Sedimentation History of Waimaluhia

Reservoir during Highway Construction, Oah

Hawaii, 1983–98

By Michael F. Wong

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 01-4001

Prepared in cooperation with the

STATE OF HAWAII DEPARTMENT OF TRANSPORTATION

and the FEDERAL HIGHWAY ADMINISTRATION

Honolulu, Hawaii

2001
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, 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 purcha

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 

MARCH 3, 1
Content

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

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

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Description of the Study Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Hydrology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Land Use and Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Method of Bathymetric Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Field Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Data Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sediment Accumulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Bathymetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sediment Yield and Trap Efficiency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Figures

1–7. Maps showing:

1. Waimaluhia Reservoir and study area, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

2. Monumented cross-section locations and reservoir bottom sample locations for the sedimentation

survey of Waimaluhia Reservoir, Oahu, Hawaii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3. Bathymetric map of Waimaluhia Reservoir, 1983, Oahu, Hawaii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

4. Bathymetric map of Waimaluhia Reservoir, 1988, Oahu, Hawaii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

5. Bathymetric map of Waimaluhia Reservoir, 1993, Oahu, Hawaii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6. Bathymetric map of Waimaluhia Reservoir, 1998, Oahu, Hawaii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

7. Areas of sediment deposition from 1983 to 1998 in Waimaluhia Reservoir, Oahu, Hawaii. . . . . . . . . . . 

Tables

1. Annual rainfall in the Kamooalii Stream drainage basin, Oahu, Hawaii, water years 1981–98 . . . . . . . . . . . 

2. Annual streamflow at stream-gaging stations in the Kamooalii Stream drainage basin, Oahu, Hawaii,

water years 1981–98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

3. Chronology of construction activities at the Halekou Interchange and Windward Highway segments

of the H-3 Highway, Kamooalii Stream drainage basin, Oahu, Hawaii, 1983–98 . . . . . . . . . . . . . . . . . . . 

4. Cross sections surveyed by calender year in Waimaluhia Reservoir, Oahu, Hawaii, 1983–98 . . . . . . . . . . . . 

5. Results of selected volumetric computation methods, Waimaluhia Reservoir, Oahu, Hawaii,

1983 survey data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6. Computed area, volume, average bottom altitude, and change in volume of Waimaluhia Reservoir,

Oahu, Hawaii, 1983–98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
iv Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983-98

7. Bulk density of bottom material from Waimaluhia Reservoir, Oahu, Hawaii, August 1993

and October 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

8. Annual suspended-sediment loads at stream-gaging stations in the Kamooalii drainage basin,

Oahu, Hawaii, water years 1981–98 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

CONVERSION FACTORS

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F−32)/1.8

Multiply By To obtain

Length

inch (in) 2.54 centimeter

foot (ft) 0.3048 meter

Area

acres 4,047 square meter

square mile (mi2

) 2.590 square kilometer

square mile (mi2

) 640 acres

Volume

acre-foot (acre-ft) 1,233 cubic meter

Volume per unit time

(includes flow)

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year

cubic foot per second (ft3/s) 0.02832 cubic meter per second

cubic foot per second-days (ft3/s-days) 0.02832 cubic meter per second-days

cubic foot per second-days per year (ft3/s-days/yr) 0.02832 cubic meter per second-days per year

gallon per minute (gal/min) 0.06308 liter per second

million gallons per day (Mgal/d) 0.04381 cubic meter per second

Density

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter

pound per cubic foot (lb/ft3

) 0.016 grams per cubic centimeter

Weight

ton (ton) 0.9072 metric ton

ton per square mile per year (ton/mi2/yr) 0.3503 metric ton per square kilometer per year
Sedimentation History of Waimaluhia Reservoir durin

Highway Construction, Oahu, Hawaii, 1983–98

By Michael F. Wong

Abs

Abstract

Nine sedimentation surveys conducted from

1983 to 1998 at Waimaluhia Reservoir determined

the rate of sediment accumulation in the reservoir

during H-3 Highway construction upstream of the

reservoir. Rates of storage-capacity loss ranged

from 1.1 acre-feet per year between 1983 and 1988

to 4.9 acre-feet per year between 1988 and 1992.

The average loss rate during the period of intensive

construction between 1983 to 1992 was 2.7 acre-ft

per year. The average loss rate during the study

period between 1983 and 1998 equals the design

loss rate of 2.0 acre-feet per year. The average bulk

density of deposited sediments was 29 pounds per

cubic foot. From the bulk density data, loss of storage capacity, and suspended-sediment data collected downstream of the reservoir, a total of

26,950 tons of sediment was delivered to the reservoir from 1983 to 1998, of which 19,100 tons were

trapped in the reservoir. From these sediment

loads, a sediment yield of 565 tons per square mile

per year and trap efficiency of 71 percent were

computed. A trap efficiency of 60 percent, bulk

density of 65 pounds per cubic foot, and sediment

yield of 1,500 tons per square mile per year were

used to compute the design loss rate of 2.0 acre-feet

per year.

INTRODUCTION

Waimaluhia Reservoir is located within the

Kamooalii Stream drainage basin on the eastern part of

the island of Oahu (fig. 1). The reservoir was designed

and constructed as part of the U.S. Army Corps of Engineers Kaneohe-Kailua Flood Control Project in

response to heavy flooding in Kaneohe during t

1960’s. Construction of the earth-fill dam starte

1977 and was completed in 1980. The reservoir 

impounded in October 1980. Built at the former 

ence of Kuou and Kamooalii Streams, Waimalu

ervoir was designed to maintain a constant pool 

of 160 ft above mean sea level via an outlet stru

the pool, allowing a 50 percent turnover of wate

reservoir each week (U.S. Army Corps of Engin

Honolulu District, 1981). The reservoir pool is p

larger flood control reservoir. The main dam (fi

with crest altitude of 222 ft is designed to retain 

imum flood stage of 217 ft. A spillway on the w

end of the dam (fig. 2) becomes effective at flo

tudes over 202 ft. At maximum flood stage, the 

voir pool would cover 152 acres and hold 3,800 

of water (U.S. Army Corps of Engineers, Honol

trict, 1981). The H-3 Highway was constructed

upstream of the reservoir between 1983 and 19

Because the highway construction involved sub

disturbance of the land surface, concerns were r

over accelerated erosion from the construction a

sequent deposition in the reservoir, which poten

could deplete the storage capacity faster than the 

loss rate of 2 acre-ft/yr. To assess the impact of t

way construction on the reservoir, the U.S. Geo

Survey in cooperation with the State of Hawaii 

ment of Transportation and the Federal Highwa

Administration, conducted a number of bathym

surveys of Waimaluhia Reservoir.

