and 2011) 

experienced rainfall of less than 31.04 in. However, several months of 

rainfall amounts are missing from 1994 and 2008. If the average monthly 

rainfall for each month were used for the missing months, the total rainfall 

in 1994 would be 29.67 in. If the same calculations were made for 1998, 

the rainfall total would be 32.79 in., which is classified as an average year. 

The driest year on record was 1948 with 21.41 in. of rain. In that year, less 

than an inch of rain was recorded in April, June, July, October, and

December. The only month that had a rainfall total exceed the monthly 

average was January. The total rainfall from January to July 1948 was less 

than half of the average rainfall during that time period. In 1954, only 

October and November rainfall totals were greater than the average for 

each month. Less than 2 in. of rainfall was recorded in eight separate 

months during 1954. The third driest year on record was 1956; however, 

6.15 in. of rain fell in December of that year. 1956 was the driest year from 

January through November. Less than an inch of rain fell between 24 
ERDC/CHL TR-20-9 34

February and 16 June 1956 while less than 2 in. of rain fell between 1 May 

and 31 July 1956. 

Although 9.3 in. of rain fell in September 1963 (Hurricane Cindy), the rest 

of the year was very dry. More than 30% of the rain that fell in 1978 

occurred in January; the rest of the year was extremely dry. In total, 2005 

was a drier than average year. The driest month compared to the average

was August. The second driest year on record was 2011. December 2011 

was the only month where more than 2.75 in. of rain was recorded. Four 

separate months recorded less than an inch of rain. During the 4-month 

period between early March and early July 2011, only 1.64 in. of rain fell. 

3.2.2 Mayport, FL

Several stations in the immediate area were available; however, the 

Jacksonville International Airport Station site was the nearest to Mayport, 

FL, and had the most complete monthly rain totals from 1948 to 2014.

Rainfall totals for each year are shown in Figure 21. Based on historical 

data between 1948 and 2014, the average rainfall for the site was 

calculated as 49.67 in. A year with 25% greater precipitation, 62.1 in. or 

more, was considered a wetter year. A drier year in which 25% less 

precipitation fell was classified as less than 37.25 in. of rainfall per year. 

Nine years had annual precipitation greater than 62.1 in. Those years were 

1953, 1979, 1983, 1991, 1994, 1995, 2009, 2012, and 2014. The year with 

the highest precipitation was 1995. Eight years had an annual precipitation 

less than 37.35 in. Those years were 1954, 1977, 1980, 1981, 1990, 1999, 

2006, and 2010. 
ERDC/CHL TR-20-9 35

Figure 21. Yearly precipitation totals, Mayport, FL, 1948–2014. 

3.3 Dredged volume comparison methods 

The assumption was made that a higher rainfall or storm activity in the 

months or years prior to dredging will lead to increased infilling and 

therefore a larger volume of sediment to be removed. Two principal 

methods were used to classify years based on rainfall totals and tropical 

storm activity and predict dredged volume. These methods included the 

analysis of the influence of storms and rainfall at a variety of intervals 

prior to dredging at both Galveston, TX, and Mayport, FL. 

The first method (Method 1 – Time between Dredging Events, discussed in 

Section 3.3.1) analyzed the time between historical dredging events. 

Annual rainfall and storm Impact Factors following one dredge event were 

compared to the dredging volume of the succeeding dredge event. Since 

operational decisions are made well in advance of a dredging event, two 

alternatives to this Method 1 (Method 1a and Method 1b) were also 

performed: (1) an approximate period between 6 months before the first 

event and 6 months before the second event and (2) the period between 1 

year prior to the first event and 1 year before the second event was 

analyzed. This timing may be more representative because a decision to 

dredge and the volume required to justify the dredging is made several 
ERDC/CHL TR-20-9 36

months before a dredge makes its way to the site. These two alternates to 

Method 1 (6 months before, and 1 year before) are presented in Appendix 

B Method 1a, and Appendix B Method 1b, respectively

For the second method (Method 2 – Set Blocks of Time, discussed in 

Section 3.3.2), every 2- and 3-year interval between 1948 and the present 

was analyzed. The dredged volumes, rainfall totals, and storm Impact 

Factors were totaled over each interval time period. This procedure 

provides additional information related to rainfall and storm trends. This 

method allowed for a certain amount of smoothing of spikes or dips in 

dredging from year to year. Grouping the dredge events gives more of an 

average volume that should typically be seen over a given interval and 

shows how the rainfall or storms will cause a divergence from this 

expected volume. One benefit of this method is that it may more closely 

mirror how decisions are made over a multi-year budget or multi-year 

dredging cycle for planning purposes. Alternatives to this Method 2 of 

examining 2- and 3-year intervals (Method 2a and Method 2b, 

respectively), examined 5- and 6-year intervals and are presented in 

Appendix B.

These analysis methods were performed for both Galveston, TX, and 

Mayport, FL; however, the Galveston, TX, site will be used to demonstrate 

each of the two methods.

3.3.1 Method 1 – Time between dredging events

The first method tested was the analysis of the time between dredging 

events. There was a total of 31 dredging events in Galveston Harbor, TX, 

between 1947 and 2012. For each time period between dredging events, 

the actual rainfall and storm Impact Factor were calculated. The average 

rainfall for the given months between events was calculated based on 

monthly and yearly rainfall between 1946 and 2013. The actual rainfall 

was compared to the average rainfall over the time period between events 

to obtain a percentage of average rainfall. This percentage can provide 

information about drought periods or times of heavy rainfall. 

The storm Impact Factor for each period was calculated by totaling the 

Impact Factors of storms occurring since the last dredging event. An 

annualized Impact Factor was calculated as the total Impact Factor 

divided by the dredging interval. If no storm occurred during a time 
ERDC/CHL TR-20-9 37

period, or if the time period included only storms that had Impact Factors 

of zero, then there was no Impact Factor for that period. 

Table 7 lists the dates of the first dredging event and the second dredging 

event, the actual and average rainfall, the percentage of average rainfall, 

the rainfall category, and the total and annualized storm Impact Factors. 

The 10 lowest rainfall percentages were classified as low, the next 10 were 

medium, while the highest 10 rainfall totals compared to the average were 

considered high. The highest rainfall total compared to the average over 

that period of time is 138% between 27 October 1972 and 1 June 1974. The 

lowest rainfall compared to the average is 81% between 25 June 1947 and 

9 January 1950. The highest rainfall total is nearly 260 in. between 20 

March 1976 and 12 April 1982. The greatest annualized storm Impact 

Factor occurred between 31 December 2007 and 31 July 2009. The highest 

storm Impact Factor was 1.486, which occurred between 31 August 1982 

and 7 October 1985. There were 10 periods between dredging events that 

did not experience any storms. There were also three periods in which a 

weak storm with an Impact Factor of zero occurred. 

 Table 7. Rainfall and storm Impact Factors between dredging events, 

Galveston Harbor, TX, 1947–2010. 

Prior Event Event 

Actual 

Rainfall, 

in. 

Average 

Rainfall, 

in. 

Percent 

Rainfall 

Category 

Based 

on 

Rainfall 

Actual 

Impact 

Factor 

Annual 

Impact 

Factor 

6/25/1947 1/9/1950 87.32 107.99 81 Low 1.326 0.521

1/9/1950 10/23/1951 65.17 74.02 88 Medium - -

10/23/1951 4/24/1953 48.64 59.42 82 Low - -

4/24/1953 8/21/1955 85.66 93.27 92 Medium 0 0

8/21/1955 6/15/1958 76.41 115.86 66 Low 0.499 0.177

6/15/1958 12/11/1960 98.5 106.12 93 Medium 0.972 0.390

12/11/1960 7/23/1962 82.71 64.03 129 High - -

7/23/1962 5/29/1964 58.4 75.99 77 Low 0.771 0.416

5/29/1964 7/20/1965 37.04 47.83 77 Low 0.111 0.097

7/20/1965 11/21/1966 76.16 58.20 131 High - -

11/21/1966 6/2/1969 108.87 101.33 107 Medium - -

6/2/1969 10/28/1972 135.85 117.46 116 High 0.95 0.279

10/28/1972 6/1/1974 86.1 62.56 138 High 0.255 0.160

6/1/1974 3/20/1976 78.05 76.29 102 Medium 0 0

3/20/1976 4/12/1982 259.64 250.15 104 Medium 0.302 0.050

4/12/1982 8/31/1982 11.51 16.13 71 Low - -
ERDC/CHL TR-20-9 38

Prior Event Event 

Actual 

Rainfall, 

in. 

Average 

Rainfall, 

in. 

