Table 6. Analysis of covariance relating streamflow at index station to streamflow at stream-gaging stations in the H-3

highway study area, Oahu, Hawaii

[Daily mean streamflows at station 229000 and at stations 226200, 270900, 272200, and 275000 were used as the covariate and response variables,
respectively; Z was set to zero for pre-construction and | for construction; W was set to Zx streamflow at station 229000; 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; station numbers are abbreviated, complete numbers are preceded by 16]

T-ratio for
Regression coefficients for significance
Station Intercept Slope z Ww ofZ
Low flow (streamflow less than or equal to 10.0 ft3/s at station 229000)
226200 -1.43 1.17 -0.431* 0.0142 -2.33* 0.08 6.67*
270900 0.274 0.0988 0.665* 0.0154* 24,5* 4.92* 1,160*
272200 5.15 2.07 -0.325 -0.979* 1.31 208* 344*
275000 1,29 0.154 0.316 0.0545* 0.62 17.6* 37.4*
High flow (streamflow greater than 10.0 ft°/s at station 229000)
226200 0.166 0.891 -0.401* 0.313* -2.10* 4.88* 2.48
270900 -0.880 0.849 0.399* -0.176 3.05* 3.53 16.8*
272200 0.582 0.644 -0.321* 0.149 -2,.95* 3.74 13.2*
275000 -0.544 0.913 0.004 0.0654 0.030 0.487 5.50*

Streamflow Changes During Construction

Annual streamflow records used for this report
were rated as "good," "fair," or "poor" (Matsuoka and
others, 1992). 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 stream-
flow for the entire study period were considered accu-
rate to within 15 percent at stream-gaging stations
226200, 265600, 270900, and 275000, and to within 10
percent at stream-gaging stations 272200 and 229000.
Streamflow changes that are within these accuracy lim-
its cannot be considered hydrologically significant,
although they may be statistically significant.

Low flows.--The changes in regression intercepts
and slopes shown in table 6 indicate the direction and
magnitude of changes in streamflow during construc-
tion. Changes in intercepts, which are equal to the coef-
ficients for variable Z listed in table 6, are constants that
increase (positive coefficients) or decrease (negative
coefficients) flows estimated with the regression equa-
tion equally over the entire range of data. Changes in
slope, which are equal to the coefficients for variable W
listed in table 6, result in changes in estimated stream-

flow that are proportional to streamflow at stream-gag-
ing station 229000.

Relations between low flows at stream-gaging sta-
tions 226200, 270900, 272200, and 275000 and low
flows at stream-gaging station 229000 changed signifi-
cantly during construction (table 6). Regression inter-
cepts were significantly different at stations 226200 and
270900; the intercept decreased at station 226200 and
increased at station 270900. Regression slopes were
significantly different at stations 270900, 272200, and
275000; slope increased at stations 270900 and 275000,
and decreased at station 272200. Standard errors for
pre-construction regressions were 2.40 ft?/s at station
226200, 0.32 ft°/s at station 270900, 5.10 ft°/s at station
272200, and 0.54 ft°/s at station 275000.

To determine if the low-flow changes detected
using analysis of covariance were hydrologically signif-
icant, changes in low flows were estimated by applying
pre-construction regression coefficients for slope and
intercept from the analysis of covariance (table 6) to
construction-period low flows at station 229000. The
estimated low flows represent low flows that would be
expected if relations between flows at H-3 project sta-
tions 226200, 270900, 272200, and 275000 and the
index station 229000 were unchanged from pre-con-
struction conditions (table 7). 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

16 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


Foote, D.E., Hill, E.L., Nakamura, Sakuichi, and Stephens,
Floyd, 1972, Soil survey of the islands of Kauai, Oahu,
Maui, Molokai, and Lanai, State of Hawaii: U.S. Depart-
ment of Agriculture, Soil Conservation Service, 232 p.

Glysson, G.D., 1987, Sediment transport curves: U.S. Geo-
logical Survey Open-File Report 87-218, 47 p.

Guy, H.P., 1969, Laboratory theory and methods for sedi-
ment analysis: U.S. Geological Survey Techniques of
Water-Resources Investigations, book 5, chap. C1, 58 p.

Harr, R.D., Harper, W.C., Krygier, J.T., and Hsieh, F.S.,
1975, Changes in storm hydrographs after road building
and clear-cutting in the Oregon Coast Range: Water Re-
sources Research, v. 11, no. 3, p. 436-444.

Helm, R.E., 1978, Sediment discharge from highway con-
struction near Port Carbon, Pennsylvania: U.S. Geologi-
cal Survey Water-Resources Investigations Report 78-
35, 27 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in
water resources: Studies in Environmental Science 49:
Elsevier, Amsterdam, 522 p.

Hinds, N.E.A., 1925, Amphitheater valley heads: Journal of
Geology, v. 33, p. 816-818.

Hirashima, G.T., 1963, Influence of water-development tun-
nels on streamflow-groundwater relations in Haiku-Ka-
haluu area, Oahu, Hawaii: State of Hawaii Department of
Land and Natural Resources, Division of Water and
Land Development, Circular C21, Honolulu, Hawaii,
10p.

oe , 1965, Effects of water withdrawals by tunnels, Waihee
Valley, Oahu, Hawaii: State of Hawaii Department of
Land and Natural Resources, Division of Water and
Land Development, Report R28, Honolulu, Hawaii,

38 p.

oo , 1971, Tunnels and dikes of the Koolau Range, Oahu,
Hawaii, and their effects on storage depletion and move-
ment of ground water: U.S. Geological Survey Water-
Supply Paper 1999-M, 21 p.

Honolulu Board of Water Supply, 1981 through 1992, Annu-
al report and statistical summary: Honolulu, Hawaii
[published annually by fiscal year beginning July 1 and
ending June 30).

Iman, R.L., and Conover, W.J., 1983, A modern approach to
statistics: Wiley, New York, 497 p.

[U.S.] Interagency Advisory Committee on Water Data,
1981, Guidelines for determining flood flow frequency:
Bulletin 17B of the Hydrology Committee, Washington,
DC, variable pagination.

Izuka, S.K., 1992, Geology and stream infiltration of North
Halawa Valley, Oahu, Hawaii: U.S. Geological Survey
Water-Resources Investigations Report 91-4197, 21 p.

Jackson, M.C., and Multhaup, R.A., 1990, Interstate Route
H-3 Trans-Koolau Exploratory Tunnel, Haiku approach

and tunnels geology: State of Hawaii Department of
Transportation, Highways Division, Honolulu, Hawaii,
102 p.