Purpose and Scope

The purpose of this report is to document r

observed sediment deposition in Waimaluhia Re

during construction of the H-3 Highway. This r
2 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

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

Wildlife Pond Hawaii

Pacific University

Kaneohe

Interchange

Halekou Interchange

Kalanianao

Highway Right Branch

Kamooalii Stream

Kamooalii

Pali Highway

RAN

GE

KOOLAU

157 ̊49' 1

21 ̊

25'

21 ̊

22'

30"

H-3 Highway

Likelike Highway

EXPLANATION

DRAINAGE DIVIDE

STREAM-GAGING STATION--This 

 study

STREAM-GAGING STATION--Jones 

 and others (1971)

ABREVIATED STATION NUMBER--

 Complete number is 16272200

RAIN GAGE AND STATE KEY

 NUMBER

0

0 1 KILOMETER

1/2 1 MILE

OAHU,

HAWAII

Study Area

Pacific

Ocean

d

D

a

Iolekaa Stream

Heeia

Stream

Stream

Stream

Haiku

Kapunahala

South Fork

Kapunahala

Stream

Kuou

Piho Stream

Hooleinaiwa Stream

Kamooalii Str

Kaneohe Stream

Luluku Stream

Windward

Highway Segment Stream

Waimaluhia

Reservoir

d

d D

a da

a

a

2722

2722

2705

781.7

781.4

781.4

781.9

788.1

2656

Luluku rain gage

Pali

rain gage

2709

Figure 1. Waimaluhia Reservoir and study area, Oahu, Hawaii.
Introdu

SP

LI

LWAY

D A M

SP

LI L

WAY

D A M

0 100 200

0 50 100 METERS

300 400 FEET

2

3

4

41

5

1

42

26

2

40

39

B2

38

21

20

35A

K4

43 34

6

Shore

NOLL

Shore

35

8

2

36

14 33

32

7

B3

K6

K5

3113

12

27

11

10

9

17

16

15 18

19 28

23

24

25

42A

TED-NOLL

COE-TED

K3

B1

B2

R8

QW3

COE-A-WEST

COE-A-EAST

COE-C

Island

R7

A1

A2

B4

QW4

R6

QW1

R4

COE-16

COE-16

COE-21

Outlet

R3

R2

R1

R10

R9

QW2

160.0 FEET

160.0 FEET

160 FEET

COE-NOLL

o

o

o

o

o

o

o

o

N

EXPLANATION

MONUMENTED CROSS SECTION AND IDENTIFICATION NUMBERS

SHORELINE ALTITUDE--Datum is mean sea level

MONUMENT LOCATION AND NUMBER

BOTTOM MATERIAL BULK DENSITY

 SAMPLE POINT

OUTLET STRUCTURE (Lat. 21 ̊23'36"N. Long. 157 ̊48'26"W.)

Figure 2. Monumented cross-section locations and reservoir bottom sample locations for the sedimentation surve

of Waimaluhia Reservoir, Oahu, Hawaii.
4 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

describes the volume, mass, and distribution of sediments deposited in Waimaluhia Reservoir between

1983 and 1998 as calculated from bathymetric surveys,

bottom sediment sampling, and suspended-sediment

data.

Acknowledgements

The staff at the Ho’omaluhia Botanical Garden,

Department of Parks and Recreation, City and County

of Honolulu allowed access to Waimaluhia Reservoir

and provided the boats used for field data collection. Dr.

Eric DeCarlo, University of Hawaii at Manoa, provided

the core sampler.

DESCRIPTION OF THE STUDY AREA

The Waimaluhia Reservoir drainage basin originates on the precipitous windward slopes of the Koolau

Range. Elevations within the 3.20 mi2 basin range from

about 2,750 ft at the crest of the Koolau Range, to about

150 ft near the reservoir dam site. Stream-gaging station

2722 (fig. 1) is downstream of the dam, at an altitude of

116 ft, with a drainage area of 3.81 mi2

. (Four-digit gaging station numbers used in this report are abbreviated

numbers. The complete numbers are preceded by 16

and end in 00. For example, for station 2722 the complete number is 16272200.) Because the dam was constructed upstream of the confluence of Luluku and

Kamooalii Streams, streamflow at station 2722 includes

water flowing through Waimaluhia Reservoir and water

from perennial Luluku Stream that does not pass

through the reservoir. The 0.61 mi2 of area below the

reservoir and upstream of station 2722 contains the 0.44

mi2 Luluku basin upstream of station 2709 (fig. 1). Five

tributaries flow into the reservoir. The smaller two,

Kuou Stream and Piho Stream are intermittent (fig. 1)

whereas, Hooleinaiwa, Kamooalii, and Right Branch

Kamooalii Streams are perennial. Both Hooleinaiwa

and Right Branch Kamooalii Streams flow into

Kamooalii Stream upstream of the reservoir (fig. 1). Of

these tributaries, only Right Branch Kamooalii Stream

was continuously gaged at station 2656 (fig. 1).

The stream channels within these basins cut into

bedrock in the steep cliff areas and into 2 to 20 ft of alluvium in the lower areas. Stream bed material consists of

primarily small boulders, cobbles, and gravel intermixed with finer sediment, intermixed with a few large

boulders. Alluvium, which underlies most of th

age area, begins at about altitude 600 ft and ext

down to sea level. Areas above 600 ft consist o

steep, volcanic rock cliffs of the Koolau Basalt

to the east of the reservoir consist of the younge

lulu Volcanics (geology from Takasaki and oth

1969; geologic names from Langenheim and C

1987). Borings done by the U.S. Army Corps o

neers (1975a) around the reservoir and dam site 

the alluvium to be about 20 to 50 ft thick above v

tuff deposits. Basalt was encountered about 10 

below the tuff in holes drilled near altitudes 120 

ft (U.S. Army Corps of Engineers, 1975a).

