Streamflow and Suspended-Sediment Loads

Before, During, and After H-3 Highway

Construction, North Halawa, Haiku, South Fork

Kapunahala, and Kamooalii Drainage Basins,

Oahu, Hawaii,1983–99

Prepared in cooperation with the

STATE OF HAWAII DEPARTMENT OF TRANSPORTATION

and the FEDERAL HIGHWAY ADMINISTRATION

U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 02-4005
Streamflow and Suspended-Sediment Loads 

Before, During, and After H-3 Highway 

Construction, North Halawa, Haiku, South Fork 

Kapunahala, and Kamooalii Drainage Basins, 

Oahu, Hawaii,1983–99

By Michael F. Wong and Daniel S. Yeatts

U.S. GEOLOGICAL SURVEY

Water Resources Investigations Report 02-4005

Prepared in cooperation with the

STATE OF HAWAII DEPARTMENT OF TRANSPORTATION

and the FEDERAL HIGHWAY ADMINISTRATION

Honolulu, Hawaii

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased 

from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

677 Ala Moana Blvd., Suite 415 Box 25286

Honolulu, HI 96813 Denver, CO 80225-0286

U. S. DEPARTMENT OF THE INTERIO

R

MARCH 3, 1849
Contents iii

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

H-3 Highway Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Previous Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Streamflow Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Suspended-Sediment Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Streamflow Before, During, and After Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Streamflow Changes due to Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Low Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

High and Peak Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Effects of Land-Use Changes on Streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Low Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

High and Peak Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Suspended-Sediment Loads Before, During, and After Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Suspended-Sediment Load Changes due to Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Effects of Land-Use Changes on Suspended-Sediment Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Comparison with Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Figures

1–2. Maps showing:

1. Selected stream-gaging and rain-gaging stations and drainage basins in and near the H-3 Highway 

study area, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Selected stream-gaging and rain-gaging stations in the windward area of the H-3 Highway study 

area, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3–9. Graphs showing:

3. Mean monthly streamflow at streamflow-gaging station 16229000 and mean monthly upstream 

ground-water withdrawals, Oahu, Hawaii, June 1980–June 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4. Average mean daily streamflow per unit area for the before, during, and after highway construction

periods at streamflow-gaging stations in the H-3 Highway study area, Oahu, Hawaii, 1981–99 . . . . . . 21

5. Mean monthly streamflow at streamflow-gaging station 16270900 and mean monthly upstream 

ground-water withdrawals, Oahu, Hawaii, April 1984–June 1998 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6. Mean monthly streamflow at streamflow-gaging station 16272200 and mean monthly upstream 

ground-water withdrawals, Oahu, Hawaii, water years 1981–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7. Mean daily suspended-sediment yield for the before, during, and after highway construction periods

at sediment-gaging stations in the H-3 Highway study area, Oahu, Hawaii, water years 1981–99 . . . . 30

8. Before, during, and after highway-construction period relations between streamflow and suspendedsediment loads at streamflow and sediment-gaging stations in the H-3 Highway study area, Oahu,

Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
iv Reassessment of Ground-Water Recharge and Ground-Water Availability for the Hawi Area of North Kohala, Hawaii

9. Cumulative streamflow and suspended-sediment loads at streamflow and sediment-gaging stations 

in the H-3 Highway study area, Oahu, Hawaii, 1981–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Tables

1. Locations and period of record at streamflow-gaging stations in and near the H-3 Highway study area,

Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Chronology of highway construction activities within drainage basins of the H-3 Highway study area, 

1983–99, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3. Before, during, and after construction periods at streamflow-gaging stations in the H-3 Highway study 

area, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4. Basin area-weighted median annual rainfall at drainage basins in and near the H-3 Highway study area, 

Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5. Annual instantaneous peak flow at streamflow-gaging stations in and near the H-3 Highway study area, 

Oahu, Hawaii, water years 1971–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6. Annual and average rainfall at rain-gaging stations in and near the H-3 Highway study area, Oahu, Hawaii, 

water years 1983–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

7. Annual total streamflow at streamflow-gaging stations in and near the H-3 Highway study area, Oahu, 

Hawaii, water years 1981–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

8. Analysis of covariance results relating concurrent daily mean streamflow at streamflow-gaging stations 

in the H-3 Highway study area to the index station 16229000 for the before, during, and after highway 

construction periods, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

9. Estimated changes in streamflow at streamflow-gaging stations for the during and after highway construction 

periods in the H-3 Highway study area, Oahu, Hawaii, 1983–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

10. Analysis of covariance results relating instantaneous peak flow at streamflow-gaging stations in the H-3 

Highway study area to index station 16229000 for the before, during, and after highway construction 

periods, Oahu, Hawaii, water years 1971–99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

11. Annual total suspended-sediment loads at sediment-gaging stations in the H-3 Highway study area, Oahu, 

Hawaii, water years 1981–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

12. Analysis of covariance results relating randomly selected daily suspended-sediment loads to mean daily 

streamflow at sediment-gaging stations in the H-3 Highway study area, Oahu, Hawaii. . . . . . . . . . . . . . . . . . . . . 31

13. Estimated changes in suspended-sediment yields at sediment-gaging stations for the before, during, and 

after highway-construction periods in the H-3 Highway study area, Oahu, Hawaii, 1983–99 . . . . . . . . . . . . . . . . 40

14. Estimated changes in observed suspended-sediment yields due to highway construction at sediment-gaging 

stations for the during and after highway-construction periods in the H-3 Highway study area, Oahu, 

Hawaii, 1983–99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
 Contents v

Appendix

1. Daily mean sediment discharge (tons/day) for water year 1996 at sediment-gaging station 16265600, 

Right Branch of Kamooalii Stream near Kaneohe, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

2. Daily mean discharge (cubic feet per second) for water year 1997 at streamflow-gaging station 16273950,

South Fork Kapunahala Stream at Kaneohe, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3. Daily mean sediment discharge (tons/day) for water year 1997 at sediment-gaging station 16273950, 

South Fork Kapunahala Stream at Kaneohe, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

GLOSSARY

Drainage area - An area from which surface runoff or streamflow is carried away by a single drainage system. Also called 

drainage basin.

Regression equation - An equation derived by methods of regression. A mathematical relation between a response variable and 

one or more explanatory variables.

Residuals or regression error - The difference between the observed and computed values derived from a regression equation.

Sediment - Solid material that originates mostly from disintegrated rocks and is transported by, suspended in, or deposited from 

water; it includes chemical and biochemical precipitates and decomposed organic material such as humus.

Streamflow or water discharge - The rate of water flowing past a section of stream channel. Expressed as volume per unit of time, 

such as cubic feet per second.

Suspended-sediment - The sediment that at any given time is maintained in suspension by the upward components of turbulent 

currents or that exists in suspension as a colloid.

Suspended-sediment discharge or load - The rate at which sediment passes a section of a stream or is the quantity of sediment, as 

measured by dry weight, or by volume, that is discharged in a given time. Usually expressed as tons per day.

Suspended-sediment yield - The suspended-sediment discharge or load per unit of drainage area. Expressed as volume per unit 

area, such as tons per square mile.

Water year - The 12–month period, October 1 through September 30. The water year is designated by the year in which it ends. 

Thus, the water year ending September 30, 1999, is called the “1999 water year.”
1

Abstract

A long-term study (1983–99) was conducted 

to determine the effects of the H-3 Highway construction on streamflow and suspended-sediment 

transport on Oahu, Hawaii. Data were collected at 

five streamflow-gaging stations before, during, and 

after construction and at two stream-gaging stations during and after construction. Drainage areas 

at the seven streamflow-gaging stations ranged 

from 0.40 to 4.01 mi2

 and highway construction 

affected from 4 to 15 percent of these areas. Analysis of covariance and regression techniques were 

used to assess changes in streamflow and 

suspended-sediment loads during and after construction, relative to before-construction conditions.

Streamflow at the seven streamflow-gaging 

stations was compared to streamflow at an index 

station unaffected by highway construction. 

Streamflow data were divided into low- and highflow classes, and the two flow classes were analyzed separately. Additionally, instantaneous peak 

flows were analyzed at three streamflow-gaging 

stations. During construction, observed low flows 

significantly increased by 108 percent at Luluku 

Stream, a tributary to Kamooalii Stream, and 

decreased by 31 percent at Kamooalii Stream. 

After construction, low flows increased by 47 percent at North Halawa Stream near Honolulu compared to low flows during construction. Low flows 

at Luluku Stream increased by 99 percent after 

construction compared to before construction. 

Increased low flows were attributed to removal of 

vegetation for construction and the increase of 

impervious areas that reduced infiltration. 

Decreased low flows were attributed to increased 

ground-water withdrawals and construction activities.

High flows observed during highway construction compared to before construction 

increased significantly only at Haiku Stream (by 25 

percent). Observed high flows after construction 

compared to during construction increased significantly only at Kamooalii Stream (by 34 percent). 

Observed high flows after construction compared 

to before construction increased by 58 percent only 

at Luluku Stream. All increases in observed high 

flows are attributed to increased runoff from landuse changes caused by the highway construction. 

Instantaneous peak flows increased significantly at 

Luluku Stream. Luluku Stream had significant 

increases in low and high flows both during and 

after construction.

Suspended-sediment loads changed significantly at six out of seven sediment-gaging stations 

during highway construction. Construction activities increased observed suspended-sediment yields 

by 222, 426, 60, and 148 percent at North Halawa 

Stream near Kaneohe, North Halawa Stream near 

Honolulu, Right Branch Kamooalii Stream, and 

Haiku Stream, respectively. At Luluku Stream, 

observed suspended-sediment yields were lower 

during construction than before construction by 62 

Streamflow and Suspended-Sediment Loads Before, During, 

and After H-3 Highway Construction, North Halawa, Haiku, 

South Fork Kapunahala, and Kamooalii Drainage Basins, 

Oahu, Hawaii, 1983–99

By Michael F. Wong and Daniel S. Yeatts
2 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

percent. After construction, suspended-sediment 

loads also changed significantly at six out of seven 

stream-gaging stations. Observed after-construction yields increased at North Halawa Stream near 

Kaneohe, North Halawa Stream near Honolulu, 

and Right Branch Kamooalii Stream by 49, 205, 

and 36 percent, respectively, and decreased at 

Kamooalii Stream and South Fork Kapunahala 

Stream by 62 and 71 percent. The observed 

increases in yields are smaller after construction 

than during construction indicating that suspendedsediment loads are likely returning to before-construction levels.

The effects of H-3 Highway construction on 

suspended-sediment loads were generally similar 

to studies of the effects of highway construction in 

other areas of the United States where 50 to 85 percent of the sediment loads were attributed to construction activities. The percentages of the 

observed yields attributable to H-3 Highway construction are similar to the above percentages, 

ranging from 37 to 81 percent. Decreases in suspended-sediment loads due to highway construction are unique and have not been widely reported 

in the literature. Where decrease in suspended-sediment loads were determined, land use prior to construction was not pristine.

INTRODUCTION

The H-3 Highway is a major highway across the 

Koolau Range on the eastern part of the island of Oahu, 

Hawaii (fig. 1). Potential effects of construction, such as 

soil erosion and stream sedimentation, on streams along 

the route were an issue of public concern and construction began only after a lengthy environmental evaluation (U.S. Department of Transportation, Federal 

Highway Administration, and State of Hawaii Department of Transportation, 1987). In 1983, the U.S. Geological Survey, in cooperation with the State of Hawaii 

Department of Transportation and Federal Highway 

Administration, began a study to help assess the effects 

of the highway construction on streamflow and suspended-sediment transport in these streams.

Purpose and Scope

The purpose of the study was to compare data collected before, during, and after highway construction to 

determine if construction activities have affected 

streamflow and suspended-sediment transport. The purpose of this report is to identify and quantify effects of 

H-3 Highway construction on streamflow and suspended-sediment loads between 1983 and 1999, which 

included periods before, during, and after construction. 

Statistical methods used in this study follow those used 

by Hill (1996), who conducted a previous analysis using 

data collected from 1981 through 1991 covering before 

and during construction. This report extends the work 

by Hill (1996) through the end of data collection in 

1999.

Rainfall, streamflow, and suspended-sediment 

data collected at a network of stream-gaging stations 

(figs. 1 and 2) were used to determine if streamflow and 

suspended-sediment loads changed significantly during 

and after construction. Changes due to construction 

were quantified by comparing data collected during 

construction to data collected before and after construction. Daily, monthly, and annual values of streamflow, 

suspended-sediment concentration and discharge, and 

suspended-sediment particle size analyses have been 

published in the annual water-resources data reports of 

the U.S. Geological Survey of which Hill and others 

(2000) is an example. Data from two gaging stations 

were not published in the annual data reports because 

the majority of the data were considered interpretive. 

These data are for station 16265600, water year 1996, 

suspended-sediment discharge and for station 

16273950, water year 1997, streamflow and suspendedsediment discharge. Estimates and data for both these 

stations are presented at the end of the report in appendix 1 through 3. Additional streamflow and suspendedsediment data collected from 1981 were used at station 

16272200 and additional peak flow data from 1971 

were used at stations 16226000, 16270900, and 

16275000. Additional streamflow data collected at station 16226000 in North Halawa Valley was used to help 

analyze streamflow data at another North Halawa 

Stream station, 16226200. Station numbers are used 

throughout the report to refer to locations of data collection and their corresponding drainage basins. Table 1 

lists station numbers and their corresponding station 

names, drainage areas, locations, and periods of streamflow and suspended-sediment record.
Introduction 3

H-3 Highway Construction

The H-3 Highway route traverses the drainage 

basins of North Halawa, Haiku, Kapunahala, and 

Kamooalii Streams (figs. 1 and 2). The H-3 Highway 

extends from the H-1 Highway near the East Loch of 

Pearl Harbor on the leeward (southwestern) side of the 

Koolau Range to the Halekou Interchange on the windward (northeastern) side, where the H-3 Highway connects to a previously constructed section of highway 

leading from Kamehameha Highway to Kaneohe 

Marine Corps Base Hawaii. The completed H-3 

Highway consists of both on-surface cut-and-fill and 

raised viaduct sections in the lower North Halawa Valley, a viaduct through the upper North Halawa Valley, 

twin tunnels below the crest of the Koolau Range, a viaduct through the Haiku drainage basin, and a cut-andfill section through the Kapunahala and Kamooalii 

drainage basins (U.S. Department of Transportation, 

Federal Highway Administration and State of Hawaii 

Department of Transportation, 1987). Highway construction affected from 4 to 15 percent of the drainage 

basin areas upstream in the H-3 Highway study area.

Construction of the H-3 Highway proceeded in 

increments (table 2). Construction was at times halted 

by court actions, and the planned route was modified to 

avoid sites of cultural importance. Access roads were 

built in the North Halawa and Haiku Valleys before 

construction of the highway. An exploratory tunnel was 

excavated below the crest of the Koolau Range before 

the larger, traffic tunnels were excavated.

Erosion-control measures were used throughout 

construction of the H-3 Highway to reduce sediment 

delivery from construction areas in all affected drainage 

basins. These measures included silt fence barriers 

installed on hillslopes and along channels, loose-rock 

check dams in channels, and hydro mulching and installation of plastic fabric netting on cut-and-fill slope 

faces. Streamflow in several channel reaches in upper 

portion of the North Halawa Valley was diverted into 

culverts, which were then buried, during construction to 

prevent sediment disturbed by construction from reaching the stream.

Table 1. Locations and period of record at streamflow-gaging stations in and near the H-3 Highway study area, Oahu, Hawaii

[mi2, square miles; horizontal datum for latitude and longitude coordinates is Old Hawaiian]

1 Streamflow data were previously collected 1929–33

2

 Streamflow data were previously collected September 1913–April 1914 3

 Streamflow data were previously collected 1960–63 (low flows only), 1965–71, 1971–84 (annual maximum only) 4 Streamflow data were previously collected 1914–19, 1939–77

5 Suspended-sediment data were previously collected December 1983 to September 1984

Station 

number Station name

Drainage

area

(mi2

)

Latitude Longitude

Period of 

streamflow 

record

Period of suspendedsediment record

16225800 North Halawa Stream near Kaneohe 1.64 21°24′33′′ 157°52′06′′ Apr 1991 to 

Sept 1999

Apr 1991 to 

Sept 1999

16226000 North Halawa Stream near Aiea 3.45 21°23′46′′ 157°53′37′′ 1July 1953 to 

present

None

16226200 North Halawa Stream near Honolulu 4.01 21°23′04′′ 157°54′22′′ Feb 1983 to 

present

Feb 1983 to 

Sept 1999

16229000 Kalihi Stream near Honolulu 2.61 21°22′00′′ 157°50′49′′ 2July 1914 to 

present

None

16265600 Right Branch Kamooalii Stream near 

Kaneohe

1.11 21°23′22′′ 157°47′44′′ Feb 1983 to 

Sept 1997

Feb 1983 to 

Sept 1997

16270900 Luluku Stream at altitude 220 feet 

near Kaneohe

0.44 21°23′42′′ 157°48′44′′ 3Apr 1984 to 

June 1998

Apr 1984 to 

June 1998

16272200 Kamooalii Stream below Luluku 

Stream near Kaneohe

3.81 21°23′47′′ 157°48′23′′ Nov 1976 to 

present

Nov 1976 to 

Sept 1998

16273950 South Fork Kapunahala Stream at 

Kaneohe

0.40 21°24′21′′ 157°48′31′′ Oct 1987 to 

June 1998

Oct 1987 to 

June 1998

16275000 Haiku Stream near Heeia 0.97 21°24′46′′ 157°49′33′′ 4Oct 1982 to 

present

5July 1987 to Sept 

1998
4 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

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Nor ht Ha

al

wa Stream

Moanalua

Stream

aK hl i Stream

East Loch

PEARL HARBOR

KANEOHE

BAY

Waimaluhia

Res

16229000

21°26'21°22'

157°52' 157°56' 157°48'

0

0

3 MILES 2

2 3 KILOMETERS

1

1

Kaneohe

Marine Corps

Base Hawaii

H-3 Ro t u e

H 3- Rou

et

Maunawili

Ranch

TRANS-KOOLAU

TUNNEL

WILSON

TUNNEL

KOOLAU

RANGE

EXPLANATION

Kamehameha Highway

H-1 Highway

Moanalua

Freeway

L

ki el ki e

H

gi hway

Pali H

gi hway

Ford

Island

NORTH HALAWA HAIKU

KAMOOALII

LULUKU

RIGHT

BRANCH

 KAMOOALII

SOUTH FORK

KAPUNAHALA

DRAINAGE BASIN AND NAMEDRAINAGE DIVIDESTREAM-GAGING STATION AND STATION NUMBERRAIN GAGE AND STATE KEY NUMBER

16225800

16226000

16226200

16226200

771.9

771.9

771.2

772.1

22°20°

158° 156° 160°

PACIFIC

OCEAN

Kauai

Niihau

Oahu

Maui

Molokai

Lanai

Kahoolawe

Hawaii

HAWAII OAHU

Area

of map

Pacific

Ocean

Base modified from U.S. Geological Survey digital data, 1:24,000, 1983, Albers equal area projection, standard parallels 21 ̊19'40" and 21 ̊38'20", central meridian 157 ̊58'

Figure 1. Selected stream-gaging and rain-gaging stations and drainage basins in and near the H-3 Highway study area, Oahu, Hawaii.
Introduction 5

Figure 2. Selected stream-gaging and rain-gaging stations in the windward area of the H-3 Highway study area, Oahu, Hawaii.