Jones, B.L., Nakahara, R.H., and Chinn, S.S.W., 1971, Re-
connaissance study of sediment transported by streams,
island of Oahu: U.S. Geological Survey Circular C33,
Honolulu, HI, 45 p.

King, J.G., and Tennyson, L.C., 1984, Alteration of stream-
flow characteristics following road construction in north
central Idaho: Water Resources Research, v. 20, no. 8,
p. 1,159-1,163.

Matsuoka, Iwao, Tateishi, G.A., Lum, M.G., and Kunishige,
V.E., 1991, Water resources data, Hawaii and other Pa-
cific area, water year 1990, volume 1, Hawaii: U.S. Geo-
logical Survey Water-Data Report HI-90-1, 290 p.

Matsuoka, Iwao, Kunishige, V.E., and Lum, M.G., 1992,
Water resources data, Hawaii and other Pacific area, wa-
ter year 1991, volume 1, Hawaii: U.S. Geological Survey
Water-Data Report HI-91-1, 282 p.

Mink, J.F., 1960, Distribution pattern of rainfall in the lee-
ward Koolau Mountains, Oahu, Hawaii: Journal of Geo-
physical Research, v. 65, no. 9, p. 2,869-2,876.

Nakahara, R.H., Yee, J.J.S., and Domingo, J.A., 1988, Water
resources data, Hawaii and other Pacific area, water year
1987, volume 1, Hawaii: U.S. Geological Survey Water-
Data Report HI-87-1, 260 p.

Nakahara, R.H., Yee, -» Yamashiro, I., Tateishi, G.A.,
and Domingo, J.A., 1989, Water resources data, Hawaii
and other Pacific area, water year 1988, volume 1, Ha-
waii: U.S. Geological Survey Water-Data Report HI-88-
1, 265 p.

Nolan, K.M., Janda, R.J., and Galton, J.H., 1986, Sediment
sources and sediment-transport curves, in: Proceedings
of the Fourth Federal Interagency Sedimentation Confer-
ence, Las Vegas, NV, Subcommittee on sedimentation,
Interagency Advisory Committee on Water Data, p. 4-
70-4-79.

Nolan, K.M., Lisle, T.E., and Kelsey, H.M., 1987, Bankfull
discharge and sediment transport in northwestern Cali-
fornia in: Beschta, R.L., Blinn, T., Grant, G.E., Ice, G.G.,
and Swanson, F.J. (eds.), Erosion and sedimentation in
the Pacific Rim, International Association of Hydrologi-
cal Sciences Publication No. 165, p. 439-449.

Nolan, K.M., and Hill, B.R., 1989, Effects of limestone quar-
rying and cement-plant operations on runoff and sedi-
ment yields in the upper Permanente Creek basin, Santa
Clara County, California: U.S. Geological Survey Wa-
ter-Resources Investigations Report 89-4130, 48 p.

Porterfield, George, 1972, Computation of fluvial sediment
discharge: U.S. Geological Survey Techniques of Water-
Resources Investigations, book 3, chap. C3, 66 p.

References Cited 33


40 T T T T

35

30

20;

MONTHLY STREAMFLOW AND GROUND-WATER
WITHDRAWALS, IN CUBIC FEET PER SECOND

whan nn! potenHh

STREAMFLOW
GROUND WATER

====b----4~-- 4. L wl =.

1980 1981 1982 1983 1984

1985

1986 1987 1988 1989 1990 1991
YEAR

Figure 3. Monthly streamflow at stream-gaging station 16229000 and upstream ground-water

withdrawals, Oahu, Hawaii.

withdrawals were small in comparison to streamflow
and were nearly constant during the study period (fig.
3). Variations in streamflow at station 229000 were
therefore primarily the result of rainfall variations.

Streamflow data were separated into low- and
high-flow classes before analysis to permit an evalua-
tion of construction effects on peak flows and base
flows. The daily streamflow with an exceedance proba-
bility of 10 percent at station 229000, 10.0 ft/s, was
used to define the low-flow (less than or equal to 10.0
ft°/s) and high-flow (greater than 10.0 ft?/s) classes.
High-flow data were log-transformed before analysis
on the basis of the distributions of regression residuals
(Helsel and Hirsch, 1992). Low-flow data were not log-
transformed because zero-flow data at station 226200
could not be log-transformed, and because log-transfor-
mation did not significantly improve regression rela-

tions, as determined by examination of regression
residuals.

The analysis of covariance tested whether time
period accounted for variations in streamflow at stations
226200, 270900, 272200, and 275000 by comparing
three different regression equations relating streamflow
at these stations to streamflow at station 229000. One
equation, a simple bivariate equation relating the
response variable to the covariate, was expressed as

Qu-3 = A + (BX Qo29000) ay

where Qy.3 represented the response variable (daily
streamflow at one of the stream-gaging stations 226200,
270900, 272200, and 275000), Q29999 represented the
covariate (streamflow on the same day at index station
229000), and A and B were regression coefficients. The
second equation included, in addition to the covariate, a
dummy independent variable, Z, to represent time

10 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


(Neal Fujii, State of Hawaii Department of Land and
Natural Resources, Commission on Water Resource
Management, written commun., 1993). These wells
were used to irrigate the new Minami golf course (fig.
2). The combined average monthly withdrawal of these
wells from March, 1990 to September, 1991 was about
0.13 Mgal/d, equivalent to 0.20 ft°/s. This average is
equivalent to about 12 percent of the average daily
streamflow at station 265600 and about 2 percent of the
average daily streamflow at station 272200 (Matsuoka
and others, 1992). No significant effect from pumping
golf-course wells was detected using analysis of covari-
ance with monthly streamflow data at station 265600.
Pumping of ground water for golf-course irrigation does
not appear to have had a major effect on streamflow at
stations 272200 and 265600.

Ground water in the marginal dike zone of wind-
ward Oahu can flow from one drainage basin to another
between parallel dikes (Takasaki and Mink, 1985).
Wells and water-development tunnels can change the
location of ground-water divides and divert water from
one valley to another, as shown by Hirashima (1963).
Changes in withdrawals within or outside the study area
may have affected ground-water flow systems to the
extent that ground water was transferred from one
drainage basin to another. An evaluation of this scenario
is beyond the scope of this report.

H-3 highway construction.--H-3 highway con-
struction involves excavation of highway tunnels in a
ground-water recharge zone below the crest of the
Koolau Range and clearing, cutting, filling, compact-
ing, and paving of the land surface in and near areas of
ground-water discharge. These activities could poten-
tially affect low flows that are maintained by ground-
water discharge.

