ERDC/CHL TR-02-11 

Periodic Inspections of Kahului 

and Laupahoehoe Breakwaters, 

Hawaii 

Armor Unit Monitoring for Period 1992/93-2001 

Robert R. Bottin, Jr., and Daniel T. Meyers August 2002

Coastal and Hydraulics Laboratory 

Approved for public release; distribution is unlimited. 
PRINTED ON RECYCLED PAPER 

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. 

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. 
ERDC/CHL TR-02-11

August 2002

Periodic Inspections of Kahului 

and Laupahoehoe Breakwaters, 

Hawaii 

Armor Unit Monitoring for Period 1992/93-2001

by Robert R. Bottin, Jr. 

U.S. Army Engineer Research and Development Center 

3909 Halls Ferry Road 

Vicksburg, MS 39180-6199 

 Daniel T. Meyers 

U.S. Army Engineer District, Honolulu 

 Building 230

Fort Shafter, HI 96858-5440 

Final report

Approved for public release; distribution is unlimited

Prepared for U.S. Army Corps of Engineers 

Washington, DC 20314-1000 
iii

Contents 

Preface.................................................................................................................. vi

Conversion Factors, Non-SI to SI Units of Measurement................................... vii

1óIntroduction ......................................................................................................1

Monitoring Completed Navigation Projects Program .....................................1

Work Unit Objective and Monitoring Approach .............................................2

Project Locations and Brief Histories ..............................................................3

Kahului Harbor..........................................................................................3

Laupahoehoe Point boat-launching facility.............................................10

Prior Monitoring (Periodic Inspections) of Sites...........................................13

Purpose of Current Monitoring......................................................................13

2óMonitoring Plan and Data Comparison..........................................................14

Targeting and Ground Surveys......................................................................14

Aerial Photography........................................................................................19

Photogrammetric Analysis of Armor Unit Targets........................................19

Broken Armor Unit Surveys ..........................................................................31

3óSummary and Findings...................................................................................38

References ............................................................................................................40

Tables 1-11 

SF 298 

List of Figures 

Figure 1. Project locations for Kahului and Laupahoehoe...............................4 

Figure 2. Layout of Kahului Harbor, Maui, HI................................................5 

Figure 3. Aerial view of Kahului Harbor (2001)..............................................6 
iv

Figure 4. Typical cross section of 1931 Kahului breakwater trunk 

construction.......................................................................................7

Figure 5. Typical cross section for 1956 Kahului breakwater repairs..............7

Figure 6. 1996 Kahului breakwater repairs......................................................8

Figure 7. Kahului west breakwater repairs of 1973 .........................................9 

Figure 8. Layout of Laupahoehoe boat-launching facility.............................11

Figure 9. Cross section of Laupahoehoe breakwater .....................................12

Figure 10. Aerial photograph of Laupahoehoe boat-launching 

facility (2001) .................................................................................12

Figure 11. Monuments used to establish survey control at Kahului Harbor....15

Figure 12. Monuments used to establish survey control at Laupahoehoe 

boat-launching facility ....................................................................15

Figure 13. Locations of targeted armor units on Kahului east breakwater ......16

Figure 14. Locations of targeted armor units on Kahului west breakwater .....17 

Figure 15. Locations of targeted armor units on Laupahoehoe breakwater .....18

Figure 16. Example of targeted tribar ..............................................................19

Figure 17. Stereo pair photographs of outer portion of Kahului east 

breakwater.......................................................................................20

Figure 18. Stereo pair photographs of inner portion of Kahului east 

breakwater.......................................................................................21

Figure 19. Stereo pair photographs of outer portion of Kahului west 

breakwater.......................................................................................22

Figure 20. Stereo pair photographs of inner portion of Kahului west 

breakwater.......................................................................................23

Figure 21. Stereo pair photographs of Laupahoehoe breakwaters ...................24

Figure 22. Comparison of representative targeted armor unit positions 

relative to x, y, and z axes...............................................................27 

Figure 23. Photo map of head of Kahului east breakwater ..............................29

Figure 24. Photo map of head of Kahului west breakwater .............................30
v

Figure 25. Photo map of Laupahoehoe breakwater..........................................31

Figure 26. Approximate locations of broken/cracked armor units along 

outer portion of Kahului east breakwater........................................33

Figure 27. Approximate locations of broken/cracked armor units along out 

portion of Kahului west breakwater................................................34 

Figure 28. Dolos with mid-shank crack ...........................................................35

Figure 29. Dolos with fluke-shank break .........................................................35

Figure 30. Dolos with shank-fluke break .........................................................36

Figure 31. Tribar with break through center section of unit ............................36
vi

Preface 

The study reported herein was conducted as part of the Monitoring 

Completed Navigation Projects (MCNP) Program, formerly Monitoring 

Completed Coastal Projects Program. Work was conducted under Work Unit 

IM-7, "Periodic Inspections." Overall program management for MCNP is 

administered by Headquarters, U.S. Army Corps of Engineers (HQUSACE). 

The Coastal and Hydraulics Laboratory (CHL), U.S. Army Engineer Research 

and Development Center (ERDC), is responsible for technical as well as data 

management and support for HQUSACE review and technology transfer. 

Technical Monitors for the MCNP program are Messrs. Barry W. Holliday, 

Charles B. Chesnutt, and David B. Wingerd (HQUSACE). The Program 

Manager is Mr. Robert R. Bottin, Jr., (CHL). 

This report is part of a series which tracks the long-term structural response 

of the Kahului and Laupahoehoe breakwaters, HI, to their environment. Limited 

ground surveys, aerial photography, and photogrammetric analysis of the 

breakwater were conducted by Richard B. Davis, Inc., Smith River, CA, and 

David C. Smith & Associates, Inc., Portland, OR, under contract to the Corps of 

Engineers. A broken armor unit survey was conducted by Messrs. Bottin, Hugh 

F. Acuff, Larry R. Tolliver, Glenn B. Myrick, Ms. Kristi Evans (CHL), and 

Mr. Daniel T. Meyers, U.S. Army Engineer District, Honolulu (CEPOH). 

The work was conducted during the period August through October 2001 

under the general supervision of Mr. Thomas W. Richardson, Director, CHL, and 

Mr. Thomas J. Pokrefke, Jr., former Acting Assistant Director, CHL, and under 

direct supervision of Mr. Dennis G. Markle, Chief, Coastal Harbors and 

Structures Branch. This report was prepared by Messrs. Bottin, CHL, and 

Meyers, CEPOH. 

At the time of publication of this report Dr. James R. Houston was Director 

of ERDC, and COL John W. Morris III, EN, was Commander and Executive 

Director. 

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.
vii

Conversion Factors, Non-SI to 

SI Units of Measurement 

 Non-SI units of measurement used in figures, plates, and tables of this report 

can be converted to SI units as follows: 

Multiply By To Obtain 

acres 4,046.873 square meters 

cubic yards 0.7645549 cubic meters 

degrees (angle) 0.01745329 radians 

feet 30.48 centimeters 

feet 0.3048 meters 

inches 2.54 centimeters 

miles (U.S. statute) 1.609347 kilometers 

pounds (mass) 0.4535924 kilograms 

tons (2,000 pounds, mass) 907.1847 kilograms 
Chapter 1 Introduction 1

1 Introduction 

Monitoring Completed Navigation Projects 

Program 

The goal of the Monitoring Completed Navigation Projects (MCNP) 

Program (formerly the Monitoring Completed Coastal Projects Program) is the 

advancement of coastal and hydraulic engineering technology. The program is 

designed to determine how well projects are accomplishing their purposes and 

are resisting the attacks by their physical environment. These determinations, 

combined with concepts and understanding already available, will lead to 

creating more accurate and economical engineering solutions to coastal and 

hydraulic problems; to strengthening and improving design criteria and 

methodology; to improving construction practices and cost-effectiveness; and to 

improving operations and maintenance techniques. 

To develop direction for the program, the U.S. Army Corps of Engineers 

initially established an ad hoc committee of engineers and scientists. The 

committee formulated the objectives of the program, developed its operation 

philosophy, recommended funding levels, and established criteria and procedures 

for project selection. A significant result of their efforts was a prioritized listing 

of problem areas to be addressed, essentially a listing of the areas of interest of 

the program. 

Corps offices are invited to nominate projects for inclusion in the monitoring 

program as funds become available. The MCNP Program is governed by 

Engineer Regulation 1110-2-8151 (Headquarters, U.S. Army Corps of Engineers 

(HQUACE) 1997). A selection committee reviews and prioritizes the projects 

nominated based on criteria established in the regulation. The prioritized list is 

reviewed by the Program Monitors at HQUSACE. Final selection is based on this 

prioritized list, national priorities, and the availability of funding. 

The overall monitoring program is under the management of the Coastal and 

Hydraulics Laboratory (CHL), U.S. Army Engineer Research and Development 

Center (ERDC), with guidance from HQUSACE. Development of monitoring 

plans and the conduct of data collection and analyses are dependent upon the 

combined resources of CHL and the District/Division. The inspection for the 

study reported herein, was completed as part of the ìPeriodic Inspectionsî Work 

Unit of the MCNP program. 
2 Chapter 1 Introduction 

Work Unit Objective and Monitoring Approach 

The objective of the ìPeriodic Inspectionsî Work Unit in the MCNP 

Program is to periodically monitor selected coastal navigation structures to gain 

an understanding of the long-term structural response of unique structures to their 

environment. These periodic data sets are used to improve knowledge in design, 

construction, and maintenance of both existing and proposed coastal navigation 

projects. These data also will help avoid repeating past design mistakes that have 

resulted in structure failure and/or high maintenance costs. Past projects 

monitored under the MCNP Program and/or structures with unique design 

features that may have application at other sites are considered for inclusion in 

the periodic inspections monitoring program. Selected sites are presented as 

candidates for development of a periodic monitoring plan. Once the monitoring 

plan for a site is approved and funds are provided, monitoring of the site is 

initiated. Normally, base conditions are established and documented in the initial 

effort. The site then is reinspected periodically (frequency of surveys is based on 

a balance of need and funding for each monitoring site) to obtain long-term 

structural performance data. 

Relatively low-cost remote sensing tools and techniques, with limited ground 

truthing surveys, are the primary inspection tools used in the monitoring efforts. 

Most periodic inspections consist of capturing above-water conditions of the 

structure at periodic intervals using high-resolution aerial photography. Periodic 

aerial photographs are compared visually to gauge the degree of in-depth analysis 

required to quantify structural changes (primarily armor unit movement). Data 

analysis involves using photogrammetric techniques developed for and 

successfully applied at other coastal sites. At sites where local wave data are 

being gathered by other projects and/or agencies, and these data can be acquired 

at a relatively low cost, wave data are correlated with structural changes. In areas 

where these data are not available, general observations and/or documentation of 

major storms occurring in the locality are presented along with the monitoring 

data. Ground surveys are limited to the level needed to establish accuracy of the 

photogrammetric techniques. 