Percent 

Rainfall 

Category 

Based 

on 

Rainfall 

Actual 

Impact 

Factor 

Annual 

Impact 

Factor 

8/31/1982 10/7/1985 138.11 130.59 106 Medium 1.486 0.479

10/7/1985 10/17/1986 34.85 42.47 82 Low 0.595 0.579

10/17/1986 9/30/1989 121.95 122.23 100 Medium 0.488 0.165

9/30/1989 6/18/1994 212.28 192.09 111 High 0.325 0.069

6/18/1994 4/6/1998 192.77 158.16 122 High 0.1 0.026

4/6/1998 7/9/2000 103.79 92.78 112 High 0 0

7/9/2000 8/3/2003 156.17 127.01 123 High 0.319 0.104

8/3/2003 10/15/2005 91.88 93.81 98 Medium 0.455 0.207

10/15/2005 8/31/2006 32.37 34.21 95 Medium - -

8/31/2006 12/31/2007 68.83 57.31 120 High 0.555 0.416

12/31/2007 7/31/2009 39.16 62.71 62 Low 1.1 0.695

7/31/2009 12/31/2009 22.8 20.06 114 High - -

12/31/2009 3/31/2010 6.87 8.32 83 Low - -

3/31/2010 4/30/2012 63.26 85.15 74 Low - -

Figure 22 shows in chart form the actual rainfall as a percentage of the 

average rainfall. Each period between dredging events from 20 July 1965 

to 12 April 1982 experienced more rainfall than the average. No period 

between dredging events before 11 December 1960 experienced more 

rainfall than the average.

Figure 22. Actual versus average rainfall between dredging events, 

Galveston Harbor, TX, 1947–2012. 
ERDC/CHL TR-20-9 39

Figure 23 shows the cumulative storm Impact Factor between each 

dredging event. Each dredging period between 1982 and 1998 included at 

least one storm event. The period from 9 January 1950 to 21 August 1955 

was characterized by weak storms (Impact Factor of zero) or no storms. 

The longest period of weak or no storms is the present ongoing period. No 

storm impacted the Houston-Galveston area between the 31 July 2009 

dredging event and Hurricane Harvey on 25 August 2017. Harvey was an 

intense hurricane when it made landfall near Rockport, TX, but was a 

tropical storm by the time it impacted the Houston-Galveston area (Blake 

and Zelinsky 2018). Although Harvey caused severe flooding in the 

Houston-Galveston area due to unprecedented rainfall (Blake and Zelinsky 

2018), the storm Impact Factor does not take rainfall into account. Based 

on the wind speed, duration, and distance from Houston-Galveston, 

Harvey was considered a weak storm in terms of storm Impact Factor. 

However, because dredging records were not available beyond 2012, 

Harvey was not considered in the storm or precipitation analysis.

Figure 23. Storm Impact Factors between dredging events, Galveston Harbor, TX, 

1947–2012. 
ERDC/CHL TR-20-9 40

3.3.2 Method 2 – Set blocks of time

To gain a better understanding of the short-term and long-term trends for 

rainfall and hurricanes, an analysis was conducted that calculated the total 

rainfall quantities, cumulative storm Impact Factor, and total dredging 

volumes over a 2-, 3-, 5-, and 6-year period, for Galveston Harbor, TX. For 

each analysis, the final year considered was 2013. Therefore, the starting 

date for the 5-year blocks was 1949 compared to 1948 for the 2-, 3-, and 

6-year blocks of time. 

The first analysis considered thirty-three 2-year time periods from 1948 to 

2013. For each 2-year period, rainfall totals in inches, storm Impact 

Factor, and total dredged volume were calculated. Figure 24 compares 

rainfall (blue bars) for 2-year time periods to the volume dredged (red 

circles) over those 2 years. The red horizontal dashed line represents the 

threshold between an average rainfall and a wetter time period. All rainfall 

totals below the blue horizontal dashed line represent dry periods while 

rainfalls between the blue and the red lines represent average rainfall 

totals. The driest 2-year period was 2010–2011. The wettest period was 

1998–1999. Dredging did not occur in the 1948–1949, 1956–1957, 1970–

1971, 1978–1979, 1980–1981, 1990–1991, 1992–1993, and 1996–1997 time 

periods. The greatest volumes of dredging over a 2-year period occurred in 

1950–1951 and 1982–1983 when more than 8M yd3 were dredged. 

Figure 24. Rainfall and volume dredged over 2-year intervals, 

Galveston Harbor, TX, 1948–2013. 
ERDC/CHL TR-20-9 41

Figure 25 compares storm Impact Factors to volume dredged over the 

same 2-year intervals. Fourteen time periods did not experience any 

storms with Impact Factors greater than zero. The thresholds for weak and 

strong storms were based only on time periods where storms with Impact 

Factors occurred. For example, storms with Impact Factors greater than 

zero occurred during 19 of the time periods. Seven of the time periods 

were classified as strong storms, six as average, and six as weak. The 

highest Impact Factor occurred for 1982–1983, which is to be expected 

due to Hurricane Alicia. The longest period of no storm impacts was 

between 1950 and 1955. However, the decade of the 1990s only 

experienced one weak storm during the 1994–1995 time period.

Figure 25. Storm Impact Factors and volume dredged over 2-year intervals, 

Galveston Harbor, TX, 1948–2013. 

There are twenty-two 3-year time periods considered for the second 

analysis. Figure 26 shows the rainfall in inches for each 3-year period, and 

the volume dredged during the same time period. The greatest volume 

dredged occurred during the 1960–1962 time period. The 1978–1980 and 

1990–1992 time periods did not experience any dredging. The threshold 

between dry and average was 115 in. while any rainfall greater than 134 in. 

was classified as wet for a 3-year period. The driest 3-year time period was 

1954–1956 while the wettest time period was 1996–1998. The 1996–1998

time period experienced more than twice as much rain as the 1954–1956 

time period. 
ERDC/CHL TR-20-9 42

Figure 26. Rainfall and volume dredged over 3-year intervals, 

Galveston Harbor, TX, 1948–2013. 

Figure 27 shows the storm Impact Factor for each 3-year period and the 

volume dredged during the same period. Eight of the time periods did not 

have any storms with an Impact Factor greater than zero. The highest 

Impact Factor was from 1957 to 1959. The lowest Impact Factor (other 

than zero) occurred during the 1993–1995 and 1999–2001 time periods. A 

storm Impact Factor of less than 0.5 over a 3-year period was considered a 

weak storm period. 

The calculation of a storm Impact Factor is described in Part 3: “Storm 

and Precipitation Analysis,” sub-section 3.1.2 “Determination of Impact 

Factor,” of this document. If a single storm happened during the 3-year 

period, for it to be classified as having a weak storm Impact Factor, the 

storm must have been more than 100 miles from the point of interest and 

more than 150 mph, with a duration of 15 to 18 hr. However, it is unlikely 

that such a strong storm would maintain that wind speed for a long period 

of time after making landfall, so a single storm with a wind speed of 60 to 

73 mph and a duration of 3 to 6 hr in each circle (less than 25 miles, 25–50 

miles, 50–75 miles, 75–100 miles, and 100–150 mile radius) would also be 

classified as having a weak storm Impact Factor. If a smaller storm 

occurred in each one of the years, a storm of 39 to 45 mph winds with a 

duration of 3 to 6 hr inside of a 25 mile radius and between the 25 to 50 

mile radius would have a storm Impact Factor around 0.167 per year. A 
ERDC/CHL TR-20-9 43

storm or storms over the 3-year period with a storm Impact Factor of 

greater than 0.93 was considered a time period of strong storms. A single 

storm with winds of 85 to 90 mph, a track that made landfall within 

25 miles of the site of interest, and a total duration of 21 hr or longer 

would have an Impact Factor of greater than 0.93. If a smaller storm made 

landfall each year, each storm would have a wind speed between 50 and 52 

mph and a duration of 3 to 6 hr within each circle up to 75 miles away 

from the location of interest.

Figure 27. Storm Impact Factors and volume dredged over 3-year 

intervals, Galveston Harbor, TX, 1948–2013. 

While this analysis does not give specific information relating volume 

dredged to rainfall and storms over each period, it does provide 

information about the trends. It is much easier to see which periods of 

time had greater amounts of rain or larger storms, which helps develop the 

final analysis to provide a range of volumes for dry, average, or wet 

conditions or weak, average, or strong storms. By having identical lengths 

of time for each period (1 January to 31 December), each time period can 

be compared to each other. During a 5-year time period, a large dredging 

event might occur in the first year, but the rainfall over that period of time 

might be low and there might not be any storm events. Generally, larger 

dredging events correspond with storms or wet periods of time. If the 

storm happened early in the time period, the prior 5-year period would 

provide better information for rainfall totals and storms prior to the 
ERDC/CHL TR-20-9 44

dredging event. Also, choosing an appropriate time interval that 

approximately matches the dredging interval is likely the best way to apply 

this method at a site. At Galveston, a slight variation of Method 2 was used 

where the 2-year dredging totals were paired with the previous 2-year 

storm activity and rainfall totals. Table 8 presents the rainfall totals and 

storm Impact Factors based on this method. 