Seepage of ground water into the trans-Koolau
exploratory tunnel was estimated to less than 30 gal/d
by Jackson and Multhaup (1990). The estimated flow
rate is equivalent to only 0.00005 ft/s, Maximum seep-
age rates for the exploratory tunnel after heavy rain
were estimated to be 10 gal/h per 100-ft section,
roughly equivalent to 0.02 ft?/s for the entire tunnel.
Field observations by USGS personnel also indicated
very small quantities of seepage into the exploratory
tunnel. Water seeping from the roof and walls of the
tunnel later infiltrated the floor of the tunnel (Jackson
and Multhaup, 1990), and was not discharged from the
tunnel portals as surface water. The trans-Koolau tun-

nels, therefore, have probably had a minor effect on
streamflow in the study area.

Removal of vegetation during highway construc-
tion could have resulted in decreased evapotranspira-
tion and hence an increase in the volume of water
available to maintain low flows. Before highway con-
struction, much of the drainage basin upstream of sta-
tion 270900 was planted in bananas. During construc-
tion, banana trees covering about 6 percent of the drain-
age basin were removed and part of the former planta-
tion was covered with loose rock fill. This unvegetated
rock fill probably reduced evapotranspiration from
these areas to a fraction of the pre-construction rate.
Potential evaporation is about 62 percent of pan evapo-
transpiration in humid areas of Oahu (Shade, 1984). Pan
evaporation at Maunawili Ranch (fig. 1) was about 3.6
ft/yr over an 11-year period (State of Hawaii Depart-
ment of Land and Natural Resources, 1973), and poten-
tial evapotranspiration was about 2.2 ft/yr. If evapo-
transpiration equal to 2.2 ft/yr were eliminated over the
11 percent of the drainage basin directly affected by the
H-3 highway, 0.09 ft?/s of additional water would be
available to augment streamflow. Over the 1,800-day
construction period, reduced evapotranspiration would
result in an additional 165 ft?/s-d of streamflow, equal
to 28 percent of the estimated increase in low flows at
station 270900 (table 7). Increased low flows also may
have resulted in part from irrigation for highway land-
scaping and reduced agricultural streamflow diversions.

Reduced evapotranspiration may have affected
streamflow at station 272200, where the combined area
used for H-3 highway and golf course construction was
about 12 percent of total drainage basin area. Low flows
decreased during construction (table 7), however, indi-
cating that effects of increased ground-water withdraw-
als or other effects that decreased low flows were
apparently greater. Compaction of soil during highway
and golf-course construction may have reduced infiltra-
tion and decreased the amount of water available to sus-
tain low flows.

High Flows

Previous studies of the effects of roadbuilding on
streamflow have focused on increases in streamflow
peaks because of compaction of soil and increases in
impervious areas (Harr and others, 1975; Ziemer, 1981;
King and Tennyson, 1984). These effects appear to
have been minor in the H-3 highway study drainage

20 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


Streamflow and Suspended-Sediment Loads Before and
During Highway Construction, North Halawa, Haiku, and
Kamooalii Drainage Basins, Oahu, Hawaii, 1983-91

By Barry R. Hill

Abstract

Concern over potential effects from construc-
tion of the H-3 highway on Oahu, Hawaii, prompt-
ed a long-term study of streamflow and suspended-
sediment transport at a network of five stream-gag-
ing stations along the highway route. This report
presents results for 1983-91, which included pre-
construction and construction periods at all stream-
gaging stations.

Annual rainfall, streamflow, and suspended-
sediment loads were generally higher during con-
struction than before construction. Data collected
before and during construction were compared
using analysis of covariance to determine whether
streamflow and suspended-sediment loads changed
significantly during construction after accounting
for effects of increased rainfall.

Streamflow at stream-gaging stations was
compared with streamflow at an index stream-
gaging station unaffected by construction. Stream-
flow data were divided into low- and high-flow
classes, and the two flow classes were analyzed
separately. Low flows increased 117 percent dur-
ing construction at one station. This increase prob-
ably was related to the removal of vegetation for
highway construction. Low flows decreased 28
percent at another station, probably as a result of
increased ground-water withdrawals and highway
construction activities. No significant changes in
low flows were detected at the other stations, and
no significant changes in high flows were detected
at any stations.

Suspended-sediment loads increased signifi-
cantly during construction at three stations. High-
way construction contributed between 56 and 76
percent of the suspended-sediment loads measured
at these stations during construction. Loads did not
change significantly at a station downstream of a
reservoir, and loads decreased at a station down-
stream of a drainage basin that was heavily used for
agriculture before construction.

Suspended-sediment concentrations were used
to assess compliance with applicable State water-
quality standards. State water-quality standards for
suspended sediment frequently were exceeded dur-
ing construction. Standards occasionally were
exceeded before construction.

INTRODUCTION

The H-3 highway, currently (1994) under con-
struction, will be a major highway across the Koolau
Range on the island of Oahu, Hawaii (fig. 1). Construc-
tion began after a lengthy environmental evaluation
(U.S. Department of Transportation and State of Hawaii
Department of Transportation, 1987). Potential effects
of construction on streams along the route were an issue
of public concern. In 1983, the U.S. Geological Survey,
in cooperation with the State of Hawaii Department of
Transportation, began a study of streamflow and sus-
pended-sediment transport in these streams. The pur-
pose of the study is to compare data collected before,
during, and after highway construction to determine
whether construction activities have affected stream-
flow and suspended-sediment transport. The purpose of
this report is to identify and quantify effects of H-3 con-
struction on streamflow and suspended-sediment loads

Introduction 1


Table 11. Observed and estimated annual suspended-sediment yields at selected stream-gaging stations during
H-3 highway construction, Oahu, Hawaii

[Estimated yields were computed from regression equations relating annual suspended-sediment yields to annual streamflow per unit area; data
used for station 226200 were Jog-transformed and a bias-correction factor of 1.15 was applied to estimated yields; data for all other stations were
not log-transformed; tons/mi~, 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; data used in regressions includes pre-
construction data from this study and data from Jones and others (1971), Doty and others (1981), and Shade (1984); station numbers are abbrevi-
ated, complete numbers are preceded by 16]

‘Suspended-sediment yields
(tons/mi?) Difference Difference
Station Observed Estimated (tons/mi2) (percent)
226200 6,880 2,840 4,040 59
265600 5,660 2,500 3,160 56
270900 1,290 2,210 -920 71
275000 8,280 2,020 6,260 76

suspended-sediment yields at station 270900 appear to
be higher than yields for other windward drainage
basins under mixed use. The reduction in the area under
cultivation during highway construction may have led
to a reduction in sediment yield. Installation of erosion-
control measures during construction may have also
contributed to decreased soil losses.