When a coastal structure is photographed at low tide, an accurate permanent 

record of all visible armor units is obtained. Through the use of stereoscopic, 

photogrammetric instruments in conjunction with photographs, details of 

structure geometry can be defined at a point in time. By direct comparison of 

photographs taken at different times, as well as the photogrammetric data 

resolved from each set of photographs, geometric changes (i.e., armor unit 

movement and/or breakage) of the structure can be defined as a function of time. 

Thus, periodic inspections of the structures will capture permanent data that can 

be compared and analyzed to determine if structure changes are occurring that 

indicate possible failure modes and the need to monitor the structure(s) more 

closely. The Kahului and Laupahoehoe breakwaters, HI, were nominated for 

periodic monitoring by the U.S. Army Engineer District, Honolulu. Initial 

monitoring of base level conditions was completed in 1992 at Laupahoehoe and 

1993 at Kahului (Markle and Boc 1994). 
Chapter 1 Introduction 3

Two additional Honolulu District projects have been monitored previously 

under the ìPeriodic Inspectionsî Work Unit. Base conditions have been defined 

for the Nawiliwili Harbor breakwater, Kauai, HI (Bottin and Boc 1996), and the 

Ofu Harbor breakwater, American Samoa (Bottin and Boc 1997). 

Project Locations and Brief Histories 

Kahului Harbor 

Kahului Harbor is the only deep-draft harbor on the island of Maui. Maui is 

the second largest of the Hawaiian Islands. The harbor is located on Mauiís 

north shore approximately 150 km (95 miles)1

 southeast of Honolulu, Oahu, HI 

(Figure 1). The harbor is exposed to winds and waves from the north and 

northeast. Both northeast tradewind waves and northern swell, impact on 

Kahului Harbor. The trade winds predominate the summer season, producing 6- 

to 10-sec, 1.2- to 3.7-m (4- to 12-ft) deepwater waves. Intense winter storms in 

the north Pacific Ocean create northern swell during the months of October 

through March. Deepwater waves can attain heights of 7.6 m (25 ft) with wave 

periods from 12 to 18 sec. These storms, as well as hurricanes, are sources of the 

largest waves that reach the Hawaiian Islands. 

Kahului Harbor is rich in construction, repair, and rehabilitation history as 

noted in U.S. Army Engineer District, Honolulu (1981) and Sargent, Markle, and 

Grace (1988). The harbor complex was initiated when a berthing area, a dredged 

entrance channel, and a 122-m-long (400-ft-long) armor stone east breakwater 

were constructed by the Kahului Railroad Company in 1900. The Corps of 

Engineerís first involvement with the project began in 1913 when the east 

breakwater was extended 122 m (400 ft). The west breakwater was constructed 

to a length of 594 m (1,950 ft) in 1919. In 1931, the east and west breakwaters 

were extended to their current lengths of 843 and 706 m (2,766 and 2,315 ft), 

respectively. A layout of the harbor is shown in Figure 2 and an aerial view is 

shown in Figure 3. 

All construction through 1931 utilized a single layer of keyed and fitted, 

7,257-kg (8-ton) armor stone placed between the +4.0-m (+13-ft)2

 crest and an 

elevation (el) of -4.6 m (-15 ft). Side slopes above the -4.6-m (-15-ft) el were 

1V:2H on the heads and 1V:1.5H on the trunks (Figure 4). Below the -4.6-m 

(-15-ft) el, the 1V:1H sloped structure was constructed of quarry-run stone 

(11.3-kg (25-lb) minimum stone weight). 

 

1

 Units of measurement in the text of this report are shown in SI units, followed by non-SI units in 

parenthesis. In addition, a table of factors for converting non-SI units of measurement used in figures, 

plates, and tables in this report to SI units is presented on page vii. 2

 All elevations (el) and depths cited herein are in meters (feet) referred to mean lower low water (mllw).
4 Chapter 1 Introduction Figure 1. Project locations for Kahului and Laupahoehoe 
Chapter 1 Introduction 

5

Figure 2. Layout of Kahului Harbor, Maui, HI 
6 Chapter 1 Introduction Figure 3. Aerial view of Kahului Harbor (2001) 
Chapter 1 Introduction 7

Figure 4. Typical cross section of 1931 Kahului breakwater trunk construction 

Between 1931 and 1954, both breakwaters were severely damaged on numerous occasions and each repair, or rehabilitation, was completed by restoring the 

structure to its original condition with 7,257-kg (8-ton) keyed and fitted armor 

stone. In March of 1954, storm waves, with estimated 10.4-m (34-ft) breaker 

heights at the structure heads, attacked Kahului Harbor for a 3-day period. The 

outer 56.4 and 91.4 m (185 and 300 ft) of the east and west breakwaters, 

respectively, were severely damaged. This extensive damage initiated actions to 

base needed repairs on current design criteria rather than restoring the structure to 

its prestorm conditions. In 1956, repairs were completed on both breakwaters 

using 29,940-kg (33-ton) unreinforced tetrapods and a concrete cap (Figure 5). 

The new armor units were placed on the heads of both breakwaters and extended 

76.2 m (250 ft) shoreward along the sea-side face on the west breakwater trunk. 

Figure 5. Typical cross section for 1956 Kahului breakwater repairs 

A storm in 1958 with estimated wave heights of 7.6 m (25 ft) at the structures caused extensive damage to both breakwaters. A breach in excess of 

45.7 m (150 ft) was opened up on the east breakwater at the transition between 

the armor stone and tetrapods. On the west breakwater, all of the tetrapods on the 

harbor-side quarter of the head were swept away. The 1V:2H slope used in this 

area was felt to be the major design deficiency. Temporary repairs of the east 

breakwater, consisting of a large monolithic concrete cap and placement of 

10,885-kg (12-ton) or larger armor stone on the sea-side face, were completed in 

1959. 
8 Chapter 1 Introduction 

A major breakwater rehabilitation was completed in 1966. Both heads, and 

108.2 m (355 ft) of sea-side slope of the structure immediately shoreward of the 

east head were included in the repair (Figure 6). The design was model-studied at 

ERDC (Jackson 1964). The inboard quarters of both heads were armored with 

two layers of 45,360-kg (50-ton) tribars on the upper one-third of the slope, 

while the lower two-thirds was protected by a double layer of 31,750-kg (35-ton) 

tribars. A two-layer system of 31,750-kg (35-ton) tribars was placed from the 

new concrete rib cap to the toe of the rehabilitated sea-side slope of the east 

breakwater trunk. 

Figure 6. 1996 Kahului breakwater repairs 

A storm in 1967 severely damaged the west breakwater trunk. This area was 

repaired in 1969 by construction of a concrete rib cap and placement of 260 reinforced tribars, weighing 17,235 kg (19 tons) each, on the sea-side slope. In 

November of the same year, the area adjacent to the 17,235-kg (19-ton) tribars at 

the shore end was damaged by 4.6- to 6.1-m (15- to 20-ft) breaking waves. This 

area was repaired in 1973 by a 24.4-m (80-ft) shoreward extension of the concrete rip cap and 17,235-kg (19-ton) tribars. The shoreward extent of the tribars 

was buttressed with 25 tribars, weighing 31,750 kg (35 tons) each (Figure 7). 

An inspection conducted in 1973 revealed that the 29,940-kg (33-ton) tetrapods on the sea-side quadrants of both heads had sustained considerable damage 
Chapter 1 Introduction 

9

Figure 7. Kahului west breakwater repairs of 1973 
10 Chapter 1 Introduction 

and they, along with the 7,257-kg (8-ton) stone areas on both trunks, were in 

need of repair. The following repairs were completed in 1977: on the west 

breakwater, 257 reinforced dolosse weighing 27,215 kg (30 tons) each were 

placed in two layers over the 29,940-kg (33-ton) tetrapods on the sea-side 

quadrant of the head; 291 reinforced dolosse weighing 18,145 kg (20 tons) each 

were placed on the sea side of the west breakwater trunk; on the east breakwater, 

610 reinforced dolosse weighing 27,215 kg (30 tons) each were placed in a 

double layer over the 29,940-kg (33-ton) tetrapods on the sea-side quadrant of 

the head, 164 reinforced dolosse weighing 18,145 kg (20 tons) each were placed 

in a double layer on the sea-side slope of the trunk beginning shoreward of the 

31,750-kg (35-ton) tribars; and, extending shoreward, two layers of 5,445-kg (6-

ton) unreinforced dolosse (455 units) were placed on the sea-side slope of the 

east breakwater trunk. 

The most recent repairs, model-studied at ERDC (Markle 1982), were completed in 1984. This rehabilitation was carried out in an attempt to eliminate the 

need for future piecemeal repairs. On the east breakwater, one layer of 8,165-kg 

(9-ton) tribars was placed on the harbor side between sta 19+50 and 27+15. In 

addition, a concrete rib cap was constructed between sta 19+50 and the breakwater head (sta 27+66). On the west breakwater, one layer of 5,900-kg (6.5-ton) 

tribars was placed on the harbor-side slope from sta 17+75 to 22+00. A single 

layer of 9,980-kg (11-ton) tribars was also placed on the sea-side slope between 

sta 17+75 and 19+35. These tribars were buttressed with 22,680-kg (25-ton) 

tribars at their shoreward end. In addition, a concrete rib cap was constructed 

from sta 17+75 to 21+65 and tied into the existing concrete cap. 

Laupahoehoe Point boat-launching facility 

Laupahoehoe Point is located on the northeast coast of the Island of Hawaii 

(Figure 1) approximately 40 km (25 miles) north-northwest of Hilo. The County 

of Hawaiiís Laupahoehoe Point Park borders the shoreline of Laupahoehoe 

Point. The park is primarily used for day picnics, family gatherings, and as a 

tourist scenic attraction and rest stop. Historically, Laupahoehoe boat-launching 

facility served as a landing where livestock were imported to the area. The park 

has a concrete loading dock, rest rooms, a picnic area, a pavilion, and a paved 

parking lot. In addition, a concrete boat-launching ramp was constructed within 

the park limits in 1970. The launching ramp proved later to be unsafe. It was 

located within what would appear to be a sheltered cove, but waves reflecting off 

adjacent rocky shores created hazardous conditions a large percentage of the 

time. Local fishermen found launching conditions too hazardous even under 

relatively calm ocean wave conditions. For this reason, the county declared the 

ramp unsafe and posted a sign, ìBoat Ramp Closed.î 

The waters offshore of Laupahoehoe are very popular and productive for 

fishing most of the year, but the area was underutilized due to closing of the 

launching ramp. The closest safe launching area was located in Hilo, 40 km 

(25 mi) away. This extra travel time required more ice, limiting catch hauling 

capacity and available hours for fishing. As well as hampering fishing, the 
Chapter 1 Introduction 11

closed ramp severely limited the ability of the Hilo Rescue Squad and U.S. Coast 

Guard in responding to emergencies on the northeast Hawaii coast. 

Plans were developed to improve conditions in the area (U.S. Army Engineer 

District, Honolulu, 1984). In 1988, a 60.1-m-long (200-ft-long) rubble-mound 

breakwater protecting a 2.9-m-deep (9.5-ft-deep) entrance channel, 2.3-m-deep 

(7.5-ft-deep) turning basin, and a boat-launching ramp was completed. The 

design layout for the facility and stability of the breakwater were optimized 

through physical model studies conducted at ERDC (Bottin, Markle, and Mize 

1987). A layout of the boat-launching facility is shown in Figure 8. 