Hydrology

The average annual temperature ranges fro

76°F with diurnal temperature fluctuations of 8 

within the study area (Blumenstock and Price, 

The mean annual pan evaporation is about 50 in. 

and Chang, 1985) and the median annual rainfal

from about 59 in. near the coast to about 100 in. n

crest of the Koolau Range (State of Hawaii, 198

rainfall distribution is affected by the prevailing 

easterly winds and by the orographic lifting and 

which results in heavier and more frequent rainf

the Koolau Range crest. Annual rainfall totals b

year for four rain gages in the study area (fig. 1

shown in table 1. Compared to 1983–98 averag

fall, 1988–89 and 1996–97 were relatively wet, w

1984, 1992, 1995, and 1998 were relatively dry

average of the two Luluku rain gages (781.11 a

781.7) near the reservoir, which is about 75 in/y

1), represents the mean annual rainfall on the re

Three continuous streamflow-gaging statio

operated during the study period. Station 2656, 

Branch Kamooalii Stream, upstream of the Waim

Reservoir; station 2722, Kamooalii Stream belo

Luluku Stream, downstream of the reservoir; an

tion 2709, Luluku Stream at altitude 220 ft, me

flow entering Kamooalii Stream downstream of 

ervoir and upstream of station 2722 (fig. 1). Stre

data collection at station 2722 started in Novem

1976 and continues to date (2000), while suspe

sediment data collection started on November 19

ended in September 1998. Streamflow and susp

sediment data were collected from February 19

September 1997 at station 2656 and from April 

June 1998 at station 2709. Annual streamflow t
Description of the Study 

cubic feet per second-days are listed by water year in

table 2. Correlating with the rainfall data presented in

table 1, 1984–85, 1992, 1995, and 1998 were years of

low streamflow, whereas 1982, 1988–89, 1991, and

1997 were years of high streamflow (table 2). The flow

through the reservoir can be computed as streamflow at

station 2722 less streamflow at station 2709 (table 2).

The average reservoir outflow computed in this manner

for water years 1985–97 was 3,600 ft3

/s-days/year.

Perennial streamflow for most streams in the study

area begins near altitude 550 ft and increases downstream to altitude 150 ft, with most of the gain between

altitudes 225 and 150 ft (Takasaki and others, 1969).

Streamflow gains downstream of station 2709 and

upstream of Kamooalii Stream were insignificant, only

0.03 ft3

/s (Hill and others, 2000). No basal ground water

was encountered in the 58 borings, the deepest reaching

altitude 35 ft, drilled around the dam and reservoir site

by the U.S. Army Corps of Engineers (1975a). Seepage

of about 1 gal/min from coarse-grained alluvium was

encountered in only four holes at altitudes of 120 

ft. Thus, seepage into the reservoir is probably 

and would occur near the Kamooalii Stream entr

the reservoir since both Kuou and Piho Streams 

been observed to go dry. Seepage on the downs

side of the earthen dam was observed during thi

to be insignificant, not more than 0.03 ft3

/s, and 

seepage was observed flowed into Kamooalii S

upstream of station 2722.

Several municipal wells and a water tunne

upstream of station 2722. Additional municipal 

vate wells and were drilled in the study area dur

study. Average yearly pumpage from the munic

wells and tunnel from 1983 to 1996 was about 

Mgal/d (data from Honolulu Board of Water Su

annual reports, 1983–96) while average yearly 

age (1990–97) from the golf course wells is low

0.15 Mgal/d (data from Neal Fujii, Commission 

Water Resource Management, Department of L

Natural Resources, State of Hawaii, written com

1

 Only for complete years for the period 1981–98

Table 1. Annual rainfall in the Kamooalii Stream drainage basin, Oahu, Hawaii, water years 1981–98

[Numbers below gage names are State Key Numbers assigned to rain gages in Hawaii by the Commision of Water Resources Management,

Department of Land and Natural Resources, State of Hawaii; all rainfall totals are in inches; --, no data; P, partial year, more than one month 

missing data; e, estimated annual total, one or more months were estimated, value was estimated by comparison with other gages in the table

Water

Year

U.S. Geological Survey gages National Weather Service gages

 Luluku

Stream

(781.11)

 Right Branch

Kamooalii Stream

(781.9)

Luluku

(781.7)

Pali Golf

Course

(788.1)

1981 -- -- P 66.5

1982 -- -- P 127

1983 -- P P 59.4

1984 P 38.9 41.9 37.8

1985 66.8 63.9 71.2 55.8

1986 66.2 59.2 74.2 53.3

1987 66.7 67.2 e76.1 62.5

1988 95.1 86.8 98.7 130

1989 87.2 84.1 e110 103

1990 62.8 62.4 e80.8 P

1991 64.9 68.5 P 80.1

1992 e55.9 42.2 e75.9 50.1

1993 61.6 P 76.2 110

1994 71.2 P 91.5 84.6

1995 49.1 e40.2 P 68.8

1996 73.7 e60.1 92.4 97.2

1997 e81.5 e75.9 e105 109

1998 44.7 P P 40.7

Average1 67.7 62.4 82.8 78.6
6 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

2000). Hill (1996) found no statistical link between

ground-water withdrawals and streamflow during

1983–91 in the study area.

Land Use and Cover

Most of the area upstream of the Waimaluhia Reservoir is occupied by a botanical garden, two golf

courses, and the Hawaii Loa campus of Hawaii Pacific

University. The 420-acre Ho’omaluhia Botanical Garden (fig. 1) surrounding the reservoir is a public park

operated by the City and County of Honolulu and was

built at the same time as the reservoir. The park specializes in trees and shrubs from tropical locations worldwide with areas for camping and horseback riding. In

addition to the 26-acre Waimaluhia Reservoir, a smaller

1.5 acre wildlife pond was built along Hooleinaiwa

Stream (fig. 1). Upstream of the park and reservoir to

the east and southeast is the 216-acre Pali Golf Course

completed by 1957, the 220 acre Koolau (originally

Minami) Golf Course built between 1989 and 1991, and

the Hawaii Loa campus which occupies about 24 of 142

acres within the watershed. Residential areas upstream

of the reservoir occupy about 50 acres with mos

housing located to the east. The H-3 Highway w

crosses the basin roughly east to west occupies 

120 acres including easements. The remaining 

acres is undeveloped conservation zoned land. P

both Likelike and Pali Highways cross the drain

basin near the Koolau Range (fig. 1).