Exceedance of State Water-Quality Standards

The exceedance of standards during the study
period coincided in most cases with H-3 construction
and with high rainfall; however, standards were not
exceeded in every year of construction at stream-gaging
stations 270900 and 272200 and standards were
exceeded in 2 years before construction at stations
270900 and 275000 (table 10). Standards were also
exceeded in 6 of 9 construction years at station 272200,
although the analysis of covariance detected no signifi-
cant effects of construction. Construction of the H-3
was probably a factor affecting exceedance of the stan-
dards, but other land uses as well as variations in rainfall
probably were involved.

State water-quality standards (State of Hawaii
Department of Health, 1990) are designed to minimize
the amount of time that ambient suspended-sediment
concentrations exceed threshold concentrations. No
standards exist for suspended-sediment loads, that is,
for the total amount of sediment transported by streams.
A stream with occasional high loads could be in compli-
ance with the standards, whereas a stream with persis-
tent moderate loads could exceed the standards while
transporting a lower suspended-sediment load. Fluvial
sediment transport can be highly episodic, with most of
the annual load being transported in just a few days
(Nolan and others, 1987; Nolan and Hill, 1989). Com-

pliance with the present State water-quality standards
therefore does not necessarily indicate that sediment
loads are low (Doty and others, 1981).

The standards are the same for wet years and dry
years. Because of the interrelations between rainfall,
streamflow, and sediment transport, standards will be
exceeded more often during wet years than in dry years.

Comparison With Highway Construction Effects in
Other Areas

The estimates of the percentage of suspended-sed-
iment loads resulting from highway construction in this
study range from 56 to 76 percent at the three stream-
gaging stations where increases in suspended-sediment
loads during construction were found to be significant
(table 11). Previous studies in other areas found that 29
to 85 percent of the sediment loads were attributable to
construction activities. Effects of H-3 highway con-
struction on suspended-sediment loads at stations
226200, 265600, and 275000 appear to be comparable
to effects of highway construction elsewhere. The
decrease in suspended-sediment yield during highway
construction period at station 270900 is unusual in view
of results of previous studies and probably resulted
from reduced agricultural activity and increased erosion
control during highway construction.

CONCLUSIONS

Construction of the H-3 highway coincided with
high rainfall. Annual streamflow and suspended-sedi-
ment loads increased during construction, partly in
response to increased rainfall and partly in response to
effects of highway construction and other land uses.

Conclusions 31


Table 7. Estimated changes in streamflow resulting from
altered drainage-basin conditions during H-3 highway
construction, Oahu, Hawaii

[Estimated streamflows were computed by applying pre-construction
regression coefficients listed in table 6 to daily mean streamflows at station
229000 during 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 (ft°/s-d); <, less than; station numbers are
abbreviated, complete numbers are preceded by 16]

Construction-period

streamflow Difference

Station Observed Estimated Difference (percent)
Low flow (streamflow less than or equal to 10.0 ts at

station 229000)

226200 2,800 3,260 460 -14

270900 1,090 502 588 117

272200 23,000 32,100 -9,100 -28

275000 1,920 1,710 210 12

High flow (streamflow greater than 10.0 ft/s at

‘station 229000)

226200 2,270 2,300 -30 -l

270900 488 456 32 7

272200 5,150 5,140 10 <l

275000 1,280 1,150 130 ll

procedure accounts for the effects of rainfall by using
streamflow at the index station as a covariate. Estimated
changes range from a decrease of 28 percent of esti-
mated low flows at station 272200 to an increase of 117
percent at station 270900 (table 7). Only the estimated
changes at stations 270900 and 272200 were greater
than the limits of accuracy for the streamflow records
used in the analyses. The estimated changes for stations
226200 and 275000 are within accuracy limits and
therefore cannot be considered hydrologically signifi-
cant.

High flows.--Relations between high flows at
stream-gaging stations 270900, 272200, and 275000
and high flows at index stream-gaging station 229000
changed significantly during construction (table 6). The
intercept increased at station 270900 and decreased at
station 272200. Neither Z nor W were significant indi-
vidually at station 275000, but their combined effect
was significant. No significant changes in high flows
were detected for station 226200, although both Z and
W were significant variables individually if both were
included in the regression.

Changes in high flows resulting from altered drain-
age-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 1.12 to 1.24. Standard errors, in log
units, ranged from 0.214 to 0.286.

Estimates of changes in high flows required
extrapolation of the pre-construction regression beyond
the range of pre-construction data at stations 226200,
272200, and 275000. The use of these estimates
requires the assumption that the pre-construction rela-
tion between streamflow at index station 229000 and
streamflow at H-3 project stations 226200, 270900,
272200, and 275000 remains linear at flows higher than
any observed during the pre-construction period. To
check this assumption, annual streamflow at station
229000 was compared with annual streamflow at sta-
tion 226000 for the period 1954-87 and to annual
streamflow at station 275000 for the period 1960-76
using double-mass curves (Searcy and Hardison, 1960).
These periods included higher annual streamflows than
the 1983-91 study period. No deviations from a gener-
ally linear pattern were detected, and the extrapolation
was considered reasonable for station 275000 and for
station 226200, which is about 1 mi downstream of sta-
tion 226000. No long-term data are available to test the
validity of the assumption for station 272200; changes
estimated for this station should be considered less reli-
able than those for other stations.

Changes in high flows ranged from a decrease of
1 percent at station 226200 to an increase of 11 percent
at station 275000 (table 7). All of these estimated
changes are within the accuracy limits for streamflow
records, and cannot be considered hydrologically sig-
nificant.

Streamflow at stream-gaging station 265600.--
Only a few days of pre-construction data were available
for stream-gaging station 265600. A meaningful com-
parison of pre-construction and construction data could
not be made with so few pre-construction data. Instead,
construction effects on streamflow at stream-gaging
station 265600 were assessed by comparing construc-
tion-period streamflow data at this station to pre-con-
struction data for the same days at nearby stream-
gaging station 270900 using the Wilcoxon signed-ranks
test (Iman and Conover, 1983). Streamflow data were
divided by drainage basin areas to allow direct compar-
ison of data for the two stations.