Figure 8. Layout of Laupahoehoe boat-launching facility 

The breakwater is armored with 27,215-kg (30-ton) reinforced dolosse and 

the crest is stabilized with a concrete rib cap. The toe of the dolosse was keyed 

into the hard basalt bottom by means of a trench excavated around the perimeter 

of the breakwater. The rib cap is supported on concrete pipe columns. A stable 

breakwater core was achieved through the innovative design of a reinforced 

concrete pipe rib cage forming a containment area for core and capstone. A cross 

section of the breakwater is presented in Figure 9, and an aerial view of the area 

is shown in Figure 10. 
12 Chapter 1 Introduction 

Figure 9. Cross section of Laupahoehoe breakwater 

Figure 10. Aerial photograph of Laupahoehoe boat-launching facility (2001) 
Chapter 1 Introduction 13

Prior Monitoring (Periodic Inspections) of Sites 

The Kahului breakwaters were initially monitored during the period October 

1991 - August 1993; and the Laupahoehoe breakwater from October 1991 ñ 

November 1992 (Markle and Boc 1994) as part of the ìPeriodic Inspectionsî 

Work Unit of the MCNP Program. Work included armor unit targeting, limited 

ground surveys, aerial photography, and a photogrammetric analyses of armor 

units. The information obtained during the monitoring effort established base 

level conditions for the breakwaters. Very precise positions of targeted armor 

units were obtained. Minimal target movement occurred during the initial 

monitoring effort. Between October 1991 and August 1993, horizontal and 

vertical movements of targeted armor units ranged from 0.0 to 0.058 m (0.0 to 

0.19 ft) and 0.0 to 0.091 m (0.0 to 0.3 ft), respectively, on the Kahului east 

breakwater; and from 0.0 to 0.061 m (0.0 to 0.2 ft) and 0.0 to 0.052 m (0.0 to 

0.17 ft) on the Kahului west breakwater. On the Laupahoehoe breakwater , 

horizontal and vertical movements of targeted armor units ranged from 0.0 to 

0.046 m (0.0 ft to 0.15 ft) and 0.0 to 0.37 m (0.0 to 0.12 ft), respectively, from 

October 1991 to November 1992. Average horiztonal and vertical movements of 

targeted armor units, respectively, were 0.021 and 0.021 m (0.07 and 0.07 ft) for 

the Kahului east breakwater; 0.046 and 0.015 m (0.15 and 0.05 ft) for the 

Kahului west breakwater; and 0.009 and 0.012 m (0.03 and 0.04 ft) for the 

Laupahoehoe breakwater. 

Purpose of Current Monitoring 

The purposes of the study reported herein were to: 

a. Utilize methodology previously developed using limited land-based 

surveying, aerial photography, and photogrammetric analysis to assess 

the long-term stability response of the concrete armor units on the 

Kahului and Laupahoehoe breakwaters. 

b. Conduct limited land surveys, a broken armor unit inspection, aerial 

photography, and photogrammetric analyses to accurately define armor 

unit movement above the waterline. 

c. Compare the breakwater's armor unit positions to those obtained during 

the surveys completed in 1992/1993 and define changes that have 

occurred. 
14 Chapter 2 Monitoring Plan and Data Comparison 

2 Monitoring Plan and Data 

Comparison 

The objective of the current monitoring effort in the ìPeriodic Inspectionsî 

Work Unit was to re-examine the targeted concrete armor units on the outer 

portions of the Kahului east and west breakwaters, and the Laupahoehoe 

breakwater, and determine changes that have occurred since the last inspections 

in 1992-1993. The monitoring plan consisted of targeting armor units, limited 

ground surveys, aerial photography, photogrammetric analysis of armor unit 

locations, ground-based broken armor unit surveys, and comparisons of current 

armor unit positions with those obtained previously. 

 Targeting and Ground Surveys 

To serve as control for the ground-based surveys as well as the photogrammetric work, existing monuments from previous surveys were located and 

resurveyed using Trimble real-time kinemetic global positioning system 

equipment and electronic surveying techniques. Monuments at the sites used to 

establish vertical and horizontal control are shown in Figures 11 and 12 for the 

Kahului and Laupahoehoe projects, respectively. 

In addition, targets were re-established on concrete armor units. As 

previously reported (Markle and Boc 1994), 10 targeted armor units were 

monitored on the Kahului east breakwater, 10 on the Kahului west breakwater, 

and five on the Laupahoehoe breakwater . A description of the targeted units is 

presented in Table 1. On the Kahului east breakwater, two of the targeted units 

were 8,165-kg (9-ton) tribars, five were 27,215-kg (30-ton) dolos, two were 

31,750-kg (35-ton) tribars, and one was a 5,445-kg (6-ton) dolos. On the 

Kahului west breakwater, two of the targeted units were 5,900-kg (6.5-ton) 

tribars, one was a 9,980-kg (11-ton) tribar, five were 27,215-kg (30-ton) dolos, 

and two were 31,750-kg (35-ton) tribars. All five units targeted on the 

Laupahoehoe breakwater were 27,215-kg (30-ton) dolos. Units were distributed 

on the sea and harbor sides of the breakwaters as well as around their heads, and 

from the breakwater crest to the waterline. Figures 13ñ15 show the locations of 

targeted armor units on the Kahului east and west breakwaters and the 

Laupahoehoe breakwater , respectively. 
Chapter 2 Monitoring Plan and Data Comparison 15

Figure 11. Monuments used to establish survey control at Kahului Harbor 

Figure 12. Monuments used to establish survey control at Laupahoehoe boatlaunching facility 

Units were originally chosen for targeting in 1991 that had flat surfaces close 

to horizontal to maximize their visibility in aerial photography and allow for 

accurate representation of armor unit movement. Each armor unit selected for 

targeting was painted with three, 30.5-cm- (12-in.-) diam targets. The targets 

were divided into four quadrants that were painted alternately white and black. 

This style of contrasting target provides a precise center point for which 
16 Chapter 2 Monitoring Plan and Data Comparison 

 Figure 13. Locations of targeted armor units on Kahului east breakwater 

measurements can be made by both land surveys and photogrammetric work. A 

high quality epoxy-based marine paint was used to minimize the need for repainting, and a 2.54-cm- (1-in.-) cross was chiseled at the center of each target for 

identification in subsequent surveys. Each targeted unit was labeled conspicuously with 15.2-cm- (6-in.-) high white-lettered alphanumeric characters. The 

alpha characters identify the unit and the breakwater in which it resides, and the 
Chapter 2 Monitoring Plan and Data Comparison 17 Figure 14. Locations of targeted armor units on Kahului west breakwater 
18 Chapter 2 Monitoring Plan and Data Comparison 

Figure 15. Locations of targeted armor units on Laupahoehoe breakwater 

numeric characters identify the target on the armor unit. For example, armor unit 

ìKEAî indicates a unit on the Kahului east breakwater that is unit A of 10 units 

(A through J) targeted on the breakwater. The unit has three targets labeled 

KEA-1, KEA-2, and KEA-3. An example of a targeted armor unit is shown in 

Figure 16. 

Limited ground surveys of some of the concrete armor unit targets were 

conducted in August 2001 to serve as control to check the accuracy of the 

subsequent photogrammetric work. Target coordinates were established using a 

Wild T-2000 total station surveying instrument. Horizontal positions were based 

on the Hawaii State Plane Coordinate System, Zone 2 for Kahului and Zone 1 for 

Laupahoehoe. Elevations at both sites were referenced to mean lower low water 

(mllw) datum. 
Chapter 2 Monitoring Plan and Data Comparison 19

Figure 16. Example of targeted tribar 

Aerial Photography 

Aerial photography is an effective means of capturing images of large areas 

for later analysis, study, visual comparison to previous or subsequent photography, or measurement and mapping. Its chief attribute is the ability to freeze a 

moment in time, while capturing extensive detail. 

Aerial photography was obtained along the Kahului and Laupahoehoe breakwaters with a Zeiss RMK A 15/23 aerial mapping camera (9-in. by 9-in. format). 

Color photos were secured from a fixed-wing aircraft flying at an appropriate 

altitude, which resulted in high resolution images and contact prints with scales 

of 1:1,200. Photographic stereo pairs were obtained during the flights. Stereo 

pairs secured for the Kahului east and west breakwaters and the Laupahoehoe 

breakwater are shown in Figures 17-21. Aerial photography was obtained at 

Kahului on 26 August 2001 and at Laupahoehoe on 5 September 2001. 

Photogrammetric Analysis of Armor Unit Targets 

When aerial photography is planned and conducted so that each photo image 

overlaps the next by 60 percent or more, the two photographs comprising the 

overlap area can be positioned under an instrument called a stereoscope, and 

viewed in extremely sharp three-dimensional (3-D) detail. If properly selected 

survey points on the ground have previously been targeted and are visible in the 

overlapping photography, accurate measurements of any point appearing in the 

photographs can be obtained. This technique is called photogrammetry. 
20 Chapter 2 Monitoring Plan and Data Comparison 

Figure 17. Stereo pair photographs of outer portion of Kahului east breakwater 
Chapter 2 Monitoring Plan and Data Comparison 21

Figure 18. Stereo pair photographs of inner portion of Kahului east breakwater 
22 Chapter 2 Monitoring Plan and Data Comparison 

Figure 19. Stereo pair photographs of outer portion of Kahului west breakwater 
Chapter 2 Monitoring Plan and Data Comparison 23

Figure 20. Stereo pair photographs of inner portion of Kahului west breakwater 
24 Chapter 2 Monitoring Plan and Data Comparison 

Figure 21. Stereo pair photographs of Laupahoehoe breakwaters 
Chapter 2 Monitoring Plan and Data Comparison 25

The stereo pair images obtained during aerial photography at Kahului and 

Laupahoehoe breakwaters were viewed in a Zeiss P-3 Analytical Stereoplotter, 

and stereomodels were oriented to the ground control point data previously 

obtained. In the stereomodel, accurate horizontal and vertical measurements can 

be made of any point on any armor unit appearing in the print. The stereomodel 

was used for all photogrammetric compilation and the development of photo 

maps. To establish the accuracy of the photogrammetric work, comparisons of 

the coordinates for selected targets obtained during the ground surveys with those 

of the aerial surveys (stereomodels) were conducted and indicated very close 

agreement. For the Kahului east breakwater, maximum differences were 0.098 

and 0.067 m (0.32 and 0.22 ft), respectively, for the horizontal and vertical 

positions. An average of all horizontal and vertical positions indicated 

differences of 0.027 m (0.09 ft) and 0.03 m (0.1 ft), respectively. For the 

Kahului west breakwater, maximum differences were 0.061 and 0.037 m (0.2 and 

0.12 ft), respectively, for the horizontal and vertical positions. An average of all 

horizontal and vertical positions indicated differences of 0.024 m (0.08 ft) and 

0.024 m (0.08 ft), respectively. For the Laupahoehoe breakwater, maximum 

differences were 0.043 and 0.024 m (0.14 and 0.08 ft), respectively, for the 

horizontal and vertical positions. An average of all horizontal and vertical 

positions indicated differences of 0.021 m (0.07 ft) and 0.009 m (0.03 ft), 

respectively. 