Table 8. Total rainfall and storm Impact Factors for 2-year intervals, 

Galveston Harbor, TX, 1947–2012. 

 

2-year Interval 2-year volume, yd3 

Previous 2-year 

Interval 

Total Impact 

Factor Total Rainfall, in. 

1947-1948 6,082,994 1945-1946 0.34 80.1

1949-1950 5,004,824 1947-1948 0.6 66.1

1951-1952 3,212,051 1949-1950 0.73 85.6

1953-1954 2,894,868 1951-1952 68.7

1955-1956 3,902,472 1953-1954 0 63.5

1957-1958 2,149,535 1955-1956 0 56.7

1959-1960 4,032,000 1957-1958 0.5 75.4

1961-1962 5,376,500 1959-1960 0.97 63.8

1963-1964 1,777,693 1961-1962 98.9

1965-1966 8,483,063 1963-1964 0.88 72.5

1967-1968 0 1965-1966 90.4

1969-1970 4,312,942 1967-1968 83.2

1971-1972 4,055,450 1969-1970 0.2 92.9

1973-1974 3,482,921 1971-1972 0.75 70.6

1975-1976 4,993,000 1973-1974 0.26 104.7

1977-1978 0 1975-1976 87.0

1979-1980 0 1977-1978 0 82.3

1981-1982 8,284,695 1979-1980 0.23 95.4

1983-1984 0 1981-1982 0.18 70.1

1985-1986 5,567,703 1983-1984 1.18 89.7

1987-1988 0 1985-1986 0.72 74.7

1989-1990 4,038,896 1987-1988 0.12 89.5

1991-1992 0 1989-1990 0.69 76.9

1993-1994 5,162,753 1991-1992 105.9

1995-1996 0 1993-1994 80.2

1997-1998 5,400,565 1995-1996 0.1 91.8

1999-2000 3,818,488 1997-1998 0 132.3

2001-2002 0 1999-2000 0 58.3

2003-2004 819,428 2001-2002 0.1 88.6
ERDC/CHL TR-20-9 45

 

2-year Interval 2-year volume, yd3 

Previous 2-year 

Interval 

Total Impact 

Factor Total Rainfall, in. 

2005-2006 3,820,552 2003-2004 0.34 91.9

2007-2008 2,956,986 2005-2006 0.34 77.6

2009-2010 4,317,019 2007-2008 1.65 61.7

2011-2012 2,084,922 2009-2010 66.4

3.4 Classification of years

Periods between events and in 2-year intervals were categorized based on 

both their rain totals and storm activity. For the 2-year interval method, 

the prior 2 years of storm activity were used to rank the following 2-year 

total dredging volume. The categories of low, medium, or high were 

assigned based on a relative relationship with the other events occurring 

within the dredging record period. Both percentage of average rainfall and 

storm Impact Factor were categorized into low, medium, and high for each 

time period and 2-year interval.

The storms were ranked according to percentile thresholds for both the 

total Impact Factor and the annualized Impact Factor. Those Impact 

Factors below the thirty-third percentile were categorized as low, those 

between the thirty-third and sixty-seventh percentile were categorized as 

medium, and those above the sixty-seventh percentile were ranked as 

high. Similarly, the percentage of average rainfall was used to categorize 

the rainfall totals along these thresholds. The calculation of the modified 

storm Impact Factor (Table 8) is fairly conservative so that any storms 

that have a calculated Impact Factor greater than zero are fairly 

significant. The moderate-to-high categories are assigned to any period 

above the thirty-third percentile because the majority of periods 

categorized as low have either a relatively low ranking Impact Factor, a 

total Impact Factor of zero, or no storm activity at all.

Table 9 shows the categorization of storm activity based on the total 

Impact Factor from the previous 2-year interval at Galveston. To 

demonstrate the usefulness of using the period between dredging events, 

Method 1 was used at Mayport, FL, to compare storm and rainfall activity 

from the previous dredge event to the succeeding dredge event. Table 10 

shows the categorization of storm activity based on the time period 

between dredging events at Mayport, FL. Because the time between 

dredging is variable, the Impact Factor total and dredging volume are

presented in an annualized fashion as well.
ERDC/CHL TR-20-9 46

Table 9. Two-year interval categorization based on storm Impact Factor, 

Galveston, TX, 1947–2012. 

2-year Interval 

2-year Volume, 

yd3 

Previous 

2-year 

Interval 

Total Impact 

Factor 

Impact 

Factor 

Category 

1947-1948 6,082,994 1945-1946 0.34 Moderate

1949-1950 5,004,824 1947-1948 0.6 Moderate

1951-1952 3,212,051 1949-1950 0.73 High

1953-1954 2,894,868 1951-1952 Low

1955-1956 3,902,472 1953-1954 0 Low

1957-1958 2,149,535 1955-1956 0 Low

1959-1960 4,032,000 1957-1958 0.5 Moderate

1961-1962 5,376,500 1959-1960 0.97 High

1963-1964 1,777,693 1961-1962 Low

1965-1966 8,483,063 1963-1964 0.88 High

1967-1968 0 1965-1966 Low

1969-1970 4,312,942 1967-1968 Low

1971-1972 4,055,450 1969-1970 0.2 Moderate

1973-1974 3,482,921 1971-1972 0.75 High

1975-1976 4,993,000 1973-1974 0.26 Moderate

1977-1978 0 1975-1976 Low

1979-1980 0 1977-1978 0 Low

1981-1982 8,284,695 1979-1980 0.23 Moderate

1983-1984 0 1981-1982 0.18 Moderate

1985-1986 5,567,703 1983-1984 1.18 High

1987-1988 0 1985-1986 0.72 High

1989-1990 4,038,896 1987-1988 0.12 Low

1991-1992 0 1989-1990 0.69 High

1993-1994 5,162,753 1991-1992 Low

1995-1996 0 1993-1994 Low

1997-1998 5,400,565 1995-1996 0.1 Low

1999-2000 3,818,488 1997-1998 0 Low

2001-2002 0 1999-2000 0 Low

2003-2004 819,428 2001-2002 0.1 Low

2005-2006 3,820,552 2003-2004 0.34 Moderate

2007-2008 2,956,986 2005-2006 0.34 Moderate

2009-2010 4,317,019 2007-2008 1.65 High

2011-2012 2,084,922 2009-2010 Low
ERDC/CHL TR-20-9 47

Table 10. Classification of rainfall and storm Impact Factors, Mayport, FL, 

1954–2008. 

 

Prior Event 

 

Event 

 

Volume, 

yd3 

Actual 

Impact 

Factor 

 

Category 

Annualized 

Impact 

Factor 

 

Category 

1/1/1954 8/1/1956 346,312 0 Low 0 Low

8/1/1956 10/1/1959 897,777 0.13 Moderate 0.04 Moderate

10/1/1959 10/1/1962 1,411,640 0.38 High 0.13 High

10/1/1962 1/1/1964 559,092 0.25 High 0.20 High

1/1/1964 3/1/1965 289,050 1.43 High 1.23 High

3/1/1965 12/1/1966 1,962,067 0 Low 0 Low

12/1/1966 9/1/1969 868,479 0.7 High 0.25 High

9/1/1969 8/1/1972 1,158,181 0 Low 0 Low

8/1/1972 3/1/1974 570,972 0 Low 0 Low

3/1/1974 2/1/1975 547,565 0 Low 0 Low

2/1/1975 3/1/1978 736,084 0 Low 0 Low

3/1/1978 10/1/1978 1,789,701 0 Low 0 Low

10/1/1978 7/1/1979 173,558 0 Low 0 Low

7/1/1979 3/1/1982 47,148 0.69 High 0.26 High

3/1/1982 11/1/1983 1,793,031 0 Low 0 Low

11/1/1983 8/1/1984 129,363 0 Low 0 Low

8/1/1984 6/1/1985 223,000 0.67 High 0.80 High

6/1/1985 1/1/1990 1,280,151 0.34 High 0.07 Moderate

1/1/1990 5/1/1994 1,600,135 0 Low 0 Low

5/1/1994 1/1/1997 1,230,507 0 Low 0 Low

1/1/1997 3/1/2000 1,099,371 0.2 Moderate 0.06 Moderate

3/1/2000 10/1/2001 1,097,800 0 Low 0 Low

10/1/2001 4/1/2003 174,832 0.03 Moderate 0.02 Moderate

4/1/2003 1/1/2005 1,289,138 0.28 High 0.16 High

1/1/2005 5/1/2008 1,069,754 0.2 Moderate 0.06 Moderate

5/1/2008 1/1/2010 629,034 0.26 High 0.16 High

3.5 Methods discussion

The two methods reviewed have both advantages and disadvantages for 

predicting dredging volumes at a site. The main distinction between the 

methods is the time period prior to a dredging event that is used to analyze 

the storms and rainfall. Deciding when a dredging decision should be 

made to capture the correct period of conditions that influence the channel 

makes choosing the appropriate period difficult. For the purpose of this 
ERDC/CHL TR-20-9 48

study, two methods are used to find the relationship between dredging 

volumes and varying site conditions: (1) Method 1 – Time between 

dredging events (the storms occurring during the 2 years prior to the 

succeeding 2-year total of dredging volumes) and (2) Method 2 – Set 

blocks of time (the storms occurring between dredging events). 