Station 270900 was used for the comparison
because of its proximity to station 265600, which would

Streamflow Before and During Construction 17


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Streamflow Before and During Construction 23


MONTHLY GROUND-WATER WITHDRAWALS,
IN CUBIC FEET PER SECOND
.
T

UPSTREAM OF STATION 16272200
UPSTREAM OF STATION 16270900

1980 1981 1982 1983 1984

1985 1986 1987 1988 1989 1990 1991

YEAR

Figure 6. Monthly ground-water withdrawals upstream of stream-gaging stations 16272200 and

16270900, Oahu, Hawaii.

construction can be computed using Board of Water
Supply pumping data (Honolulu Board of Water Sup-
ply, 1981 through 1992). Average rates of ground-water
withdrawals were computed for the pre-construction
and construction periods at station 272200. The pre-
construction average was 3.8 ft/s and the construction-
period average was 4.7 ft?/s. The difference between
these two averages, 0.9 ft/s, was multiplied by the
3,143 days in the construction period at station 272200
to obtain an estimate of 2,829 ft?/s-d that potentially
could have been diverted from the stream by increased
municipal withdrawals. This estimate is equivalent to
31 percent of the estimated decrease in low flows at sta-
tion 272200 during construction (table 7). This analysis
requires the assumption that all of the water attributed
to increased municipal withdrawals would otherwise
have flowed to the stream. The actual proportion was
probably less, and the true effect of increased municipal

withdrawals on low flows at station 272200 was proba-
bly less than the estimated decrease of 2,829 ft /s-d.
However, because municipal ground-water withdraw-
als increased upstream of station 272200 coincident
with an apparent decrease in low flows at that station
(tables 6 and 7), some of the decrease in low flows may
be attributable to the increased withdrawals.

Although municipal withdrawals increased signif-
icantly (p<0.05) in the drainage basin upstream of sta-
tion 270900 during construction, low flows increased.
Any effects of increased withdrawals on low flows at
this station were apparently less than other effects that
increased low flows. One such possible effect is dis-
cussed in this report in the section "H-3 highway con-
struction."

Ground water also was withdrawn from two wells
upstream of station 265600 beginning in March, 1990

Streamflow Before and During Construction 19


Low flows changed significantly during construc-
tion at two stream-gaging stations. Low flows increased
117 percent at station 270900 and decreased 28 percent
at station 272200. Changes in low flows were probably
the result of changes in ground-water withdrawal rates
and highway construction.

No significant changes in high flows were
detected. The relatively small areas affected by con-
struction probably account for the lack of any signifi-
cant construction effects on high flows.

Data were insufficient to determine changes in
streamflow at station 265600. Comparison of stream-
flow data at this station under construction conditions
with data at station 270900 under pre-construction con-
ditions indicates that streamflows at station 265600
were significantly lower. This difference was probably
caused by differences in the hydrogeology of the two
drainage basins rather than by construction. Ground-
water withdrawals from wells upstream of station
265600 may have decreased low flows slightly.

Suspended-sediment loads increased significantly
during construction at stream-gaging stations 226200,
265600, and 275000. Highway construction contributed
between 56 and 76 percent of the suspended-sediment
loads measured at these stations during construction.
Loads did not change significantly at station 272200,
which is downstream of a reservoir that traps sediment
from construction areas. Loads decreased during con-
struction at station 270900, which is downstream of a
drainage basin heavily used for agriculture before con-
struction. The decreased loads at this station may have
been because of decreased agricultural activity and ero-
sion-control measures installed for highway construc-
tion. Effects of H-3 highway construction on
suspended-sediment loads were generally similar to
effects of highway construction in other areas. State
water-quality standards for suspended sediment were
frequently exceeded during construction. Standards
were exceeded occasionally before construction.

REFERENCES CITED

Chinn, S.S., Tateishi, G.A., and Yee, J.J.S., 1983, Water re-
sources data, Hawaii and other Pacific area, water year
1982, volume 1, Hawaii: U.S. Geological Survey Water-
Data Report HI-82-1, 243 p.

sores, , 1984, Water resources data, Hawaii and other Pacific
area, water year 1983, volume 1, Hawaii: U.S. Geologi-
cal Survey Water-Data Report HI-83-1, 253 p.

oes, , 1985, Water resources data, Hawaii and other Pacific
area, water year 1984, volume 1, Hawaii: U.S. Geologi-
cal Survey Water-Data Report HI-84-1, 297 p.

------, 1986, Water resources data, Hawaii and other Pacific
area, water year 1985, volume 1, Hawaii: U.S. Geologi-
cal Survey Water-Data Report HI-85-1, 302 p.

oo , 1988, Water resources data, Hawaii and other Pacific
area, water year 1986, volume 1, Hawaii: U.S. Geologi-
cal Survey Water-Data Report HI-86-1, 295 p.S

Cline, M.G., 1955, Soil survey of the territory of Hawaii, U.S.
Department of Agriculture, Soil Conservation Service,
644 p.

Cohn, T.A., 1988, Adjusted maximum likelihood estimation

of the moments of lognormal populations from type I

censored samples: U.S. Geological Survey Open-File

Report 88-350, 34 p.

-, 1992, Estimating fluvial transport of trace constituents

using a regression model with data subject to censoring:

American Statistical Association Proceedings, August 9-

12, 1992, Boston (in press).

Dalrymple, Tate, and Benson, M.A., 1967, Measurement of
peak discharge by the slope-area method: U.S. Geologi-
cal Survey Techniques of Water-Resources Investiga-
tions, book 3, chap. A2, 12 p.

Doty, R.D., Wood, H.B., and Merriam, R.A., 1981, Suspend-
ed sediment production from forested watersheds on
Oahu, Hawaii: Water Resources Bulletin, v. 17, no. 3,
p. 399-405.

Duan, N., 1983, Smearing estimate: a nonparametric retrans-
formation method: Journal of the American Statistics
Association, v. 78, no. 383, p. 605-610.

Eckhardt, D.A.V., 1976, Sediment discharge from an area of
highway construction, Applemans Run Basin, Columbia
County, Pennsylvania: U.S. Geological Survey Water-
Resources Investigation Report 76-111, 25 p.

Edwards, T.K., and Glysson, G.D., 1988, Field methods for
measurement of fluvial sediment: U.S. Geological Sur-
vey Open-File Report 86-531, 118 p.

El-Swaify, S.A., Dangler, E.W., and Armstrong, C.L., 1982,
Soil erosion by water in the tropics: College of Tropical
Agriculture and Human Resources, University of Ha-
waii, Research Extension Series 024, Honolulu, Hawaii,
173 p.

Fishman, M.J., and Friedman, L.C., 1989, Methods for deter-
mination of inorganic substances in water and fluvial
sediments (3d ed.): U.S. Geological Survey Techniques
of Water-Resources Investigations, book 5, chap. Al,
545 p.