A photogrammetric analysis of the targeted armor units was conducted for 

the Kahului east and west breakwaters and the Laupahoehoe breakwater, and x, 

y, and z (easting, northing, and el) coordinates were obtained. Data obtained 

during the current (August/September 2001) surveys were compared to those 

obtained at Kahului and Laupahoehoe during the aerial surveys of August 1993 

and November 1992, respectively. Comparisons of the aerial survey data are 

presented in Tables 2-4. 

For the Kahului east breakwater, comparisons of target coordinates (Table 2) 

show relatively close agreement between the two surveys for most of the targets. 

Maximum movement in the horizontal and vertical directions was 0.933 m 

(3.06 ft) and 1.515 m (4.97 ft), respectively, however, this level of difference 

occurred for only one target for the horizontal (KEE2) and one target in the 

vertical (KED1) position. Both these units (KED and KEE) are situated around 

the seaward head of the structure. The average movement of all horizontal and 

vertical targets, respectively, was 0.155 m (0.51 ft) and 0.165 m (0.54 ft). If the 

extreme horizontal and vertical movements of targets KEE2 and KED1 are 

neglected, average movement was 0.143 m (0.47 ft) and 0.113 m (0.37 ft), 

respectively, for the horizontal and vertical targets. Even though targets on 

armor units KEE and KED have moved about 0.91 to 1.52 m (3 to 5 ft), 

respectively, visual observations indicate the units have not broken and continue 

to be functional. Note in Table 2 that no data are presented for target KEE3 and 

KEJ2. Armor unit KEE moved slightly horizontally and the target was not 

visible from the air since it was blocked by an adjacent armor unit. Accessibility 

to target KEJ2 was difficult due to wave action and re-establishment of the target 

was inadvertently missed. 
26 Chapter 2 Monitoring Plan and Data Comparison 

For the Kahului west breakwater, comparisons of target coordinates (Table 3) 

also show relatively close agreement between the 1993 and 2001 surveys for 

most of the targets. Maximum movement in the horizontal and vertical directions 

was 1.158 m (3.8 ft) and 0.582 m (1.91 ft), respectively; however, this level of 

difference occurred on only one armor unit (KWH). This unit is located on the 

harbor- side head of the structure. Visual observations revealed the armor unit 

was intact and functional. The average movement of all horizontal and vertical 

targets, respectively, was 0.128 m (0.42 ft) and 0.11 m (0.36 ft). 

For the Laupahoehoe breakwater, comparisons of target coordinates 

(Table 4) reveal close agreement between the surveys indicating minimal horizontal and vertical movement of the targeted concrete armor units. Maximum 

movement in the horizontal and vertical directions was 0.104 m (0.34 ft) and 

0.131 m (0.43 ft), respectively. The average movement of all horizontal and 

vertical targets, respectively was 0.03 m (0.1 ft) and 0.049 m (0.16 ft). 

With the x, y, and z (easting, northing, and el) coordinates defined for each 

target on the various armor units, the coordinates of the centroid (center of mass) 

of each targeted armor unit were computed for the 2001 aerial survey. In addition, the position of each armor unit relative to the x, y, and z axes was 

determined and compared with previous data. Figure 22 shows, in three 

dimensions, the orientation and comparison of representative armor units to the 

three axes for the two surveys. The centroid coordinates of each targeted armor 

unit on the Kahului east and west breakwaters and the Laupahoehoe breakwater 

are shown in Tables 5-7 and compared with the aerial survey results of 1992/ 

1993. Maximum movement of the centroids for the Kahului east breakwater was 

0.536 m (1.76 ft) and 0.671 m (2.2 ft) in the horizontal and vertical directions, 

respectively, while average movements were 0.119 m (0.39 ft) and 0.17 m 

(0.57 ft) in the horizontal and vertical directions. As noted earlier, data were not 

obtained for two targets (KED1 and KEE2) on the Kahului east breakwater, 

however, based on information available and known dimensions of these armor 

units, their centroid positions were calculated. For the Kahului west breakwater, 

maximum horizontal and vertical centroid movements, respectively, were 0.64 m 

(2.1 ft) and 0.186 m (0.61 ft), while average movements were 0.113 (0.37 ft) and 

0.64 m (0.21 ft) in the horizontal and vertical directions. Maximum movement of 

the centroids for the Laupahoehoe breakwater was 0.091 m (0.3 ft) and 0.085 m 

(0.28 ft) in the horizontal and vertical directions, respectively, while average 

movements were 0.03 m (0.1 ft) and 0.034 m (0.11 ft) in the horizontal and 

vertical directions. The targeted armor unitsí orientation (rotation angle relative 

to the x, y, and z axes) are presented in Tables 8-10 for the east and west Kahului 

breakwaters and the Laupahoehoe breakwater and compared with the aerial 

survey results of 1992/ 1993. For the Kahului east breakwater, changes in the 

rotation angle of the targeted armor units varied from 0.03 to 24.57 deg with an 

average of 3.09 deg. Changes in rotation angles varied from 0.0 to 17.32 deg for 

the Kahului west breakwater with an average of 2.02 deg. For the Laupahoehoe 

breakwater , changes in rotation angles varied from 0.01 to 0.36 deg with an 

average of 0.1 deg. 
Chapter 2 Monitoring Plan and Data Comparison 27Figure 22. Comparison of representative targeted armor unit position relative to x, y, and z axes 
28 Chapter 2 Monitoring Plan and Data Comparison 

 Photo maps combine the image characteristics of a photograph with the geometric qualities of a map. The image is rectified and free from skewness and distortion, and therefore, precise horizontal measurements may be obtained using an 

engineer scale. Photo maps were prepared for the outer portions of the Kahului 

east and west breakwaters and the Laupahoehoe breakwater for the 2001 survey. 

They were produced on mylar sheets at a scale of 1:240. Examples of photo 

maps for the Kahului east and west breakwater heads and the Laupahoehoe 

breakwater are shown in Figures 23-25. In an effort to quantify horizontal 

movement of nontargeted concrete armor units on the Kahului and Laupahoehoe 

breakwaters, photo maps obtained for the 1992/1993 and 2001 were compared. 

Eight 27,215-kg (30-ton) dolosse around the seaward quadrant of the head of the 

Kahului east breakwater (including targeted units KED and KEE) appeared to 

have slightly changed positions. Movement appeared to be on the order or 0.3 to 

0.9 m (1 to 3 ft). These units have not broken and are considered functional. 

Just a few additional units on the remaining portion of the Kahului east 

breakwater, as well as on the Kahului west breakwater, had moved slightly with 

no concentrations in any specific areas. Negligible movement of nontargeted 

units on the Laupahoehoe breakwater was detected between the surveys. 

In summary, detailed and accurate information relative to the armor unit 

positions for the Kahului and Laupahoehoe breakwaters have been captured by 

means of aerial photography and photogrammetric analysis. Comparisons of 

2001 target data to that obtained previously in 1993 for the Kahului breakwaters 

indicated horizontal movements ranging from 0.0 to 0.0.933 m (0.0 to 3.06 ft) 

and 0.0 to 1.158 m (0.0 to 3.8 ft) for the east and west breakwaters, respectively, 

and vertical movements ranging from 0.003 to 1.515 m (0.01 to 4.97 ft) and 

0.018 to 0.582 m (0.06 to 1.91 ft). Additional comparisons of 2001 centroid data 

to that of 1993 revealed horizontal movements ranging from 0.003 to 0.536 m 

(0.01 to 1.76 ft) and 0.0 to 0.64 m (0.0 to 2.1 ft) for the east and west 

breakwaters, respectively, and vertical movements ranging from 0.015 to 0.671 

m (0.05 to 2.2 ft) and 0.0 to 0.186 m (0.0 to 0.61 ft). Comparisons of 2001 target 

data to that obtained at the Laupahoehoe breakwater in 1992, indicated horizontal 

movements ranging from 0.003 to 0.104 m (0.01 to 0.34 ft) and vertical 

movements ranging from 0.0 to 0.131 m (0.0 to 0.43 ft). Comparisons of 

centroid data at Laupahoehoe revealed horizontal movements ranging from 0.0 to 

0.091 m (0.0 to 0.3 ft) and vertical movements ranging from 0.003 to 0.085 m 

(0.01 to 0.28 ft). Comparisons of nontargeted armor units on the rectified photo 

maps of the breakwaters indicated movement of several units along the sea-side 

quadrant of the Kahului east breakwater. Movement was on the order of 0.3 to 

0.9 m (1 to 3 ft), however, the units were intact and considered functional. On the 

Kahului west breakwater a few units had moved slightly with no concentrations 

in any specific area. Negligible movement occurred on the Laupahoehoe 

breakwater . 

Full-scale hard copies of aerial photographs and photo maps are on file at the 

authors' offices at CHL and the Honolulu District. In addition, all photogrammetric compilations and analyses have been stored on diskettes in 

MICROSTATION files for future use. Data are stored and can be retrieved and 

compared against data obtained during subsequent monitoring. Thus, armor unit 

movement may continue to be quantified precisely in future years. 
Chapter 2 Monitoring Plan and Data Comparison 29

Figure 23. Photo map of head of Kahului east breakwater 
30 Chapter 2 Monitoring Plan and Data Comparison 

Figure 24. Photo map of head of Kahului west breakwater 
Chapter 2 Monitoring Plan and Data Comparison 31

Figure 25. Photo map of Laupahoehoe breakwater 

Broken Armor Unit Surveys 

During the period 21-23 August 2001, a survey of broken/cracked armor 

units above the waterline was conducted for the Kahului east and west breakwaters and Laupahoehoe breakwater. During the inspection, each broken armor 

unit was identified and photographed, and its approximate location relative to 

breakwater station and distance from a baseline was recorded. The baseline was 

the approximate center line of the structure. On the Kahului east breakwater, 
32 Chapter 2 Monitoring Plan and Data Comparison 

29 broken or cracked armor units were identified and 58 were observed on the 

Kahului west breakwater during the walking survey. No broken or cracked 

armor units were found on the Laupahoehoe breakwater . 

 The approximate locations of broken/cracked armor units along the Kahului 

east and west breakwaters are shown in Figures 26 and 27, respectively, and 

detailed data obtained during the broken armor unit inventory are shown in 

Table 11. Armor unit numbers identified in Figures 26 and 27 correspond to 

those listed in Table 11. Of the 29 broken armor units on the Kahului east 

breakwater, 19 were 5,445-kg (6-ton) dolosse; two were 8,165-kg (9-ton) tribars; 

four were 27,215-kg (30-ton) dolosse; and four were 31,750-kg (35-ton) tribars. 