The biggest lesson learned when working through each of the methods 

listed in Section 3.3.1 (Method 1) and Section 3.3.2 (Method 2) is that 

using the rainfall or storm activity as the sole predictor to determine a 

single value of dredging is difficult and likely unrealistic. This type of 

deterministic approach to accurately predict the volume that will be seen 

in the next year or over the next interval of dredging years would require 

more data points than are presently available at most sites. The results of 

the analysis conducted at a site have not shown that storm or rain activity 

can accurately and consistently provide a single deterministic value for 

expected dredging. Alternatively, integrating a probabilistic approach 

could provide valuable information about how dredging volumes change 

under varying levels of storms or rainfall. The results of the analysis will 

include the range of volumes dredged following each rainfall or storm 

activity level, an average volume seen at each level, and the probability of 

exceeding the annual average dredging rate based on the level of rainfall or 

storms. For Galveston Harbor, TX, the analysis method chosen was 

Method 1, the 2-year interval blocks for totaling storm Impact Factor and 

dredge volumes, and for Mayport, FL, Method 2, the method using the 

time between dredging events, was chosen.
ERDC/CHL TR-20-9 49

4 Results and Discussion

4.1 Galveston Harbor, TX

Analysis at Galveston Harbor, TX, consisted of both categorizing years 

based on their storm and rainfall activity to extract trends in dredging. For 

Galveston Harbor, the analysis was completed based exclusively on total 

storm Impact Factor over 2-year intervals as presented in section 3.4.

Establishing an average annual dredging rate is a common first step in 

predicting future dredging at a site. It is typically a linear regression of the 

cumulative dredging volume in which the slope of that line represents an 

estimate for the average annual dredging rate. Figure 28 is the cumulative 

dredging plotted against time for a period of 65 years from 1947 to 2012. 

The line of best fit is shown along with the equation of linear regression.

Figure 28. Linear regression of cumulative dredging at Galveston, TX. 

This regression gives an average annual rate of 1,520,600 yd3, and the 

equation represents a linear model of cumulative dredging at Galveston, 

TX. The residual differences between the actual cumulative dredging 

volumes and the modeled results can bring insight into how storms can 

cause variation from the expected average annual dredging rate. Table 11 

lists the cumulative, modeled, and residual volume values. Negative 

residuals indicate a lesser-than-average dredging rate, and positive 

residuals indicate a greater than average rate.

y = 1,520,603x - 3E9

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

1940 1960 1980 2000 2020

Cumulative volume dredged, yd3

Year
ERDC/CHL TR-20-9 50

Table 11. Cumulative volume and residuals from modeled dredging volume, 

Galveston Harbor, TX, 1947–2012. 

2-Year Interval 

Actual Cumulative 

Dredging Volume, 

yd3 

Modeled 

Cumulative 

Dredging Volume, 

yd3 

Residual 

Dredging 

Volume, yd3 

1947-1948 6,082,994 11,632,487 -5,549,493

1949-1950 11,087,818 14,673,693 -3,585,875

1951-1952 14,299,869 17,714,899 -3,415,030

1953-1954 17,194,737 20,756,105 -3,561,368

1955-1956 21,097,209 23,797,311 -2,700,102

1957-1958 23,246,744 26,838,517 -3,591,773

1959-1960 27,278,744 29,879,723 -2,600,979

1961-1962 32,655,244 32,920,929 -265,685

1963-1964 34,432,937 35,962,135 -1,529,198

1965-1966 42,916,000 39,003,341 3,912,659

1967-1968 42,916,000 42,044,547 871,453

1969-1970 47,228,942 45,085,753 2,143,189

1971-1972 51,284,392 48,126,959 3,157,433

1973-1974 54,767,313 51,168,165 3,599,148

1975-1976 59,760,313 54,209,371 5,550,942

1977-1978 59,760,313 57,250,577 2,509,736

1979-1980 59,760,313 60,291,783 -531,470

1981-1982 68,045,008 63,332,989 4,712,019

1983-1984 68,045,008 66,374,195 1,670,813

1985-1986 73,612,711 69,415,401 4,197,310

1987-1988 73,612,711 72,456,607 1,156,104

1989-1990 77,651,607 75,497,813 2,153,794

1991-1992 77,651,607 78,539,019 -887,412

1993-1994 82,814,360 81,580,225 1,234,135

1995-1996 82,814,360 84,621,431 -1,807,071

1997-1998 88,214,925 87,662,637 552,288

1999-2000 92,033,413 90,703,843 1,329,570

2001-2002 92,033,413 93,745,049 -1,711,636

2003-2004 92,852,841 96,786,255 -3,933,414

2005-2006 96,673,393 99,827,461 -3,154,068

2007-2008 99,630,379 102,868,667 -3,238,288

2009-2010 103,947,398 105,909,873 -1,962,475

2011-2012 106,032,320 108,951,079 -2,918,759
ERDC/CHL TR-20-9 51

Based on the categorization of periods preceding a dredge event, ranges of 

annual dredged volumes were established from the historical trends for a 

given period type. The 2-year dredging volumes were halved to give an 

annualized dredging volume. Table 12 presents the ranges based on type of 

storm period prior to dredging along with the average dredging rate by 

period type and difference from the average dredging rate.

Table 12. Range of annual dredged volumes and average annual dredged volumes 

based on previous 2-year interval storm period level, Galveston Harbor, TX. 

Period Type 

Minimum, 

yd3 

Maximum, 

yd3 

Average, 

yd3 

Difference from 

Mean, yd3 

Low/ No Storm 409,714 2,700,283 1,136,330 -494,936

High Storm 1,478,493 4,241,532 2,049,111 417,844

A t-test can be used to determine if the difference in average between two 

groups is indicative of a significance difference. A t-test was used to 

determine if the difference in mean dredge volume under each storm 

intensity classification is statistically significant. As described previously, 

mean dredge volumes following low or no storm periods and high storm 

intensity conditions were compared. The difference between the average 

volumes dredged following a low storm period versus a high storm period 

is statistically significant at the 95% confidence interval with a p-value of 

0.013.

4.2 Mayport Basin, FL

Analysis at Mayport, FL, consisted of categorizing years based on their 

storm and rainfall activity. As discussed previously, there seems to be a 

clearer relationship between storms and dredging at this site, so the 

results will focus on storm activity as it relates to dredging volume. 

Establishing an average annual dredging rate is a common first step in 

predicting future dredging at a site. It is typically done with a linear 

regression of the cumulative dredging volume in which the slope of that 

line represents an estimate for the average annual dredging rate. Figure 29

is the cumulative dredging plotted against time for a period of 56 years 

from 1954 to 2010. The line of best fit is shown along with the equation of 

linear regression.
ERDC/CHL TR-20-9 52

Figure 29. Linear regression of cumulative dredging at Mayport, FL. 

This regression gives an average annual rate of 423,105 yd3, and the 

equation represents a linear model of cumulative dredging at Mayport, FL. 

The residual differences between the actual cumulative dredging volumes 

and the modeled results can bring insight into how storms can cause 

variation from the expected average annual dredging rate. Table 13 lists 

the cumulative, modeled, and residual volume values. Negative residuals 

indicate a lesser-than-average dredging rate, and positive residuals 

indicate a greater than average rate.

Table 13. Cumulative volume and residuals from modeled dredging volume, 

Mayport, FL, 1954–2010. 