32 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


PRE-CONSTRUCTION

FA.

DURING CONSTRUCTION

MEAN DAILY STREAMFLOW PER UNIT AREA, IN CUBIC
FEET PER SECOND-DAY PER SQUARE MILE

16226200

16272200 16275000

STREAM-GAGING STATION

Figure 4. Mean daily streamflow before and during H-3 highway construction at selected

stream-gaging stations, Oahu, Hawaii.

study period were therefore not particularly high. The
highest peak flows of the 9-year study period (1983-91)
were small enough that they recur on average every 2
years.

No long-term records are available for flood-fre-
quency analyses in the Kamooalii drainage basin, but
records at nearby stream-gaging station 274499 (fig. 2)
indicate that recurrence intervals between 1981 and
1991 ranged from about 1 year in 1983 to 4 years in
1982. The second highest peak was in 1987, with a
recurrence interval of 3 years, and the third highest peak
was in 1990, with a similar recurrence interval. Peak
flows during the study period therefore were moderate
in the vicinity of the Kamooalii drainage basin, and did
not differ much between pre-construction and construc-
tion periods.

The highest annual peak flow of the study period at
station 226000 was recorded during construction, in
1991. The second-highest peak flow was in 1988, also
during construction. At station 275000 the two highest
peak flows occurred before construction in 1988 and
1987, respectively. Streamflow peaks at stations
265600, 270900, and 272200 were highest in 1987 and
1988 (U.S. Geological Survey, 1982; Chinn and others,
1983, 1984, 1985, 1986, 1988; Nakahara and others,
1988, 1989; Matsuoka and others, 1991, 1992). The
highest streamflow peaks of the study period, therefore,
were during construction at stations 265600 and 272200
and before construction at station 270900.

14 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


high rainfall (Stearns and Vaksvik, 1935; Wentworth,
1943; White, 1949; Scott and Street, 1976; Wilson and
others, 1992).

Soils of the study area have been classified as low
humic latosols, humic ferruginous latosols, humic lato-
sols, and hydrol humic latosols (Cline, 1955). The dis-
tribution of soils is related to rainfall; low humic
latosols and humic ferruginous latosols are found on
drier leeward stations, hydrol humic latosols are found
in areas of high rainfall, and humic latosols occupy
intermediate stations (Tamura and others, 1953; Sher-
man and Ikawa, 1967). Soils on the windward side pri-
marily are humic latosols (Foote and others, 1972).
Most of the mountainous areas of the study drainage
basins were classified as "rough mountainous land" or
"rock outcrop" (Foote and others, 1972), and little infor-
mation is available on the soils of these areas.

Most of the native vegetation on the windward side
of the study area has been replaced by cultivated crops,
other non-native plants, and residential and commercial
developments. Vegetation in the North Halawa Valley
is representative of undisturbed forest in the leeward
Koolau Range and includes native and introduced spe-
cies.

North Halawa.--The North Halawa drainage
basin is on the leeward side of the crest of the Koolau
Range. North Halawa Stream flows into the East Loch
of Pearl Harbor after joining South Halawa Stream
downstream of stream-gaging station 226200 (figs. 1
and 2; numbers of stream-gaging stations used in this
report are abbreviated by omitting the first two digits,
16, from the full station numbers). The drainage area
upstream of station 226200, at an altitude of 160 ft, is
4.01 mi2. Overall stream gradient is 0.074 fv/ft. The
lower valley is deeply incised, with only a few small
ephemeral tributaries. The 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 drainage
basin, channels are cut into bedrock and include several
waterfalls. The stream is more than 100 ft above the
basal water table throughout the valley (C.K. Went-
worth, written commun., 1942; Izuka, 1992), and flow
in the main channel is intermittent in most years.

When completed, the H-3 highway will constitute
about 4 percent of the drainage area upstream of station
226200. Before highway construction began in Novem-

ber, 1987, this drainage basin was undeveloped with the
exception of the Halawa Shaft, built by the Honolulu
Board of Water Supply in 1940 to collect ground water
from the basal aquifer. There are no streamflow diver-
sions in the drainage basin except temporary channel
diversions related to highway construction; these diver-
sions do not transfer surface water out of the drainage
basin.

Rainfall, streamflow, and suspended-sediment
data collection at station 226200 began in February,
1983. Rainfall and streamflow data have been continu-
ously collected at station 226000 (fig. 1) since 1953.
Data collection at station 225800 (fig. 1) began in April,
1991.

Haiku.--The Haiku drainage basin is on the wind-
ward side of the Koolau Range and adjoins the North
Halawa drainage basin along the crest of the range (fig.
2). Drainage area upstream of stream-gaging station
275000, at an altitude of 272 ft, is 0.97 mi, Overall
stream gradient is 0.267 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. At station 275000, Haiku Stream flows peren-
nially. Haiku Stream joins Iolekaa Stream downstream
of station 275000 to form Heeia Stream, which flows
into Kaneohe Bay (fig. 2).

Almost all of the drainage basin upstream of sta-
tion 275000 is used for a U.S. Coast Guard navigational
facility. A municipal well and water tunnel are located
upstream of station 275000. The tunnel was constructed
in 1940; the well was brought into service during the H-
3 highway construction period in 1989. Highway con-
struction in the Haiku drainage basin began in October
of 1988 (table 1). The H-3 within Haiku drainage basin
is constructed entirely as a viaduct, and covers about 3
percent of the drainage area for station 275000.

Streamflow data were collected before this study at
station 275000 from 1914 through 1919 and from 1939
through 1977. Streamflow data collection for the H-3
study began in October, 1982, and suspended-sediment
data were collected from December, 1983 through Sep-
tember, 1984 and from July, 1987 through the present
(1994).

The South Fork Kapunahala drainage basin lies
adjacent to the Haiku drainage basin on its southeast
boundary. The drainage basin above station 273950, at

6 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


other areas have shown that construction can contribute
as much as five times the amount of sediment contrib-
uted from all other sources (table 2).

Regional Comparison of Suspended-Sediment
Yields

Annual suspended-sediment yields reported for
other areas of Oahu (Jones and others, 1971; Doty and
others, 1981; Shade, 1984) were used to extend the
range of pre-construction data at H-3 study stream-gag-
ing stations in order to estimate the effects of construc-
tion. Annual suspended-sediment yields during
construction at stations 226200, 265600, and 275000
were higher than pre-construction yields and yields
from nearby drainage basins unaffected by highway
construction for comparable values of annual water
yield (streamflow per unit area); (fig. 10). Yields during
construction at station 270900, however, were within
the range of yields for drainage basins unaffected by
highway construction. Suspended-sediment yields at
station 272200 cannot be compared with yields at other
stations because the reservoir upstream of the station
traps sediment and reduces the yield at the station.