Base modified from U.S. Geological Survey digital data, 

1:24,000, 1983, Albers equal area projection, 

standard parallels 21 ̊19'40" and 21 ̊38'20", 

central meridian 157 ̊58'

Kamehameha Highway

Kaneohe Bay Drive

Trans-Koolau

Tunnel

Ho'omaluhia

Botanical Garden

Koolau

Golf

Course

NUUANU

VALLEY

KANEOHE

 BAY

Kahekili Highway

H-3 Higway

Pali

Golf

Course

Hawaii Loa

Campus

Kaneohe

Interchange

Halekou

Interchange

Kalanianaole

Highway Right Branch

Kamooalii Stream

Kamooalii

Pali Highway

RANGE

KOOLAU

157 ̊49' 157 ̊46'30"

21 ̊

25'

21 ̊

22'

30"

H-3 Highway

Likelike Highway

EXPLANATION

DRAINAGE DIVIDE

STREAM-GAGING STATION

 AND STATION NUMBER

RAIN GAGE AND STATE KEY

 NUMBER

0 

0 1 KILOMETER 

1/2 1 MILE

OAHU,

HAWAII

Windward

Oahu H-3

Study Area

Pacific

Ocean

Iolekaa Stream

Heeia

Stream

Stream

Stream

Haiku

Kapunahala

South Fork

Kapunahala

Stream

Kuou

Piho Stream

Hooleinaiwa Stream

Kamooalii Stream

Kaneohe Stream

Luluku Stream

Stream

Waimaluhia

Reservoir

16272200

16275000

16275000

16273950

781.11

781.7

788.1

839.3

781.4

781.9

16265600

16270900
6 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Table 2. Chronology of highway construction activities within drainage basins of the H-3 Highway study area, 1983–99, Oahu, 

Hawaii

[Locations of streamflow-gaging stations are shown in figures 1–2; do., ditto. Start and end dates provided by the State of Hawaii, Department of 

Transportation, (written commun., 1999)]

1 Data collection did not start until April 1991

2 This is the official completion date for all work on the tunnel, however for the Haiku Valley portion of the tunnel construction, all land disturbance work was completed by 11/94, so for the purpose of determining the post-construction dates, 11/94 will be used. In North Halawa Valley, channel and earthwork by the tunnel continued until 09/97, so 09/30/97 will be used for the purpose of determining the post-construction 

dates.

3 Same construction activities and dates apply to station 16226000 except for N. Halawa Valley highway Unit I Phase 1A 4 Work on Halekou Interchange interrupted multiple times by court injunctions 5 Includes highway construction activities listed under stations 16265600 and 16270900, as these drainage basins drain into Kamooalii Stream

Station Drainage basin and highway construction activities Start date End date

16225800 N. Halawa Stream1

Trans-Koolau tunnel.............................................................................. 03/19/91 02/07/982

N. Halawa viaduct................................................................................. 02/21/92 06/95

16226200 N. Halawa Stream3

N. Halawa access road.......................................................................... 11/02/87 03/89

Exploratory tunnel ................................................................................ 02/27/89 03/90

Drilled shaft test program...................................................................... 11/13/90 02/91

Trans-Koolau tunnel.............................................................................. 03/19/91 02/07/982

N. Halawa viaduct................................................................................. 02/21/92 06/95

N. Halawa Valley highway Unit I Phase 1A........................................... 04/11/94 09/95

N. Halawa Valley highway Unit I Phase 1B........................................... 05/24/95 12/12/97

N. Halawa Valley highway Unit II......................................................... 08/01/94 12/12/97

16265600 Right Branch Kamooalii Stream

Halekou Interchange4............................................................................ 02/22/83 12/01/83

do............................................................................................. 03/02/84 07/31/85

do............................................................................................. 11/04/85 02/28/86

do............................................................................................. 11/02/86 12/31/86

do............................................................................................. 06/15/87 09/30/88

Windward highway............................................................................... 06/19/89 06/92

16270900 Luluku Stream

Windward highway............................................................................... 06/19/89 06/92

Kaneohe Interchange............................................................................ 01/19/93 12/22/95

16272200 Kamooalii Stream5

Windward highway............................................................................... 06/19/89 06/92

16273950 S. Fork Kapunahala Stream

Hospital Rock tunnel............................................................................. 03/06/89 05/92

Kaneohe Interchange............................................................................ 01/19/93 12/22/95

16275000 Haiku Stream

Haiku access road................................................................................. 10/24/88 06/90

Exploratory tunnel................................................................................. 02/27/89 03/90

Haiku Valley bridges............................................................................. 08/07/89 03/91

Windward viaduct ................................................................................ 01/08/90 05/13/93

Trans-Koolau tunnel.............................................................................. 10/01/90 02/07/982
Introduction 7

Study Area

The Koolau Range is the eroded remnant of the 

larger and younger of the two major shield volcanoes 

that formed the island of Oahu (Hunt, 1996). Much of 

the windward side of the original Koolau Volcano has 

been eroded, leaving a steep windward slope indented 

with short, broad, amphitheater-shaped valleys (Hinds, 

1925). In contrast, the gentle leeward slope is deeply 

dissected by long, roughly linear valleys.

Geology of the study area consists primarily of 

Koolau Basalt that was extruded in numerous gently 

dipping thin (average of less than 10 ft) flows of lava 

that are intruded by near-vertical dense basaltic dikes 

near the crest of the present Koolau Range (Hunt, 

1996). More recent volcanic rocks are exposed in small 

areas on the windward side of the study area (Takasaki 

and others, 1969). The gently sloping lower parts of the 

windward drainage basins and the valley floor of the 

North Halawa drainage basin are underlain by alluvium 

derived from erosion of the Koolau Range (Takasaki 

and others, 1969; Izuka, 1992).

The climate of Oahu is warm and humid. Average 

annual temperature near the study area is about 74°F 

and monthly averages range from 65°F to 84°F 

(Owenby and Ezell, 1992). Temperatures above 95°F 

and below 50°F are rare on Oahu (Blumenstock and 

Price, 1967). The distribution of rainfall is affected by 

the prevailing northeasterly trade winds and the topography of the island. Because of the Koolau Range, 

which has an altitude range of 2,000 to 3,000 ft above 

mean sea level, there is orographic lifting and cooling of 

marine air masses moving with the trade winds which 

result in heavier and more frequent rainfall on the windward side and near the crest of the Koolau Range. The 

heaviest rainfall occurs about 0.5 to 1 mi leeward of the 

crest (C.K. Wentworth, Honolulu Board of Water Supply, written commun., 1942; Mink, 1960). Rainfall varies seasonally, with most rainfall falling between 

November and April. Median annual precipitation 

ranges from 60 to 120 in. on the windward side of the 

study area, and from 40 to more than 120 in. on the leeward side (Division of Water and Land Development, 

1982). Average annual pan evaporation is between 50 to 

60 in. on the windward side and between 30 to 70 in. on 

the leeward side of the study drainage basins (Ekern and 

Chang, 1985).

The temporal and spatial distribution of streamflow in the study area is determined almost exclusively 

by geology and climate. Streams on the windward side 

respond rapidly to the direct runoff that takes place during heavy rainfall. Large quantities of rainfall and the 

presence of numerous low-permeability dikes result in 

storage of high-level ground water that maintains the 

base flow of streams on the windward side (Takasaki 

and others, 1969). As a result of the highly permeable 

bedrock and the orientation of dikes, ground water is 

known to flow between windward drainage basins. 

Rainfall infiltrating in one valley may emerge as 

streamflow in another (Hirashima, 1963; 1971; 

Takasaki and others, 1969). On the leeward side of the 

Koolau Range, dikes are uncommon (Takasaki and 

Mink, 1985). Most infiltrating rainfall in the North Halawa Valley percolates to the basal aquifer and does not 

maintain base flows in the streams located there (Izuka, 

1992). Streamflow in North Halawa Stream is intermittent and is dependent primarily on direct runoff that 

occurs during heavy rainfall. Streamflow is supplemented by the discharge of small quantities of ground 

water from alluvial aquifers that extend recession 

streamflows from rainfall only to a minor extent (Izuka, 

1992).

The dramatic topography of the study area has 

been attributed to chemical weathering (Wentworth, 

1928; Scott and Street, 1976), stream piracy (Wentworth, 1928; Stearns and Vaksvik, 1935), rapid weathering at the water table (Wentworth, 1928), and plungepool erosion and ground-water sapping or piping 

(Stearns and Vaksvik, 1935). The most obvious process 

of physical erosion is mass wasting of shallow soil and 

saprolite (weathered bedrock) on steep hillslopes in 

areas of high rainfall (Stearns and Vaksvik, 1935; 

Wentworth, 1943; White, 1949; Scott and Street, 1976; 

Wilson and others, 1992). Processes observed during 

the period of this study included numerous debris flows 

in North Halawa Valley (Hill and others, 1998), plunge 

pool erosion in all streams in the study area, and 

ground-water sapping at stations 16265600 and 

16275000.

Soils in the North Halawa drainage basin are classified as low permeability, very stony clays of the 

Kaena series (Foote and others, 1972). Soils in the 

Haiku, South Fork Kapunahala, and Kamooalii drainage basins are classified as Lokelaa with some Kaneohe 

and Hanalei series silty clays. These types of silty clays 

have moderate permeability and are highly erodible on 
8 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

steep slopes (Foote and others, 1972). Most of the 

mountainous areas in the study area are classified as 

rough mountainous land, rock land, or rock outcrop 

(Foote and others, 1972), and little information is available on the soils of these areas.

The study area is completely covered with one 

form or another of vegetation, except for several areas 

of urban development. Most of the native vegetation on 

the windward side of the Koolau Range has been 

replaced by cultivated crops, non-native plants, and residential and commercial developments. Vegetation in 

the North Halawa Valley is representative of undisturbed forest on the leeward side of the Koolau Range 

and includes both native and non-native species.

North Halawa.--The North Halawa drainage basin 

is on the leeward side of the crest of the Koolau Range. 

North Halawa Stream joins the South Halawa Stream 

downstream of stream-gaging station 16226200 (fig. 1) 

before flowing into the East Loch of Pearl Harbor. The 

drainage area upstream of station 16226200 is 4.01 mi2

and altitudes range from 160 to 2,800 ft above mean sea 

level. The stream gradient of North Halawa Stream is 

0.077 ft/ft. The lower valley of North Halawa is deeply 

incised, with only a few small ephemeral tributaries. 

The stream channel in the lower valley is cut about 3 to 

6 ft into the alluvium that forms the valley floor. The 

steep upper part of the drainage basin is less deeply 

incised, and has a dendritic drainage pattern with several intermittent tributaries. In the upper part of the 

drainage basin, channels are cut into bedrock and 

include several waterfalls. The stream is more than 100 

ft above the freshwater-lens water table throughout the 

valley (Izuka, 1992), and flow in the main channel is 

intermittent in most years.

The H-3 Highway constitutes about 4 percent of 

the drainage area upstream of station 16226200. Before 

highway construction began in November 1987, this 

drainage basin was undeveloped but the lower valley 

was used for agriculture from 1850 to 1947 (Spear, 

1990). A major water source, the Halawa Shaft, built by 

the Honolulu Board of Water Supply in 1940 to collect 

ground water from the freshwater lens is located 200 ft 

downstream from station 16226200. Pumpage from the 

Halawa Shaft does not affect streamflow at station 

16226200 (Izuka, 1992). There are no streamflow 

diversions in the drainage basin except for the temporary channel diversions that were related to highway 

construction. The temporary diversions did not transfer 

surface water out of the drainage basin. Rainfall, 

streamflow, and suspended-sediment data collection at 

station 16226200 began in February 1983. Suspendedsediment data collection ended in September 1999. 

Rainfall and streamflow data have been continuously 

collected at station 16226000 (fig. 1), which is located 

1.3 mi upstream of 16226200, since 1953. Peak flow 

data from 16226000 was used to determine if the highway had an effect on peak flows due to the long period 

of annual peaks at station 16226000. No streamflow 

data analysis was done on streamflow data collected at 

station 16226000 because mean daily streamflow data 

between 1622600 and 16226200 from February 1983 to 

September 1999 is highly correlated (linear correlation 

coefficient of 0.99) so results from station 16226200 

data should be representative of station 16226000. No 

suspended-sediment data were collected at 16226000.

Data collection at station 16225800 (fig. 1) began 

in April 1991 and ended in September 1999. This station was established during the period of highway construction to help differentiate the suspended-sediment 

contributions of the upper North Halawa Valley, where 

construction was all viaduct, and the lower valley, 

where construction included both viaduct and cut-andfill. The drainage area upstream of station 16225800 is 

1.64 mi2

 and altitudes range from of 646 to 2,800 ft 

above mean sea level. The stream gradient upstream of 

this station is 0.151 ft/ft, substantially steeper then the 

stream gradient upstream of station 16226200 which is 

0.077 ft/ft. 

During the period of highway construction about 

3,600 ft of stream channel was lined with concrete and 

boulders upstream of station 16225800 and about 2,000 

ft of channel was lined downstream of station 16225800 

but upstream of station 16226200 (Richard Dahilig, 

Parsons Brinckerhoff-Hirota Associates, written commun., 1999). The 3,600 ft of lined channel is about 43 

percent of the channel length from the Trans-Koolau 

tunnel to station 16225800. The 2,000 ft of lined channel between stations 16225800 and 16226200 represents about 10 percent of the channel length between the 

two stations. The total 5,600 ft of lined channel represents about 20 percent of the channel length from the 

Trans-Koolau tunnel to station 16226200.

Large amounts of material were removed and 

deposited in the valley during various phases of the construction. Construction of the access road, exploratory 

tunnel and Trans-Koolau tunnel (table 5) removed 
Introduction 9

530,000,000 cubic yards and filled 95,400,000 cubic 

yards (Q.D. Truong, Parsons Brinckerhoff, Quade, and 

Douglas, Inc., written commun., 1993). During construction of the North Halawa viaduct and Highway 

units I and II (table 2) about 350,000 cubic yards of 

material was excavated and 59,800 cubic yards filled 

upstream of station 16225800 and about 578,000 cubic 

yards was cut and 286,000 cubic yards was filled downstream of station 16225800 but upstream of station 

16226200 (Richard Dahilig, Parsons BrinckerhoffHirota Associates, written commun., 1999). Excavated 

material not used as construction fill was deposited at 

disposal sites in the valley.

Haiku.--The Haiku drainage basin is on the windward side of the Koolau Range and adjoins the North 

Halawa drainage basin along the crest of the range (fig. 

2). The drainage area upstream of stream-gaging station 

16275000 is 0.97 mi2

, and altitudes range from 272 to 

2,500 ft. The stream gradient is 0.390 ft/ft. The headwaters of Haiku Stream consist of steep cliffs where water 

flows over exposed bedrock and saprolite. An alluviated 

valley floor occupies the lower parts of the drainage 

basin, where the channel is composed mostly of boulders and cobbles. Perennial streamflow begins at about 

an altitude of 500 ft and continues downstream past station 16275000 (Izuka and others, 1993). Haiku Stream 

joins Iolekaa Stream downstream of station 16275000 

to form Heeia Stream, which flows into Kaneohe Bay 

(fig. 2).

Almost all of the drainage basin upstream of station 16275000 was part of a U.S. Coast Guard navigational facility which was operated from 1944 to 

September 30, 1997. A municipal well and water development tunnel are located upstream of station 

16275000. The tunnel was constructed in 1940; the well 

was brought into service during the H-3 Highway construction period in 1989. Highway construction in the 

Haiku drainage basin began in October 1988 (table 2). 

The portion of the H-3 Highway located within the 

Haiku drainage basin was constructed entirely as a viaduct, and covers about 3 percent of the drainage area 

upstream from station 16275000. Construction activities in the basin included excavation of about 256,000 

cubic yards of material and fill of about 92,500 cubic 

yards (Emilio Barroga Jr., State of Hawaii, Department 

of Transportation, written commun., 2000). 

Streamflow data were collected before this study at 

station 16275000 from 1914 through 1919 and from 

1939 through 1977. Streamflow data collection for the 

H-3 Highway study began in October 1982, and suspended-sediment data were collected from December 

1983 through September 1984 and from July 1987 

through September 1998.

South Fork Kapunahala.--The South Fork 

Kapunahala drainage basin lies to the southeast of the 

Haiku drainage basin (fig. 2). The drainage area 

upstream from station 16273950 is of 0.40 mi2

, and altitudes range from 111 to 2,800 ft above mean sea level. 

The stream gradient is 0.394 ft/ft. The headwaters of 

this small basin start in the steep cliffs of the Koolau 

Range and flow is perennial downstream from about the 

200 ft elevation. The drainage basin consists of residential and agricultural lands. The stream channel consists 

mostly of boulders, cobbles, and gravel. H-3 Highway 

construction began in March 1989 in the drainage basin 

(see table 5), with the construction activities occurring 

in the upper basin near the 400 ft elevation and in the 

lower basin starting in January 1993. The H-3 Highway 

covers about 15 percent of the drainage area upstream 

of station 16273950 and not 3 percent as previously 

published (Hill 1996; Wong and Young, 2001). During 

construction about 779,000 cubic yards of material were 

removed and 771,000 cubic yards were filled. (Emilio 

Barroga Jr., State of Hawaii, Department of Transportation, written commun., 2000.) Streamflow and suspended-sediment data were collected from October 

1987 to June 1998.

Kamooalii.--The Kamooalii drainage area 

upstream of stream-gaging station 16272200 is 3.81 

mi2, and altitudes range from 116 to 2,820 ft above 

mean sea level (fig. 2). The Kamooalii drainage basin 

includes the 1.11 mi2 Right Branch Kamooalii drainage 

basin upstream of stream-gaging station 16265600 and 

the 0.44 mi2 Luluku drainage basin upstream of streamgaging station 16270900. Streamflow is perennial at all 

three stations. Kamooalii Stream joins Kapunahala 

Stream downstream of station 16272200 to form 

Kaneohe Stream, which flows into Kaneohe Bay. 

Waimaluhia Reservoir, a 26-acre flood-control reservoir, was constructed between 1976 to 1981 upstream 

of the confluence of Luluku and Kamooalii Streams. 

Streamflow at station 16272200 includes water flowing 

through Waimaluhia Reservoir and water from Luluku 

Stream that does not pass through the reservoir. The 

stream gradient upstream of station 16272200 is 0.094 

ft/ft. The channels within the drainage basin are cut 

between 2 and 20 ft into alluvium, and are composed 
10 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

mainly of cobbles and gravel intermixed with finer sediment.

The Hoomaluhia Botanical Garden surrounding 

the Waimaluhia Reservoir is a public park operated by 

the City and County of Honolulu (fig. 2). Below the 

Botanical Garden, most of the drainage basin has been 

developed for residential use. Upstream of the Botanical 

Garden to the east and southeast is the Pali Golf Course 

built in 1957, the Koolau Golf Course built between 

1989 and 1991, and the Hawaii Loa Campus of Hawaii 

Pacific University (fig. 2). The remaining land area in 

the Kamooalii drainage basin is banana plantations or 

undeveloped land. Parts of both Likelike and Pali Highways cross the drainage basin near the Koolau Range 

(fig. 2).

Several municipal wells and a water development 

tunnel are located in the Kamooalii drainage basin, 

including two wells that were brought into operation 

during the H-3 Highway-construction period. Two private wells that are used for golf course irrigation were 

drilled upstream from station 16265600 during the construction period. Average yearly pumpage from the 

municipal wells and tunnel from 1983 to 1999 was 

about 3 to 4 Mgal/d (data from Honolulu Board of 

Water Supply annual reports, 1981–99). Average yearly 

pumpage from 1990 to 1997 from the golf course wells 

was about 0.15 Mgal/d (computed from data provided 

by Neal Fujii, Commission on Water Resource Management, Department of Land and Natural Resources, State 

of Hawaii, written commun., 2000). Water is sometimes 

pumped from Luluku Stream upstream from station 

16270900 to irrigate banana plantations.