The majority of the broken units (66 percent) were 5,445-kg (6-ton) dolosse 

located on the seaward side of the inner half of the concrete-armored portion of 

the structure. These broken units were concentrated between stas 19+60 and 

20+84. Seventy-four percent of the broken 5,445-kg (6-ton) dolosse were 

located on the lower portion of the seaward slope in the active wave zone. Most 

the remaining broken units on the east breakwater were sporadically located 

around the head of the structure with no specific concentrations. Of the 

58 broken armor units on the Kahului west breakwater, four were 5,900-kg 

(6.5-ton) tribars; one was a 9,980-kg (11-ton) tribar; 16 were 17,235-kg (19-ton) 

tribars; 18 were 18,145-kg (20-ton) dolosse; 11 were 27,215-kg (30-ton) dolosse; 

five were 29,940-kg (33-ton) tetrapods; and three were 31,750-kg (35-ton) 

tribars. On the west breakwater, 90 percent of the broken units were located on 

the seaward side of the outer half of the concrete-armored section of the 

breakwater. Concentrations of broken units occurred on the sea side of the 

breakwater between stas 20+50 and 21+50 and stas 22+50 and 23+50. Most 

broken units (66 percent) also were located on the lower portion of the seaward 

breakwater slope in the active wave zone. 

Types of breaks for the dolosse included shank and fluke breaks. These were 

characterized as mid-shank, shank-fluke (shank broken in vicinity of fluke), and 

fluke-shank (fluke broken off at junction with shank). Also recorded were 

straight breaks (broken straight across) and angled breaks (broken at some angle 

to the dolos limb). For the tribars and tetrapods, types of breaks included those 

through the center section of the unit where one or more legs were separated 

from the unit, and those in which just a portion of one of the legs was broken off. 

 Views of representative types of breaks for the armor units are shown in Figures 

28-31. Armor units with hairline cracks on one side were not counted, only those 

that were cracked all the way through were considered a break for recording 

purposes. 

Considering the types of breaks for the 52 broken dolosse on both the 

Kahului structures, 75 percent had shank-fluke breaks, 16 percent had flukeshank breaks, and 9 percent had mid-shank breaks. Of the dolosse breaks 

recorded, 78 percent were straight and 22 percent were angled. Considering the 

types of breaks for the 35 tribars and tetrapods on the Kahului breakwaters, 89 

percent included units with breaks through the center sections where one or more 

legs had separated, and 11 percent had just portions of a leg broken off the unit. 
Chapter 2 Monitoring Plan and Data Comparison 33

Figure 26. Approximate locations of broken/cracked armor units along outer portion of 

Kahului east breakwater 

During the previous study, documentation of broken/cracked armor units by 

foot was not conducted as part of the periodic inspection. Instead, low-level 

helicopter inspections were made of the Kahului and Laupahoehoe breakwaters 

in April 1992, to obtain a count of visible armor unit breakage. Findings 

revealed three broken armor units on the Kahului east breakwater, 13 on the 
34 Chapter 2 Monitoring Plan and Data Comparison Figure 27. Approximate locations of broken/cracked armor units along outer portion of Kahului west breakwater 
Chapter 2 Monitoring Plan and Data Comparison 35

Figure 28. Dolos with mid-shank crack 

Figure 29. Dolos with fluke-shank break 

Kahului west breakwater, and none on the Laupahoehoe breakwater . A walking 

inspection of the Kahului breakwaters in September 1992, however, was 

conducted as part of an ongoing research study funded by another work unit. 

This inspection indicated a considerably larger number of broken armor units 

than obtained during the aerial surveillance. Eleven and 28 broken units were 

identified on the east and west breakwaters, respectively. The difference is 
36 Chapter 2 Monitoring Plan and Data Comparison 

Figure 30. Dolos with shank-fluke break 

Figure 31. Tribar with break through center section of unit 

associated with the level of visibility between the two methods. The aerial 

inspection does not identify the cracked, but yet unbroken units; broken units in 

shadows; broken units in splash zones; and broken units in the underlayers. 

A comparison of the number of broken armor units for the current (2001) 

survey on the Kahului breakwaters with those obtained during the walking 
Chapter 2 Monitoring Plan and Data Comparison 37

inspection of 1992 indicates significantly more broken units for the later survey 

(29 versus 11 and 58 versus 28 for the east and west breakwaters, respectively). 

Since no known major storm events occurred during this time period to cause the 

additional breakage, it is assumed that the 2001 survey was much more thorough 

than the 1992 survey. Therefore, the current broken armor unit survey will serve 

as a base condition for comparison of subsequent surveys. It was noted that 

concentrations of broken armor units on the Kahului breakwaters occurred in 

similar areas for both the 1992 and 2001 surveys. 

As stated earlier, no broken or cracked armor units were found on the 

Laupahoehoe breakwater. It was noted, however, that some of the underlayer 

stone fill below the concrete rip cap was lost between stas 1+55 and 1+75. Also, 

armor stones on the harbor side of the structure between stas 0+85 and 0+95 have 

been displaced creating a small void. It appears that waves overtopping the 

structure are blowing these stones out and they are perched against the void. 
38 Chapter 3 Summary and Findings 

3 Summary and Findings 

The Kahului Harbor breakwaters have been repeatedly subjected to major 

storm events since completion of their construction in 1931. As a result, extensive breakwater damage has occurred. Major rehabilitations were completed in 

1956, 1966, 1973, and 1984. The structures were originally armored with keyedand-fitted stone, but now have several sizes of tetrapod, tribar, and dolos concrete 

armor units. The Kahului breakwaters are some of the most complex rubblemound structures the Corps has constructed. The Laupahoehoe Point boatlaunching facility breakwater was constructed in 1988 with 27,215-kg (30-ton) 

dolosse armor and appears to have been much more stable. 

Sound, quantifiable data relative to the positions of the concrete armor units 

were initially obtained for the Kahului breakwaters during the period October 

1991 - August 1993, and for the Laupahoehoe breakwater during the period 

October 1991 ñ November 1992, under the ìPeriodic Inspectionsî Work Unit of 

the Monitoring Completed Navigation Projects Program. Data from limited 

ground-based surveys, aerial photography, and photogrammetric analysis were 

obtained to establish precise base level conditions for the breakwaters. Accuracy 

of the photogrammetric analysis was validated and defined through comparison 

of ground and aerial survey data on control points and targets established on the 

structure. A method of high resolution, stereo aerial photographs, a stereoplotter, 

and MICROSTATION-based software was developed to analyze the entire 

above-water armor unit fields and quantify armor positions and subsequent 

movement. Minimal target movement occurred during the initial monitoring 

effort. Average movement of targets in both the horizontal and vertical 

directions was 0.046 m (0.15 ft) or less on the Kahului breakwaters, and less than 

0.015 m (0.05 ft) on the Laupahoehoe structure. 

Similar data were obtained during 2001 and compared with the 1992/1993 

data obtained previously. An analysis of these data indicated some armor unit 

movements on the Kahului breakwaters (particularly the east breakwater) and 

negligible movement on the Laupahoehoe breakwater . On the Kahului east 

breakwater, one target moved about 0.9 m (3 ft) horizontally and one moved 

almost 1.5 m (5 ft) vertically. Both these units were located around the seaward 

head of the structure. The average movement of the targets, however, was on the 

order of about 0.15 m (0.5 ft). An evaluation of nontargeted units indicated 

several had changed horizontal positions (on the order of 0.3 to 0.9 m (1 to 3 ft)) 

also around the seaward quadrant of the head of the east breakwater. These units 

are intact, however, and continue to be functional. For the Kahului west 
Chapter 3 Summary and Findings 39

breakwater, comparisons of target coordinates showed relatively close agreement 

with those obtained in 1993. The average movement of all targets in both the 

horizontal and vertical directions was less than 0.015 m (0.5 ft). For the 

Laupahoehoe breakwater , average target movement in both the horizontal and 

vertical directions was less than 0.06 m (0.2 ft). Considering the movements of 

targeted armor unitsí centroids, average movements in both the horizontal and 

vertical directions were less than 0.18 m (0.6 ft) for the Kahului east breakwater, 

less than 0.12 m (0.4 ft) for the Kahului west breakwater, and around 0.03 m (0.1 

ft) for the Laupahoehoe breakwater . 

A total of 29 broken/cracked armor units on the Kahului east breakwater and 

58 on the Kahului west breakwater were identified during the current (2001) 

survey. These data establish a base from which to evaluate future breakage in 

subsequent surveys. No broken/cracked armor units were found on the Laupahoehoe breakwater . 

The Kahului and Laupahoehoe breakwaters will be revisited in the future 

under the ìPeriodic Inspectionsî Work Unit to gather data by which assessments 

can be made on the long-term response of the structures to their environment. 

The areas of concentrated breakage on the Kahului east and west breakwaters 

should be inspected annually to monitor any increase in breakage and thus 

reduction in stability. The insight gathered from these efforts will allow 

engineering decisions to be made, based on sound data, as to whether or not 

closer surveillance and/or repair of the structures might be required to reduce 

their chances of failing catastrophically. Also, the periodic inspection methods 

developed and validated for these breakwaters may be used to gain insight into 

other Corps structures. 
40 References 

References 

Bottin, R. R., Jr., and Boc, S. J. (1996). ìPeriodic inspection of Nawiliwili 

Harbor breakwater, Kauai, Hawaii: Report 1, base conditions,î Technical 

Report CERC-96-5, U.S. Army Engineer Waterways Experiment Station, 

Vicksburg, MS. 

Bottin, R. R., Jr., and Boc, S. J. (1997). ìPeriodic Inspection of Ofu Harbor 

breakwater, America Samoa: Report 1, base conditions,î Technical Report 

CHL-97-32, U.S. Army Engineer Waterways Experiment Station, Vicksburg, 

MS. 

Bottin, R. R., Jr., Markle D. G., and Mize, M. G. (1987). ìDesign for navigation 

improvements, wave protection, and breakwater stability for proposed boatlaunching facility, Laupahoehoe Point, Hawaii,î Technical Report CERC-87-

3, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. 

Headquarters, U.S. Army Corps of Engineers. (1997). ìMonitoring completed 

navigation projects; engineer and design,î ER 1110-2-8151, Washington, 

DC. 

Jackson, R. A. (1964). ìDesigns for rubble-mound breakwater repair, Kahului 

Harbor, Maui, Hawaii,î Technical Report No. 2-644, U.S. Army Engineer 

Waterways Experiment Station, Vicksburg, MS. 

Markle, D. G. (1982). Kahului breakwater, stability study, Kahului, Maui, 

Hawaii,î Technical Report HL-82-14, U.S. Army Engineer Waterways 

Experiment Station, Vicksburg, MS. 

Markle, D. G., and Boc, S. J. (1994). ìPeriodic inspections of Kahului and 

Laupahoehoe breakwaters, Hawaii: Report 1, base conditions,î Technical 

Report CERC-94-12, U.S. Army Engineer Waterways Experiment Station, 

Vicksburg, MS. 

Sargent, F., Markle, D., and Grace, P. (1988). ìCase histories of Corps 

breakwater and jetty structures: Report 4, Pacific Ocean Division," 

Technical Report REMR-C0-3, U.S. Army Engineer Waterways Experiment 

Station, Vicksburg, MS. 