Annual water yields (streamflow per unit area) and
suspended-sediment yields for drainage basins in the
leeward Koolau Range were combined with pre-con-
struction data for station 226200 (fig. 10) to compute a
regression equation relating suspended-sediment yield
to water yield under pre-construction conditions for lee-
ward Koolau drainage basins. This regression equation
was used to estimate the suspended-sediment yields
expected at station 226200 during the construction
period without the effects of highway construction.
Transformation to common logarithms was used to
obtain a more linear relation, which was expressed:

log Sy = -2.91 + (1.96 x log Qy), (5)

where Sy represented annual suspended-sediment yield
and Qy represented annual water yield. A total of 18
annual suspended-sediment yields was used to compute
the regression, which had a coefficient of determination
of 86 percent and a standard error of 0.22 log units.

The same procedure was used for stations 265600,
270900, and 275000 using pre-construction data from
these stations and for windward stations used in previ-
ous studies (fig. 10), except that log-transformation was
not necessary. The regression equation, computed with
14 measured suspended-sediment yields, was expressed
as:

Sy = 30 + (0.529 x Qy). 6)

The coefficient of determination for equation 6
was 56 percent, and the standard error was 336 t/mi?.
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.

Annual suspended-sediment yields expected in the
absence of construction effects were estimated by
applying regression equations 5 and 6 to construction-
period annual water yields. For station 226200, a bias-
correction factor of 1.15 was applied to correct for
retransformation error (Duan, 1983). These estimates
were subtracted from observed annual suspended-sedi-
ment yields. The resulting differences represent the
increased or decreased yields attributable to construc-
tion. Sums of the annual differences were divided by
sums of observed annual construction-period yields and
multiplied by 100 to obtain the percentages of the con-
struction-period suspended-sediment yields resulting
from highway construction.

Sums of annual differences ranged from -920
mi? equivalent to -71 percent of the observed sus-
pended-sediment yield, at station 270900, to 6,260
t/mi2, or 76 percent of the observed yield, at station
275000 (table 11). The increased yield at station 226200
was equivalent to 59 percent of the observed yield, and
the increased yield at station 265600 was equivalent to
56 percent of the observed yield (table 11). The sus-
pended-sediment loads resulting from construction
activities therefore ranged from 56 to 76 percent of the
measured loads at the three stations where significant
increases in suspended-sediment loads were detected.

The negative difference for station 270900 (table
11) indicates that suspended-sediment yields during
construction would have been higher under pre-con-
struction conditions than under construction conditions.
Before construction, most of the drainage basin
upstream of station 270900 was under cultivation for
bananas. Although agricultural practices generally
increase sediment yields (El-Swaify and others, 1982),
no studies have documented sediment yields from
banana plantations in Hawaii. 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. Pre-construction

Suspended-Sediment Loads Before and During Construction 29


tion and added to the apparent effects of highway con-
struction. However, data are insufficient to quantify the
effects of golf course construction or to determine the
relative importance of highway or golf course construc-
tion on sediment loads at station 265600.

Evaluation of State Water-Quality Standards

The State of Hawaii Department of Health has
established standards for total nonfilterable residue for
streams in the State of Hawaii (State of Hawaii Depart-
ment of Health, 1990). Separate standards were estab-
lished for the dry season (May 1 through October 31)
and the wet season (November | through April 30). The
standards are as follows: for the dry season, geometric
mean not to exceed 10 mg/L, concentrations not to
exceed 30 mg/L for more than 10 percent of the time or
55 mg/L for more than 2 percent of the time; for the wet
season, geometric mean not to exceed 20 mg/L, concen-
trations not to exceed 50 mg/L for more than 10 percent
of the time or 80 mg/L for more than 2 percent of the
time.

Total nonfilterable residue is similar to suspended-
sediment concentration in that both are measures of the
amount of suspended material present in a water sam-
ple. Total nonfilterable residue is determined for an ali-
quot of sample that may not be representative of the
whole sample, especially if large quantities of sand are
present. Sand settles quickly, and aliquots removed for
total nonfilterable residue are likely to be either
depleted or enriched in sand, depending on where the
aliquot was collected in the sample bottle. Whole sam-
ples are used for suspended-sediment concentration
analyses. For this reason, suspended-sediment concen-
tration is generally a more accurate measure of sus-
pended materials (Fishman and Friedman, 1989, p.
443).

During the H-3 highway study, 13 samples col-
lected concurrently with suspended-sediment samples
were analyzed for total nonfilterable residue. Sus-
pended-sediment concentrations for these pairs of sam-
ples ranged from 6 to 659 mg/L. Suspended-sediment
concentrations were higher than total nonfilterable resi-
due for each sample pair. The average difference was 35
percent of the suspended-sediment concentration. Sus-
pended-sediment concentrations therefore tend to over-
estimate total nonfilterable residue concentrations by
about 35 percent, and these two measures of suspended

material cannot be considered equivalent. However,
because both suspended-sediment concentration and
total nonfilterable residue are measures of suspended
material in streams, and because suspended-sediment
concentration data are available on a daily basis and
total nonfilterable residue data are not, suspended-sedi-
ment concentrations were substituted for total nonfilter-
able residue concentrations in the analysis of water-
quality standards compliance. Although results cannot
be used directly to determine whether highway con-
struction caused exceedance of water-quality standards,
they provide a general assessment of standards compli-
ance before and during construction.

Daily values of suspended-sediment concentra-
tion, separated into wet and dry season data, were used
to assess compliance with State water-quality stan-
dards. The geometric mean was computed as the antilog
of the arithmetic mean of log-transformed data. The
time percentages that daily concentrations were
exceeded were determined by sorting and ranking the
concentration data for each year, and dividing the ranks
by the number of days in the season (wet or dry) for that
year to get a cumulative relative frequency. These fre-
quencies were subtracted from 1.00 to obtain the per-
centage of time each concentration was equalled or
exceeded. Daily values of concentration reported as 0
were replaced with estimates derived from log-probit
regression (Helsel and Hirsch, 1992) to permit compu-
tation of the geometric mean.