Dredge Event Actual Cumulative 

Dredging Volume, yd3 

Modeled Cumulative 

Dredging Volume, yd3 

Residual Dredging 

Volume, yd3 

1/6/1954 346,312 406,816 -60,504

8/1/1956 1,244,089 1,494,138 -250,049

10/19/1959 2,655,729 2,855,029 -199,300

10/20/1962 3,214,821 4,126,662 -911,841

1/1/1964 3,503,871 4,634,388 -1,130,517

3/1/1965 5,465,938 5,127,045 338,893

12/1/1966 6,334,417 5,868,928 465,489

9/1/1969 7,492,598 7,033,915 458,683

8/4/1972 8,063,570 8,271,932 -208,362

Volume (CY) = 423,105x - 8E+08

0

5

10

15

20

25

30

1950 1960 1970 1980 1990 2000 2010 2020

Cumulative Volume Dredged, 

Millions CY

Year

Individual Dredge

Events

Linear (Individual

Dredge Events)
ERDC/CHL TR-20-9 53

Dredge Event Actual Cumulative 

Dredging Volume, yd3 

Modeled Cumulative 

Dredging Volume, yd3 

Residual Dredging 

Volume, yd3 

3/25/1974 8,611,135 8,965,129 -353,994

2/1/1975 9,347,219 9,327,956 19,263

10/24/1978 11,310,478 10,905,616 404,862

7/5/1979 11,357,626 11,200,051 157,575

3/1/1982 13,150,657 12,324,467 826,190

11/19/1983 13,280,020 13,052,439 227,581

8/24/1984 13,503,020 13,375,854 127,166

6/1/1985 14,783,171 13,701,587 1,081,584

1/1/1990 16,383,306 15,643,233 740,073

5/21/1994 17,613,813 17,499,099 114,714

1/29/1997 18,713,184 18,639,744 73,440

3/27/2000 19,810,984 19,976,292 -165,308

10/22/2001 19,985,816 20,641,668 -655,852

4/24/2003 21,274,954 21,278,064 -3,110

1/1/2005 22,344,708 21,994,445 350,263

5/19/2008 22,973,742 23,424,887 -451,145

1/30/2010 23,148,683 24,144,745 -996,062

Based on the categorization of periods preceding a dredge event, ranges 

were established based on the minimum and maximum dredging volumes 

recorded under each storm categorization. Dredging volumes were 

considered on an annual basis and on an event basis. Hence, if 800,000 yd3

were dredged 2 years after the previous event, the annual volume would be 

400,000 yd3, and the event volume would be 800,000 yd3. Table 14 

presents the ranges based on type of storm period prior to dredging.

Table 14. Range of dredging volumes on annual and per-event basis for low and high 

storm periods, Mayport, FL. 

Annual Dredge Volume Volume by Dredge Event 

Period Type 

Minimum, 

yd3 Maximum, yd3 Period Type 

Minimum, 

yd3 Maximum, yd3 

Low/ No Storm 67,752 858,373 Low/ No Storm 47,148 1,789,701

Stormy Period 186,059 1,685,069 Stormy Period 174,941 1,962,067
ERDC/CHL TR-20-9 54

Table 14 shows the full range of possibilities seen at Mayport, FL, and it is 

highly varied. The average annual dredging rate is 423,100 yd3/year as 

determined by the linear regression of cumulative dredging (Figure 29) 

and the average volume dredged on an event basis is 857,360 yd3.

Table 15 presents statistics for the mean dredging volumes for annualized 

and event totals. Statistics provided in Table 14 and Table 15 provide a 

starting point on understanding how dredging at Mayport, or another site 

of interest, is impacted by varying levels of hurricane and tropical storm 

activity. 

Table 15. Deviation from average dredging volume on annual and per-event basis for 

low and high storm periods, Mayport, FL. 

Annual Dredge Volume Average: 423,105 yd3 Volume by Dredge Event Average: 857,359 yd3 

Period Type 

Average, 

yd3 

Difference 

From Mean, 

yd3 Period Type Average, yd3 

Difference 

From Mean, 

yd3 

Low/ No Storm 340,737 -85,794 Low/ No Storm 652,951 -204,408

Stormy Period 568,121 +145,016 Stormy Period 1,102,696 +245,337

A t-test was used to determine if the difference in mean dredge volume 

under each storm intensity classification is statistically significant. As 

described previously, mean dredge volumes following low- or no-storm 

periods and high storm intensity conditions were compared. The

difference between the average annual volumes dredged following a 

low-storm period versus a high storm period is statistically significant at 

the 90% confidence interval with a p-value of 0.05. The difference between 

the average volumes dredged on an event basis following a low storm 

period versus a high storm period is statistically significant at the 95% 

confidence interval with a p-value of 0.013.
ERDC/CHL TR-20-9 55

5 Conclusions

Several factors play a role in the volume removed and frequency with 

which a channel or harbor is dredged. Because the aim of this effort was to 

develop a simple generalized methodology applicable to a wide range of 

sites using only readily available storm and rainfall data, predicting a 

single future volume of dredging that occurs during a given period is 

difficult. Dredging does not correlate to either one factor or another factor 

solely, and attempting to correlate to one factor would likely yield 

inaccurate results. If a similar methodology were developed on a sitespecific basis, a more deterministic result could be accurately developed. 

Still, in this generalized approach, using storm and/or rainfall data as a 

means of gaining better understanding about how little or how much a 

given channel or harbor responds to different levels of hurricane activity 

or rainfall is a valuable application of available data.

If the analysis methods provided in this report are applied for different 

channels elsewhere in the country, they would also provide insight into how 

different conditions cause variations in infilling patterns for different areas 

at coastal inlets, harbors, or inland waterways. Furthermore, if sediment 

information is known, it could provide guidance on a range of volumes for a 

given type of sediment, an important aspect of beneficial use planning.

The statistical significance for results determined with the methods in this 

report may be limited by the sample size available at a site. A site with 30 

dredging events dating back 60 years is considered a fairly long record, 

and many sites have fewer available records or less frequent dredging. As 

additional historical dredging records are gathered, and future dredging 

volumes are collected and retained, this approach will become more 

robust, and more confidence can be placed on the results.
ERDC/CHL TR-20-9 56

References

Barlow, M. 2011. “Influence of Hurricane-Related Activity on North American Extreme 

Precipitation.” Geophysical Research Letters 38: L04705. 

doi:10.1029/2010GL046258

Blake, E. S., and D. A. Zelinsky. 2018. National Hurricane Center Tropical Cyclone 

Report, Hurricane Harvey. https://www.nhc.noaa.gov/data/tcr/AL092017_Harvey.pdf

Doehring, F., I. W. Duedall, and J. M. Williams. 1994. Florida Hurricanes and Tropical 

Storms 1871-1993: An Historical Survey. Technical Paper 71. Melbourne, FL: 

Florida Institute of Technology, Division of Marine and Environmental Systems.

http://aquaticcommons.org/360

Houston-Galveston Navigation Safety Advisory Committee. 2011. Navigating the 

Houston Ship Channel: A Reference for Commercial Users.

http://www.uscg.mil/d8/vtsHouston/docs/Navigating%20the%20Houston%22Ship%20Channe

l_1Jun11.pdf

Kerr, Jessie L. 2010. “A Look Back: Remembering Dark Days When Hurricane Dora Hit 

46 Years Ago.” Jacksonville.com. Florida Times-Union, 20 September 2010. 

http://www.jacksonville.com/article/20100919/NEWS/801244571

National Research Council. 1984. Hurricane Alicia: Galveston and Houston, Texas, 

August 17-18, 1983. Washington, DC: The National Academies Press. 

https://doi.org/10.17226/19411

NHC CPHC (National Hurricane Center and Central Pacific Hurricane Center). 2020. The 

Saffir-Simpson Hurricane Wind Scale. Accessed 20 May. 

http://www.nhc.noaa.gov/aboutsshws.php

NOAA. (National Oceanic and Atmospheric Administration). 1999. Hurricane Basics. 

https://www.hsdl.org/?view&did=34038

NOAA. (National Oceanic and Atmospheric Administration). 2015a. NOAA Historical 

Hurricane Tracks. http://coast.noaa.gov/hurricanes/

NOAA. (National Oceanic and Atmospheric Administration). 2015b. Remembering Carla 

50th Anniversary. http://www.srh.noaa.gov/crp/?n=hurricanecarla

NOAA NHC (National Oceanic and Atmospheric Administration, National Hurricane 

Center). 2020. Accessed 20 May. https://www.nhc.noaa.gov/surge/surge_intro.pdf

Smith, T. J. III, G. H. Anderson, and G. Tiling. 2007. “A Tale of Two Storms: Surges and 

Sediment Deposition from Hurricanes Andrew and Wilma in Florida’s Southwest 

Coast Mangrove Forests.” Science and the Storms: The USGS Response to the 

Hurricanes of 2005. Edition: Circular 1306, Chapter: 6. Edited by G. S. Farris, G. 