U.S. Army Engineer District, Honolulu. (1981). ìBreakwater rehabilitation, 

Kahului Harbor, Maui, HI,î General Design Memorandum, Ft. Shafter, HI. 
References 41

U.S. Army Engineer District, Honolulu. (1984). ìLaupahoehoe navigation 

improvements, Laupahoehoe, Hawaii,î Final Detailed Project Report and 

Environmental Impact Statement, Ft. Shafter, HI. 
Table 1 

Description of Targeted Armor Units on Kahului and Laupahoehoe 

Breakwaters 

Location Unit Description 

Kahului East Breakwater KEA 8,165-kg (9-ton) Tribar 

 KEB 8,165-kg (9-ton) Tribar 

 KEC 31,750-kg (35-ton) Tribar 

 KED 27,215-kg (30-ton) Dolos 

 KEE 27,215-kg (30-ton) Dolos 

 KEF 27,215-kg (30-ton) Dolos 

 KEG 31,750-kg (35-ton) Tribar 

 KEH 27,215-kg (30-ton) Dolos 

 KEI 27,215-kg (30-ton) Dolos 

 KEJ 5,445-kg (6-ton) Dolos 

Kahului West Breakwater KWA 9,980-kg (11-ton) Tribar 

 KWB 31,750-kg (35-ton) Tribar 

 KWC 27,215-kg (30-ton) Dolos 

 KWD 27,215-kg (30-ton) Dolos 

 KWE 27,215-kg (30-ton) Dolos 

 KWF 27,215-kg (30-ton) Dolos 

 KWG 31,750-kg (35-ton) Tribar 

 KWH 27,215-kg (30-ton) Dolos 

 KWI 5,900-kg (6.5-ton) Tribar 

 KWJ 5,900-kg (6.5-ton) Tribar 

Laupahoehoe Breakwater LA 27,215-kg (30-ton) Dolos 

 LB 27,215-kg (30-ton) Dolos 

 LC 27,215-kg (30-ton) Dolos 

 LD 27,215-kg (30-ton) Dolos 

 LE 27,215-kg (30-ton) Dolos 
Table 2 

Comparison of 2001 and 1993 Aerial Survey Data Obtained for Armor Unit Targets on Kahului East Brea

2001 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

TargetID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E01-E93, cm (ft) 

KEA1 566164.42 206888.54 +1.67 (+5.48) 566164.38 206888.41 +1.61 (+5.28) 1.22 (0.04) KEA2 566169.30 206885.41 +1.70 (+5.58) 566169.26 206885.34 +1.63 (+5.34) 1.22 (0.04) KEA3 566164.25 206882.77 +1.40 (+4.59) 566164.15 206882.66 +1.34 (+4.41) 3.05 (0.10) KEB1 565756.22 207111.02 +1.96 (+6.42) 565756.76 207112.94 +1.97 (+6.45) 16.46 (0.54) KEB2 565754.66 207106.09 +1.14 (+3.74) 565755.49 207107.54 +1.43 (+4.70) 25.30 (0.83) 4KEB3 565750.89 207110.54 +1.26 (+4.15) 565751.33 207111.64 +1.47 (+4.82) 13.41 (0.44) KEC1 565596.51 207201.75 +2.37 (+7.78) 565596.80 207201.62 +2.38 (+7.82) 8.84 (0.29) KEC2 565591.78 207210.39 +3.17 (+10.39) 565592.19 207210.26 +3.25 (+10.66) 12.50 (0.41) KEC3 565601.95 207209.66 +3.37 (+11.07) 565602.26 207209.47 +3.36 (+11.01) 9.45 (0.31) KED1 565608.34 207274.05 +4.01 (+13.16) 565609.27 207271.74 +5.53 (+18.13) 28.35 (0.93) KED2 565620.74 207273.28 +4.10 (+13.46) 565621.08 207272.81 +4.36 (+14.31) 10.36 (0.34) KED3 565613.74 207262.91 +3.58 (+11.75) 565614.50 207262.25 +3.67 (+12.04) 23.16 (0.76) KEE1 565669.50 207296.57 +4.23 (+13.89) 565669.87 207298.86 +4.22 (+13.84) 11.28 (0.37) KEE2 565681.76 207294.80 +4.60 (+15.09) 565682.00 207297.86 +4.97 (16.32) 7.32 (0.24) KEE3 565675.77 207287.77 +3.73 (+12.24) KEF1 565723.01 207265.81 +4.02 (+13.19) 565722.83 207265.55 +4.15 (+13.63) 5.49 (0.18) KEF2 565732.58 207272.08 +2.43 (+7.98) 565732.38 207271.71 +2.58 (+8.46) 6.10 (0.20) KEF3 565732.66 207259.22 +2.73 (+8.95) 565732.52 207259.09 +2.82 (+9.25) 4.27 (0.14) KEG1 565750.05 207222.05 +2.89 (+9.48) 565749.82 207222.09 +2.96 (+9.71) 7.01 (0.23) KEG2 565755.68 207228.84 +3.16 (+10.37) 565755.48 207228.80 +3.22 (+10.55) 6.10 (0.20) KEG3 565758.80 207220.58 +2.78 (+9.12) 565758.51 207220.59 +2.82 (+9.25) 8.84 (0.29) 
Table 2 (Concluded) 

2001 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

Target ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E01-E93, cm (ft) 

KEH1 565996.17 207058.29 +4.72 (+15.49) 565996.06 207058.36 +4.86 (+15.93) 3.35 (0.11) KEH2 566006.22 207065.09 +5.52 (+18.12) 566006.22 207065.14 +5.46 (+17.90) 0.00 (0.00) KEH3 566007.65 207052.97 +4.65 (+15.24) 566007.53 207053.06 +4.64 (+15.23) 3.66 (0.12) KEI1 566180.75 206939.81 +3.64 (+11.94) 566180.15 206939.43 +3.51 (+11.51) 18.29 (0.60) KEI2 566188.57 206944.49 +5.36 (+17.58) 566187.76 206945.04 +5.17 (+16.97) 24.69 (0.81) KEI3 566188.95 206933.70 +4.78 (+15.69) 566189.19 206934.43 +4.66 (+15.30) 7.32 (0.24) KEJ1 566270.11 206882.16 +2.69 (+8.83) 566270.83 206882.86 +2.86 (+9.37) 21.95 (0.72) KEJ2 566276.13 206887.23 +2.41 (+7.91) KEJ3 566276.73 206882.91 +3.65 (+11.99) 566277.32 206881.72 +3.83 (+12.56) 17.98 (0.59) 
Table 3 

Comparison of 2001 and 1993 Aerial Survey Data Obtained for Armor Unit Targets on Kahului West Brea

2001 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

Target ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E01-E93, cm (ft) 

KWA1 564375.25 206990.93 +2.54 (+8.33) 564374.97 206990.72 +2.59 (+8.51) 8.53 (0.28) KWA2 564378.32 206987.20 +3.68 (+12.08) 564378.20 206986.89 +3.71 (+12.16) 3.66 (0.12) KWA3 564373.13 206985.60 +3.25 (+10.67) 564372.42 206985.46 +3.18 (+10.43) 21.64 (0.71) KWB1 564486.29 207060.01 +2.35 (+7.70) 564486.33 207060.14 +2.39 (+7.84) 1.22 (0.04) KWB2 564491.65 207064.83 +2.79 (+9.16) 564491.58 207064.87 +2.86 (+9.38) 2.13 (0.07) KWB3 564493.35 207057.97 +2.19 (+7.17) 564493.30 207058.06 +2.26 (+7.43) 1.52 (0.05) KWC1 564614.41 207111.49 +3.20 (+10.49) 564614.52 207111.51 +3.30 (+10.84) 3.35 (0.11) KWC2 564607.79 207105.18 +5.04 (+16.52) 564607.90 207105.11 +5.08 (+16.67) 3.35 (0.11) KWC3 564603.75 207114.02 +3.54 (+11.63) 564603.96 207114.05 +3.71 (12.16 6.40 (0.21) KWD1 564698.37 207141.38 +3.54 (+11.60) 564698.17 207141.53 +3.58 (+11.74) 6.10 (0.20) KWD2 564694.17 207153.33 +3.84 (+12.61) 564694.02 207153.42 +3.90 (+12.78) 4.57 (0.15) KWD3 564687.27 207143.88 +5.12 (+16.80) 564687.20 207144.06 +5.17 (+16.95) 2.13 (0.07) KWE1 564786.75 207172.45 +4.25 (+13.94) 564787.80 207173.35 +4.28 (+14.04) 32.00 (1.05) KWE2 564789.34 207184.49 +3.72 (+12.20) 564788.82 207185.43 +3.57 (+11.70) 15.85 (0.52) KWE3 564777.54 207180.59 +3.42 (+11.23) 564777.48 207179.97 +3.69 (+12.10) 1.83 (0.06) KWF1 564804.20 207148.16 +4.04 (+13.26) 564803.79 207148.67 +4.01 (+13.17) 12.50 (0.41) KWF2 564816.30 207149.37 +3.02 (+9.90) 564815.93 207150.07 +3.07 (+10.07) 11.28 (0.37) KWF3 564810.86 207157.86 +5.28 (+17.33) 564810.39 207158.10 +5.44 (+17.84) 14.33 (0.47) KWG1 564796.14 207100.21 +3.33 (+10.92) 564795.64 207100.53 +3.40 (+11.17) 15.24 (0.50) KWG2 564805.84 207098.03 +2.77 (+9.10) 564805.24 207098.32 +2.84 (+9.31) 18.29 (0.60) KWG3 564802.94 207107.64 +3.23 (+10.60) 564802.41 207107.89 +3.27 (+10.74) 16.15 (0.53) 
Table 3 (Concluded)

2001 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

Target ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E01-E93, cm (ft) 

KWH1 564753.05 207041.65 +3.51 (+11.52) 564753.72 207044.76 +2.95 (+9.69) 20.42 (0.67) KWH2 564743.16 207034.90 +2.21 (+7.26) 564744.62 207035.91 +2.80 (+9.17) 44.50 (1.46) KWH3 564753.12 207029.25 +3.66 (+12.02) 564756.05 207033.05 +3.96 (+12.98) 89.31 (2.93) KWI1 564592.61 207032.58 +2.42 (+7.93) 564592.49 207032.86 +2.45 (+8.05) 3.66 (0.12) KWI2 564597.43 207031.08 +1.98 (+6.48) 564597.32 207031.31 +2.05 (+6.73) 3.35 (0.11) KWI3 564593.24 207027.83 +1.82 (+5.97) 564593.24 207028.03 +1.85 (+6.06) 0.00 (0.00) KWJ1 564472.09 206971.63 +1.43 (+4.70) 564471.91 206971.46 +1.45 (+4.76) 5.49 (0.18) KWJ2 564469.07 206967.42 +1.34 (+4.38) 564468.89 206967.24 +1.36 (+4.46) 5.49 (0.18) KWJ3 564467.00 206972.16 +1.43 (+4.69) 564466.73 206972.00 +1.48 (+4.84) 8.23 (0.27) 
Table 4 

Comparison of 2001 and 1992 Aerial Survey Data Obtained for Armor Unit Targets on Laupahoehoe Bre

2001 Aerial Survey 1992 Aerial Survey 

Absolu

Between 20

Target ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E92) Northing (N92) 