Highway construction within the Waimalu

ervoir drainage basin began in 1983 (table 3) w

construction of the Halekou Interchange upstre

station 2656 (fig. 1). Numerous court injunction

delayed the construction at various times (table 

struction of the Windward Highway segment of 

3 Highway, which affects most of the basin, be

the summer of 1989 and ended in the summer o

(table 3). The highway segments upstream of th

voir were constructed by cut and fill techniques

Windward Highway from Likelike Highway to 

Halekou interchange was briefly opened to traff

March 1992 to August 1993. The entire H-3 Hi

system was opened in December of 1997.

Soils in the study basin have been classifie

mostly Lolekaa with some Kaneohe silty clays 

Table 2. Annual streamflow at stream-gaging stations in the Kamooalii Stream drainage basin, Oahu, Hawaii, wate

years 1981–98

[Values in cubic feet per second-days; --, no data; P, partial year, more than one month of no data; complete station numbers are preceded by 16 

end in 00]

Water Year

Station 2656 Right

Branch Kamooalii

Stream

Station 2722

Kamooalii Stream

Station 2709 Luluku

Stream

Reservoir outflow,

Kamooalii Stream

less Luluku Stream

1981 -- 3,140 -- --

1982 -- 8,040 -- --

1983 P 4,090 -- --

1984 122 1,600 P --

1985 284 2,290 152 2,140

1986 406 2,940 150 2,790

1987 612 3,760 327 3,430

1988 986 6,070 508 5,560

1989 1,040 5,930 532 5,400

1990 532 4,280 488 3,790

1991 762 5,000 737 4,260

1992 308 3,030 471 2,560

1993 605 3,610 394 3,220

1994 609 4,240 519 3,720

1995 216 2,605 606 2,000

1996 504 3,580 520 3,060

1997 721 5,370 554 4,820

1998 -- 2,730 P --
Description of the Study 

humic latosols great soil group (Foote and others,

1972). These soils are well drained, dark red to brown,

and highly erodible on steep slopes (Foote and others,

1972).

Erosion-mitigation methods used during highway

construction consisted of erosion-cloth barriers or silt

fences used along stream channels, loose-rock check

dams in channels upstream of station 2656, and hydromulching and fabric covering on cut-and-fill slopes.

Erosion-mitigation methods used during the golf course

construction were not determined for this study.

Most of the basin is covered with vegetation, either

natural or cultivated. Natural vegetation is diverse, with

hau trees growing along the stream channels and guava

and Java plum trees, false staghorn fern, and various

grasses predominating elsewhere (U.S. Army Corps of

Engineers, 1974). A 16-acre forest of eucalyptus and

aracaria trees is to the southeast of the reservoir and

about 30 acres of banana cultivation continues in the

park to the northwest of the reservoir (U.S. Army Corps

of Engineers, 1974). Other cultivated areas include

grasses on two golf courses. Downstream of the reservoir are additional banana plantations in the Luluku

Stream basin both upstream (about 40 percent of the

drainage area) and downstream of station 2709.

Previous Studies

A number of design memorandums covering the

hydrology, geology, and design of the flood control reservoir and surrounding park and background of the

study area were published by the U.S. Army Corps of

Engineers (1972, 1973, 1974, 1975a, 1975b) alo

a number of environmental impact statements (

such as U.S. Army Corps of Engineers (1975c)

tional background information on the study area 

found in the many EIS for the H-3 Highway su

U.S. Department of Transportation, Federal Hig

Administration (1980) as well as the Kamooalii 

shed Wells EIS (City and County of Honolulu, B

Water Supply, 1984).

Jones and others (1971) conducted a sedim

transport reconnaissance study for Oahu and op

station 2705 from 1967 to 1969 immediately do

stream of the dam and Luluku Stream inflow (fi

suspended-sediment yield of 910 tons/mi2

/year 

estimated for the drainage basin of this station. 

and others (1971) also computed specific weigh

density) for suspended sediment from five wind

Oahu streams. These values ranged from 53 to 6

with an average of 57 lb/ft3. With the completio

flood-control project in 1981, an operations and 

nance manual was published (U.S. Army Corps 

Engineers, Honolulu District, 1981). The reserv

designed to hold 260 acre-ft of water but becau

island within the reservoir was built larger than p

the estimated volume at the time of completion 

was 235 acre-ft (Jim Pennaz, U.S. Army Corps 

neers, written comm., 1990). The design sedim

osition rate of 2 acre-ft/yr was based on an annu

sediment yield of 1,500 tons/mi2

/yr from the dr

area contributing to the reservoir, an average se

bulk density of 65 lb/ft3

, and a reservoir trap eff

of 60 percent (U.S. Army Corps of Engineers, H

District, 1981). Trap efficiency is the percentag

1

 Work on Halekou Interchange interrupted by court injunctions

Table 3. Chronology of construction activities at the Halekou Interchange and Windward Highway segments of the H

Highway, Kamooalii Stream drainage basin, Oahu, Hawaii, 1983–98

[Locations of construction activities and stream-gaging stations are shown in figure 1; start and end dates provided by the State of Hawaii, De

ment of Transportation]

Construction activity

Downstream gaging

stations Start date End date

Halekou Interchange1 2656, 2722 02/22/83 12/01/83

03/02/84 07/31/85

11/04/85 02/28/86

11/02/86 12/31/86

06/15/87 09/30/88

Windward Highway segment 2656, 2709, 2722 06/19/89 06/92
8 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

sediment delivered to the reservoir that is trapped and

deposited in the reservoir. The U.S. Army Corps of

Engineers conducted a sediment survey in 1990 and

determined the reservoir volume to be 218.1 acre-ft

(Jim Pennaz, U.S. Army Corps of Engineers, written

commun., 1990).