Highway construction in the Kamooalii drainage 

basin began in 1983 (table 2). The H-3 Highway constitutes about 4 percent of the drainage area upstream from 

station 16272200. The area affected by the H-3 Highway includes about 5 percent, not 11 percent as previously published (Hill, 1996; Wong and Young, 2001), 

of the drainage area upstream from station 16270900 

and about 5 percent of the drainage area upstream from 

station 16265600. A total of about 800,000 cubic yards 

of material was excavated and 700,000 cubic yards 

filled during construction in the Kamooalii drainage 

basin (Emilio Barroga Jr., State of Hawaii, Department 

of Transportation, written commun., 2000). 

Streamflow and suspended-sediment data collection at station 16272200 began in 1976 and suspendedsediment data collection ended in September 1998. Data 

from October 1980, after dam closure for the Waimaluhia Reservoir, through September 1998 are used in this 

report. Streamflow and suspended-sediment data collection at station 16265600 started in February 1983 and 

ended in September 1997. At station 16270900, streamflow and suspended-sediment data were collected from 

April 1984 to June 1998. Streamflow data previously 

were collected at station 16270900 from 1960–63 (low 

flow only), 1965–71, and 1971–84 (annual maximum 

only).

Streamflow index station.--Streamflow data from 

gaging station 16229000, Kalihi Stream, was used an 

index or control for the statistical analyses described 

below. The Kalihi drainage basin is on the leeward side 

of the Koolau Range directly to the southwest of the 

Kamooalii drainage basin (fig. 1). The Kalihi drainage 

area upstream of station 16229000 is 2.61 mi2, and altitudes range from 116 to 2,700 ft above mean sea level. 

Land use in the Kalihi drainage basin is about 1 percent 

residential near gaging station 16229000 and the Likelike Highway and Wilson Tunnel, built in the 1950s, 

occupies about 1 percent of the drainage area along the 

length of the Kalihi Valley (fig. 1). The remaining area 

is entirely covered with native and non-native vegetation. Streamflow at station 16229000 was unaffected by 

H-3 Highway construction, diversions, or any major 

change in land use. Water was withdrawn from tunnels 

until March 1989 and an aerator well since March 1989 

upstream of the station, but these withdrawals were 

small, average yearly pumpage was 0.10 Mgal/d from 

1981–99 (data from Honolulu Board of Water Supply 

annual reports, 1981–99) in comparison to streamflow 

and were nearly constant during the study period (fig. 

3).

Previous Studies

Hill (1996) discussed the construction effects of 

the H-3 Highway up to 1991 on the streamflow and

suspended-sediment loads at stations 16226200, 

16265600, 16270900, 16272200, and 16272200. Hill 

(1996) concluded that low flows increased at station 

16270900 and decreased at station 16272200 during 

construction, and that suspended-sediment loads 

increased at station 16226200, 16265600, and 

16275000, did not change at station 16272200, and 

decreased at station 16270900 as a result of highway 

construction.
Introduction 11

Hill (1996) also summarized previous studies of 

suspended-sediment yields from drainage basins along 

the Koolau Range. Suspended-sediment yields on the 

leeward side of the Koolau Range ranged from 24 to 

1,770 (tons/mi2

)/yr while yields from windward drainage basins ranged from 8.6 to 1,400 (tons/mi2)/yr. Hill 

(1996) derived two regression equations using the previously published suspended-sediment yields and 

before-construction suspended-sediment yields from 

gages in this study. These two equations, one for leeward basins and one for windward basins, can be used 

for estimating suspended-sediment yields from available streamflow data along the Koolau Range.

No previous studies of hydrologic effects of highway construction are available for Oahu or other similar 

central Pacific islands. Investigations from other locations, however, can provide some indication of the 

potential effects of road building. Studies dealing with 

streamflow changes attributable to construction of logging roads in the Pacific Northwest region of the continental United States showed that peak flows 

significantly increased only if roads and other compacted surfaces constituted at least 12 percent of drainage basin area (Harr and others, 1975; Ziemer, 1981; 

and King and Tennyson, 1984). These studies were conducted in small, less than 0.57 mi2

, drainage basins 

where rainfall was the dominant form of precipitation. 

These studies did not detect changes in other streamflow characteristics except for King and Tennyson 

(1984), who determined statistically significant changes 

in high flows, one increasing and one decreasing, in two 

out of seven basins monitored. Both basins had about 4 

percent of their area affected by logging road construction.

Several studies have evaluated changes in sediment loads following highway construction in small 

drainage basins located in the eastern United States. 

Vice and others (1969) studied a 4.54 mi2 drainage 

basin with 11 percent of the area affected by highway 

construction and 30 percent by farming and concluded 

Figure 3. Mean monthly streamflow at streamflow-gaging station 16229000 and mean monthly upstream ground-water withdrawals, Oahu, 

Hawaii, June 1980–June 1999.

0

5

10

15

20

25

30

35

40

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

MEAN MONTHLY STREAMFLOW AND GROUND-WATER WITHDRAWALS,

IN CUBIC FEET PER SECOND 

GROUND-WATER WITHDRAWALS

 (Data from Honolulu Board

 of Water Supply)

STREAMFLOW

YEAR
12 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

that 85 percent of the total sediment load was due to 

highway construction. Eckhardt (1976) monitored a 

1.99 mi2 drainage basin with 1 percent of the area 

affected by highway construction and 38 percent by 

farming. Eckhardt (1976) attributed 50 percent of the 

suspended-sediment load to highway construction. 

Reed (1980) studied several small drainage basins ranging from 0.38 to 0.77 mi2

 in size with highway construction affecting from 5 to 12 percent of the basin areas and 

farming less than 10 percent and determined that 63 to 

79 percent of the suspended-sediment load was due to 

highway construction. Ward and Appel (1988) monitored a 4.54 mi2

 relatively pristine drainage basin with 

6 percent of the basin area disturbed by 

highway construction, and attributed 50 percent of the 

suspended-sediment load to highway construction. 

Ward and Appel (1988) also monitored a much larger 

862 mi2 drainage basin, and could not detect any 

changes in suspended-sediment load due to highway 

construction in the larger basin.

A statistical summary of hydrologic and waterquality data collected in the H-3 study area for water 

years 1983–89 was presented in Wong and Hill (1992). 

Wong and Young (2001) presents an updated statistical 

summary of hydrologic and water-quality data through 

water year 1999. This summary presented annual rainfall, streamflow, suspended-sediment loads, particle 

size, and concentrations, and water-quality data from 

streamflow and suspended-sediment gaging stations in 

the H-3 study area.

Additional background information on the H-3 

Highway study area can be found in the many Environmental Impact Statements (EIS) such as U.S. Department of Transportation, Federal Highway 

Administration, and State of Hawaii Department of 

Transportation (1987). Information on individual drainage basins in the study area have been presented in other 

studies. Izuka (1992) discusses the geology and lowflow characteristics of North Halawa Valley. Hill and 

DeCarlo (1991) analyze sediment mineralogy and suspended-sediment concentrations before and during 

highway construction in North Halawa and Haiku Valleys using data from 1983–89. Hillslope soil-erosion 

rates were determined for North Halawa Valley by Hill 

and others (1997). A sediment budget and an analysis of 

sediment budget errors using sediment fingerprinting 

techniques for North Halawa Valley can be found in 

Hill and others (1998). This study concluded that 33 

percent of the fine (less than 62 micron) suspendedsediment load in water year 1991 and 90 percent of the 

fine suspended-sediment load in water year 1992 were 

due to highway construction (Hill and others, 1998). An 

analysis of the sedimentation of Waimaluhia Reservoir 

can be found in Wong (2001) which concludes that the 

rate of sedimentation from 1983 to 1998 did not exceed 

the design rate of 2.0 acre-ft per year.

Acknowledgments

The authors gratefully acknowledge retired U.S. 

Geological Survey employees Harold Sexton, George 

Dayag, and Frank Romualdo for their assistance with 

instrumentation and data collection. Mr. Ted Kamisato 

assisted in collecting suspended-sediment samples at 

station 16265600. Start and end dates for highway construction activities were provided by Dennis Higa, Earl 

Kobataki, and Emilio Barroga Jr. of the State of Hawaii 

Department of Transportation. Ground-water withdrawal data from the Koolau Golf Course wells were 

provided by Neal Fujii of the State of Hawaii Commission on Water Resource Management. Streamflowgaging stations 16226000, 16275000, and 16272200 

were operated in cooperation with the State of Hawaii 

Commission on Water Resource Management, Honolulu Board of Water Supply, and the U.S. Army Corps 

of Engineers, respectively. Suspended-sediment data 

from 1976 to 1997 at station 16272200 were collected 

in cooperation with the U.S. Army Corps of Engineers.

APPROACH

The approach used in this study is a statistical comparison of data collected before and after highway construction with data collected during construction and a 

comparison of data collected before construction with 

data collected after construction. The first two comparisons were done to determine the effects of construction 

on streamflow and suspended-sediment loads in the 

affected basins, and the last comparison was done to see 

if streamflow and suspended-sediment loads after construction had returned to before-construction levels. 

Streamflow data used in this report are daily mean values, unless otherwise noted, and the first day of construction upstream of each gaging station was used to 

define the periods before and during construction, and 

the last day of construction was used to define the periods during and after construction (tables 2 and 3). These
Approach 13

periods are not the same at all stations because start 

dates for data collection and for construction varied. 

Stream-gaging stations 16226200, 16270900, 

16272200, 16273950 and 16275000 have reasonably 

long periods of data before and during construction 

(table 3). Stream-gaging station 16265600 has only a 

few days of before-construction data, and this short 

period is not sufficient for the before- and duringconstruction analyses described below. Streamflow and 

suspended-sediment data are available only after construction began at stream-gaging station 16225800 and 

so cannot be used to compare streamflow and 

suspended-sediment loads before and during construction.

Statistical procedures used in data analysis were 

designed to remove the variations in streamflow and 

suspended-sediment loads that resulted from changes in 

rainfall. Since streamflow generally increases when 

rainfall increases, and sediment transport is in part a 

function of streamflow. Periods with high rainfall tend 

to have higher streamflow and sediment loads than periods of low rainfall, even in the absence of highway construction or other land-use effects. By minimizing the 

effects of rainfall fluctuations, the remaining variability 

could then be attributed to land-use effects. Effects of 

rainfall were minimized by using analysis of covariance 

procedures (Helsel and Hirsch, 1992; Wildt and Ahtola, 

1978). Analysis of covariance is a linear regressionbased procedure that assesses relations between two 

hydrologic variables during different time periods. In 

this case, the time periods were the periods before and 

during, during and after, and before and after construction of the H-3 Highway. The use of the term “time 

period” in this report refers to the periods before, during, and after construction listed in table 3. One of the 

variables, known as the explanatory variable or covariate, represented natural variations resulting from rainfall, with no effect from highway construction. The 

other variable is known as the response variable. The 

response variable was potentially subject to effects of 

highway construction. The analysis of covariance tested 

whether the relation between the covariate and the 

response variable changed significantly during construction. If a significant change was detected, it was 

considered the result of a change in drainage-basin conditions that coincided with construction. Hydrologic 

significance was tested by comparing observed streamflows with estimates of streamflow derived from the 

regression equations determined by analysis of covariance. Differences larger than the accuracy of the 

streamflow data were considered significant. Accuracy 

in this context is equivalent to the margin of error. 

Accuracy of streamflow records are rated on an annual 

basis as “good,” “fair,” or “poor” (Hill and others, 

2000). Records rated as “good” are considered to have 

95 percent of the published daily values within 10 percent of their true values. Records rated as “fair” are considered to have 95 percent of the published daily values 

within 15 percent of the true values. Records rated as 

“poor” are less accurate than “fair” records. On the basis 

of the annual ratings of streamflow records for stations 

used in this report, daily mean values of streamflow for 

the entire study period were considered accurate to 

within 15 percent of the true values at all streamflowgaging stations. Because hydrologic significance was 

determined from regression estimates based on streamflow at index (covariate) station 16229000, the accuracy 

of streamflow at station 16229000, 15 percent, was used 

as the accuracy of all streamflow regression relationships. The combined accuracy of streamflow data at the 

Table 3. Before, during, and after construction periods at streamflow-gaging stations in the H-3 Highway study area, Oahu, Hawaii

1 Sediment data at station 16275000 are discontinuous; sediment data are available for 12/01/83 to 09/30/84 and from 07/20/87 to 09/30/98

Before construction During construction After construction

Station Start End

Number 

of days Start End

Number

of days Start End

Number

of days

16225800 -- -- 0 04/05/91 09/30/97 2,371 10/01/97 09/30/99 730

16226200 02/01/83 11/01/87 1,735 11/02/87 12/12/97 3,694 12/13/97 09/30/99 657

16265600 02/01/83 02/21/83 21 02/22/83 06/30/92 3,417 07/01/92 09/30/97 1,918

16270900 04/01/84 06/18/89 1,905 06/19/89 12/22/95 2,378 12/23/95 06/30/98 921

16272200 10/01/80 02/21/83 874 02/22/83 12/22/95 4,687 12/23/95 09/30/98 1,013

16273950 10/01/87 03/05/89 523 03/06/89 12/22/95 2,482 12/23/95 06/30/98 921

162750001 10/01/82 10/23/88 2,215/7671 10/24/88 11/30/94 2,229 12/01/94 09/30/98 1,400
14 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

study streamflow-gaging stations (15 percent) with the 

regression estimates (15 percent) is 21 percent. The 21 

percent accuracy was computed as the square root of the 

sum of squares of each accuracy value (Benjamin and 

Cornell, 1970; Rabinovich, 1995). Streamflow changes 

that are within the accuracy limit of 21 percent cannot 

be considered hydrologically significant, although they 

may be statistically significant.

A similar test was done with the suspendedsediment data. Only if both statistical and hydrological 

significance criteria were met, would any changes in 

either streamflow or suspended-sediment data be attributed to highway construction. The applications of this 

method are described more fully in the sections on 

streamflow and suspended-sediment analyses below. 

Results of all statistical tests were reported as significant if the probability of obtaining the results by 

chance was less than or equal to 5 percent. This is equivalent to setting the α level for all statistical hypothesis 

tests to 0.05.

Data Collection

Rainfall data was collected at stream-gaging stations 16226000, 16226200, 16265600, 16270900, and 

in Haiku Valley (figs. 1 and 2). Both tipping bucket and 

float-type rain gages were used with standard National 

Weather Service 8-in. diameter rain collectors. Streamflow data were collected at stations 16225800, 

16226000, 16226200, 16229000, 16265600, 16270900, 

16272200, 16273950, and 16275000 using continuous 

gage-height recorders and periodic measurements of 

streamflow following standard practices for streamflow 

data collection (Rantz and others, 1982). Suspendedsediment samples were collected at stream-gaging 

stations 16225800, 16226200, 16265600, 16270900, 

16272200, 16273950, and 16275000 using both single 

point automatic suspended-sediment samplers and periodic depth-integrated cross-sectional samples using the 

equal-width-increment method (Edwards and Glysson, 

1999). Suspended-sediment concentrations were determined at the U.S. Geological Survey office in Honolulu 

and suspended-sediment loads were computed using 

suspended-sediment concentrations and streamflow 

records, as described by Porterfield (1972). Additional 

details on data collection can be found in Wong and 

Young (2001).

Table 4. Basin area-weighted median annual 

rainfall at drainage basins in and near the H-3 

Highway study area, Oahu, Hawaii

[Basin area-weighted median rainfall values from Wong (1994); 

*, computed by Wong (1994) but not previously published]

Streamflow Analysis

Streamflow at stream-gaging stations 16225800, 

16226200, 16265600, 16270900, 16272200, 16273950, 

and 16275000 was used as the response variable and 

streamflow at index stream-gaging station 16229000 

(figs. 1 and 2) was used as the covariate in the analysis 

of covariance. As previously discussed streamflow at 

station 16229000 is unaffected by H-3 Highway construction, diversions, or change in land use. Variations 

in streamflow at station 16229000 were therefore primarily the result of rainfall variations. Rainfall distribution, as determined by area-weighted average of median 

annual rainfall (Wong, 1994), is similar among all study 

basins and the index station (table 4). Therefore, the use 

of streamflow data from streamflow-gaging station 

16229000 as covariate would account for the streamflow variations at the study stations due to rainfall.

Mean daily streamflow data were separated into 

low- and high-flow classes before analysis to permit 

separate evaluations of construction effects on low 

flows and high flows. The daily streamflow with an 

exceedance probability of 10 percent at station 

16229000, which was determined by Hill (1996) to be 

10.0 ft3

/s, was used to define the low-flow (less than or 

equal to 10.0 ft3/s) and high-flow (greater than 10.0 

ft3

/s) classes. Data sets varied in size depending on station and time period but for low-flow analysis all data 

sets were greater than 1000 data points in size and for 

high flow analysis all were greater than 100 data points 

in size. Another analysis was done using annual peak 

flows, which are the highest instantaneous peak flows 

during a water year. High-flow and peak-flow data were 

log-transformed before analysis to improve regression 

relations on the basis of the distributions of regression 

Station Basin area-weighted median annual 

rainfall in inches

16226200 118*

16229000 120

16270900 108

16272200 92*

16275000 108
Approach 15

residuals (Helsel and Hirsch, 1992). Low-flow data 

were not log-transformed because zero-flow data at stations 16225800 and 16226200 could not be log-transformed and because log-transformation did not 

significantly improve regression relations at the other 

stations, as determined by examination of regression 

residuals.

The analysis of covariance tested whether time 

period (before, during, and after construction) 

accounted for variations in streamflow at stations 

16225800, 16226200, 16265600, 16270900, 16272200, 

16273950, and 16275000 by comparing regression 

equations relating streamflow at these stations to 

streamflow at the index station 16229000 for each time 

period. A comparison of low streamflow before and 

during construction at station 16275000 is presented 

below as an example. Similar analyses were done to 

compare the other time periods at this station: during 

and after, and before and after construction. These three 

comparisons were then repeated for each of the other 

stations.

The first equation, simply relates the response variable to the covariate, and is expressed as

Q16275000 = A + (B × Q229000), (1)

where Q16275000 represents the response variable 

(streamflow at stream-gaging station 16275000), 

Q16229000 represented the covariate (low streamflow on 

the same day at index station 16229000), and A and B 

were regression coefficients. The second equation 

included, in addition to the covariate, a dummy 

independent variable, Z, to represent time period. The 

variable Z was assigned the values of zero for data 

before construction and 1 for data during construction. 

This second equation was expressed as

Q16275000 = A + (B × Q16229000) + (C × Z), (2)

where C was a regression coefficient. The coefficient C 

represented the change in the intercept of the regression 

relation during construction. The third equation 

included a third independent variable, an interaction 

term W. The variable W was computed as the product of 

Z and streamflow at station 16229000. This third 

equation was expressed as

Q16275000 = A+ (B × Q16229000) + (C × Z) + (D × W),(3)

or as 

Q16275000 = A + (B × Q16229000) + (C × Z) + (D × Z × 

Q16229000), (4)

where D was a regression coefficient. The interaction 

term was zero when Z equalled zero, and was equal to 

the covariate for all dates during construction. The 

coefficient D represented the change in the slope of the 

regression relation during construction.