Elevation (El92), m (ft) E01-E92, cm (ft) 

LA1 588382.69 421935.37 +3.62 (+11.87) 588382.68 421935.34 +3.64 (+11.94) 0.30 (0.01) LA2 588392.93 421929.06 +4.65 (+15.26) 588392.89 421929.03 +4.68 (+15.35) 1.22 (0.04) LA3 588383.18 421922.72 +3.20 (+10.50) 588383.29 421922.77 +3.20 (+10.51) 3.35 (0.11) LB1 588392.41 421884.06 +3.14 (+10.31) 588392.30 421884.27 +3.27 (+10.74) 3.35 (0.11) LB2 588398.26 421874.44 +4.76 (+15.61) 588398.31 421874.78 +4.85 (+15.91) 1.52 (0.05) LB3 588387.15 421872.49 +3.18 (+10.44) 588387.44 421872.70 +3.20 (+10.50) 8.84 (0.29) LC1 588389.69 421862.56 +1.62 (+5.33) 588389.73 421862.53 1.69 (+5.55) 1.22 (0.04) LC2 588399.39 421858.22 +3.61 (+11.84) 588399.46 421858.29 +3.62 (+11.89) 2.13 (0.07) LC3 588390.98 421850.04 +2.36 (+7.74) 588391.03 421850.21 +2.41 (+7.90) 1.52 (0.05) LD1 588354.57 421851.96 +1.65 (+5.42) 588354.75 421851.86 +1.71 (+5.60) 5.49 (0.18) LD2 588361.82 421845.16 +3.96 (+12.99) 588361.93 421844.95 +3.98 (+13.06) 3.35 (0.11) LD3 588350.98 421840.30 +2.76 (+9.05) 588351.06 421840.29 +2.77 (+9.09) 2.44 (0.08) LE1 588362.36 421894.26 +2.50 (+8.21) 588362.41 421894.20 +2.50 (+8.21) 1.52 (0.05) LE2 588362.22 421881.60 +2.67 (+8.77) 588362.25 421881.54 +2.66 (+8.73) 0.91 (0.03) LE3 588352.18 421888.19 +3.70 (+12.15) 588352.26 421888.10 +3.72 (+12.20) 2.44 (0.08) 
Table 5 

Comparison of Centroid Data for Targeted Armor Units for 2001 and 1993 Aerial Survey Data for Kahulu

2001 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

Armor Unit ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E01-E93, cm (ft) 

KEA 566166.30 206885.98 0.78 (2.56) 566166.21 206885.86 0.71 (2.34) 2.74 (0.09) KEB 565754.80 207110.15 0.73 (2.38) 565755.12 207111.37 0.84 (2.76) 9.75 (0.32) KEC 565597.12 207208.81 1.64 (5.38) 565597.33 207208.70 1.67 (5.47) 3.66 (0.12) KED 565614.58 207270.38 2.84 (9.31) 565614.07 207270.16 3.51 (11.51) 6.10 (0.20) KEE 565675.76 207293.83 2.98 (9.79) 565676.39 207295.59 3.29 (10.79) 19.20 (0.63) KEF 565728.13 207265.44 2.07 (6.79) 565727.94 207265.23 2.19 (7.20) 5.79 (0.19) KEG 565754.78 207224.41 1.71 (5.60) 565754.50 207224.42 1.76 (5.78) 8.53 (0.28) KEH 566003.54 207059.38 3.91 (12.84) 566003.31 207059.37 3.23 (12.89) 7.01 (0.23) KEI 566187.53 206939.66 3.77 (12.38) 566187.07 206940.03 3.62 (11.87) 14.02 (0.46) KEJ 566275.09 206883.48 2.21 (7.24) 566275.38 206882.55 2.41 (7.91) 8.84 (0.29) 
Table 6 

Comparison of Centroid Data for Targeted Armor Units for 2000 and 1993 Aerial Survey Data for Kahulu

2000 Aerial Survey 1993 Aerial Survey 

Absolu

Between 20

Armor Unit ID Easting (E00) Northing (N00) 

Elevation (El00), m (ft) Easting (E93) Northing (N93) 

Elevation (El93), m (ft) E00-E93, cm (ft) 

KWA 564376.70 206986.50 2.47 (8.09) 564376.20 206986.40 2.45 (8.04) 15.24 (0.50) KWB 564490.40 207061.70 1.41 (4.64) 564490.50 207061.80 1.48 (4.85) 3.05 (0.10) KWC 564608.00 207108.80 3.12 (10.25) 564608.10 207108.90 3.22 (10.55) 3.05 (0.10) KWD 564692.00 207146.00 3.18 (10.42) 564691.80 207146.20 3.22 (10.58) 6.10 (0.20) KWE 564784.90 207178.80 2.74 (8.99) 564784.80 207179.20 2.79 (9.14) 3.05 (0.10) KWF 564809.50 207153.40 3.21 (10.54) 564809.10 207154.00 3.29 (10.81) 12.19 (0.40) KWG 564800.90 207102.50 1.72 (5.64) 564800.30 207102.70 1.78 (5.85) 18.29 (0.60) KWH 564751.10 207035.30 2.14 (7.03) 564752.20 207037.40 2.20 (7.23) 33.53 (1.10) KWI 564594.00 207031.40 1.39 (4.57) 564594.00 207031.60 1.44 (4.72) 0.00 (0.00) KWJ 564469.40 206970.60 0.67 (2.19) 564469.20 206970.40 0.67 (2.19) 6.10 (0.20) 
Table 7 

Comparison of Centroid Data for Targeted Armor Units for 2001 and 1992 Aerial Survey Data for Laupah

2001 Aerial Survey 1992 Aerial Survey 

Absolu

Between 20

Armor Unit ID Easting (E01) Northing (N01) 

Elevation (El01), m (ft) Easting (E92) Northing (N92) 

Elevation (El92), m (ft) E01-E92, cm (ft) 

LA 588387.30 421929.50 2.81 (9.23) 588387.40 421929.50 2.83 (9.29) 3.05 (0.10) LB 588393.90 421876.40 2.72 (8.94) 588394.10 421876.70 2.81 (9.22) 6.10 (0.20) LC 588394.90 421856.50 1.59 (5.21) 588394.90 421856.60 1.62 (5.33) 0.00 (0.00) LD 588357.20 421844.50 1.90 (6.23) 588357.30 421844.40 1.92 (6.30) 3.05 (0.10) LE 588358.00 421887.90 1.93 (6.33) 588358.00 421887.80 1.93 (6.34) 0.00 (0.00) 
Table 8 

Comparison of Rotation Angles for Targeted Armor Units for 2001 and 1993 Aerial Survey Data for Kahu

2001 Rotation Angle (deg) 1993 Rotation Angle (deg) 

Differe

1993 R

Armor Unit ID x-axis y-axis z-axis x-axis y-axis z-axis x-axis KEA 10.75 -0.99 -31.83 10.22 -0.60 -32.35 0.53 KEB 16.42 -23.19 13.26 10.25 -16.30 16.92 6.17 KEC 19.56 -3.82 -2.46 20.05 -1.99 -2.95 -0.49 KED 27.23 7.80 -128.30 2.66 10.34 -122.33 24.57 KEE 10.93 -18.93 120.15 12.68 -7.26 120.24 -1.75 KEF 4.52 -4.31 -88.66 4.33 -3.58 -88.89 0.19 KEG 5.96 -5.76 50.66 6.57 -5.47 50.36 -0.61 KEH 15.94 -1.13 156.04 18.16 -3.17 156.59 -2.22 KEI 4.74 20.14 142.71 6.18 20.17 148.07 -1.44 KEJ -15.81 13.02 50.82 -13.49 12.02 42.89 -2.32 
Table 9 

Comparison of Rotation Angles for Targeted Armor Units for 2000 and 1993 Aerial Survey Data for Kahu

2000 Rotation Angle (deg) 1993 Rotation Angle (deg) 

Differe

1993 R

Armor Unit ID x-axis y-axis z-axis x-axis y-axis z-axis x-axis KWA -4.17 -37.89 -46.53 -0.82 -36.08 -51.23 -3.35 KWB 9.94 -9.09 44.32 9.27 -9.94 44.11 0.67 KWC -4.65 5.94 -13.26 -2.89 6.93 -13.93 -1.76 KWD 4.73 4.56 -71.40 4.46 4.72 -71.60 0.27 KWE 18.81 -4.47 20.53 19.18 1.82 25.38 -0.37 KWF -2.59 -15.45 -174.66 -5.56 -14.24 -174.60 2.97 KWG 10.89 1.82 46.90 10.87 2.46 46.54 0.02 KWH 13.70 -19.67 39.74 11.25 -2.35 44.68 2.45 KWI 5.41 -22.28 100.99 3.79 -22.17 100.99 1.62 KWJ 4.00 -0.11 -6.06 4.31 0.88 -5.47 -0.31 
Table 10 

Comparison of Rotation Angles for Targeted Armor Units for 2001 and 1992 Aerial Survey Data for Laup

2001 Rotation Angle (deg) 1992 Rotation Angle (deg) 

Differe

Armor 1992 RUnit ID x-axis y-axis z-axis x-axis y-axis z-axis x-axis LA 8.36 -6.18 93.44 7.91 -6.48 93.54 -0.04 LB 1.41 0.55 65.38 0.93 -1.1 57.03 -0.15 LC 0.34 10.81 95.62 1.08 10.74 95.63 -0.01 LD -2.9 16.61 73.84 -2.63 16.04 73.18 -0.1 LE 10.86 -2.55 -90.08 10.44 -2.35 -90.05 -0.03 
Table 11 

Broken Armor Unit Inventory Data

Offset from Center line, 

m (ft) Armor 

Unit 

No. 