Wong and Hill (1992) presented bathymetric maps

for Waimaluhia Reservoir for years 1983 and 1988 as

well as a brief discussion of the data collection methodology. Hill (1996) discussed the construction effects of

the H-3 Highway as of 1991 on the streamflow and suspended-sediment loads at stations 2656, 2709, and

2722. Hill (1996) concluded that low-flows increased at

station 2709 and decreased at station 2722 during construction, and that suspended-sediment loads increased

at station 2656, did not change at station 2722, and

decreased at station 2709 as a result of highway construction.

METHOD OF BATHYMETRIC SURVEY

Sediment accumulation in Waimaluhia Reservoir

was calculated by conducting bathymetric surveys

using monumented cross sections. A total of 30 cross

sections were established (fig. 2). The end points of

each cross section were monumented with pipes set in

concrete. Horizontal angles, vertical angles, distances

between monuments and an arbitrary horizontal datum

were measured by the State of Hawaii, Department of

Transportation, Highway Division, in December 1983

and used to compute northings, eastings and altitudes

for all monuments. All altitudes are relative to mean sea

level.

Field data for each survey were processed using a

geographical information system (GIS) program to plot

all data points for manual drawing of bathymetric contours of the reservoir bottom. These contours were then

digitized back into the GIS program which was used to

compute the area and volume for each survey.

Cross-sectional surveys were made in September

1983, November 1988, August 1990, September 1991,

September 1992, August 1993, July 1994, September

1995, and July 1998 (table 4). In 1983, all 30 original

cross sections were surveyed, whereas in the other years

between 20 to 26 cross sections were surveyed. Table 4

lists the cross sections surveyed in each year that were

converted into digital form to be used in the GIS program. Cross sections A1 and A2 were used only 

1995 and 1998 surveys and were created to avoi

the long COE-A-East and -West cross-sections 

Field Techniques

During each survey, a tagline made of buo

non-stretching material was attached to the two 

ments defining each cross section. Because of w

action and wind deflection, positional coordina

determined from the tagline are considered accu

the nearest foot. The water surface altitude of th

voir was monitored at a staff plate mounted on th

structure (fig. 2) to the nearest hundredths of a 

the beginning, midpoint, and end of each day of 

vey. The depths from the water surface to the bo

the reservoir were determined to a precision of 

with an accuracy of 0.05 ft because of wave act

Depths were measured with an electronic sounde

1983 survey. The 1990 and 1991 surveys used 

ent electronic sounder than the 1983 survey and 

1992 to 1998 surveys used a manual sounding w

The manual sounding weight used in the 1990 t

surveys was constructed with an 8-in. diameter 

rated base designed to prevent sinking into soft 

ments. The 1988 survey used a surveying rod w

precision of 0.1 ft and a manual sounding weigh

precision of 0.01 ft and an estimated accuracy o

The surveying rod used in 1988, and in subsequ

veys where vegetation growth near the shorelin

fered with use of the sounder, was modified for 

soft sediment. The modification involved the ad

of an 8-in. diameter perforated wood base desig

prevent the rod from sinking into soft sediment

the surveying rod and the manual sounding weig

constructed in a way that all readings were dire

Bulk density, also called unit or specific we

the ratio of mass to the bulk (volume plus pore sp

a soil sample and is used to estimate the mass o

ume of soil too large to weigh, such as an acre-ft 

1965). Samples of one-liter volume were collect

the reservoir bottom using a clam-shell sampler 

selected locations in August 1993 (fig. 2). A 2-in

eter core sampler was used in October 2000 to 

samples of various volumes depending on core 

Bulk density was then computed by drying the 

at 105°C to a constant weight, weighing, and di

the sample mass by sample volume (Blake, 196
Method of Bathymetric S

Data Processing

Northings, eastings, and altitudes (x, y, and z coordinates) for all points along the cross sections were

computed with a computer program written in BASIC

using the coordinates of the cross sectional monuments,

the altitude of the water surface, measurements of distances between monuments, and measured depths. The

design shoreline altitude of 160.0 ft was used for creating the bathymetric contour maps and as the datum in

the reservoir volume calculations. The initial shoreline

was digitized from a 1983 aerial photograph wi

scale of 1:1,200. The data points were plotted on 

of the reservoir and the bathymetric contour lin

drawn manually at a 2 ft-contour interval for ea

vey. The 1983 bathymetric map was drawn usin

contour intervals with additional data from the C

Engineers. The contours were then digitized int

GIS program. Reservoir volumes were compute

the digitized contours by the GIS program using 

gulated irregular network (TIN) algorithm. A T

sists of thousands of adjoining triangles with x, 

Table 4. Cross sections surveyed by calender year in Waimaluhia Reservoir, Oahu, Hawaii, 1983–98

[X, cross section surveyed; -, not surveyed; unpublished data in files at U.S. Geological Survey, Hawaii District]

Cross section

Sept.

1983

Nov.

1988

Aug.

1990

Sept.

1991

Sept.

1992

Aug.

1993

July

1994

Sept.

1995

Ju

199

A1 - - - - - - - X X

A2 - - - - - - - X X

B1 X X X X X X X X X

B2 X X X X X X X X X

B3 X - X X X X X X X

B4 X X X X X X X X X

COE-16 X--------

COE-19 X--------

COE-21 X X-------

COE-A-EAST XXXXXXX - -

COE-A-WEST XXXXXXX - -

COE-C XXXXXXXXX

COE-NOLL X--------

COE-TED XXXXXXXXX

K3 X - X X X X X X X

K4 X X X X X X X X X

K5 X X X X X X X X X

K6 X - X X X X X X X

QW1 X X X X X X X X X

QW2 X X X X X X X X X

QW3 X - X X X X X X X

QW4 X X X X X X X X X

R1 X X X X X X X X X

R2 X X X X X X X X X

R3 X - X X X X X X X

R4 X - X X X X X X X

R6 X X X X X X X X X

R7 X X X X X X X X X

R8 X X X X X X X X X

R9 X X X X X----

R10 X X X X X X X X X

TED-NOLL X -XXXXXXX

Total number surveyed 30 20 26 26 26 25 25 25 25
10 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

coordinates assigned to all vertices, creating a tridimensional surface model of the reservoir bottom.

Volume is then computed by summing the individual

volumes determined by multiplying the area of the triangular plane by its altitude. The number of digitized

points used to define the contours determined the number of triangular planes used to determine the volume.