If time period did not significantly affect relations 

between the response variable and the covariate, a single intercept and slope would adequately describe the 

relation throughout the study. In such a case, the coefficients for Z and W (C and D) would not be significantly 

different from zero. If changes in relations between the 

covariate and the response variable coincided with the 

period of construction, however, either the intercept or 

the slope or both should differ for the two time periods, 

and coefficients for Z and/or W would be significantly 

different from zero. Changes in intercept and slope can 

be positive or negative.

The significance of the regression coefficient for Z

in the equation using all three independent variables 

(the covariate, Z, and W) was tested using a t-test (for 

example, Helsel and Hirsch, 1992). A t-statistic is computed as the coefficient for Z divided by its standard 

error (for example, Iman and Conover, 1983). If this 

value exceeded the critical t-value for the appropriate 

degrees of freedom, the coefficient for Z was considered 

to be significantly different from zero, and the intercept 

of the regression was considered to be affected by time 

period.

The significance of the regression coefficient for W

and of the combined effect of Z and W were determined 

with F-tests (for example, Helsel and Hirsch, 1992). Ftests in analysis of covariance are based on regression 

errors. Regression errors are differences between 

observed values of the response variable and values 

estimated by the regression equation corresponding to 

the same values of the covariate. Errors are in the units 

of the response variable. If the response variable has 

been transformed to logarithms, for example, the errors 

will be in the transformed units. Error sums of squares 

are the sums of the squares of all regression errors for a 

regression equation. Mean-square errors are error sums 

of squares divided by the degrees of freedom for the 

regression. The standard error is the square root of the 

mean-square error, and is a measure of average scatter 

of observed data about the regression line.
16 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

F-statistics were used to test the significance of the 

coefficient for W by comparing the error terms of 

regressions that included the covariate (streamflow at 

station 16229000), the dummy variable (Z), and the 

interaction term (W) to those of regressions computed 

using the covariate and Z as independent variables. 

F-statistics were computed as the ratio of the difference 

between the error sums of squares for the two regression 

relations, divided by their difference in degrees of freedom, to the mean-square error of the regression that 

included all three independent variables. If the magnitude of the F-statistic exceeded the appropriate critical 

value of the F-distribution (critical values of the Fdistribution can be found in many statistical textbooks 

such as Iman and Conover, 1983), the effect of time 

period on the slope of the relation between streamflow 

at the project station and streamflow at the index station 

was considered to be significant.

F-statistics were similarly used to test the overall 

significance of time period by comparing the error 

terms of regressions that included the covariate (streamflow at station 16229000), the dummy variable (Z), and 

the interaction term (W) with those of regressions computed using only the covariate as an independent variable. If the magnitude of the F-statistic exceeded the 

appropriate critical value of the F-distribution, the overall effect of time period on the relation between streamflow at the project station and streamflow at the index 

station was considered to be significant.

The t-ratios and F-statistics reported for variables Z

and W indicate whether changes in intercept and slope 

individually were significant when both Z and W were 

included in the regression. Both Z and W can be individually significant, therefore, when the overall effect of 

time period is not; conversely, the overall effect of time 

period can be significant when Z and W individually are 

not.

The analysis of covariance on annual peak flow 

data was slightly different from the approach used on 

daily mean streamflow for the low- and high-flow 

classes, described previously, because of the limited 

amount of annual peak flow data. The analysis of covariance was conducted using annual peak flows at gaging 

stations 16226000, 16270900, and 16275000 as the 

response variable with peak flows at 16229000 as the 

covariate. The peak flow analysis was only conducted 

with data from stations 16226000, 16270900, and 

16275000 because the number of annual peaks available for analysis at these stations was greater than 20. A 

smaller number of data points was considered inadequate for statistical analysis due to potential inaccuracies in using statistical tests on small data sets. Analysis 

of covariance was not conducted with data from station 

16272200 because peak flows at this site are regulated 

by the upstream flood control reservoir. The peak flow 

data were divided into only two categories, before 

construction and during and after construction, rather 

than into three categories, before, during, and after construction as was done with the daily mean streamflow 

data. This was done due to the limited number of annual 

peak flows available. Annual peak flow data extending 

back to 1971 were used so that more than 20 annual 

peaks were available for the analyses and to give a 

roughly equal number of before-construction to duringand after-construction annual peaks. The actual number 

of annual peak flows at stations 16226000, 16270900, 

and 16275000 were 29, 26, and 24 respectively (table 

5).

Suspended-Sediment Analysis

Analysis of covariance was used to assess changes 

in relations between streamflow and suspended-sediment loads at stream-gaging stations 16225800, 

16226200, 16265600, 16270900, 16272200, 16273950, 

and 16275000 due to construction of the H-3 Highway. 

The analysis-of-covariance procedure tested whether 

time period accounted for variations in suspendedsediment loads, after streamflow variations were 

removed, by computing regression equations relating 

suspended-sediment load to streamflow. Time period 

was again represented by a dummy variable, Z, that took 

the value of zero for data before construction and 1 for 

data during construction, or the value of zero for data 

during highway construction and 1 for data after construction. An interaction term, W, was computed as the 

product of Z and streamflow. As described earlier for 

streamflow, the analysis of covariance compared three 

regression equations: one using only the covariate as an 

independent variable, a second including Z, and a third 

including Z and W.

Mean daily streamflow and daily total suspendedsediment load data were transformed to base 10 logarithms before analysis. A number of daily total suspended-sediment loads were reported as 0 tons in two 

situations: (1) loads were 0 tons on many days at stations 16225800 and 16226200 when streamflow at
Approach 17

Table 5. Annual instantaneous peak flow at streamflow-gaging stations in and near the H-3 Highway study area, Oahu, Hawaii, 

water years 1971–99

[--, no data; shaded values represent annual peak flows occurring during periods of highway construction]

Instantaneous peak flow in cubic feet per second

Station

Water 

Year 16225800 16226000 16226200 16229000 16265600 16270900 16272200 16273950 16275000

1971 -- 1,750 -- 1,970 -- 651 -- -- 4,420

1972 -- 538 -- 1,470 -- 180 -- -- 328

1973 -- 153 -- 137 -- 6 -- -- 30

1974 -- 1,360 -- 1,100 -- 159 -- -- 565

1975 -- 950 -- 1,420 -- 180 -- -- 721

1976 -- 758 -- 822 -- 112 -- -- 456

1977 -- 593 -- 1,070 -- 96 968 -- 203

1978 -- 295 -- 316 -- 56 217 -- --

1979 -- 453 -- 714 -- 81 439 -- --

1980 -- 5,470 -- 2,630 -- 400 1,500 -- --

1981 -- 872 -- 1,010 -- 150 715 -- --

1982 -- 1,970 -- 5,120 -- 548 916 -- --

1983 -- 695 -- 608 -- 250 281 -- 165

1984 -- 299 330 218 -- -- 142 -- 33

1985 -- 528 710 1,100 842 96 645 -- 419

1986 -- 734 868 782 713 232 470 -- 650

1987 -- 916 1,020 2,160 1,160 299 1,430 -- 743

1988 -- 1,140 1,180 2,070 1,310 -- 1,650 207 754

1989 -- 884 868 1,080 697 260 994 152 640

1990 -- 836 880 878 486 132 366 86 700

1991 -- 1,320 1,780 2,840 936 247 970 118 743

1992 468 614 860 926 443 231 284 90 732

1993 307 217 294 1,270 856 232 850 116 290

1994 460 1,100 1,640 1,790 670 380 1,070 106 710

1995 275 335 501 1,100 611 144 615 94 160

1996 403 422 778 1,060 2,800 957 1,760 181 640

1997 329 354 849 834 566 302 538 -- 754

1998 296 413 423 210 -- 58 266 32 189

1999 335 665 496 576 -- -- 187 -- 133
18 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

those stations was 0 ft3/s; (2) loads were reported as 0 

tons at all stations when the product of streamflow, 

suspended-sediment concentration, and a unit-conversion coefficient was less than 0.005 tons. Loads 

reported as 0 tons could not be log-transformed. Loads 

reported as 0 tons on days of no streamflow were not 

used in the analysis of covariance. Loads reported as 0 

tons when their computed values were below 0.005 tons 

are censored data (unquantified but known to be less 

than 0.005 tons) and cannot be analyzed with the ordinary least-squares regression normally used in analysis 

of covariance (Helsel and Hirsch, 1992). Tobit regression (Amemiya, 1985; Cohn, 1988) was used in place of 

ordinary least squares regression to allow the use of 

censored data. Daily suspended-sediment loads 

reported as 0 tons for days when streamflow was greater 

than 0 ft3

/s were assigned an arbitrary value slightly 

below the reporting limit of 0.005 tons/day. Randomly 

selected subsamples of 500 suspended-sediment loadstreamflow data pairs were used for the analysis of 

covariance to avoid high correlation between streamflow and Z, the variable representing construction, especially if streamflow was affected by construction 

activities. A low correlation between streamflow and Z

(construction) would validate the implicit assumption in 

analysis of covariance that independent variables, 

streamflow and Z (construction) in this case, are not correlated (Wildt and Ahtola, 1978).

The significance of the regression coefficient for Z

was tested using a likelihood ratio (Cohn, 1988), which 

is similar to the t-test used to evaluate the coefficient for 

Z in the analysis of covariance done on streamflow 

described previously. If the likelihood ratio exceeded 

the critical value for the appropriate degrees of freedom, 

the coefficient for Z was considered to be significantly 

different from zero, and the intercept of the regression 

was considered to be affected by time period.

F-statistics were used to test the significance of the 

coefficient for W by comparing the error terms of 

regressions that included the covariate (streamflow), the 

dummy variable (Z), and the interaction term (W) to 

those of regressions computed using the covariate and Z

as independent variables. F-statistics were computed as 

described above for streamflow. If the magnitude of the 

F-statistic exceeded the appropriate critical value of the 

F-distribution, the effect of time period on the slope of 

the relation between streamflow and suspendedsediment load was considered to be significant.

F-statistics were used similarly to test the overall 

significance of time period by comparing the error 

terms of regressions that included the covariate (streamflow), the dummy variable (Z), and the interaction term 

(W) to those of regressions computed using only the 

covariate as an independent variable. If the magnitude 

of the F-statistic exceeded the appropriate critical value 

of the F-distribution, the overall effect of time period on 

the relation between streamflow and suspendedsediment load was considered to be significant.

STREAMFLOW BEFORE, DURING, AND 

AFTER CONSTRUCTION

Hydrologic conditions during the study.--Annual 

streamflow was generally higher during the years of 

high rainfall (tables 6 and 7). For much of the H-3 Highway study area, the years of highest streamflow during 

the study period coincided with years of high rainfall 

(table 6) and with the during highway-construction 

period (table 3). Records available for streamflowgaging stations 16226000 and 16272200 show that 

annual streamflow was higher prior to highway construction in 1982 than for any year during the 1983–99 

highway construction period (table 7). Average mean 

daily streamflow per unit area was higher before construction than during or after construction at stations 

16272200 and 16273950, and higher during construction than either before or after construction at the 

remaining stations (fig. 4). There were no before construction data collected at station 16225800 and just a 

few days at station 16265600 (table 3).

Flood frequency.--Recurrence intervals for annual 

instantaneous peak flows were computed using methods of the Interagency Advisory Committee on Water 

Data (1982) for three gaging stations in the study area 

with long (more than 30 years) periods of record: 

stream-gaging station 16226000 in North Halawa Valley (fig. 1), station 16270900 Luluku Stream in the 

Kamooalii drainage basin (fig. 2) and station 16275000 

in Haiku Valley (fig. 2). Recurrence intervals for annual 

peak flows at station 16226000 ranged from 1 to 2 years 

throughout the study periods. Annual peak flows at station 16270900 had recurrence intervals of 2 years 

before construction, 1 to 5 years during construction, 

and from 1 to 50 years after construction. At station 

16275000, before construction recurrence intervals 

ranged from 1 to 2 years, construction-period
Streamflow Before, During, and After Construction 19

recurrence intervals were all about 2 years, and after 

construction recurrence intervals ranged from 1 to 2 

years. The majority of peak flows during the study 

period were small enough that they recur on average 

every 2 years. The highest peak flows based on recurrence intervals during the study period occurred at station 16270900 in the Kamooalii drainage basin, during 

the after construction period in January 1996. The peak 

at station 16270900 was caused by a locally intense 

storm and had a recurrence interval of 50 years based on 

at station frequency analysis (Interagency Advisory 

Committee on Water Data, 1982). On the basis of 

regional frequency analysis (Wong, 1994), the recurrence interval for the 1996 peak at station 16270900 

was about 25 years.

The highest annual peak flow at station 16226000 

was recorded prior to highway construction in 1980 

(table 5). The highest peak flow during construction 

occurred in 1991. At station 16270900 the highest peak 

flow occurred after construction in 1996. The second 

highest peak flow occurred before construction in 1971. 

At station 16275000 peak flows were higher before and 

after construction in 1971, 1988, and 1997 than during 

construction (table 5). Streamflow peaks during the 

study period at stations with shorter periods of record 

such as stations 16265600 and 16272200 in the

Table 6. Annual and average rainfall at rain-gaging stations in and near the H-3 Highway study area, Oahu, Hawaii, water 

years1983–99

[All values in inches; NWS, National Weather Service; --, no data; P, partial year of record, more than one month of record missing; e, estimated 

annual total, one or more days were estimated, data were estimated by comparison with nearby rain gages; Numbers below gage numbers or names 

are 4 digit State key numbers assigned to rain gages in Hawaii by the Commission on Water Resource Management, Department of Land and Natural 

Resources, State of Hawaii]

1Average is for complete years only for the period 1983–99

Drainage 

basin

USGS Stations NWS Stations

North 

Halawa

North 

Halawa

R.Branch 

Kamooalii Luluku Haiku

North 

Halawa Kamooalii

R.Branch 

Kamooalii

Water 

year

16226000

(772.1)

16226200

(771.9)

16265600

(781.9)

16270900

(781.11)

Haiku

(839.3)

Halawa

(771.2)

Luluku

(781.7)

Pali Golf 

Course

(788.1)

1983 65.4 P P -- -- P P 59.4

1984 44.1 23.5 38.9 P -- P 41.9 37.8

1985 61.6 40.7 63.9 66.8 -- 43.2 71.2 55.8

1986 60.9 32.9 59.2 66.2 P 36.3 74.2 53.3

1987 68.3 33.8 67.2 66.7 75.4 38.1 e76.1 62.5

1988 90.6 56.5 86.8 95.1 113 49.8 98.7 130

1989 e91.2 55.5 84.1 87.2 105 e59.1 e110 103

1990 66.5 35.3 62.4 62.8 92.0 e40.1 e80.0 P

1991 80.2 41.2 68.5 59.9 e101 e51.7 P 80.1

1992 52.8 27.3 42.2 e55.9 69.0 36.5 e75.9 50.1

1993 e58.7 e33.5 P 61.6 69.5 37.4 76.2 110

1994 P 23.6 P 71.2 91.2 e39.0 91.5 84.6

1995 49.4 e43.8 e40.2 49.1 64.2 e29.2 P 68.8

1996 53.7 43.4 e60.1 73.7 83.7 e49.8 92.4 97.2

1997 63.8 61.0 e75.9 e81.5 99.6 P e105 109

1998 33.3 23.7 P 44.7 48.6 e26.9 P 40.7

1999 35.9 31.8 -- -- -- e31.9 56.9 P

Average1 61.0 38.0 62.4 67.7 84.4 40.6 80.8 76.2
20 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Kamooalii drainage basin were highest during construction in 1988 and after construction in 1996. The highest 

streamflow peaks at station 16273950 occurred both 

before and after construction in 1988 and 1996, respectively. At the other two stations in the North Halawa 

valley, stations 16225800 and 16226200, streamflow 

peaks were higher during construction in 1988, 1991, 

and 1994 at station 16226200 and in 1992 and 1994 at 

station 16225800. In general, streamflow peaks during 

construction were higher in the North Halawa and 

Kamooalii drainage areas and lower in the Haiku and 

South Fork Kapunahala drainage areas.

Streamflow Changes due to Construction

Low Flows

The changes in regression intercepts and slopes for 

the analysis of covariance shown in table 8 indicate the 

direction and magnitude of changes in streamflow during construction. Changes in intercepts, which are equal 

to the coefficients for variable Z listed in table 8, are 

constants that increase (positive coefficients) or 

decrease (negative coefficients) predicted flows equally 

over the entire range of data. Changes in slope, which 

are equal to the coefficients for variable W listed in table 

8, result in changes in estimated streamflow that are 

proportional to streamflow at stream-gaging station 

16229000.

Table 7. Annual total streamflow at streamflow-gaging stations in and near the H-3 Highway study area, Oahu, Hawaii, water years 

1981–99

[--, no data; shaded values represent data collected during periods of highway construction]

1

Data from February to September

2

Data from April to September

3Data from October to June

 stream- Annual total streamflow in cubic feet per second

Water

year

Station

16225800 16226000 16226200 16229000 16265600 16270900 16272200 16273950 16275000

1981 -- 918 -- 1,320 -- -- 3,140 -- --

1982 -- 4,300 -- 4,400 -- -- 8,040 -- --

1983 -- 964 1203 1,300 1267 -- 4,090 -- 877

1984 -- 517 525 745 122 442 1,600 -- 520

1985 -- 827 969 1,170 284 152 2,290 -- 604

1986 -- 1,590 1,580 1,840 406 150 2,940 -- 674

1987 -- 1,440 1,540 1,930 612 327 3,760 -- 790

1988 -- 3,140 3,700 3,120 986 508 6,070 1,020 1,270

1989 -- 3,040 3,640 3,350 1,040 532 5,930 1,050 1,420

1990 -- 1,670 1,840 1,720 532 488 4,280 847 888

1991 2458 2,740 3,440 3,170 762 737 5,000 938 1,230

1992 818 1,030 1,135 1,430 308 471 3,030 828 806

1993 1,020 1,410 1,480 1,850 605 394 3,610 860 738

1994 1,560 2,150 2,449 2,540 609 519 4,240 838 941

1995 708 1,030 1,294 1,430 216 606 2,600 704 618

1996 801 1,260 1,640 1,540 504 520 3,580 722 735

1997 1,200 1,890 2,703 2,370 721 554 5,370 894 1,030

1998 506 609 824 1,050 -- 3341 2,730 3540 696

1999 565 1,220 1,213 1,340 -- -- 1,800 -- 566
Streamflow Before, During, and After Construction 21

Before and during construction.--Relations 

between low flows at stream-gaging stations 16226200, 

16270900, 16272200, 16273950, and 16275000 and 

low flows at index station 16229000 changed significantly during the highway construction period for the 

before and during highway construction analysis of 

covariance (table 8). Regression intercepts were significantly different at stations 16226200, 16270900, and 

16273950; the intercept decreased at stations 16226200 

and 16273950 and increased at station 16270900. 

Regression slopes were significantly different at stations 16270900, 16272200, 16273950, and 16275000; 

slope increased at station 16275000, and decreased at 

stations 16270900, 16272200, and 16273950. 

To determine if the low-flow changes detected 

using analysis of covariance were hydrologically significant, changes in low flows were estimated by applying 

before highway-construction regression coefficients for 

slope and intercept from the analysis of covariance 

(table 8) to the during highway-construction period low 

flows at station 16229000. The estimated low flows represent low flows that would be expected if relations 

between streamflows at stations 16226200, 16270900, 

16272200, 16273950, and 16275000 and the index station 16229000 were unchanged by construction (table 

9). The differences between observed and estimated low 

flows during construction are estimates of changes 

resulting from factors other than rainfall variations, 

since the analysis of covariance procedure accounts for 

the effects of rainfall by using streamflow at the index 

station as a covariate. Percent differences were computed by equation 5 and represent the percent change of 

the during- or after-construction low flows attributed to 

construction.