J. Smith, M. P. Crane, C. R. Demas, L. L. Robbins, and D. L. Lavoie. Reston, VA: 

US Geological Survey. https://pubs.usgs.gov/circ/1306/pdf/c1306_ch6_g.pdf
ERDC/CHL TR-20-9 57

Appendix A: Additional Houston-Galveston, 

TX, Channels Dredging History

Channel locations are shown in Figure 1.

Table A-1. Comprehensive dredging data for the Houston-Galveston navigation channels. 

Date 

Volume, 

yd3 Location(s) 

6/25/1947 6,082,994 Galveston Harbor

1/9/1950 5,004,824 Galveston Harbor

10/23/1951 3,212,051 Galveston Harbor

4/24/1953 2,894,868 Galveston Harbor

8/21/1955 3,902,472 Galveston Harbor

6/15/1958 2,149,535 Galveston Harbor

12/11/1960 4,032,000 Galveston Harbor

7/23/1962 5,376,500 Galveston Harbor

5/29/1964 1,777,693 Galveston Harbor

7/20/1965 3,640,080 Galveston Harbor

11/21/1966 4,842,983 Galveston Harbor

6/2/1969 4,312,942 Galveston Harbor

3/19/1972 3,150,027 Entrance Channel

10/28/1972 4,055,450 Galveston Harbor

3/4/1973 1,892,841 Entrance Channel

4/24-

6/1/1974 4,669,594 Galveston Harbor, Inner Bar, Entrance Channel

5/13/1975 1,702,292 Entrance Channel

3/20/1976 4,993,000 Galveston Harbor

7/8/1976 1,293,203 Entrance Channel

3/25/1977 1,686,819 Entrance Channel

9/7/1979 3,667,687 Inner Bar, Entrance Channel

8/5/1980 1,170,578 Inner Bar, Outer Bar, Entrance Channel

4/12/1982 6,022,633 Galveston Harbor

8/31/1982 2,262,062 Galveston Harbor

7/25/1984 4,487,405 Inner Bar, Outer Bar, Entrance Channel

10/7/1985 4,301,050 Galveston Harbor

7/31/1986 2,212,568 Inner Bar, Outer Bar, Entrance Channel

10/17/1986 1,266,653 Galveston Harbor

10/4/1988 949,621 Inner Bar, Outer Bar, Entrance Channel

9/30/1989 4,097,834 Galveston Harbor, Inner Bar, Outer Bar, Entrance Channel

12/5/1990 2,171,188 Inner Bar, Outer Bar, Entrance Channel

8/25/1993 2,596,462 Inner Bar, Outer Bar, Entrance Channel

6/18/1994 5,162,753 Galveston Harbor

9/21/1995 691,683 Inner Bar

5/6/1996 8,653 Inner Bar

3/31/1997 1,921,837 Inner Bar, Outer Bar, Entrance Channel

4/6/1998 5,400,565 Galveston Harbor

7/9/2000 3,818,488 Galveston Harbor

3/31/01 9,005,085 Bolivar Roads, Inner Bar, Outer Bar
ERDC/CHL TR-20-9 58

Date 

Volume, 

yd3 Location(s) 

6/28-

8/3/2003 3,504,669 Galveston Harbor, Entrance Channel

9/17/2004 6,412,367

Bolivar Roads, Inner Bar, Outer Bar, Entrance Channel, Extended 

Entrance Channel

10/15/2005 998,152 Galveston Harbor

8/22/2006 5,347,564

Bolivar Roads, Galveston Harbor, Inner Bar, Entrance Channel, 

Extended Entrance Channel

12/31/2007 2,956,986 Galveston Harbor

1/31/2009 2,042,695 Inner Bar, Outer Bar 

7/31/2009 2,448,267 Galveston Harbor

12/31/2009-

1/31/2010 3,778,737

Galveston Harbor, Entrance Channel, Extended Entrance 

Channel

3/31/2010 899,667 Galveston Harbor

12/31/2011 1,952,526

Inner Bar, Outer Bar, Entrance Channel, Extended Entrance 

Channel

4/30/2012 2,084,922 Galveston Harbor

11/30/2012 775,000

Inner Bar, Outer Bar, Entrance Channel, Extended Entrance 

Channel

12/31/2013 2,151,298

Inner Bar, Outer Bar, Entrance Channel, Extended Entrance 

Channel

Table A-2. Bolivar Roads Channel 

dredging quantities or history. 

Date Volume, yd3 

12/5/1990 22,535

3/31/2001 1,631,075

9/17/2004 255,453

8/22/2006 67,172

Total 1,976,235

Table A-3. Inner Bar Channel dredging. 

Date Volume, yd3 

11/24/1965 4,147,166*

5/20/1974 247,746

9/7/1979 1,136,736

8/5/1980 130,552

7/25/1984 1,382,393

7/31/1986 469,624

10/4/1988 319,240

9/30/1989 21,951

12/5/1990 769,126

8/25/1993 708,020

9/21/1995 691,683

5/6/1996 8,653
ERDC/CHL TR-20-9 59

Date Volume, yd3 

3/31/1997 377,611

3/31/2001 4,936,613

9/17/2004 1,741,064

8/22/2006 77,291

1/31/2009 1,634,156

12/31/2011 155,500

11/30/2012 480,000

12/31/2013 882,300

Total 20,317,425

* Deepening

Table A-4. Outer Bar Channel dredging. 

Date Volume, yd3 

9/7/1979 144,503

8/5/1980 67,730

7/25/1984 195,505

7/31/1986 86,475

10/4/1988 162,052

9/30/1989 11,143

12/5/1990 30,373

8/25/1993 136,992

3/31/1997 87,215

3/31/2001 2,437,397

9/17/2004 252,533

1/31/2009 408,539

12/31/2011 38,875

11/30/2012 120,000

12/31/2013 220,575

Total 4,399,907

 
ERDC/CHL TR-20-9 60

Table A-5. Entrance Channel dredging. 

Date Volume, yd3 

3/14/1971 1,910,021

3/19/1972 3,150,027

3/4/1973 1,892,841

4/24/1974 938,927

5/13/1975 1,702,292

7/8/1976 1,293,203

3/25/1977 1,686,819

9/7/1979 2,530,951

8/5/1980 972,296

7/25/1984 2,909,507

7/31/1986 1,656,469

10/4/1988 468,329

9/30/1989 25,844

12/5/1990 1,371,689

8/25/1993 1,751,450

3/31/1997 1,457,011

6/28/2003 2,685,241

9/17/2004 1,930,702

8/22/2006 1,009,951

1/31/2010 1,404,826

12/31/2011 879,076

11/30/2012 87,500

12/31/2013 524,212

Total 34,239,184

Table A-6. Extended Entrance 

Channel dredging. 

Date Volume, yd3 

7/16/1999 3,271,463

9/17/2004 2,232,615

8/22/2006 1,370,750

1/31/2010 1,404,826

12/31/2011 879,075

11/30/2012 87,500

12/31/2013 524,211

Total 9,770,440

 
ERDC/CHL TR-20-9 61

Table A-7. Anchorage Area dredging. 

Date Volume, yd3 

5/25/1968 3,554,498

7/9/1978 1,130,462

8/5/1980 408,300

10/4/1988 89,325

12/5/1990 1,235,500

8/25/1993 296,160

3/31/1997 603,695

Total 7,317,940

Table A-8. GIWW – East dredging. 

Date Volume, yd3 

12/13/1943 1,350,023

12/20/1947 400,943

1/15/1950 330,161

4/11/1952 1,563,402

12/9/1954 760,151

2/25/1956 79,464

3/23/1957 438,074

1/18/1959 698,219

2/29/1960 240,615

3/3/1962 2,352,746

2/4/1963 123,635

6/29/1964 705,485

8/9/1966 665,283

2/12/1967 731,948

3/26/1969 812,722

3/20/1971 422,302

3/16/1972 764,667

10/12/1974 804,143

10/13/1978 572,765

9/9/1980 301,633

7/21/1983 1,668,601

11/22/1985 755,164

12/31/1987 227,793
ERDC/CHL TR-20-9 62

Date Volume, yd3 

10/4/1989 522,137

4/24/1991 709,799

5/13/1993 667,975

7/23/1995 467,293

10/31/1996 474,603

7/6/1997 24,052

2/7/2000 695,622

5/26/2001 423,489

3/1/2004 358,653

8/21/2004 604,113

5/16/2005 369,706

10/17/2006 412,800

4/16/2008 118,243

6/23/2009 463,487

5/4/2011 478,829

Total 23,560,740

Table A-9. GIWW – West dredging. 