The TIN and previous volume-calculation methods

such as the stage-area curve (Heinemann and Dvorak,

1963), average contour area (Heinemann and Dvorak,

1963), prismoidal formula (Moffit and Bouchard,

1987), and modified prismoidal or conic method (Heinemann and Dvorak, 1963), were compared using the

1983 survey data. The areas between the 2 ft-contour

intervals used in all these other computation methods

were computed by the GIS program. The results are

shown in table 5 ranked by computation accuracy, with

the stage-area curve being the least accurate. Results of

this comparison indicate that the TIN computed volume

is slightly less than those computed by other methods in

this particular case.

The 1983, 1988, and 1990 data were processed

with the ARC/INFO GIS program version 5.0, the 1991

to 1993 data were processed using version 6.0 and the

1994 to 1998 used version 7.0. Computational differences in the TIN algorithms between versions were

slight, the main modifications were between versions

5.0 and 6.0, with version 6.0 adding computations in

double precision (Environmental Systems Research

Institute, 1991).

Although quality control of bathymetric data consisted of surveying the same cross sections for each survey, this was not always possible because of vegetation

growth near the shoreline and next to some cross section

monuments. Some monuments were lost between surveys and were re-established as close as possible to the

original location. Graphical plots of each cross section

were compared with plots of the same cross section

from previous surveys to verify that the correct start and

end points of the monuments were used. To verify horizontal distances, the first 200 ft of tagline distance was

rechecked in 1994 against a steel tape and found to be

within 0.1 ft accuracy. Therefore, the location differences are considered insignificant and volume calculation differences are considered negligible. Accuracy of

vertical measurements was confirmed by checking the

first 10 ft of the sounder before each survey. Volumetric

computations were corroborated by comparing a mean

depth computed by dividing the volume by the area versus the mean depth computed from all the data 

collected.

SEDIMENT ACCUMULATION

Rates of sediment accumulation in Waima

Reservoir were determined by comparing the ch

in reservoir volume between surveys. These vo

were computed from the bathymetric maps deri

from the field data. Bulk-density data were used 

determine the sediment yield of the basin and th

efficiency of the reservoir.

Computed reservoir area and volume for e

vey are shown in table 6. The total loss of volum

ing the study period (1983–98, 14.9 years) was 

acre-ft which corresponds to an average loss rat

acre-ft/yr. During the 1983–88 construction of th

kou Interchange (table 3) the loss was 5.9 acre-f

average loss rate of 1.1 acre-ft/yr. In the 3.9 yea

between the November 1988 and September 19

veys, 19.0 acre-ft of sediment was deposited, wh

responds to an average sedimentation rate of 4.

ft/year. Construction of the Windward Highway 

ment spanned most of this period; the Koolau g

course was also built in this period. The total los

ervoir volume from 1992 to 1998 after all intens

struction work was completed was 5.4 acre-ft w

corresponds to a loss rate of 0.9 acre-ft/yr. For th

period of intensive construction works during 1

the total loss was 24.9 acre-ft for a loss rate of 2

ft/yr.

Bathymetry

Figures 3, 4, 5, and 6 are the bathymetric m

1983, 1988, 1993, and 1998 surveys, respective

These maps illustrate that the shape of the reserv

tom changed most on the eastern side of the res

where Kamooalii Stream flows into the reservo

ure 7 shows that between 1983 and 1998, most 

deposition occurred where the streams flow into 

ervoir and in the lower altitudes of the reservoir

6 shows a reduction in reservoir surface-area wi

Each survey indicated loss of reservoir vol

except for 1993, which indicated gain (table 6). 

data from this survey showed that some cross s

were deeper in 1993 than in 1992. This was mo
Sediment Accumu

the eastern and southern parts by cross sections B1, B2,

COE-A East and West, COE-C, COE-TED, QW 1,

QW4, R7, and R8 (fig. 2). Other cross-section depths

were equal or shallower than in 1992. A possible explanation for this volume increase could be the settlement

or compaction of sediments following the high rates of

deposition during 1990–92. Bulk-density data (table 7)

and visual observation indicate that most of the sediment deposited by 1993 was fine sediment consisting of

silts and clays less than 0.062 mm in size. Such material

can be subject to compaction.

Sediment Yield and Trap Efficiency

The sediment yield of the surrounding drainage

basin and trap efficiency of Waimaluhia Reservoir were

determined from the bulk-density and suspendedsediment data. Bulk-density data determined fro

tom samples are shown in table 7. All samples 

were, except for a few leaves and shells from fre

clams, close to 100 percent finer than 0.062 mm 

visual examination. The average density of the 

ples collected in 1993 was 25 lb/ft3

 (0.40 g/cm3

samples at deeper penetration depths (table 7) w

lected in 2000. These samples were visually als

to 100 percent finer than 0.062 mm in particle s

Samples taken at cross sections B4, COE-C, an

TED contained some sand and gravel only in th

to 3 inches of the reservoir bottom. The average 

of the 6 samples collected in 2000 (table 7) was 2

(0.46 g/cm3), not much different from the 1993 

densities. This density is low compared to the a

densities of 40 to 65 lb/ft3 for submerged clay-s

ture sediments (Geiger, 1963; Lara and Pember

Table 5. Results of selected volumetric computation methods, Waimaluhia

Reservoir, Oahu, Hawaii, 1983 survey data

Method

Volume

(acre-feet)

Stage-area curve 242.8

Average contour area 242.7

Prismoidal 242.7

Modified prismoidal or conic 241.5

Triangular irregular network 239.6

Table 6. Computed area, volume, average bottom altitude, and change in volume of Waimaluhia Reservoir, Oahu,

Hawaii, 1983–98

[Area, volume, and calculated bottom-altitude values are relative to 160.0 feet mean sea level reservoir pool altitude; bottom altitude calculate

dividing volume by area, and subtracting that value from 160.0 feet; change in volume calculated by subtracting volume for previous survey’

volume; --, not applicable]

Date of survey

Number of

measurements

Mean

bottom

altitude

(feet)

Maximum

depth

(feet)

Surface

area

(acre)

Volume

(acre-feet)

Calculated

bottom

altitude

(feet)

Change in

volume

(acre-feet)

Tim

betwe

surve

(yea

September 1983 1,418 151.5 17.8 26.8 239.6 151.1 -- --

November 1988 1,585 151.9 16.2 26.7 233.7 151.3 -5.9 5.2

August 1990 1,709 152.1 15.9 26.5 223.1 151.6 -10.6 1.8

September 1991 1,674 152.2 15.9 26.3 218.6 151.7 -4.5 1.