Figure 4. Average mean daily streamflow per unit area for the before, during, and after highway construction periods at streamflowgaging stations in the H-3 Highway study area, Oahu, Hawaii, 1981–99.

0

1

2

3

4

5

6

7

8

16225800 16226200 16265600 16270900 16272200 16273950 16275000

STREAMFLOW-GAGING STATION

AVERAGE MEAN DAILY STREAMFLOW,

IN CUBIC FEET PER SECOND PER SQUARE MILE

BEFORE HIGHWAY CONSTRUCTION

DURING HIGHWAY CONSTRUCTION

AFTER HIGHWAY CONSTRUCTION
22 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Table 8. Analysis of covariance results relating concurrent daily mean streamflow at streamflow-gaging stations in the H-3 Highway study area to the index station 16229000 for the before, during, and after highway construction periods, Oahu, Hawaii

[Daily mean streamflows at station 16229000 and at stations 16225800, 16226200, 16265600, 16270900, 16272200, 16273950, and 16275000 were 

used as the covariate and response variables, respectively; Z was set to zero for before construction and 1 for construction; or zero for construction 

and 1 for after construction, W was set to (Z × streamflow at station 16229000); high-flow data were log-transformed; * indicates significant effect 

of period on the basis of t-ratio or F-test; critical t-ratio is 1.96; critical F-values are 3.84 for significance of W and 3.00 for significance of Z and W

together]

Regression coefficients for

t-ratio for

 significance

 of Z

F-statistics for 

significance of

Station Intercept Slope Z W W Z + W

Before and during highway construction periods

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16226200 -1.43 1.17 -0.42* 0.04 -2.86* 0.69 7.04*

16270900 0.27 0.11 0.70* -0.02* 30.0* 5.70* 1200*

16272200 5.15 2.07 -0.39 -1.04* -1.72 292* 492*

16273950 1.98 0.11 -0.08* -0.04* -2.02* 22.9* 75.6*

16275000 1.29 0.15 -0.07 0.04* -1.87 16.3* 11.2*

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16226200 0.10 0.94 -0.38 0.29 -1.75 3.38 1.71

16270900 -0.88 0.86 0.28* -0.11 2.55* 1.92 16.7*

16272200 0.57 0.67 -0.37* 0.17* -3.15* 4.26* 15.4*

16273950 -0.13 0.54 -0.03 -0.03 -0.33 0.16 5.90*

16275000 -0.59 0.94 -0.03 0.07 -0.24 0.70 4.12*

During and after highway construction periods

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16225800 -0.97 0.72 0.17* -0.05* 2.08* 5.83* 3.61*

16226200 -1.85 1.21 0.16 0.14* 0.73 4.00* 9.06*

16265600 0.43 0.13 -0.22* 0.04 -3.14* 3.42 5.86*

16270900 0.97 0.09 -0.11* 0.01 -3.55* 2.94 8.74*

16272200 4.76 1.03 -0.16 0.42* -0.82 63.5* 81.9*

16273950 1.90 0.07 -0.17* 0.02* -7.10* 6.53* 43.2*

16275000 1.22 0.19 0.07 -0.02* 1.56 4.70* 2.44

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16225800 -0.33 1.10 0.01 -0.04 0.17 1.36 0.74

16226200 -0.28 1.23 0.04 -0.01 0.07 0.00 0.10

16265600 -1.36 1.30 -0.02 0.03 -0.06 0.04 0.19

16270900 -0.60 0.75 0.03 0.02 0.20 0.04 2.42

16272200 0.21 0.84 0.04 0.05 0.22 0.11 4.82*

16273950 -0.16 0.52 -0.11 0.11 -0.85 1.29 1.73

16275000 -0.62 1.02 -0.03 -0.03 -0.17 0.07 2.79

Before and after highway construction periods

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16226200 -1.43 1.17 -0.27 0.17* -1.51 8.96* 5.36*

16270900 0.27 0.11 0.59* -0.00 24.2* 0.00 887*

16272200 5.15 2.07 -0.54 -0.62* -1.54 40.8* 87.6*

16273950 1.98 0.11 -0.25* -0.03* -6.17* 7.04* 122*

16275000 1.29 0.15 -0.00 0.01 -0.04 2.37 3.33*

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16226200 0.10 0.94 -0.34 0.29 -0.77 0.65 0.35

16270900 -0.88 0.86 0.32 -0.09 1.54 0.33 14.5*

16272200 0.57 0.67 -0.32 0.21 -1.77 2.54 1.85

16273950 -0.13 0.54 -0.14 0.08 -0.93 0.52 0.98

16275000 -0.59 0.94 -0.06 0.04 -0.31 0.08 0.05
Streamflow Before, During, and After Construction 23

Percent change = [(OBS − EST)/ EST] × 100 (5)

Where OBS represents the observed low flow and 

EST the estimated low flow. Estimated changes in low 

flows during the highway-construction period range 

from a decrease of 31 percent of observed low flows at 

station 16272200 to an increase of 108 percent at station 

16270900 (table 9). Only the estimated changes at stations 16270900 and 16272200 were greater than the 

limits of accuracy for the streamflow records used in the 

analyses which was 21 percent. The estimated changes 

for stations 16226200, 16273950, and 16275000 were 

21 percent or less (table 9) and therefore cannot be considered hydrologically significant.

During and after construction.--Relations 

between low flows at all streamflow-gaging stations 

except 16275000 and low flows at index station 

16229000 changed significantly after the highwayconstruction period in the during and after construction 

analysis (table 8). Regression intercepts were significantly different at stations 16225800, 16265600, 

16270900, and 16273950; the intercept decreased at stations 16265600, 16270900, and 16273950 and 

increased at station 16225800. Regression slopes were 

significantly different at stations 16225800, 16226200, 

16272200, 16273950, and 16275000; slope increased at 

stations 16226200, 16272200, and 16273950, and 

decreased at stations 16225800 and 16275000. Only the 

change at station 16226200 was hydrologically significant with low flows increasing by an estimated 47 percent after construction (table 9).

Before and after construction.--Relations 

between low flows at all stream-gaging stations and low 

flows at index station 16229000 changed significantly 

after the highway-construction period in the before and 

after construction analysis (table 8). Regression intercepts were significantly different at stations 16270900, 

and 16273950; the intercept decreased at stations 

16273950 and increased at station 16270900. Regression slopes were significantly different at stations 

16226200, 16272200, and 16273950; slope increased at 

station 16226200 and decreased at stations 16272200 

and 16273950. Only the change at station 16270900 

was hydrologically significant with low flows increasing by an estimated 99 percent after construction compared to before construction (table 9).

High and Peak Flows

Before and during construction.--Relations 

between high flows at streamflow-gaging stations 

16270900, 16272200, 16273950, and 16275000 and 

high flows at index station 16229000 changed significantly during the highway-construction period in the 

before and during construction analysis (table 8). The 

intercept increased at station 16270900 and decreased at 

station 16272200. The slope increased at station 

16272200. Neither Z nor W were significant individually at stations 16273950 and 16275000, but their combined effect was significant.

Changes in high flows resulting from altered drainage-basin conditions during highway construction were 

estimated in the same manner as described for low 

flows. Estimated high flows were back-transformed 

from logarithmic units and adjusted for bias using the 

nonparametric method of Duan (1983). Bias-correction 

factors ranged from 1.08 to 1.80 (table 9) and were used 

to increase the back-transformed intercept prior to estimating high flows. Percent changes in high flows were 

computed using equation 5 with OBS being the 

observed high flow and EST equal to the estimated high 

flow. Only the change at station 16275000 was statistically and hydrologically significant with high flows 

increasing by an estimated 25 percent during construction (table 9).

Estimates of changes in high flows during highway 

construction required extrapolation of the beforeconstruction regression equation beyond the range of 

before-construction high flow data at index station 

16229000 only at station 16226200. Extrapolation was 

defined as a daily mean high flow being more than 100 

percent greater than the highest daily mean high flow 

used to compute the before highway-construction 

regression equation at index station 16229000. The use 

of these estimates requires the assumption that the 

before construction relation between streamflow at 

index station 16229000 and streamflow at station 

16226200 remains linear at flows higher than any 

observed during the before construction period. Hill 

(1996) checked this assumption by comparing annual 

streamflow at station 16229000 with long term annual 

streamflow at station 16226000 using double-mass 

curves (Searcy and Hardison, 1960). Hill (1996) found 

no deviations from a linear pattern, so the extrapolation 

was considered reasonable for station 16226200, which 

is about 1.3 mi downstream of station 16226000 (fig. 1).
24 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Table 9. Estimated changes in streamflow at streamflow-gaging stations for the during and after highway-construction periods in the H-3 

Highway study area, Oahu, Hawaii, 1983–99

[Estimated streamflows were computed by applying before and during construction regression coefficients listed in table 10 to daily mean streamflows at station 

16229000 during and after the construction period; differences were computed as observed streamflow less estimated streamflow; percent differences were 

computed as differences divided by the estimated streamflow and multiplied by 100; all streamflow data are sums of daily mean streamflows and are in cubic 

feet per second-days (ft3/s-d); * indicates significant hydrologic effect of period because the difference is greater than the accuracy of the streamflow records 

which is 21 percent]

During highway 

construction

Station

Observed streamflow 

(ft3/s)

Estimated streamflow using 

before construction relation 

equation 

(ft3/s)

Equation standard 

error of estimate

Equation bias 

correction factor

Difference between 

observed and estimated 

streamflow

(percent)

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16226200 6,900 7,910 2.90 -- −13

16270900 2,730 1,310 0.42 -- 108*

16272200 33,500 48,400 3.35 -- –31*

16273950 4,780 5,260 0.38 -- −9

16275000 3,740 3,600 0.65 -- 4

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16226200 16,800 13,700 0.355 1.13 23*

16270900 713 596 0.236 1.22 20

16272200 14,100 15,600 0.249 1.12 −10

16273950 967 1,110 0.168 1.08 −13

16275000 2,340 1,870 0.252 1.20 25*

After highway 

construction

Station

Observed streamflow 

(ft3/s)

Estimated streamflow using 

during construction relation 

equation 

(ft3/s)

Equation standard 

error of estimate

Equation bias 

correction factor

Difference between 

observed and estimated 

streamflow

(percent)

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16225800 605 569 1.65 -- 6

16226200 931 634 2.98 -- 47*

16265600 1,280 1,470 1.33 -- −13

16270900 1,010 1,060 0.44 -- −5

16272200 8,320 7,300 2.99 -- 14

16273950 1,700 1,800 0.34 -- −6

16275000 2,300 2,320 0.66 -- −1

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16225800 466 522 0.352 1.26 −11

16226200 710 692 0.372 1.25 3

16265600 1,460 1,130 0.498 1.80 29*

16270900 279 212 0.211 1.11 32*

16272200 2,710 2,010 0.259 1.20 35*

16273950 300 268 0.172 1.08 12

16275000 659 716 0.259 1.18 −8
Streamflow Before, During, and After Construction 25

After highway 

construction

Station

Observed streamflow 

(ft3

/s)

Estimated streamflow using 

before construction relation 

equation 

(ft3/s)

Equation standard 

error of estimate

Equation bias 

correction factor

Difference between 

observed and estimated 

streamflow

(percent)

Low flow (mean daily streamflow less than or equal to 10.0 ft3/s at station 16229000)

16226200 931 845 2.34 -- 10

16270900 1,010 507 0.34 -- 99*

16272200 8,320 10,500 4.17 -- −21

16273950 1,700 1,980 0.37 -- −14

16275000 2,300 2,250 0.53 -- 2

High flow (mean daily streamflow greater than 10.0 ft3/s at station 16229000)

16226200 710 626 0.283 1.13 13

16270900 279 176 0.268 1.22 58*

16272200 2,710 2,500 0.233 1.12 8

16273950 300 313 0.179 1.08 −4

16275000 659 610 0.270 1.20 8

Table 9. Estimated changes in streamflow at streamflow-gaging stations for the during and after highway-construction periods in the H-3 

Highway study area, Oahu, Hawaii, 1983–99--Continued

[Estimated streamflows were computed by applying before and during construction regression coefficients listed in table 10 to daily mean streamflows at station 

16229000 during and after the construction period; differences were computed as observed streamflow less estimated streamflow; percent differences were 

computed as differences divided by the estimated streamflow and multiplied by 100; all streamflow data are sums of daily mean streamflows and are in cubic 

feet per second-days (ft3/s-d); * indicates significant hydrologic effect of period because the difference is greater than the accuracy of the streamflow records 

which is 21 percent]
26 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

During and after construction.--For the during 

and after highway-construction analysis, only the high 

flow relations between streamflow-gaging station 

16272200 and index station 16229000 changed significantly. Neither Z nor W were significant individually at 

station 16272200, but their combined effect was significant. Both intercept and slope increased slightly (table 

8) and estimated high flows increased by 35 percent at 

station 16272200 (table 9). High flows at stations 

16270900 and 16265600 were both hydrologically significant (table 9) but not statistically significant (table 

8).

Before and after construction.--For the before and 

after highway-construction analysis, only relations 

between high flows at streamflow-gaging station 

16270900 and high flows at index station 16229000 

changed significantly after construction (table 8). 

Again, neither Z nor W were significant individually, 

but their combined effect was. The intercept increased 

and slope decrease slightly at station 16270900 (table 8) 

and the estimated change in high flows increased by 58 

percent (table 9).

Peak flows.--Relations between peak flows at stations 16226000, 16270900, and 16275000 and peak 

flows at index station 16229000 changed significantly 

only at station 16270900 (table 10). The regression 

intercept increased indicating an increase in peak flows 

at 16270900 during and after construction. Because 

annual peak flows are instantaneous, hydrologic significance could not be determined using the same procedure as for low- and high-flows.

Effects of Land-use Changes on Streamflow

Significant changes in streamflow between time 

periods are unlikely to have occurred as a result of random streamflow variations, and are probably the result 

of changes in drainage-basin conditions related to landuse activities. H-3 Highway construction is a possible 

cause of the changes in streamflow, but other activities, 

such as ground-water development, that coincided with 

construction may have also affected streamflow.

Low Flows

Low flows are maintained by ground-water discharge in the study area (Takasaki and others, 1969; 

Izuka, 1992). Any alterations of the ground-water flow 

system could affect low flows (Hirashima, 1963; 1971). 

The most likely activities that may have affected the 

ground-water flow system during and after construction 

of the H-3 Highway include municipal ground-water 

withdrawals and H-3 construction.

Municipal ground-water withdrawals from tunnels 

and wells represent the largest development of ground 

water in the study area (Takasaki and Mink, 1985). 

Municipal withdrawals increased during the highway 

construction period in the drainage basins upstream of 

stream-gaging stations 16270900 and 16272200 (figs. 5 

and 6). These increased withdrawals may have reduced 

low flows at these stations (Takasaki and Mink, 1985), 

but are unlikely to account for the increased low flows 

at station 16270900.

Table 10. Analysis of covariance results relating instantaneous peak flow at streamflow-gaging stations in the H-3 Highway study 

area to index station 16229000 for the before, during, and after highway construction periods, Oahu, Hawaii, water years 1971–99

[Instantaneous peak flows at station 16229000 and at stations 16226000, 16270900, and 16275000 were used as the covariate and response variables, respectively; Z was set to zero for before-construction and 1 for during and after construction; W was set to (Z × instantaneous peak flow at 

station 16229000); peak flow data were log-transformed; * indicates significant effect of period on the basis of t-ratio or F-test; critical t-ratio is 

2.05; critical F-values are 4.22 for significance of W and 3.37 for significance of Z and W together]

Before-construction and during- and after-construction periods

Regression 

coefficients for

t-ratio for

 significance

 of Z

F-statistics for 

significance of

Station Intercept Slope Z W W Z + W

16226000 0.77 0.71 -0.05 -0.00 -0.33 0.30 1.21

16270900 -1.30 1.16 0.50* -0.00 2.61* 3.76 3.55*

16275000 -1.52 1.38 0.38 -0.00 1.87 4.18 2.15
Streamflow Before, During, and After Construction 27

A number of H-3 Highway construction activities 

could potentially affect low flows that are maintained 

by ground-water discharge. The excavation of highway 

tunnels in a ground-water recharge zone below the crest 

of the Koolau Range could increase or decrease low 

flows. Hill (1996) analyzed the ground-water seepage in 

the Trans-Koolau tunnels and determined that seepage 

from the tunnels would have only a minor effect, if any, 

on the streamflow in the study area. Activities such as 

vegetation removal, reduced agricultural streamflow 

diversions, irrigation for highway landscaping, and 

highway runoff from compacted or paved areas could 

increase low flows. Activities such as cutting, filling, 

compacting, and paving of the land surface in and near 

areas of ground-water recharge could decrease low 

flows through reduced infiltration. Road cuts could also 

serve as potential ground-water loss areas affecting 

ground-water movement and storage (Parizek, 1971).

The increased low flows at station 16226200 that 

were significant after highway construction in comparison to during construction is partly related to the channelization of North Halawa Stream in the areas of 

streamflow loss or infiltration, as most of the channelization occurred in the areas of streamflow loss which is 

upstream of altitude 400 ft (Izuka, 1992). About 20 percent of the stream channel upstream of station 

16226200 was channelized, which would reduce the 

streamflow loss to ground water and increase flows 

downstream. Additionally, areas of North Halawa 

Stream where there is streamflow gains also receive 

flow from highway runoff.

Low flows increased during and after construction 

at station 16270900 when compared to low flows before 

construction. Removal of vegetation during highway 

construction could have resulted in decreased evapotranspiration and hence an increase in the volume of

Figure 5. Mean monthly streamflow at streamflow-gaging station 16270900 and mean monthly upstream ground-water withdrawals, 

Oahu, Hawaii, April 1984 to June 1998.

GROUND-WATER WITHDRAWALS

 (Data from Honolulu Board

 of Water Supply)

STREAMFLOW

89

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

MEAN MONTHLY STREAMFLOW AND GROUND-WATER WITHDRAWALS,

IN CUBIC FEET PER SECOND

BEFORE HIGHWAY CONSTRUCTION DURING HIGHWAY CONSTRUCTION AFTER HIGHWAY

CONSTRUCTION

YEAR
28 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

ground water available to maintain low flow. Hill 

(1996) determined that highway construction removed 

banana trees covering about 6 percent of the Luluku 

drainage basin. The effect of this vegetation removal in 

the drainage basin could potentially increase streamflow due to decreased evapotranspiration. Most likely 

reduced agricultural streamflow diversions for irrigation of the removed banana trees and highway runoff 

contribute to the increased low flows.

Low flows decreased at station 16272200 during 

highway construction in relation to low flows before 

construction. Upstream of station 16272200, the combined area affected by H-3 Highway and golf course 

construction was about 12 percent of the Kamooalii 

drainage basin area. Reduced evapotranspiration due to 

vegetation removal during construction would likely 

increase low flows, but low flows decreased during construction. The decrease in low flows indicates that the 

effects of increased ground-water withdrawals and 

compaction of soil during highway and golf-course construction (reduced infiltration) likely decreased the 

amount of water available to sustain low flows. 

High and Peak Flows

In comparing the before and during highwayconstruction data, high flow increases were significant 

at only streamflow-gaging station 16275000 (tables 8 

and 9). The increased high flows are probably the result 

of increased runoff from the clearing of vegetation and 

compaction (less infiltration) of areas used for highway 

construction. Only the increase in high flows at station 

16272200 was significant in comparing the during and 

after periods of construction. The increased high flows 

at this station are probably the result of the same factors 

at station 16275000 and possibly the new golf course. 