Date Volume, yd3 

5/22/1954 2,692,498

3/23/1957 585,924

8/16/1960 718,256

3/3/1962 181,126

5/24/1963 737,464

1/28/1966 859,340

7/8/1968 754,837

9/11/1970 368,304

6/6/1973 658,908

12/5/1978 788,695

5/8/1982 753,923

12/25/1986 622,368

10/31/1996 570,919

5/26/2001 550,033

3/1/2004 365,515

10/17/2006 345,532

6/23/2009 473,723

Total 11,862,037
ERDC/CHL TR-20-9 63

Table A-10. Bolivar Roads to 

Redfish Reef dredging. 

Date Volume, yd3 

12/15/1950 4,162,149

10/23/1963 6,204,956

12/22/1971 1,949,878

4/24/1978 1,892,890

9/5/1984 1,790,978

3/6/1991 1,143,815

7/19/2000 10,298,831

4/24/2012 360,952

Total 27,804,449
ERDC/CHL TR-20-9 64

Appendix B: Alternate Dredge Volume 

Comparison Methods, Galveston, 

TX

Generally, decisions about dredging are made several months prior to the 

initiation of dredging. Therefore, it is important to conduct an analysis of 

the time period prior to each dredging event. For the first additional 

analysis, the time period 6 months prior to the first event until 6 months 

prior to the second dredging event is considered. For example, the first 

two dredging events occurred on 25 June 1947 and 9 January 1950. The 

first time period considered in this analysis is 25 December 1946 to 9 July 

1949. The purpose of this secondary analysis is to determine if any large 

storm or rainfall event occurred in the 6 months prior to each dredging 

event. If such an event occurred during that time, it is possible that 

dredging volumes were based on previous estimates, and the channel 

might not have been dredged to the specified depth. Table B-1 lists the 

rainfall and storm impacts between 6 months prior to dredging events. In 

most cases, “high” rainfall or storm categories remain “high,” and “low” 

rainfall or storm categories remain “low.” The rainfall category only 

changed seven times. The changes were generally from low to medium, 

high to medium, or medium to high. In one case, the category changed 

from high to low. In this case, the period between dredging events was 

only 5 months; therefore, shifting the time period of interest by 6 months 

resulted in no overlap of time. The previous 6 months had much heavier 

rainfall than the 5 months between dredging events. The rainiest period 

compared to the average for that period of time was between 6 October 

1997 and 9 January 2000. The driest period compared to the average 

rainfall values was between 15 April 2005 and 28 February 2006. The 

stormiest period was between 30 June 2007 and 31 January 2009. 
ERDC/CHL TR-20-9 65

Method 1a: Between dredging events (6 months prior)

Table B-1. Rainfall and storm Impact Factors between dredging events (6 months prior), 

Galveston, TX. 

 

 

Start Date 

 

 

End Date 

 

Dredge 

Date 

Actual 

Rainfall, 

in. 

Average 

Rainfall, 

in. 

 

Percent 

Rainfall 

 

 

Category 

Actual 

Impact 

Factor 

Annual 

Impact 

Factor 

12/25/1946 7/9/1949 1/9/1950 78.34 102.28 77 Low 0.597 0.235

7/9/1949 4/23/1951 10/23/1951 69.39 73.99 94 Medium 0.729 0.407

4/23/1951 10/24/1952 4/24/1953 58.85 64.92 91 Medium - -

10/24/1952 2/21/1955 8/21/1955 79.89 95.66 84 Medium 0 0

2/21/1955 12/15/1957 6/15/1958 85.54 117.16 73 Low 0.499 0.177

12/15/1957 6/11/1960 12/11/1960 82.79 99.82 83 Medium 0.972 0.390

6/11/1960 1/23/1962 7/23/1962 91.8 69.98 131 High - -

1/23/1962 11/29/1963 5/29/1964 58.67 76.72 76 Low 0.771 0.417

11/29/1963 1/20/1965 7/20/1965 42.72 47.11 91 Medium 0.111 0.097

1/20/1965 5/21/1966 11/21/1966 59.23 52.05 114 High - -

5/21/1966 12/2/1968 6/2/1969 110.68 108.10 102 Medium - -

12/2/1968 4/28/1972 10/28/1972 136.92 137.95 99 Medium 0.95 0.279

4/28/1972 12/1/1973 6/1/1974 90.39 68.86 131 High 0.255 0.160

12/1/1973 9/20/1975 3/20/1976 80.41 73.87 109 High 0 0

9/20/1975 10/12/1981 4/12/1982 262.11 251.38 104 Medium 0.302 0.050

10/12/1981 2/28/1982 8/31/1982 12 14.80 81 Low - -

2/28/1982 4/7/1985 10/7/1985 131.98 127.23 104 Medium 1.361 0.438

4/7/1985 4/17/1986 10/17/1986 31.63 42.18 75 Low 0.219 0.213

4/17/1986 3/30/1989 9/30/1989 117.61 122.72 96 Medium 0.618 0.209

3/30/1989 12/18/1993 6/18/1994 226.92 197.21 115 High 0.696 0.147

12/18/1993 10/6/1997 4/6/1998 171.57 157.36 109 High 0.1 0.026

10/6/1997 1/9/2000 7/9/2000 124.35 93.36 133 High 0 0

1/9/2000 2/3/2003 8/3/2003 154.27 126.71 122 High 0.1 0.033

2/3/2003 4/15/2005 10/15/2005 94.37 88.68 106 High 0.336 0.153

4/15/2005 2/28/2006 8/31/2006 20.24 37.72 54 Low 0.338 0.387

2/28/2006 6/30/2007 12/31/2007 66.53 53.40 125 High - -

6/30/2007 1/31/2009 7/31/2009 54.29 68.29 80 Low 1.655 1.040

1/31/2009 6/30/2009 12/31/2009 8.58 14.48 59 Low - -

6/30/2009 9/30/2009 3/31/2010 9.06 13.28 68 Low - -

9/30/2009 10/30/2011 4/30/2012 62.54 86.02 73 Low - -
ERDC/CHL TR-20-9 66

The actual rainfall compared to the average rainfall as a percentage for 

each period of time is shown in Figure B-1. The rainfall total between 25 

December 1946 and 11 June 1960 is significantly below the average. The 

longest period of above average rainfall occurred between 30 March 1989 

and 15 April 2005.

Figure B-1. Actual versus average rainfall between dredging events (6 months prior), 

Galveston, TX. 

The cumulative storm Impact Factors for each time period are shown in 

Figure B-2. The period between 30 June 2007 and 31 January 2009 had the 

highest storm Impact Factor, 1.65. Both the time periods of 18 December 

1993 to 6 October 1997 and 9 January 2000 to 3 February 2001 had a total 

storm Impact Factor of 0.1, which was the lowest Impact Factor excluding 

time periods that did not have storms.
ERDC/CHL TR-20-9 67

Figure B-2. Storm Impact Factors between dredging events (6 months prior), 

Galveston, TX. 

Method 1b: Between dredging events (1 year prior)

To further understand when specific events impact the dredging needs, 

the time period between 1 year prior to the first dredging event and 1 year 

before the second dredging event was analyzed. For example, the first 

dredging event occurred on 25 June 1947 and the second was on 9 

January 1950. Therefore, the first time period used in this analysis was 

from 25 June 1946 to 9 January 1949. Table B-2 lists the start date and 

end date, actual and average rainfall, actual and annualized storm Impact 

Factor, the percent rainfall, and the rainfall categories. The wettest time 

period compared to the average was 12 April 1981 to 31 August 1981. The 

driest period compared to the average was 31 December 2008 to 31 

March 2009. Eighteen of the time periods resulted in an Impact Factor, 

two had an Impact Factor of zero, and 10 time periods were not impacted 

by any storms.
ERDC/CHL TR-20-9 68

Table B-2. Rainfall and storm Impact Factors between dredging events (1 year prior), 

Galveston, TX. 

Start Date End Date 

 

Dredge 

Date 

Actual 

Rainfall, 

in. 

Average 

Rainfall, 

in. 