September 1992 1,638 152.0 15.9 26.3 214.7 151.8 -3.9 1.0

August 1993 1,464 152.1 15.7 26.4 215.8 151.8 +1.1 0.9

July 1994 1,630 152.3 15.4 26.3 213.9 151.9 -1.9 0.9

September 1995 1,596 152.2 15.7 26.4 212.3 152.0 -1.6 1.2

July 1998 1,584 152.2 15.7 26.2 209.3 152.0 -3.0 2.8
12 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

N

Island

EXPLANATION

BATHYMETRIC CONTOUR--Shows depth, in feet, below 

 shoreline, 1983. Contour interval variable.

SHORELINE--Altitude 160.0 feet above mean sea level.

OUTLET STRUCTURE (Lat. 21 ̊23'36"N. Long. 157 ̊48'26"W.)

0 100

10

200

0 50 100 METERS

300 400 FEE

SP

LI

LWAY

D A M

SP

LI L

WAY

D A M

2

4

6

2

2

2 4

6

10

8

12

14

4

6

8

10

4

2

8

10

8

8

10

16

16

20

14

12

4 6 8

12

12

14

16

12

10

10

10

6 4

8

10

18

14

2

4

6

2

2

2 4

6

10

8

12

14

4

6

8

4

2

2

8

10

8

8

10

16

16

18

20

14

14

4

6 8

12

12 16

12

10

10

10

6 4

8

Figure 3. Bathymetric map of Waimaluhia Reservoir, 1983, Oahu, Hawaii (from Wong and Hill, 1992).
Sediment Accumu

N

Island

0 100 200

0 50 100 METERS

300 400 FEE

EXPLANATION

BATHYMETRIC CONTOUR--Shows depth, in feet, below 

 shoreline, 1988. Contour interval variable.

SHORELINE--Altitude 160.0 feet above mean sea level.

OUTLET STRUCTURE (Lat. 21 ̊23'36"N. Long. 157 ̊48'26"W.)

10

SP

LI

LWAY

D A M

SP

LI L

WAY

D A M

2

4

6

2

2

2 4

6

10

12

4

6

8

4

2

2

8

10

8

8

16

18

20

14

12

6 6 8

12

12

12

16

12

10

10

10

4

6

8

2

4

6

2

2

2 4

6

10

12

4

6

8

4

2

2

8

10

8

8

16

18

20

14

14

4

6 8

12

12

14

16

12

10

10

10

4

6

8

Figure 4. Bathymetric map of Waimaluhia Reservoir, 1988, Oahu, Hawaii (from Wong and Hill, 1992).
14 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

N

Island

0 100 200

0 50 100 METERS

300 400 FEET

EXPLANATION

BATHYMETRIC CONTOUR--Shows depth, in feet, below 

 shoreline, 1993. Contour interval 2 feet.

SHORELINE--Altitude 160.0 feet above mean sea level.

OUTLET STRUCTURE (Lat. 21 ̊23'36"N. Long. 157 ̊48'26"W.)

10

SP

LI

LWAY

D A M

SP

LI L

WAY

D A M

2

4 6

2

2

2 4

6

6

8

4

2

2

8

10

8

8

10

16

18

16

20

14

4 6

8

12

12

14

16

10

10

10

10

4

6

8

6

2

4 6

2

2

2 4

6

6

8

4

2

2

8

10

8

6

8

10

16

18

16

20

14

2 4

6

12

12

12

14

10

8

10

10

4

6

8

Figure 5. Bathymetric map of Waimaluhia Reservoir, 1993, Oahu, Hawaii.
Sediment Accumu

N

Island

0 100 200

0 50 100 METERS

300 400 FEE

EXPLANATION

BATHYMETRIC CONTOUR--Shows depth, in feet, below 

 shoreline, 1998. Contour interval 2 feet.

SHORELINE--Altitude 160.0 feet above mean sea level.

OUTLET STRUCTURE (Lat. 21 ̊23'36"N. Long. 157 ̊48'26"W.)

10

SP

LI

LWAY

D A M

SP

LI L

WAY

D A M

2

4 6

2

2

2 4

6

12

8

6

8

4

2

2

8

10

8

8

10

16

16

14

2 4

6

12

12

14

16

12

8

10

6

6

8

2

4 6

2

2

2

4

6

12

8

6

8

4

2

2

8

10

8

8

10

16

16

14

2

4

6

12

12

12

14

10

8

10

4

6

8

Figure 6. Bathymetric map of Waimaluhia Reservoir, 1998, Oahu, Hawaii.
16 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

N

Island

SP

LI

LWAY

D A M

0 100 200

0 50 100 METERS

300 400 FEE

EXPLANATION

AREA OF DEPOSITION

SHORELINE--Altitude 160.0 feet. Datum is mean sea level

SP

LI L

WAY

D A M

Figure 7. Areas of sediment deposition from 1983 to 1998 in Waimaluhia Reservoir, Oahu, Hawaii.
Sediment Accumu

Table 7. Bulk density of bottom material from Waimaluhia Reservoir, Oahu, Hawaii, August 1993 and October 200

[cm3, cubic centimeter; g/cm3, grams per cubic centimeter]

Cross section

Station

(feet)

Depth to

bottom

(feet)

Change in

depth

since 1983

(feet)

 Penetration depth

of sample

(feet)

Mass

(gram)

Volume

(cm3)

Bulk

density

(g/cm3)