Irrigation of the golf course could cause an increase in 

high flows due to higher soil moisture. Station 

16270900 was the only station that had a significant

Figure 6. Mean monthly streamflow at streamflow-gaging station 16272200 and mean monthly upstream ground-water withdrawals, Oahu, 

Hawaii, water years 1981–99.

GROUND-WATER WITHDRAWALS

 (Data from Honolulu Board

 of Water Supply)

STREAMFLOW

0

10

20

30

40

50

60

MEAN MONTHLY STREAMFLOW AND GROUND-WATER WITHDRAWALS,

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

IN CUBIC FEET PER SECOND

BEFORE

HIGHWAY

CONSTRUCTION

DURING HIGHWAY CONSTRUCTION AFTER

HIGHWAY

CONSTRUCTION

WATER YEAR
Suspended-Sediment Loads Before, During, and After Construction 29

increase in high flows when comparing the before and 

after construction data. Station 16270900 also had a 

significant increase in peak flows as well. The increased 

high and peak flows here are most likely due to 

increased runoff from the highway.

SUSPENDED-SEDIMENT LOADS BEFORE, 

DURING, AND AFTER CONSTRUCTION

Annual suspended-sediment loads were low during 1983–86 (table 11) when rainfall and streamflow 

were low and loads were high during 1988–89, 1991, 

and 1996–97 when rainfall and streamflow were high 

and after construction had begun upstream of all sediment stations. The highest annual suspended-sediment 

load was at station 16226200 in 1997 (table 11), the last 

year of construction activities in North Halawa Valley.

Mean daily suspended-sediment yields were computed for before, during, and after construction periods 

by dividing mean daily suspended-sediment loads by 

drainage basin areas. Suspended-sediment yields were 

highest before construction at stream-gaging stations 

16272200 and 16273950, highest during construction at 

stations 16225800, 16226200, 16265600, and 

16275000, and highest after construction at station 

16270900 (fig. 7). As noted previously, there were no 

before-construction data collected at stations 16225800 

and 16265600.

Suspended-Sediment Load Changes due to 

Construction

The analysis of covariance procedure requires that 

the covariate, streamflow, be independent of the factor 

represented by the dummy variable, in this case, construction (Wildt and Ahtola, 1978). This assumption

Table 11. Annual total suspended-sediment loads at sediment-gaging stations in the H-3 Highway study area, Oahu, Hawaii, water 

years 1981−99

[--, no data; shaded values represent data collected during periods of highway construction]

1 Data from February to September

2

 Data from April to September

3

 Data from December to September

4

 Data from July to September

5 Data from October to June

Annual total suspended-sediment load in tons

Water

year 

Station

16225800 16226200 16265600 16270900 16272200 16273950 16275000

1981 -- -- -- -- 723 -- --

1982 -- -- -- -- 3,210 -- --

1983 -- 15 113 -- 173 -- --

1984 -- 31 24 21 77 -- 36

1985 -- 314 541 43 336 -- --

1986 -- 362 472 91 322 -- --

1987 -- 615 631 402 1,190 -- 4114

1988 -- 3,500 1,730 485 2,240 187 1,310

1989 -- 16,600 1,220 180 1,290 488 3,400

1990 -- 2,260 1,160 53 593 73 1,660

1991 2894 5,220 512 333 1,270 435 2,970

1992 3,650 4,290 65 70 148 82 1,610

1993 3,810 3,460 421 185 801 102 359

1994 2,180 9,180 278 193 606 182 665

1995 663 2,505 64 66 222 49 75

1996 267 5,040 1,940 884 1,370 57 683

1997 397 19,600 146 135 424 131 770

1998 286 2,780 -- 515 131 525 87

1999 179 573 -- -- -- -- --
30 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

was checked by the analysis of covariance for high 

flows, since most sediment transport occurs during the 

period of high flows. The significant effects on high 

flows for the three analyses (before and during, during 

and after, and before and after highway-construction 

periods) determined at stations 16270900, 16272200, 

and 16275000 (tables 8 and 9) may affect the analysis 

of covariance results for suspended-sediment during the 

same highway-construction periods. However, this is 

unlikely as the data used in the tobit regression program 

were 500 randomly selected data points using 

suspended-sediment load data with both low and high 

flow data. The complete randomization of the data set 

helped to create independence between streamflow and 

the dummy variable, Z, as no linear correlation coefficient was higher than 0.46 in any tobit regression data 

set.

Before and during construction.--Analysis of 

covariance results indicate that relations between 

streamflow and suspended-sediment loads changed significantly at sediment-gaging stations 16226200, 

16270900, 16272200, 16273950, and 16275000 (table 

12; fig. 8). Changes in regression intercepts were significant at all stations except 16275000. The regression 

intercept increased during construction at stations 

16226200, 16270900, and 16273950 and decreased at 

station 16272200 (table 12). Changes in regression 

slopes were significant at all stations except 16273950. 

Regression slopes increased during construction at stations 16226200, 16272200, and 16275000 and 

decreased at station 16270900. 

During and after construction.--Relations 

between streamflow and suspended-sediment loads 

changed significantly after the highway-construction 

period for the during and after highway analysis of 

covariance at all sediment-gaging stations except 

16275000 (table 12). Changes in regression intercepts 

were significant at all stations except 16275000. 

Regression intercepts increased at station 16273950 and 

decreased at the remaining stations. Changes in 

Figure 7. Mean daily suspended-sediment yield for the before, during, and after highway construction periods at sediment-gaging 

stations in the H-3 Highway study area, Oahu, Hawaii, water years 1981–99.

0

1

2

3

4

5

6

16225800 16226200 16265600 16270900 16272200 16273950 16275000 

SEDIMENT-GAGING STATION

MEAN DAILY SUSPENDED-SEDIMENT YIELD,

IN TONS PER SQUARE MILE

BEFORE HIGHWAY CONSTRUCTION

DURING HIGHWAY CONSTRUCTION

AFTER HIGHWAY CONSTRUCTION
Suspended-Sediment Loads Before, During, and After Construction 31

regression slopes were significant at stations 16226200, 

16270900, 16272200, and 16273950. Regression slopes 

increased after construction at stations 16270900 and 

16272200 and decreased at stations 16226200 and 

16273950. 

Before and after construction.--Analysis of covariance results indicate that relations between streamflow and suspended-sediment loads for the before and 

after highway-construction periods changed significantly at sediment-gaging stations 16226200, 

16270900, 16272200, 16273950, and 16275000 (table 

12). Intercept changes were significant at all stations. 

Regression intercepts increased at stations 16226200, 

16273950, and 16275000 and decreased at stations 

16270900 and 16272200 (table 12). Changes in regression slopes were significant at all stations except 

16275000. Regression slopes increased at stations 

16226200, 16270900, and 16272200 and decreased at 

station 16273950. 

Streamflow and suspended-sediment load relations.--Changes in regression coefficients indicate how 

streamflow-sediment relations were affected during the 

highway-construction periods compared. Changes in 

regression slopes and intercepts reflect changes in the 

availability of suspended sediment. Figure 8 graphically 

illustrates the changes in slope and intercept of tobit 

regression lines in table 12. The significant decrease in 

intercept at station 16225800 after construction, and the 

lack of significant change in slope, indicate that suspended-sediment loads decreased relative to streamflow 

after construction (table 12, fig. 8). This decrease 

affected the entire range of streamflow at this station as 

would be expected once land disturbances from highway-construction stopped. At station 16226200, the 

increase in slope and intercept during construction compared to before construction indicate that suspendedsediment loads increased relative to streamflow during 

construction (table 12, fig. 8). As a result of the increase

Table 12. Analysis of covariance results relating randomly selected daily suspended-sediment loads to mean daily streamflow at sediment-gaging stations in the H-3 Highway study area, Oahu, Hawaii

[Common logarithms of daily mean streamflow and suspended-sediment load were used as the covariate and response variable, respectively; Z was set 

to zero for pre-construction and 1 for construction; W was set to (Z × log-streamflow); tobit regression (Cohn, 1988) was used to compute likelihood 

ratio and F-statistics; * indicates significant effect of period on the basis of likelihood ratio or F-test; critical likelihood ratio is 1.96; critical F-values 

are 3.84 for significance of W and 3.00 for significance of Z and W together]

Station

Regression coefficients for

Likelihood 

ratio for

 significance of Z

F-statistic for

 significance of

Intercept Slope Z W W Z + W

Before and during highway construction periods

16226200 –1.97 0.368 0.978* 0.919* 119* 219* 144*

16270900 –1.75 2.74 0.247* -0.830* 27.7* 23.8* 24.2*

16272200 –1.60 1.10 –0.573* 0.562* 10.6* 11.8* 6.43*

16273950 -2.06 2.98 0.141* 0.049 3.70* 1.00 15.5*

16275000 –2.63 3.08 –0.104 0.444* 1.19 5.49* 7.18*

During and after highway construction periods

16225800 -0.824 1.39 -0.709* 0.128 67.9* 3.28 35.4*

16226200 -1.04 1.25 -0.708* -0.385* 45.6* 19.7* 21.0*

16265600 -1.45 2.41 -0.689* 0.278 97.7* 2.02 53.7*

16270900 -1.51 1.82 -0.542* 1.37* 97.8* 26.6* 51.8*

16272200 -2.01 1.50 -0.403* 0.454* 9.42* 12.4* 6.85*

16273950 -2.03 3.33 0.286* -0.819* 22.7* 25.0* 13.2*

16275000 -2.54 3.45 -0.111 0.244 1.37 1.95 1.95

Before and after highway construction periods

16226200 –2.08 0.287 0.471* 0.718* 27.3* 85.6* 43.4*

16270900 –1.82 2.74 -0.368* 0.890* 31.0* 19.0* 21.2*

16272200 –1.80 1.30 –0.379* 0.348* 12.8* 12.1* 7.60*

16273950 -2.10 2.92 0.380* -0.522* 39.6* 13.1* 48.2*

16275000 –2.80 3.46 0.232* -0.188 6.37* 1.04 5.17*
32 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Figure 8. Before, during, and after highway-construction period relations between streamflow and suspended-sediment loads at streamflow- and 

sediment-gaging stations in the H-3 Highway study area, Oahu, Hawaii.

16225800 North Halawa Stream near Kaneohe

-3 -2 -1 0 1 2

LOG OF DAILY SUSPENDED-SEDIMENT LOAD LOG OF DAILY SUSPENDED-SEDIMENT LOAD LOG OF DAILY SUSPENDED-SEDIMENT LOAD

-5

-4

-3

-2

-1

0

1

2

DURING CONSTRUCTION

AFTER CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION

16226200 North Halawa Stream near Honolulu

-3 -2 -1 0 1 2 3 -4

-3

-2

-1

0

1

2

3

16265600 Right Branch Kamooalii Stream near Kaneohe

LOG OF MEAN DAILY STREAMFLOW

LOG OF MEAN DAILY STREAMFLOW

-2 -1 0 1 2 -6

-4

-2

0

2

4

16270900 Luluku Stream at altitude 220 feet near Kaneohe

-2 -1 0 1 2 -8

-6

-4

-2

0

2

4

6

BEFORE CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION

BEFORE CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION

BEFORE CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION

BEFORE CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION

16272200 Kamooalii Stream below Luluku Stream near Kaneohe 

-1 0 1 2 3 -4

-3

-2

-1

0

1

2

3

16273950 South Fork Kapunahala Stream at Kaneohe

012 -2

-1

0

1

2

3
Suspended-Sediment Loads Before, During, and After Construction 33

in slope, the construction regression line is actually 

below the before construction regression line for flows 

less than 0.08 ft3

/s. Because little sediment is transported at such low flows, the intersection of the regression lines is not significant in assessing the effects of 

construction on sediment loads. The slope and intercept 

decreased after construction when compared to duringconstruction data at station 16226200, which indicates 

decreased suspended-sediment loads relative to streamflow after construction. The slope of the afterconstruction relationship line is higher than the before 

construction line and the two lines intersect at about 

0.27 ft3/s. Again, at such low flows very little sediment 

is transported so the intersection of the regression lines 

is not significant in assessing the effects of construction 

on sediment loads. For stations 16225800 and 

16226200, the differences in slope of cumulative suspended-sediment loads and streamflow between the 

before, during, and after highway-construction periods 

can clearly be seen (fig. 9). Additionally, figure 9 shows 

the large increases in suspended-sediment loads that are 

generated by storms especially for the during highwayconstruction period. The cumulative suspended-sediment load graphs for 16225800 and 16226200 also 

show that from April 1991 to September 1999, 12,300 

tons of suspended sediment passed station 16225800. 

For that same time period, 48,800 tons of suspended 

sediment passed station 16226200. Thus, from April 

1991 to September 1999, station 16225800, with 41 percent of the drainage area of station 16226200, contributed 25 percent of the suspended-sediment load at 

station 16226200.

At sediment station 16265600, the analysis of 

covariance intercept decreased and slope increased after 

construction than during construction. However, the 

change in slope was not significant. The plot of the tobit 

regression lines (fig. 8) indicates a decrease in suspended-sediment load over the entire range of streamflow. Excluding the January 1996 storm, the cumulative 

suspended-sediment load graph (fig. 9) shows a lower 

slope in the cumulative totals after construction than 

during construction.

At sediment-gaging station 16270900, the analysis 

of covariance slope decreased and intercept increased 

(fig. 8) during construction in comparison to the beforeconstruction data. The before- and during-construction 

regression lines intersect at about 1.8 ft3

/s. Suspendedsediment loads are estimated to be higher before construction for streamflows above 1.8 ft3/s and higher during construction for streamflows lower than 1.8 ft3/s. 

After construction the slope increased and intercept 

decreased compared to both the before and during construction time periods (table 12, fig. 8). Streamflows 

higher than about 3.1 ft3

/s had a higher suspendedsediment load after construction than streamflows 

higher than 3.1 ft3

/s before construction. The same is 

true for streamflow above 2.4 ft3

/s after construction 

than during construction. The differences in slope are 

not as clearly seen in the cumulative suspended-sediment load graph (fig. 9) between the time periods compared, however, the curve does show larger increases 

before and after construction than during construction.

At sediment-gaging station 16272200, the analysis 

of covariance slope increased and intercept decreased in 

all three comparisons (fig. 8). The intersection point of 

the regression lines was about 11, 16, and 11 ft3/s for the 

before and during, during and after, and before and after 

highway-construction period comparisons, respectively. Thus, suspended-sediment loads in relation to 

high streamflow increased both during and after construction than before construction. For lower streamflows, suspended-sediment loads were higher in the 

before construction period than either during or after 

construction. This can be seen in the lower mean daily 

suspended-sediment yields for this station for the during 

and after highway construction periods compared to the

Figure 8. Before, during, and after highway-construction period 

relations between streamflow and suspended-sediment loads at 

streamflow- and sediment-gaging stations in the H-3 Highway study 

area, Oahu, Hawaii--Continued.

16275000 Haiku Stream near Heeia

LOG OF MEAN DAILY STREAMFLOW

-1 1 2 0 3

LOG OF DAILY SUSPENDED-SEDIMENT LOAD -3

-2

-1

0

1

2

3

4

5

BEFORE CONSTRUCTION

DURING CONSTRUCTION

AFTER CONSTRUCTION
34 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Figure 9. Cumulative streamflow and suspended-sediment loads at streamflow and sediment-gaging stations in the H3 Highway study area, Oahu, Hawaii, 1981–99.

16225800 North Halawa Stream near Kaneohe 

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

91 92 93 94 95 96 97 98 99

YEAR

CUMULATIVE SUSPENDED-SEDIMENT LOAD, IN TONS 

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

SUSPENDED-SEDIMENT LOAD

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW

SUSPENDED-SEDIMENT LOAD

STREAMFLOW

16226200, North Halawa Stream near Honolulu

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

YEAR

CUMULATIVE SUSPENDED-SEDIMENT LOAD, IN TONS

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

START GAGE

START NORTH HALAWA VIADUCT CONSTRUCTION

START CONSTRUCTION NOVEMBER 1987

APRIL 1989 STORMAND LANDSLIDE ONACCESS ROAD

MARCH 1994 STORM

NOVEMBER 1996 STORM

DECEMBER 1997END CONSTRUCTIONHIGHWAY OPENS

SEPTEMBER 1992 STORM

JULY 1993 STORM

MARCH 1994 STORM

END VIADUCT CONSTRUCTION

JUNE 1995

END CONSTRUCTION DECEMBER 1997
Suspended-Sediment Loads Before, During, and After Construction 35

Figure 9. Cumulative streamflow and suspended-sediment loads at streamflow and sediment-gaging stations in the H3 Highway study area, Oahu, Hawaii, 1981–99--Continued.

16270900 Luluku Stream at altitude 220 feet near Kaneohe 

0

500

1,000

1,500

2,000

2,500

3,000

3,500

84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

DATE

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

16265600 Right Branch Kamooalii Stream near Kaneohe

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

83 84 85 86 87 88 89 90 91 92 93 94 95 96 97

YEAR

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

CONSTRUCTION STARTS FEBRUARY 1983

NEW YEARS STORM JANUARY 1, 1988

END HALEKOU INTERCHANGESEPTEMBER 1988

START WINDWARD HIGHWAY JUNE 1989

END CONSTRUCTIONJUNE 1992

JANUARY 1996 STORM

NEW YEARS STORM JANUARY 1, 1988

START WINDWARD HIGHWAYCONSTRUCTION JUNE 1989

END WINDWARDHIGHWAY CONSTRUCTIONJUNE 1992

JANUARY 1996 STORM

END CONSTRUCTIONDECEMBER 1995

START KANEOHE INTERCHANGE CONSTRUCTIONJANUARY 1993

SUSPENDED-SEDIMENT LOAD

STREAMFLOW

SUSPENDED-SEDIMENT LOAD

STREAMFLOW
36 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Figure 9. Cumulative streamflow and suspended-sediment loads at streamflow and sediment-gaging stations in the H3 Highway study area, Oahu, Hawaii, 1981–99--Continued.

16272200 Kamooalii Stream below Luluku Stream near Kaneohe

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

80 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

YEAR

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

0

10,000

20,000

30,,000

40,000

50,000

60,000

70,000

80,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

81

16273950 South Fork Kapunahala Stream at Kaneohe 

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

87 88 89 90 91 92 93 94 95 96 97 98

YEAR

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

SUSPENDED-SEDIMENT LOAD

STREAMFLOW

AUGUST 1992 STORM 

END CONSTRUCTIONDECEMBER 1995 

START HALEKOU INTERCHANGECONSTRUCTIONFEBRUARY 1983 

NEW YEARS STORMJANUARY 1, 1988 

END HALEKOU CONSTRUCTION 

START WINDWARDHIGHWAYCONSTRUCTION 

END WINDWARD HIGHWAYCONSTRUCTION

SUSPENDED-SEDIMENT LOAD

STREAMFLOW

START CONSTRUCTION MARCH 1989HOSPITAL ROCK TUNNEL

MARCH 1991 STORM

END HOSPITAL ROCKCONSTRUCTION

START KANEOHE INTERCHANGE CONSTRUCTION

END CONSTRUCTIONDECEMBER 1995

JANUARY 1996 STORM
Suspended-Sediment Loads Before, During, and After Construction 37

before (fig. 7). The slope of the cumulative suspendedsediment load graph for station 16272200 (fig. 9) shows 

a steeper slope only during the construction of the 

Windward Highway segment of H-3 Highway and not 

the earlier Halekou Interchange construction which 

shows a flatter slope similar to the before and after construction time periods. The cumulative suspended-sediment load graph for stations 16270900 and 16272200 

(fig. 9) indicates that station 16270900, with 11 percent 

of the drainage area, contributed 29 percent of the suspended-sediment load to station 16272200 during April 

1984 to June 1998. The remaining suspended-sediment 

load at station 16272200 was that which had passed 

through the reservoir upstream of the station.