Station 

No. Type of Armor Unit Sea Side Harbor Side Type of Break, Comments 

East Breakwater 

 1 19+60 5,445-kg (6-ton) Dolos 8.23 (27) End of fluke broken off (straight) 

 2 19+80 5,445-kg (6-ton) Dolos 4.27 (14) Straight fluke-shank break 

 3 19+82 5,445-kg (6-ton) Dolos 10.67 (35) Straight shank-fluke break 

 4 19+84 5,445-kg (6-ton) Dolos 10.67 (35) Straight shank-fluke break 

 5 20+01 5,445-kg (6-ton) Dolos 4.27 (14) Straight shank-fluke break 

 6 20+15 5,445-kg (6-ton) Dolos 4.57 (15) Mid-shank crack 

 7 20+16 5,445-kg (6-ton) Dolos 6.71 (22) Two straight fluke-shank breaks 

 8 20+20 5,445-kg (6-ton) Dolos 8.84 (29) Straight shank-fluke break 

 9 20+22 5,445-kg (6-ton) Dolos 9.45 (31) Straight shank-fluke break 

10 20+24 5,445-kg (6-ton) Dolos 8.23 (27) Straight fluke-shank and straight 

shank-fluke breaks 

11 20+25 5,445-kg (6-ton) Dolos 8.84 (29) Two straight shank-fluke breaks 

12 20+35 5,445-kg (6-ton) Dolos 4.27 (14) Straight shank-fluke break 

13 20+39 5,445-kg (6-ton) Dolos 4.89 (16) Straight shank-fluke break 

14 20+48 5,445-kg (6-ton) Dolos 9.45 (31) Angled shank-fluke break 

15 20+50 5,445-kg (6-ton) Dolos 10.97 (36) Straight shank-fluke break 

16 20+75 5,445-kg (6-ton) Dolos 8.23 (27) Straight fluke-shank break 

17 20+79 5,445-kg (6-ton) Dolos 7.62 (25) Straight shank-fluke break 

18 20+80 5,445-kg (6-ton) Dolos 7.92 (26) Straight shank-fluke break 

19 20+84 5,445-kg (6-ton) Dolos 9.14 (30) Straight shank-fluke break 

20 23+32 8,165-kg (9-ton) Tribar 7.32 (24) Broken through center of unit 

21 25+47 31,750-kg (35-ton) Tribar 14.94 (49) Leg broken off unit 

22 26+31 8,165-kg (9-ton) Tribar 7.01 (23) Angled crack through center of 

unit 

23 26+59 31,750-kg (35-ton) Tribar 16.46 (54) Leg broken off unit 

24 26+87 27,215-kg (30-ton) Dolos 23.16 (76) Angled shank-fluke break 

25 27+35 31,750-kg (35-ton) Tribar 5.18 (17) Crack through leg and center of 

unit 

26 27+71 31,750-kg (35-ton) Tribar 23.47 (77) Leg broken off unit 

27 27+84 27,215-kg (30-ton) Dolos 16.76 (55) Straight shank-fluke crack 

28 28+03 27,215-kg (30-ton) Dolos 4.57 (15) Straight shank-fluke break 

29 28+11 27,215-kg (30-ton) Dolos 7.32 (24) Straight fluke-shank break 

(Sheet 1 of 3)
Table 11 (Continued)

Offset from Center line, 

Armor m (ft) Unit 

No. 

Station 

No. Type of Armor Unit Sea Side Harbor Side Type of Break, Comments 

West Breakwater 

 1 17+73 5,900-kg (6.5-ton) Tribar 11.28 (37) Leg broken off unit 

 2 18+37 5,900-kg (6.5-ton) Tribar 4.89 (16) Broken through center of unit 

 3 18+46 5,900-kg (6.5-ton) Tribar 7.62 (25) Broken through center of unit 

 4 18+89 9,980-kg (11-ton) Tribar 3.96 (13) Broken through center of unit 

 5 19+53 17,235-kg (19-ton) Tribar 13.72 (45) Crack through center of unit 

 6 20+27 5,900-kg (6.5-ton) Tribar 7.32 (24) Hairline crack through center of unit 

 7 20+53 17,235-kg (19-ton) Tribar 14.02 (46) Broken through center of unit, one 

leg missing 

 8 20+55 17,235-kg (19-ton) Tribar 16.76 (55) Leg broken off unit 

 9 20+67 17,235-kg (19-ton) Tribar 18.29 (60) Leg broken off unit 

10 20+68 17,235-kg (19-ton) Tribar 17.68 (58) One half leg broken off unit 

11 20+85 17,235-kg (19-ton) Tribar 16.76 (55) One half leg broken off unit 

12 20+85 17,235-kg (19-ton) Tribar 17.68 (58) Leg broken off unit 

13 20+89 17,235-kg (19-ton) Tribar 18.29 (60) Leg broken off unit 

14 20+89 17,235-kg (19-ton) Tribar 16.76 (55) Leg broken off unit 

15 20+89 18,145-kg (20-ton) Dolos 19.20 (63) Straight shank-fluke break 

16 20+96 18,145-kg (20-ton) Dolos 20.73 (68) Angled shank-fluke break 

17 20+96 18,145-kg (20-ton) Dolos 19.81 (65) Angled shank-fluke break 

18 21+05 18,145-kg (20-ton) Dolos 20.73 (68) Straight shank-fluke break 

19 21+14 17,235-kg (19-ton) Tribar 12.19 (40) Broken up in pieces 

20 21+19 18,145-kg (20-ton) Dolos 16.76 (55) Angled shank-fluke break 

21 21+21 17,235-kg (19-ton) Tribar 4.57 (15) Broken through center of unit 

22 21+24 17,235-kg (19-ton) Tribar 12.19 (40) Leg broken off unit 

23 21+34 17,235-kg (19-ton) Tribar 12.19 (40) Leg broken off unit 

24 21+69 17,235-kg (19-ton) Tribar 11.58 (38) Broken through center of unit 

25 21+74 17,235-kg (19-ton) Tribar 10.67 (35) Broken through center of unit 

26 21+74 18,145-kg (20-ton) Dolos 17.68 (58) Angled shank-fluke break 

27 21+74 29,940-kg (33-ton) Tetrapod 15.24 (50) Leg broken off unit 

28 21+96 17,235-kg (19-ton) Tribar 7.62 (25) Crack through leg 

29 22+04 18,145-kg (20-ton) Dolos 11.28 (37) Straight shank-fluke crack 

30 22+10 18,145-kg (20-ton) Dolos 18.90 (62) Straight shank-fluke break 

31 22+43 29,940-kg (33-ton) Tetrapod 14.63 (48) Leg broken off unit 

32 22+44 18,145-kg (20-ton) Dolos 13.41 (44) Straight shank-fluke break 

33 22+49 18,145-kg (20-ton) Dolos 17.98 (59) Straight shank-fluke break 

(Sheet 2 of 3)
Table 11 (Concluded)

Offset from Center line, 

Armor m (ft) Unit 

No. 

Station 

No. Type of Armor Unit Sea Side Harbor Side Type of Break, Comments 

34 22+50 18,145-kg (20-ton) Dolos 16.46 (54) Straight shank-fluke break 

35 22+50 18,145-kg (20-ton) Dolos 10.97 (36) Straight shank-fluke break 

36 22+60 29,940-kg (33-ton) Tetrapod 17.68 (58) Leg broken off unit 

37 22+60 18,145-kg (20-ton) Dolos 18.29 (60) Straight shank-fluke break 

38 22+79 18,145-kg (20-ton) Dolos 13.72 (45) Angled mid-shank break 

39 22+82 18,145-kg (20-ton) Dolos 19.81 (65) Angled shank-fluke break 

40 22+83 18,145-kg (20-ton) Dolos 21.34 (70) Straight shank-fluke break 

41 22+84 18,145-kg (20-ton) Dolos 15.85 (52) Straight shank-fluke break 

42 22+89 18,145-kg (20-ton) Dolos 8.53 (28) Angled mid-shank break 

43 22+89 31,750-kg (35-ton) Tribar 21.34 (70) Part of leg broken off unit 

44 22+89 31,750-kg (35-ton) Tribar 10.67 (35) Crack across leg of unit 

45 22+99 31,750-kg (35-ton) Tribar 17.37 (57) Part of leg broken off unit 

46 22+99 29,940-kg (33-ton) Tetrapod 9.14 (30) Leg broken off unit 

47 23+11 27,215-kg (30-ton) Dolos 9.14 (30) Angled shank-fluke break 

48 23+15 27,215-kg (30-ton) Dolos 14.33 (47) Straight shank-fluke break 

49 23+15 27,215-kg (30-ton) Dolos 14.33 (47) Straight shank-fluke break 

50 23+21 27,215-kg (30-ton) Dolos 10.97 (36) Straight fluke-shank crack 

51 23+28 27,215-kg (30-ton) Dolos 12.19 (40) Straight mid-shank break 

52 23+33 27,215-kg (30-ton) Dolos 13.11 (43) Straight fluke-shank break 

53 23+33 29,940-kg (33-ton) Tetrapod 0.91 (3) Leg broken off unit 

54 23+46 27,215-kg (30-ton) Dolos 14.94 (49) Straight shank-fluke break 

55 23+53 27,215-kg (30-ton) Dolos 4.27 (14) Angled fluke-shank break 

56 23+57 27,215-kg (30-ton) Dolos 0.30 (1) Straight shank-fluke crack 

57 23+57 27,215-kg (30-ton) Dolos 1.83 (6) Straight shank-fluke break 

58 23+94 27,215-kg (30-ton) Dolos 1.52 (5) Straight mid-shank break 

(Sheet 3 of 3)
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

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1. REPORT DATE (DD-MM-YYYY)

 August 2002 

2. REPORT TYPE

 Final report

3. DATES COVERED (From - To)

 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Periodic Inspections of Kahului and Laupahoehoe Breakwaters, Hawaii; 

Armor Unit Monitoring for Period 1992/93-2001 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

Robert R. Bottin, Jr., Daniel T. Meyers 

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT 

 NUMBER

U.S. Army Engineer Research and Development Center 

Environmental Laboratory 

3909 Halls Ferry Road 

Vicksburg, MS 39180-6199; 

U.S. Army Engineer District, Honolulu 

Building 230 

Fort Shafter, HI 96858-5440

 ERDC/CHL TR-02-11 

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

U.S. Army Corps of Engineers 

Washington, DC 20314-1000 

11. SPONSOR/MONITOR’S REPORT 

 NUMBER(S)

 

12. DISTRIBUTION / AVAILABILITY STATEMENT 

 Approved for public release, distribution is unlimited.

13. SUPPLEMENTARY NOTES

14. ABSTRACT

 Selected coastal navigation structures are periodically monitored under the “Periodic Inspections” Work Unit of the Monitoring 

Completed Navigation Projects Program. Such monitoring is done to gain an understanding of the long-term structural response of unique 

structures to their environment. Periodic data sets are used to improve knowledge in design, construction, and maintenance of both existing 

and proposed coastal navigation projects. 

 The Kahului Harbor breakwaters and the Laupahoehoe boat-launching facility breakwater, HI, were nominated for periodic monitoring 

by the U.S. Army Engineer District, Honolulu. The positions of the above-water, concrete armor units (tetrapods, tribars, and/or dolosse) 

on the breakwaters were initially obtained during the period 1991-1993 through limited ground surveys, aerial photography, and 

photogrammetric analysis. The structures were revisited in 2001 to determine changes that had occurred. Results indicated that some 

armor units had moved along the seaward quadrant of the head of the Kahului east breakwater. These units were intact, however, and are 

still functional. Armor unit movements on the Kahului west breakwater and the Laupahoehoe breakwater were minimal. A detailed

inventory of broken armor units on these structures was obtained. 

 The sites will be revisited in the future and the long-term structural response of the structures to their environment will continue to be 

tracked. These data sets will facilitate engineering decisions concerning whether or not closer surveillance and/or repair of the breakwaters 

might be required to reduce their chances of failing catastrophically. The periodic inspection methods developed and validated for the 

Hawaii breakwaters may also be used to gain insight into other Corps structures. 

15. SUBJECT TERMS

Aerial photography Dolosse Rubble-mound Photogrammetry Kahului Harbor, Maui, HI 

Breakwaters Periodic inspections Tribons Remote sensing 

Concrete armor units Armor stability Tetrapods Laupahoehoe-boat-launching facility, HI 

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OF ABSTRACT 

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a. REPORT 

UNCLASSIFIED 

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Standard Form 298 (Rev. 8-98)

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