August 1993

B3 205 9.19 -0.58 0.3 400 1,000 0.40

B4 245 7.16 -1.15 0.3 368 1,000 0.37

COE-C 130 8.12 -0.49 0.3 452 1,000 0.45

COE-TED 130 1.72 -4.83 0.3 168 440 0.38

QW1 120 9.57 -0.70 0.3 392 1,000 0.39

QW2 140 12.02 -0.68 0.3 391 1,000 0.39

October 2000

B4 265 6.95 -1.53 1.61 366 890 0.41

COE-C 140 8.04 -0.72 1.18 264 650 0.41

COE-TED 125 2.17 -4.71 1.14 489 630 0.78

K6 115 11.35 -6.51 1.17 285 650 0.44

QW1 125 10.18 -0.36 1.41 262 780 0.34

QW2 140 11.56 -1.35 1.35 272 740 0.37

Table 8. Annual suspended-sediment loads at stream-gaging stations in the Kamooalii drainage basin, Oahu, Haw

water years 1981–98

[Values in tons; --, no data; P, partial year, more than one month of no data; complete station numbers are preceded by 16 and end in 00; e, es

mated; estimated values of suspended-sediment loads were estimated using the partial years of record at station 2709 and by comparison of

monthly suspended-sediment load data for the concurrent periods of record at stations 2709 and 2722]

Water

Year

Station 2656

Right Branch

Kamooalii

Stream

Station 2722

Kamooalii

Stream

Station 2709

Luluku

Stream

Pass-through load

Kamooalli Stream

less Luluku Stream

1981 -- 723 -- --

1982 -- 3,210 -- --

1983 P 173 -- --

1984 23.7 76.6 P e45.5

1985 541 336 43.0 293

1986 472 322 91.1 231

1987 631 1,190 402 788

1988 1,730 2,240 485 1,755

1989 1,220 1,290 180 1,110

1990 1,160 593 52.6 540

1991 512 1,270 333 937

1992 64.8 148 70.4 77.6

1993 421 801 185 616

1994 278 606 193 413

1995 63.7 222 66.1 156

1996 1,940 1,370 884 486

1997 146 424 135 289

1998 -- 131 P e116
18 Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983–98

1963) and suspended-sediments (57 lb/ft3) sampled by

Jones and others (1971). However, the 29 lb/ft3

 value

falls within the range of densities, 20 to 120 lb/ft3

, sampled throughout the United States for permanent pool

reservoirs (Lara and Pemberton, 1963).

Multiplying the total volume of sediment deposited in the reservoir, 30.3 acre-ft, by the average bulk

density, 29 lb/ft3 gives a total of 19,100 tons for the net

mass of sediment trapped in the reservoir from 1983 to

1998. This mass includes bedload (the part of sediment

usually made up of gravel, cobbles, and boulders, that

moves along the streambed by rolling or sliding), and

suspended-sediment load. For the period of 1985 to

1997, where complete years of data are available, the

suspended-sediment load that passed through the reservoir was 7,690 tons. This load was computed by subtracting the suspended-sediment load at station 2709

from the suspended-sediment load at station 2722 (table

8). Bedload at both stations was ignored because all

bedload into the reservoir is trapped. For the period of

the sediment surveys, 1983 to 1998, the suspended-sediment load at station 2709 for water years 1984 and

1998 was estimated. Loads for these years were estimated by using the partial years of record from water

years 1984 and 1998 at station 2709 and by comparison

of monthly suspended-sediment load data for the period

of concurrent record from both stations 2709 and 2722.

Estimates of suspended-sediment load for these two

water years increases the suspended-sediment load that

passed through the reservoir to 7,850 tons (table 8). The

total amount of sediment delivered to the reservoir is the

sum of the 19,100 tons deposited and the 7,850 tons discharged, or 26,950 tons. This number divided by the

reservoir’s drainage area of 3.20 mi2

 and the time of

14.9 years gives a mean annual sediment yield of 565

tons/mi2

/yr. This number is about 38 percent of the

1,500 tons/mi2

/yr used in the reservoir design.

The trapping efficiency of the reservoir was computed by the following equation:

, (1)

where Et = trap efficiency,

Lt = total sediment load trapped in reservoir =

19,100 tons, and

Lp = suspended sediment load passed through

reservoir = 7,850 tons.

A trapping efficiency of 71 percent was co

using equation 1. This value compares closely w

estimate of trap efficiency using the capacity/in

relationship described by Brune (1953). Inflow 

reservoir was computed using the simple water

relation that outflow equals inflow. Because gro

water seepage was negligible and the seepage th

observed flowed into the stream upstream of sta

2722, and because rainfall on the reservoir (75 

exceeded the evaporation from the reservoir (le

50 in/yr), the flow measured at station 2722 mi

flow at station 2709 equals the outflow. From t

the average outflow from water years 1995 to 19

3,600 ft3

/s-days/yr or 7,140 acre-ft/yr. The capa

the reservoir was 209.3 acre-ft in 1998, using thi

the capacity/inflow is 0.03. From figure 6 in Br

(1953) the trap efficiency is 70 percent with a p

range of 60 to 80 percent. Both the value from th

(1953) method and the value calculated in equa

are higher than the 60 percent design value.

SUMMARY

A major highway constructed upstream of 

aluhia Reservoir, in a high-rainfall area on the is

Oahu, began in 1983 and ended in 1998. The U

logical Survey in cooperation with the Hawaii S

Department of Transportation and the Federal H

Administration conducted periodic bathymetric 

to measure sediment accumulation in the reserv

ing this period. The objective of these surveys w

determine if the decrease in the reservoir storage

ity resulted from sediment deposition during hi

construction and if the loss rate exceeded the de

storage-capacity loss rate of 2.0 acre-feet per yea

of the land disturbances associated with the hig

construction occurred from 1983 to 1992 and w

ticularly intense between 1989 and 1992, coinc

with the construction of a golf course upstream 

reservoir.

The monuments used for the bathymetric s

were established in 1983. Bathymetric surveys 

conducted in 1983, 1988, annually from 1990 t

and in 1998. The bulk densities of several samp

sediments deposited in the reservoir were meas

1993 and 2000. Suspended-sediment loads wer

sured since 1983 at one station upstream of the re

and at another station downstream of the reservo

Et Lt Lt Lp = ( ) ⁄ ( ) + × 100 percent
References 

rate of sediment accumulation for the study period

(from 1983 to 1998) was 2.0 acre-feet per year equaling

the design loss rate. During the period of intense construction activities (1983–92), the loss rate was 2.7

acre-feet per year. The highest loss rate of 4.9 acre-feet

per year was during the period of greatest land disturbances from 1988 to 1992.

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Wong––Sedimentation History of Waimaluhia Reservoir during Highway Construction, Oahu, Hawaii, 1983-98––WRIR 01-4001