At sediment station 16273950, the analysis of 

covariance slope and intercept increased during highway construction when compared to the before construction relation. The increase in slope was not 

significant, however. The tobit regression line (fig. 8) 

does shows an increase in suspended-sediment load 

over the entire range of streamflow. The slope 

decreased and intercept increased after construction 

when compared to both during and before construction 

data. The suspended-sediment load decreased for all 

streamflows except for flows below 2.1 ft3

/s after construction when compared to during construction. The 

suspended-sediment load decreased in relation to 

streamflow after construction compared to before construction data for streamflows greater than about 4 ft3/s. 

The cumulative suspended-sediment load graph (fig. 9) 

shows a near constant slope throughout the study period 

with a slightly lower slope only in the after construction 

period.

Figure 9. Cumulative streamflow and suspended-sediment loads at streamflow and sediment-gaging stations in the H-3 

Highway study area, Oahu, Hawaii, 1981–99--Continued.

16275000 Haiku Stream near Heeia

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

87 88 89 90 91 92 93 94 95 96 97 98

YEAR

CUMULATIVE SUSPENDED-SEDIMENT DISCHARGE, IN TONS

0

2,000

4,000

6,000

8,000

10,000

12,000

SUSPENDED-SEDIMENT LOAD

CUMULATIVE STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW

HIGHWAY OPENSDECEMBER 1997

END TRANS-KOOLAU TUNNEL EARTHWORKNOVEMBER 1994

ENDCONSTRUCTION

END WINDWARDVIADUCT, MAY 1993

MARCH 1991 STORM

START WINDWARD VIADUCT, 1990

APRIL 1989 STORM

START CONSTRUCTION, OCTOBER 1988
38 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

At sediment-gaging station 16275000, the analysis 

of covariance slope increased and intercept decreased 

during highway construction when compared to before 

construction data. The decrease in intercept was not significant, however. The increase in slope did however, 

affect the entire range of streamflow (fig. 8). Neither 

slope nor intercept were significant in comparing the 

during and after construction data. Figure 8 shows that 

the after-construction relation has a lower suspendedsediment load throughout the entire range of streamflow 

compared to the during-construction regression line, but 

is still higher than the before construction relation. This 

is because only the increase in intercept was significant 

in the comparison of the before and after construction 

data. The cumulative suspended-sediment load graph 

(fig. 9) shows a steeper slope during the construction 

period than in either the before or after time periods. 

The before and during highway-construction 

period regression equations cannot be used to estimate 

construction effects on suspended-sediment loads similar to streamflows because of limitations of the statistical techniques used. Limitations at stations 16226200, 

16272200, and 16275000, were that the range of 

streamflow data during construction exceeds the range 

of streamflow before construction. Extrapolation 

beyond the range of data used to develop the regression 

equations can lead to serious errors because sediment 

transport relations commonly change as streamflow 

increases (Nolan and others, 1986; Glysson, 1987). 

Also, the use of tobit regression in place of ordinary 

least squares regression means that residuals cannot be 

used to determine the appropriate regression relations or 

bias-correction factors (Cohn, 1988; Helsel and Hirsch, 

1992). Instead, regional sediment-transport relations 

determined by Hill (1996) were used to estimate the 

construction effects.

Effects of Land-Use Changes on SuspendedSediment Loads

Hill (1996) derived two equations useful for estimating the annual suspended-sediment yields expected 

in the absence of construction effects or other major 

land-use changes. Using annual suspended-sediment 

yields reported for other areas of Oahu and beforeconstruction suspended-sediment yields at H-3 study 

stream-gaging stations, Hill (1996) used regression 

analysis with annual water yield (streamflow per unit 

area) to derive the two equations.

The first equation for estimating the annual suspended-sediment yields is based on data from drainage 

basins in the leeward Koolau Range and the before 

highway-construction period data from station 

16226200 and was used to estimate the suspendedsediment yields expected at stations 16225800 and 

16226200 during and after the construction period without the effects of highway construction. Data used to 

derive equation 6 was transformed to common logarithms to obtain a more linear relation, and was 

expressed as:

log Sy = -2.91 + (1.96 × log Qy), (6)

where Sy represented annual suspended-sediment yield 

and Qy represented annual water yield. A total of 18 

annual suspended-sediment yields were used to compute the regression, which had a coefficient of determination of 86 percent and a standard error of 0.22 log 

units. A bias-correction factor of 1.15 was applied to 

correct for re-transformation error (Duan, 1983) when 

applying the equation to stations 16225800 and 

16226200.

The second equation for estimating the annual 

suspended-sediment yields is based on data from windward Oahu stations and the before highway-construction data from stations 16265600, 16270900, and 

16275000, with no log-transformation needed. Hill 

(1996) did not use the before-construction data at station 16273950 as the suspended-sediment loads were 

not computed at that time. The addition of this one 

annual yield (water year 1988) would not significantly 

change the equation. This equation was expressed as:

Sy = 30 + (0.529 × Qy). (7)

Equation 7 was based on 14 measured suspendedsediment yields and had a coefficient of determination 

of 56 percent with a standard error of 336 tons/mi2. For 

both the leeward and windward regressions, yields from 

drainage basins under mixed use were combined with 

yields from undisturbed drainage basins, since land use 

other than highway construction was not clearly a factor 

affecting yields. Suspended-sediment yields at station 

16272200 cannot be estimated by strictly using equation 6 because the reservoir upstream of the station traps 

sediment and reduces the yield at the station. Estimated 

yields at station 16272200 were determined in part 

using data from Wong (2001) and is explained in the 

following section.
Suspended-Sediment Loads Before, During, and After Construction 39

Annual suspended-sediment yields expected in the 

absence of highway construction effects were estimated 

by applying regression equations 6 and 7 with the 

adjustment factors described in the next paragraph to 

construction-period annual water yields. The annual 

suspended-sediment yields were then summed for the 

construction period and compared to the total observed 

suspended-sediment yields for the construction-period 

at each station. The estimated yields were subtracted 

from the observed yields and the resulting differences 

represented the increase or decrease in yields attributable to highway construction. The percent change was 

computed using equation 5 with OBS equal to the 

observed suspended-sediment yield and EST equal to 

the estimated yield. The percent change represents the 

percent of the estimated suspended-sediment yield 

attributed to highway construction and are presented in 

table 13. The after-construction estimates of suspendedsediment yields were computed and compared in the 

same way except the after-construction annual water 

yields were used in equations 6 and 7. The afterconstruction estimates of suspended-sediment yields 

are not dependent on either a during and after or a before 

and after construction comparison.

To determine how well equations 6 and 7 would 

work for estimating suspended-sediment yield changes 

due to highway construction, results from both equations were compared to the observed before highwayconstruction data. The percent differences from this 

comparison (table 13) were then used to create adjustment factors to better fit the estimated yields to the 

observed yields. These adjustment factors are a constant 

that is multiplied against the estimated yields from 

equations 6 and 7 to provide a better estimate of suspended-sediment yields then equations 6 and 7 alone. 

Excluding the -57 percent difference at station 

16273950 (table 13) as not being representative of the 

other stations, the average absolute value percent difference was 26 percent. This value was used as the accuracy of equations 6 and 7. Along with the 15 percent 

accuracy of the suspended-sediment records, a combined accuracy of 30 percent was computed. The 30 

percent accuracy was computed as the square root of the 

sum of squares of each accuracy value (Benjamin and 

Cornell, 1970; Rabinovich, 1995). Thus, only those percent differences greater than 30 percent can be considered hydrologically significant.

Differences in annual suspended-sediment yields 

during highway construction ranged from a decrease of 

3,460 tons/mi2 (-62 percent) of the observed suspendedsediment yield at station 16270900, to an increase of 

14,900 tons/mi2

 (426 percent) of the observed yield at 

station 16226200 (table 13). The increased yields at stations 16225800, 16226200, 16265600, and 16275000 

were all significant at 222, 426, 60, and 148 percent, 

respectively. At stations 16270900 and 16273950, the 

suspended-sediment yield significantly decreased during construction by 62 and 37 percent. The decrease of 

16 percent at station 16272200 was not significant. 

Therefore, increased suspended-sediment yields resulting from construction activities ranged from 60 to 426 

percent higher than before construction yields where 

significant increases in suspended-sediment loads were 

detected (table 12). At sediment-gaging stations 

16225800 and 16265600, the during construction 

increases in suspended-sediment yields were probably 

also statistically significant although this could not be 

tested due to no before-construction data. This is 

because the during and after construction analysis of 

streamflow and suspended-sediment load was statistically significant and that all the stations tested in the 

before and during construction analysis had statistically 

significant changes in the streamflow and suspendedsediment load relations.

Differences in suspended-sediment yields after 

highway construction ranged from a decrease of 1,410 

tons/mi2

 (-62 percent) at station 16272200 to an 

increase of 680 tons/mi2

 (36 percent) at station 

16265600 (table 13). Highest percent difference was at 

station 16226200 with 205 percent. Observed afterconstruction suspended-sediment yields were significantly higher at stations 16225800, 16262200, and 

16265600, with percent increases of 49, 205, and 36, 

respectively. Observed yields were lower at stations 

16272200 and 16273950 with percent differences of -62 

and -71 percent. Estimated increases in suspended-sediment yield after construction are most likely due to 

drainage basins still adjusting to the effects of highway 

construction. It may be a few more years before afterconstruction yields return to levels estimated if no landuse change has occurred (before construction). The 

cumulative suspended-sediment graphs (fig. 9) show 

lower slopes in most cases after construction than during which signifies a decrease in suspended-sediment 

loads after construction. This is also seen in the mean 

daily suspended-sediment values shown in figure 7. At 

stations where increases were estimated after construction (table 13), these increases were lower than the
40 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

increases during construction. The 26 percent decrease 

at station 16275000 and 8 percent increase at station 

16270900 are within the 30 percent criteria of accuracy 

and shows that suspended-sediment loads have returned 

to before-construction levels at these two stations. 

The negative difference for station 16270900 during construction (table 13) indicates that suspendedsediment yields during construction would have been 

higher under before-construction conditions than during-construction conditions. Before construction, most 

of the drainage basin upstream of station 16270900 was 

under banana cultivation. There have been no studies on 

sediment yields from banana plantations in Hawaii, but 

cultivation of plantains, which are similar to bananas, 

can result in soil losses as high as 70 percent of losses 

for bare soil (El-Swaify and others, 1982); such losses 

would be much higher than soil losses under natural 

vegetation. Before-construction suspended-sediment 

yields at station 16270900 appear to be higher than 

yields for other windward drainage basins under mixed 

use (Hill, 1996). The reduction in the area under cultivation during highway construction may have led to a 

reduction in sediment yield. Installation of erosioncontrol measures during construction may have also 

contributed to decreased soil losses. Tobit regression 

results discussed previously also showed a decrease in 

sediment during construction (table 12, fig. 8).

The negative difference after highway construction at station 16273950 is more difficult to explain 

since banana cultivation in the basin was much smaller 

and the highway construction removed only a few small 

agricultural and rural housing plots near the sedimentTable 13. Estimated changes in suspended-sediment yields at sediment-gaging stations for the before, during, and 

after highway-construction periods in the H-3 Highway study area, Oahu, Hawaii,1983–99

[Estimated suspended-sediment yields were computed from regression equations (Hill, 1996, p. 29) relating annual suspended-sediment yields to annual 

streamflow per unit area and the computed adjustment factor; data used for stations 16225800 and 16226200 were log-transformed and a bias-correction 

factor of 1.15 was applied to estimated yields; data for all other stations were not log-transformed; observed and estimated yields at station 16272200 

were adjusted due to the upstream reservoir; yields from regression equations were then multiplied by the adjustment factors listed to get estimated yields, 

adjustment factors were computed from the before construction percent difference; tons/mi2, tons per square mile; differences were computed as observed yield less estimated yield, and are reported in tons per square mile; percent differences are differences divided by estimated yields and multiplied 

by 100; *, indicates significant hydrologic effect because the difference is greater than 30 percent; --, not applicable]

Station

Suspended-sediment yields 

(tons/mi2

)

Difference between observed and 

estimated yields Computed 

adjustment 

factor

Adjustment 

factor used in 

estimating 

Observed Estimated (tons/mi yields 2) (percent)

Before highway construction

16226200 322 422 −100 −24 0.806 --

16270900 2,710 2,120 590 28 1.28 --

16273950 879 2,040 −1,160 −57 0.637 --

16275000 1,480 1,170 310 26 1.26 --

During highway construction

16225800 7,230 2,240 4,990 222* -- 0.806

16226200 18,400 3,500 14,900 426* -- 0.806

16265600 5,720 3,580 2,140 60* -- 1.28

16270900 2,150 5,610 –3,460 –62* -- 1.28

16272200 7,560 9,000 −1,440 −16 -- 1.28

16273950 3,140 4,990 −1,850 −37* -- 0.637

16275000 11,000 4,440 6,560 148* -- 1.26

After highway construction

16225800 284 191 93 49* -- 0.806

16226200 284 93 191 205* -- 0.806

16265600 2,580 1,900 680 36* -- 1.28

16270900 2,270 2,100 170 8 -- 1.28

16272200 870 2,280 −1,410 −62* -- 1.28

16273950 505 1,740 −1,240 −71* -- 0.637

16275000 1,630 2,190 −560 −26 -- 1.26
Comparison with Previous Studies 41

gaging station. Tobit regression results also showed that 

suspended-sediment loads in relation to streamflow 

increased during construction at station 16273950 (fig. 

8). The highway construction may have reduced the 

suspended-sediment yield in this drainage basin by 

diverting runoff and trapping sediment; the portion of 

H-3 is entirely on grade and bisects the upper quarter of 

the drainage basin (fig. 2). This could have the effect of 

trapping sediment (also reducing runoff) from these 

areas which include some banana acreage but mostly 

undeveloped land upstream of the highway. Also, the 

stormwater runoff channels were changed during construction resulting in runoff from the Likelike Highway 

that used to enter the stream upstream of station 

16273950 to enter downstream of the station after highway construction. However, changes in low- and highflows at station 16273950 were not hydrologically significant (table 10).

The suspended-sediment yield at station 16272200 

is affected by the Waimaluhia Reservoir. Suspendedsediment yield to the reservoir was determined to be 

8,420 tons/mi2

 from 1983 to 1998 (Wong, 2001). This 

sediment yield can be divided into 7,560 tons/mi2 during construction from 1983 to 1995 and 870 tons/mi2

after construction from 1995 to 1998. Inflow to the reservoir can be computed by a simple water budget relation in which outflows equals inflows. Because groundwater seepage from the reservoir was negligible and the 

seepage that was observed flowed into the stream 

upstream of station 16272200, and because rainfall on 

the reservoir (75 in/yr) exceeded the evaporation from 

the reservoir (less than 50 in/yr), the flow measured at 

station 16272200 minus the flow at station 16270900, a 

tributary to 16272200 that does not flow into the reservoir, equals the reservoir outflow and thus inflow to the 

reservoir (Wong, 2001). Annual streamflow yields were 

then computed from the annual inflows with estimates 

for water years 1984 and 1998 to account for the partial 

years of record at station 16270900. Equation 7 was 

applied to these annual water yields with a 1.28 adjustment factor, which was computed for use at stations 

16265600 and 16270900, applied. The total suspendedsediment yield to the reservoir was 9,000 tons/mi2 for 

water years 1984 to 1995. The difference is -1,440 

tons/mi2 from the observed sediment yield which is an 

decrease of 16 percent during construction. Equation 7 

only estimates the suspended-sediment yield and not the 

total sediment yield which was computed for the reservoir. The total sediment yield includes larger sediment 

particles such as cobbles and boulders which are moved 

during larger storms as bedload transport. Therefore, 

the use of equation 7 in this case will only provide a 

rough guide to the effects of the highway construction 

on the suspended-sediment yield to the reservoir and 

station 16272200. The 16 percent difference is, however, within the accuracy range of the suspendedsediment records so even though the tobit regression 

analysis indicated an increase in suspended-sediment 

load for higher streamflows at station 16272200, the 

estimated magnitude of that increase is not significant. 

The estimated suspended-sediment yield after construction to the reservoir was computed as 2,280 tons which 

is 1,410 tons greater than that observed for a decrease of 

62 percent. The decrease is most likely due to the effects 

of the highway and golf course construction reducing 

the natural sediment load. The H-3 Highway in the 

Kamooalii Stream basin bisects the upper and lower 

portions of the drainage basin (fig. 2) and may act as a 

sediment trap to the undeveloped land upstream of the 

highway. The decrease may also be due the decreased 

suspended-sediment yields during construction at station 16270900, a tributary to station 16272200, not 

affected by the reservoir.

COMPARISON WITH PREVIOUS STUDIES

The additional streamflow and suspended-sediment load data after 1991 in the before and during highway construction analysis, did not change the low-flow 

results determined by Hill (1996). As in Hill (1996), 

both the significant low-flow increase at station 

16270900 and decrease at station 16272200 were determined. The high flow results, however, did change. 

Where Hill (1996) found no significant changes in highflows during construction, it was determined that highflows increased at station 16275000 by 25 percent compared to before construction. The suspended-sediment 

load changes at stations 16226200, 16265600, 

16270900, 16272200, and 16275000 repeated those 

determined by Hill (1996). Percent increases were 

higher than those computed by Hill (1996) at stations 

16226200, 16265600, and 16275000 and the percent 

decrease was not as low at station 16270900. No change 

in load was also determined at station 16272200.

The high flow increases determined at stations 

16270900 and 16272200 after construction and at station 16275000 during construction cannot be readily
42 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

compared to studies dealing with logging road impacts 

because of the larger drainage basin sizes of stations 

16272200 and 16275000. Logging road effects were 

analyzed in basins less than 0.57 mi2

 (Harr and others, 

1975; Ziemer, 1981; and King and Tennyson, 1984) 

while the areas at stations 16272200 and 16275000 are 

3.81 and 0.99 mi2

 (table 1). The percentages of the 

drainage areas affected by highway construction are 5, 

4, and 3 percent at stations 16270900, 16272200, and 

16275000, respectively, which are similar to the 4 percent area affected needed to detect significant high flow 

effects in King and Tennyson (1984). The only significant peak flow increase was determined at station 

16270900. Highway construction affected only about 5 

percent of the drainage basin which is less than the 12 

percent threshold for detecting increased peak flows 

due to logging road construction in forested areas (Harr 

and others, 1975).

Previous studies that have evaluated sediment 

loads due to highway construction in small drainage 

basins, have discussed the effect of the construction in 

terms of sediment load attributed to the construction and 

not a percentage increase or decrease (Vice and others, 

1969; Eckhardt, 1976; Reed, 1980; Ward and Appel, 

1988). To compare the results of this study to the other 

studies, it is necessary to compute the percent differences between the observed and estimated 

suspended-sediment yields or loads by equation 8. 

Equation 8 represents the percent change of the 

observed during- or after-construction suspended-sediment yields attributed to construction.