Percent 

Rainfall Category 

Actual 

Impact 

Factor 

Annual 

Impact 

Factor 

6/25/1946 1/9/1949 1/9/1950 90.63 107.99 84 Low 0.597 0.235

1/9/1949 10/23/1950 10/23/1951 81.17 74.02 110 High 0.729 0.408

10/23/1950 4/24/1952 4/24/1953 52.85 59.42 89 Medium - -

4/24/1952 8/21/1954 8/21/1955 75.18 93.27 81 Low - -

8/21/1954 6/15/1957 6/15/1958 86.79 115.86 75 Low 0 0

6/15/1957 12/11/1959 12/11/1960 94.35 106.12 89 Medium 1.471 0.591

12/11/1959 7/23/1961 7/23/1962 64.22 64.03 100 Medium - -

7/23/1961 5/29/1963 5/29/1964 71.35 75.99 94 Medium - -

5/29/1963 7/20/1964 7/20/1965 40.6 47.83 85 Low 0.771 0.673

7/20/1964 11/21/1965 11/21/1966 49.23 58.20 85 Low 0.111 0.083

11/21/1965 6/2/1968 6/2/1969 116.01 101.33 114 High - -

6/2/1968 10/28/1971 10/28/1972 149.87 117.46 128 High 0.95 0.279

10/28/1971 6/1/1973 6/1/1974 76.26 62.56 122 High - -

6/1/1973 3/20/1975 3/20/1976 82.46 76.29 108 High 0.255 0.142

3/20/1975 4/12/1981 4/12/1982 253.74 250.15 101 Medium 0.302 0.050

4/12/1981 8/31/1981 8/31/1982 22.63 16.13 140 High - -

8/31/1981 10/7/1984 10/7/1985 130.13 130.59 100 Medium 1.361 0.438

10/7/1984 10/17/1985 10/17/1986 47.64 42.47 112 High 0.125 0.122

10/17/1985 9/30/1988 9/30/1989 116.27 122.23 95 Medium 0.712 0.241

9/30/1988 6/18/1993 6/18/1994 223.5 192.09 116 High 0.696 0.148

6/18/1993 4/6/1997 4/6/1998 166.02 158.16 105 Medium 0.1 0.026

4/6/1997 7/9/1999 7/9/2000 125.71 92.78 135 High 0 0

7/9/1999 8/3/2002 8/3/2003 139.57 127.01 110 High 0.1 0.033

8/3/2002 10/15/2004 10/15/2005 109.66 93.81 117 High 0.336 0.153

10/15/2004 8/31/2005 8/31/2006 28.79 34.21 84 Low - -

8/31/2005 12/31/2006 12/31/2007 54.48 57.31 95 Medium 0.338 0.253

12/31/2006 7/31/2008 7/31/2009 62.98 62.71 100 Medium 0.555 0.350

7/31/2008 12/31/2008 12/31/2009 14.86 20.06 74 Low 1.1 2.624

12/31/2008 3/31/2009 3/31/2010 5.22 8.32 63 Low - -

3/31/2009 4/30/2011 4/30/2012 66.5 85.15 78 Low - -
ERDC/CHL TR-20-9 69

The actual rainfall compared to the average rainfall as a percentage for each 

period of time is shown in Figure B-3. The longest period of time in which 

the actual rainfall was greater than the average was between 21 November 

1965 and 17 October 1985. The longest period of less than average rainfall 

occurred between 23 January 1950 and 21 November 1965.

Figure B-3. Actual versus average rainfall between dredging events (1 year prior), 

Galveston, TX. 
ERDC/CHL TR-20-9 70

The storm Impact Factors for the specified time periods are shown in 

Figure B-4. The period between 15 June 1957 and 11 December 1959 had 

the highest storm Impact Factor, 1.47. The weakest storm Impact Factor, 

0.1, was calculated for the time periods of 18 June 1993 to 6 April 1997 and 

9 July 1999 to 3 August 2002.

Figure B-4. Storm Impact Factors between dredging events (1 year prior), 

Galveston, TX. 
ERDC/CHL TR-20-9 71

Method 2a: Set blocks of time (5 years)

Rainfall and volume dredged are divided into thirteen 5-year time periods 

shown in Figure B-5. The greatest dredging took place during the 5-year 

time period of 1949–1953. The least amount of dredging occurred between 

1989 and 1993. The wettest period of time was 1994–1998 when more than 

250 in. of rain fell. The driest period of time was 1954–1958. Average 

precipitation for a 5-year period ranged from 198 to 219 in.

Figure B-5. Rainfall and volume dredged over 5-year intervals, Galveston, TX. 
ERDC/CHL TR-20-9 72

Storm Impact Factors and dredged volumes are shown for 5-year intervals 

in Figure B-6. All time periods except 2009–2013 experienced at least one 

storm event which had a storm Impact Factor greater than zero. The 

weakest storm Impact Factor was 0.074 for 1974–1978. The strongest 

storm period was 2004–2008 which had a storm Impact Factor of 1.993. 

There were four storms with Impact Factors during that period of time.

Figure B-6. Storm Impact Factor and volume dredged over 5-year intervals, 

Galveston, TX. 
ERDC/CHL TR-20-9 73

Method 2b: Set blocks of time (6 years)

Figure B-7 shows rainfall and dredging volume over 6-year intervals. The 

driest 6-year time period was 1954–1959 while the wettest was 1996–2001. 

The time period with the greatest volume of dredging was 1960–1965. The 

least amount of dredging occurred between 1954 and 1959.

Figure B-7. Rainfall and volume dredged over 6-year intervals, Galveston, TX. 
ERDC/CHL TR-20-9 74

The storm Impact Factor and volume dredged over each 6-year interval 

are shown in Figure B-8. All 6-year time periods experienced at least one 

storm event with a measurable storm Impact Factor. The 1978–1983 time 

period experiences storms with the strongest Impact Factors, 1.65. Both 

1990–1995 and 1996–2001 had a single storm with an Impact Factor of 

0.1. The 12-year period from 1978 to 1989 was the period of the strongest 

storms since 1948.

Figure B-8. Storm Impact Factor and volume dredged over 6-year intervals, 

Galveston, TX. 
ERDC/CHL TR-20-9 75

Unit Conversion Factors

In this document, most units are reported as US customary units, in 

keeping with common usage. Some of the analyses were performed in 

metric units, but the results are reported in US standard units.

Multiply By To Obtain 

cubic yards 0.7645549 cubic meters

feet 0.3048 meters

miles (US statute) 1,609.347 meters

miles per hour 0.44704 meters per second

square feet 0.09290304 square meters

square mi 2.589998 E+06 square meters

square yards 0.8361274 square meters

yards 0.9144 meters
ERDC/CHL TR-20-9 76

Acronyms and Abbreviations

FY Fiscal Year 

GIWW Gulf Intracoastal Waterway 

NOAA National Oceanic and Atmospheric Administration 

NS Naval Station 

SWG Galveston District 

USACE US Army Corps of Engineers
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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE 

June2020

2. REPORT TYPE

Final Report

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Effect of Tropical Storms and Precipitation on Dredging Volumes: Houston-Galveston, TX, 

and Mayport, FL

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Ashley E. Frey and Lauren A. Coe

5d. PROJECT NUMBER

14-03

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND 

ADDRESS(ES)

Coastal and Hydraulics Laboratory

US Army Engineer Research and 

Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

US Army Corps of Engineers

Los Angeles District

911 Wilshire Blvd.

Los Angeles, CA 90017

8. PERFORMING

ORGANIZATION REPORT

NUMBER

ERDC/CHL TR-20-9

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

US Army Corps of Engineers

Washington, DC 20314-1000

10. SPONSOR/MONITOR'S ACRONYM(S)

USACE

11. SPONSOR/MONITOR'S

REPORT NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release; distribution is unlimited.

13. SUPPLEMENTARY NOTES

14. ABSTRACT

This study characterizes infilling responses within dredged navigation channels to rainfall from tropical storms and hurricanes. This 

project created a web tool based on the methods described in this report. This report discusses the different analysis methods considered 

to relate storm and rainfall to dredging volumes at two pilot sites, Galveston, TX, and Mayport, FL. A comprehensive storm Impact 

Factor for hurricanes was developed to quantify the impact at a site based on proximity, duration, and wind speed. The methods vary 

based on the length and timing of periods of storms and rainfall prior to a dredge event. At Galveston, TX, when 2-year dredging volume 

totals were compared to hurricane activity occurring in the previous 2 years, the maximum dredging volume removed was higher after 

higher hurricane activity when compared to low activity periods. The average amount dredged was higher following periods of high 

hurricane activity. At Mayport, FL, dredging volumes were compared to hurricane activity occurring since the last dredging action took 

place. Similarly to Galveston, TX, the maximum dredging volume removed was higher after higher hurricane activity periods when 

compared to low activity periods. The average amount dredged was higher following periods of high hurricane activity.

15. SUBJECT TERMS 

Channels (Hydraulic engineering), Dredging, Dredging spoil, Galveston, (Tex.), Hurricanes, Mayport (Jacksonville, Fla.), Precipitation 

(Meteorology)

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

ABSTRACT

SAR

18. NUMBER 

OF 

PAGES

87

19a. NAME OF RESPONSIBLE PERSON

a. REPORT Ashley E. Frey

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

601-634-2006

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