Percent difference= [(OBS − EST)/ OBS] × 100 (8)

Where OBS represents the observed suspendedsediment yield and EST the estimated yield. Note that 

percentages greater than -100 percent are the result of 

the computation method of equation 8 and not a reduction in suspended-sediment yield by an impossible 

amount. Percentages of the observed suspended-sediment yield that can be attributed to highway construction range from -161 to 81 percent during highway 

construction and from -245 to 67 percent after highway 

construction (table 14). Where suspended-sediment 

yields have increased due to construction, 37 to 81 percent of the observed yields are due to highway construction. This range is similar to the 50 to 85 percent range 

Table 14. Estimated changes in observed suspended-sediment yields due to highway construction at sediment-gaging stations for the 

during and after highway-construction periods in the H-3 Highway study area, Oahu, Hawaii,1983–99

[Estimated suspended-sediment yields were computed from regression equations (Hill, 1996, p. 29) relating annual suspended-sediment yields to annual streamflow per unit area and the computed adjustment factor; data used for stations 16225800 and 16226200 were log-transformed and a biascorrection factor of 1.15 was applied to estimated yields; data for all other stations were not log-transformed; observed and estimated yields at station 

16272200 were adjusted due to the upstream reservoir; yields from regression equations were then multiplied by the adjustment factors listed to get 

estimated yields, adjustment factors were computed from the before construction percent difference; tons/mi2, tons per square mile; differences were 

computed as observed yield less estimated yield, and are reported in tons per square mile; percent differences are differences divided by observed 

yields and multiplied by 100; *, indicates significant hydrologic effect because the difference is greater than 30 percent]

Suspended-sediment yields (tons/mi2) Adjustment 

factor used in 

estimating yields

Difference between observed and 

estimated yields 

Station Observed Estimated (tons/mi2)

(percent of 

observed)

During highway construction

16225800 7,230 2,240 0.806 4,990 69*

16226200 18,400 3,500 0.806 14,900 81*

16265600 5,720 3,580 1.28 2,140 37*

16270900 2,150 5,610 1.28 –3,460 −161*

16272200 7,560 9,000 1.28 −1,440 −19

16273950 3,140 4,990 0.637 −1,850 −59*

16275000 11,000 4,440 1.26 6,560 60*

After highway construction

16225800 284 191 0.806 93 33*

16226200 284 93 0.806 191 67*

16265600 2,580 1,900 1.28 680 26

16270900 2,270 2,100 1.28 170 8

16272200 870 2,280 1.28 −1,410 −162*

16273950 505 1,740 0.637 −1,240 −245*

16275000 1,630 2,190 1.26 −560 −34*
Conclusions 43

from previous studies in the eastern United States. The 

percentages of the after construction observed yields 

due to construction are smaller, ranging from 8 to 67 

percent, indicating a reduced effect of highway construction on the suspended-sediment yields.

CONCLUSIONS

Analysis of covariance and regression techniques 

were used to assess the effects of the H-3 Highway construction on streamflow and suspended-sediment loads 

in the affected drainage basins during the time periods: 

before and during construction, during and after construction, and before and after construction. Results of 

the streamflow analyses indicated that low flows before 

and during construction changed significantly at two 

stream-gaging stations. Low flows increased 108 percent at station 16270900 and decreased 31 percent at 

station 16272200 during construction. Low flows after 

construction changed significantly only at station 

16226200, increasing by 47 percent compared to low 

flows during the construction period. Low flows after 

construction compared to those before construction 

changed significantly only at station 16270900, increasing by 99 percent. Decreases in low flows at station 

16272200 were probably caused by land-use changes 

due to highway construction and by increased groundwater withdrawals which occurred during the construction period. Increased low flows at stations 16226200 

and 16270900 were attributed to highway construction.

High flows, mean daily streamflows over 10 ft3/s 

at index stream-gaging station 16229000, changed significantly only at station 16275000, increasing 25 percent during highway construction compared to before 

construction. High flows after construction changed 

significantly only at station 16272200 by an increase of 

34 percent compared to the high flows during construction. Relations between before and after construction 

high flows changed significantly only at station 

16270900, increasing by 58 percent. All increases in 

high flows were attributed to land-use changes caused 

by highway construction. Increased runoff due to a new 

golf course built during the construction period 

upstream of station 16272200 may have also contributed to the increase in high flows observed at station 

16272200. Highway construction affected about 5, 4, 

and 3 percent of the drainage areas at stations 

16270900, 16272200, and 16275000, respectively. 

These values are similar to the 4 percent of the drainage 

area affected needed to detect significant high flow 

effects of logging road construction in the Pacific 

Northwest region of the continental United States.

Instantaneous peak flows were analyzed at only 

three stations, 16226000, 16270900, and 16275000, due 

to the limited amount of peak flow data at most gaging 

stations in the study area. Peak flows increased during 

and after construction only at station 16270900. The 

increase in peak flows at this station was attributed to 

land-use changes caused by highway construction 

which affected about 5 percent of the drainage area.

Suspended-sediment loads changed significantly 

at stations 16226200, 16270900, and 16275000 during 

highway construction compared to before highway construction. Suspended-sediment loads increased at stations 16226200 and 16275000 by 426 and 148 percent 

and decreased at station 16270900 by 62 percent. 

Suspended-sediment loads also increased during construction at stations 16225800 and 16265600, by 222 

and 60 percent, but these changes could not be tested 

statistically since no before construction data were collected at these sites. All changes in suspended-sediment 

loads are attributed to highway construction. Increased 

loads are due to the land disturbance caused by the highway construction and the decreased loads due to other 

land-use changes such as a decrease in agricultural 

activities as well as erosion control measures installed 

during highway construction.

After highway construction, suspended-sediment 

loads changed significantly compared to during construction loads at all stations except 16275000. 

Suspended-sediment loads increased at stations 

16225800, 16226200, and 16265600 by 49, 205, and 

36 percent, respectively, and decreased at stations 

16272200 and 16273950 by 62 and 71 percent. The percentage increases were lower than the increases computed for the during construction period indicating that 

the suspended-sediment loads are slowly returning to 

the before construction levels which has already been 

observed at stations 16270900 and 16275000. 

Decreased loads at station 16272200 are due in part to 

the upstream Waimaluhia Reservoir trapping sediment 

and the decrease of suspended-sediment loads at station 

16270900. The decrease after construction at station 

16273950 is due to highway construction reducing the 

amount of sediment available for transport in the South 

Fork Kapunahala Stream drainage basin.
44 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99

Effects of H-3 Highway construction on suspended-sediment loads were generally similar to effects 

of highway construction in other areas. Previous studies 

in other areas of the United States found that 50 to 85 

percent of the sediment loads were attributable to highway construction activities. Effects of H-3 Highway 

construction on suspended-sediment loads at stations 

16225800, 16226200, 16265600, and 16275000 appear 

to be comparable to effects of highway construction in 

the eastern United States with 37 to 81 percent of the 

observed suspended-sediment load due to highway construction. Decreases in suspended-sediment loads due 

to highway construction are unique and have not been 

widely reported in the literature. Where decrease in suspended-sediment loads were determined, land use prior 

to construction was not pristine.

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Appendix 1. --Daily mean sediment discharge (tons/day) for water year 1996 at sediment-gaging station 16265600, Right Branch of Kamooalii Stream nearKaneohe, Oahu, Hawaii[all daily values are estimated]

Day Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sep.

1 .00 5.2 18 .01 .00 .01 .00 .01 .01 .01 .00 .092 .00 .00 .01 .00 .00 3.9 .01 .01 .01 .01 .00 .003 .00 .01 .00 .00 .00 23 .00 .02 .01 .01 .00 .004 .00 .00 .00 .02 .00 .03 .00 .01 .01 .01 .00 .015 .00 .00 .00 1.6 .00 .01 .01 .01 .01 2.5 .00 .456 .01 .00 .00 .00 .00 .00 .01 .01 .02 .60 .00 .017 .03 .00 .00 .15 .58 .00 .01 .03 .01 .08 .00 .018 .03 .01 .00 .01 2.1 .00 .01 .02 .01 .01 .00 .019 .00 .01 .00 .02 .02 .00 .00 .01 64 .01 .00 .00

10 .00 .00 .00 .21 .01 .00 .01 .01 .02 .01 .00 .0111 .00 .00 .00 .01 .01 .00 .01 .01 .01 .01 .01 .0112 .00 .01 .00 .01 .00 .00 .01 .01 .00 .02 .00 .0113 .00 .21 .00 .00 .00 .00 .01 .01 .00 .01 .00 .0114 .00 .03 .00 .01 .00 .00 .00 .01 .00 .01 .00 .0115 .00 .01 .00 .00 .00 .00 .00 .00 .00 .01 .00 .0116 .00 .00 .00 .00 .00 .00 .00 .01 .00 .01 .00 .0017 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .0118 .00 .01 .00 .03 .00 .00 .00 .01 .00 .01 .00 .0119 .00 .00 .00 .01 .00 .00 .00 .01 .00 .01 .00 .0020 .00 .01 .00 .00 .00 .00 .00 .02 .00 .01 .00 .0121 .00 .00 .00 .00 .00 .00 .00 .00 .00 .01 .00 .0122 .00 .00 .00 .00 .01 .00 .00 .00 .00 .05 .00 .0123 .00 .00 .00 .12 .01 .00 .00 .01 .14 .01 .00 .0124 .00 .00 .00 10 .01 .00 .00 .01 .01 .01 .00 .1225 .00 .00 .36 1,770 .01 .00 .00 .01 .01 .01 .00 .0126 .00 .00 .01 .04 .02 .00 .00 .00 .01 .01 .00 .0127 .00 .03 .00 4.6 1.1 .01 .00 .00 .01 5.2 .00 .0128 .05 .00 .01 .45 1.7 .01 6.4 .01 .01 .00 .00 .0129 .00 .00 .01 .00 .00 .01 .01 .02 .55 .00 .00 .0130 .00 .07 1.5 .50 --- .02 .01 .01 .01 .00 .00 .0131 .31 --- 2.1 .01 --- .32 --- .01 --- .00 6.6 ---

 TOTAL 0.43 5.61 22.00 1787.81 5.58 27.32 6.51 0.31 64.87 8.65 6.61 0.88
48 Streamflow and Suspended-Sediment Loads Before, During, and After H-3 Highway Construction, Oahu, Hawaii, 1983-99 Appendix 2.--Daily mean discharge (cubic feet per second) for water year 1997 at streamflow-gaging station 16273950, South Fork Kapunahala Stream at Kaneohe, Oahu, Hawaii [e, estimated daily value; acre-ft, acre-feet] Day Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sep. 1 e1.7 e1.6 e2.2 e2.2 e2.3 e2.1 e2.4 e2.3 e2.3 e2.2 e2.0 e1.9 2 e1.7 e2.2 e2.1 e2.4 e2.2 e2.1 e7.9 e2.3 e2.3 e2.2 e2.0 e1.9 3 e1.7 e1.8 e2.2 e11 e2.2 e2.0 e3.6 e2.3 e2.2 e2.2 e2.0 e1.9 4 e1.7 e1.7 e2.2 e6.1 e2.2 e2.4 e2.7 e2.3 e2.2 e2.2 e2.1 e1.9 5 e1.7 e5.9 e2.2 e2.5 e2.2 e5.8 e2.6 e2.6 e2.2 e2.1 e2.2 e1.8 6 e1.7 e2.2 e2.2 e2.3 e2.2 e2.2 e2.6 e2.6 e2.2 e2.3 e2.2 e1.9 7 e1.7 e1.9 e2.2 e2.2 e2.1 e2.1 e2.5 e3.1 e2.2 e2.2 e2.1 e1.9 8 e1.7 e6.5 e2.1 e2.1 e2.1 e2.0 e2.5 e7.1 e2.2 e2.2 e2.0 e1.8 9 e1.8 e2.1 e1.9 e2.1 e2.1 e2.1 e2.4 e2.6 e2.1 e2.3 e2.0 e1.8 10 e1.8 e1.9 e1.9 e2.1 e2.1 e2.1 e2.5 e2.5 e2.0 e2.3 e2.0 e1.8 11 e1.8 e1.8 e1.9 e2.0 e2.0 e5.6 e2.6 e2.6 e2.0 e2.2 e2.1 e1.9 12 e1.8 e8.6 e2.0 e2.0 e2.0 e2.1 e2.4 e2.8 e2.0 e2.2 e2.1 e2.4 13 e1.8 e8.0 e2.0 e2.0 e2.0 e2.2 e2.4 e2.5 e2.0 e2.3 e2.0 e2.1 14 e1.8 e9.6 e2.0 e2.0 e2.0 e2.0 e2.3 e6.8 e2.1 e2.3 e2.0 e2.1 15 e1.8 e3.4 e2.0 e2.0 e2.0 e2.4 e2.3 e6.2 e2.1 e2.3 e2.0 e2.0 16 e1.8 e7.4 e2.0 e2.1 e2.0 e2.1 e2.3 e3.1 e2.1 e2.2 e2.2 e2.0 17 e1.8 e6.5 e2.0 e2.0 e2.2 e9.4 e2.3 e2.7 e2.1 e2.2 e5.5 e1.9 18 e1.7 e2.8 e2.0 e2.0 e2.0 e2.5 e2.3 e2.6 e2.1 e2.1 e2.2 e1.8 19 e2.1 e2.6 e1.9 e7.0 e2.0 e2.2 e2.3 e2.5 e2.2 e2.4 e2.0 e1.9 20 e1.8 e2.5 e1.9 e3.1 e2.2 e2.2 e2.3 e2.4 e2.2 e2.0 e1.9 2.1 21 e1.7 e2.4 e2.0 e3.4 e2.2 e2.3 e2.3 e2.4 e2.3 e2.1 e1.9 2.7 22 e1.6 e2.2 e2.0 e2.6 e5.3 e2.3 e2.3 e2.5 e2.2 e3.8 e1.9 2.0 23 e1.6 e2.3 e2.1 e2.3 e2.2 e8.5 e2.2 e2.6 e2.2 e2.4 e1.9 1.9 24 e1.6 e2.8 e2.1 e2.2 e2.0 e2.9 e2.4 e2.5 e2.3 e2.2 e1.9 1.8 25 e1.5 e2.3 e2.0 e2.3 e2.0 e2.8 e2.4 e2.4 e2.2 e2.2 e1.9 1.8 26 e1.6 e2.3 e2.2 e2.2 e2.3 e2.6 e5.3 e2.4 e2.4 e2.1 e2.0 1.8 27 e1.6 e2.2 e2.8 e2.2 e2.3 e2.5 e2.7 e2.4 e2.4 e2.0 e1.9 1.8 28 e1.6 e2.2 e2.1 e2.2 e2.0 e2.6 e2.4 e2.3 e2.2 e2.0 e1.9 1.8 29 e1.6 e2.2 e2.0 e2.5 --- e2.4 e2.3 e2.3 e2.3 e2.0 e2.0 1.8 30 e1.6 e2.2 e2.0 e2.4 --- e2.3 e2.3 e2.3 e2.3 e2.0 e1.9 1.8 31 e1.6 --- e2.3 e2.4 --- e2.2 --- e2.2 --- e2.0 e2.0 --- Total 53.0 104.1 64.5 87.9 62.4 91.0 81.8 90.2 65.6 69.2 65.8 58.0 Mean 1.71 3.47 2.08 2.84 2.23 2.94 2.73 2.91 2.19 2.23 2.12 1.93 Max. 2.1 9.6 2.8 11 5.3 9.4 7.9 7.1 2.4 3.8 5.5 2.7

 Min. 1.5 1.6 1.9 2.0 2.0 2.0 2.2 2.2 2.0 2.0 1.9 1.8

Acre-ft 105 206 128 174 124 180 162 179 130 137 131 115
References Cited 49

Appendix 3. --Daily mean sediment discharge (tons/day) for water year 1997 at sediment-gaging station 16273950, South Fork Kapunahala Stream at Kaneohe, Oahu, Hawaii[e, estimated daily value]

Day Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sep.

 1 e.09 e.08 e.06 e.07 e.14 e.12 e.06 e.14 e.09 e.14 e.12 e.12 2 e.10 e.22 e.05 e.08 e.13 e.12 e4.0 e.13 e.12 e.13 e.12 e.12 3 e.11 e.13 e.05 e7.8 e.12 e.11 e.32 e.13 e.09 e.12 e.12 e.12 4 e.12 e.09 e.05 e2.4 e.12 e.27 e.11 e.13 e.09 e.11 e.12 e.12 5 e.13 e3.2 e.05 e.13 e.12 e2.2 e.11 e.34 e.10 e.10 e.13 e.12 6 e.14 e.12 e.05 e.11 e.12 e.14 e.11 e.23 e.10 e.13 e.13 e.12 7 e.15 e.11 e.05 e.09 e.12 e.12 e.07 e.28 e.10 e.10 e.11 e.12 8 e.16 e3.9 e.05 e.09 e.11 e.12 e.07 e3.5 e.10 e.09 e.09 e.12 9 e.19 e.06 e.05 e.10 e.11 e.12 e.06 e.25 e.10 e.12 e.09 e.12

 10 e.18 e.05 e.05 e.10 e.11 e.12 e.07 e.15 e.09 e.12 e.08 e.12 11 e.17 e.04 e.10 e.10 e.11 e2.3 e.11 e.23 e.09 e.11 e.07 e.12 12 e.16 e6.9 e.06 e.11 e.11 e.13 e.07 e.29 e.08 e.11 e.06 e.18 13 e.15 e6.0 e.06 e.12 e.11 e.13 e.07 e.16 e.06 e.12 e.07 e.14 14 e.14 e8.8 e.27 e.12 e.11 e.12 e.07 e3.4 e.05 e.12 e.09 e.15 15 e.13 e.14 e.06 e.12 e.11 e.16 e.07 e2.8 e.05 e.12 e.11 e.14 16 e.13 e5.1 e.06 e.12 e.11 e.14 e.07 e.32 e.03 e.11 e.16 e.16 17 e.12 e2.5 e.05 e.11 e.12 e9.7 e.07 e.24 e.03 e.11 e2.0 e.17 18 e.11 e.11 e.05 e.11 e.11 e.24 e.07 e.20 e.04 e.11 e.14 e.14 19 e.34 e.09 e.05 e3.5 e.11 e.14 e.07 e.12 e.06 e.16 e.12 e.10 20 e.12 e.06 e.05 e.79 e.12 e.14 e.07 e.12 e.08 e.10 e.11 .13 21 e.12 e.06 e.05 e.63 e.12 e.14 e.07 e.11 e.11 e.12 e.11 .53 22 e.12 e.05 e.05 e.27 e2.1 e.14 e.07 e.11 e.08 e.57 e.11 .15 23 e.14 e.05 e.05 e.15 e.12 e5.7 e.07 e.18 e.10 e.14 e.11 .11 24 e.14 e.17 e.05 e.14 e.11 e.22 e.08 e.11 e.11 e.14 e.11 .09 25 e.11 e.06 e.05 e.15 e.11 e.15 e.08 e.11 e.12 e.14 e.11 .09 26 e.09 e.06 e.10 e.14 e.22 e.08 e1.9 e.10 e.14 e.13 e.13 .08 27 e.07 e.06 e.20 e.14 e.15 e.05 e.36 e.10 e.15 e.12 e.12 .08 28 e.06 e.06 e.06 e.13 e.11 e.08 e.14 e.10 e.11 e.12 e.11 .07 29 e.04 e.06 e.05 e.16 --- e.05 e.14 e.10 e.13 e.12 e.13 .07 30 e.06 e.06 e.05 e.14 --- e.06 e.14 e.10 e.14 e.12 e.12 .07 31 e.08 --- e.09 e.14 --- e.05 --- e.09 --- e.12 e.12 ---

 Total 3.97 38.39 2.12 18.36 5.36 23.36 8.77 14.37 2.74 4.17 5.32 3.97