State water-quality standards were exceeded at all
H-3 stations during most but not all years of the con-
struction periods (table 10), on the basis of the analysis
described above. Standards also were exceeded in 2
years of the pre-construction periods at stations 270900
and 275000. In many cases, standards were exceeded by
much more than the 35 percent error that could be
attributed to the substitution of suspended-sediment
concentrations for total nonfilterable residue concentra-
tions.

Estimated Magnitude of Highway-Construction
Effects on Suspended-Sediment Loads

Highway construction can accelerate erosion and
suspended-sediment transport through disturbance of
soil and vegetation cover, channel realignments, and
decreased hillslope stability as a result of cutting and
filling. Previous studies of highway construction in

26 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


between 1983 and 1991, which included periods before
and during construction. Additional data collected
before 1983 were used at one station.

Rainfall, streamflow, and suspended-sediment
data collected at a network of stream-gaging stations
and miscellaneous sites (fig. 2) were used to determine
whether streamflow and suspended-sediment loads
changed significantly during construction. Changes due
to construction were quantified by comparing data col-
lected during construction to data collected before con-
struction. Suspended-sediment concentrations were
used to assess compliance with applicable State water-
quality standards related to sediment transport. Daily,
monthly, and annual values of streamflow, suspended-
sediment concentration and discharge, and suspended-
sediment size analyses have been published in the
annual water-resources data reports of the U.S. Geolog-
ical Survey (U.S. Geological Survey, 1982; Chinn and
others, 1983, 1984, 1985, 1986, 1988; Nakahara and
others, 1988; Nakahara and others, 1989; Matsuoka and
others, 1991, 1992).

H-3 Highway Construction

The H-3 highway route traverses four drainage
basins: North Halawa, Haiku, Kapunahala, and
Kamooalii, which includes the Luluku drainage basin
(figs. 1 and 2). The H-3 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 connects to a previously constructed section
leading from Kamehameha Highway to Kaneohe
Marine Corps Base Hawaii. The completed highway
will consist of a cut-and-fill section in the lower North
Halawa Valley, a viaduct through the upper North Hal-
awa Valley, twin tunnels below the crest of the Koolau
Range, a viaduct through the Haiku drainage basin, and
a cut-and-fill section through the Kapunahala and
Kamooalii drainage basins (U.S. Department of Trans-
portation, Federal Highways Administration and State
of Hawaii Department of Transportation, 1987). When
completed, the total area affected by highway construc-
tion will constitute from 3 to 11 percent of the drainage
basin areas upstream of the stream-gaging stations dis-
cussed in this report.

Construction of the H-3 highway has proceeded by
sections (table 1). Construction has at times been halted

by court actions, and the route has been 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 have been used through-
out construction of the H-3 highway to reduce sediment
delivery from construction areas in all affected drainage
basins. These measures include erosion-cloth barriers
installed on hillslopes and along channels, loose-rock
check dams in channels, and hydromulching and instal-
lation of plastic netting on cut-and-fill slopes. Stream-
flow in several channel reaches in upper North Halawa
Valley was diverted into culverts and buried during
construction to prevent sediment disturbed by construc-
tion from reaching the stream.

Study Drainage Basins

The Koolau Range is the eroded remnant of the
larger and younger of the two major shield volcanoes
that formed the island of Oahu (Visher and Mink,
1964). Much of the windward side of the original
Koolau Volcano has been eroded, leaving a steep wind-
ward slope indented with amphitheater-shaped valleys
(Hinds, 1925), and a gentle leeward slope deeply dis-
sected by roughly linear valleys.

Lithology of the study area consists primarily of
basalt that was extruded in numerous gently dipping
thin (less than 10 ft) flows of aa and pahoehoe lava
(Visher and Mink, 1964). These flows are intruded by
near-vertical dikes in the rift zone near the crest of the
present Koolau Range (Visher and Mink, 1964). 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 Hal-
awa 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 ranges from 74° to 76°F in the
study area; temperatures above 95°F and below 50°F
are rare (U.S. Department of Commerce, 1961). The
distribution of rainfall is affected by the prevailing
northeasterly trade winds and the topography of the
island. Orographic lifting and cooling of marine air

Introduction 3


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2 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


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Streamflow Before and During Construction 15

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Table 1. Chronology of construction activities, H-3 highway construction project, 1983-92, Oahu, Hawaii
[Locations of construction activities and stream-gaging stations are shown in figures 1-3; station numbers are abbreviated, complete numbers are
preceded by 16; do., ditto; --, construction activity in progress as of September 30, 1991. Start and end dates provided by the State of Hawaii, De-

partment of Transportation, written commun., 1993}

Construction activity Start date End date
N. Halawa drainage basin—downstream stream-gaging station 226200
N. Halawa access road... 06.6... cece cence ene nen en ene nnn ee 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 ~
N, Halawa viaduct ..... 0.00... cece cece eee nett tnt t eet ene ee 02/21/92 ~
Haiku drainage basin—downstream stream-gaging station 275000
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 ~
Trans-Koolau tunnel . 10/01/90 -
Kamooalii drainage basin—downstream stream-gaging stations 265600, 270900, and 272200
H-3 highway . . 06/19/89 06/92
Right Branch Kamooalii drainage basin—downstream stream-gaging stations 265600 and 272200
Halekou interchange!.. 0.1... cece eee eee een een eens 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
(C0 sees 06/15/87 09/30/88
Luluku drainage basin—downstream stream-gaging stations 270900 and 272200
Hospital Rock tunnel . 03/06/89 05/92

1 Work on Halekou interchange interrupted by court injunctions

masses moving with the trade winds 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, written commun., 1942; Mink, 1960).
Rainfall varies seasonally, with most rainfall falling
between November and April. Average annual precipi-
tation ranges from 75 to 150 in. on the windward side of
the study area, and from 40 to more than 150 in. on the
leeward side (U.S. Department of Commerce, 1961).

Streamflow in the study area is determined by
geology and climate. 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 can
flow between windward drainage basins. Rainfall infil-
trating in one valley may emerge as streamflow in
another (Hirashima, 1963; Takasaki and others, 1969).
On the leeward side of the Koolau Range, dikes are

uncommon (C.K. Wentworth, written commun., 1942).
Infiltrating rainfall in the North Halawa Valley perco-
lates to the basal aquifer and does not maintain base
flows (C.K. Wentworth, written commun., 1942; Izuka,
1992). Streamflow in North Halawa Stream is intermit-
tent and is dependent on runoff during rainfall, although
discharge of small quantities of ground water from allu-
vial aquifers extends recession flows (Izuka, 1992).

The relative importance of the geomorphic pro-
cesses responsible for the dramatic topography of the
study area has been debated for many years. The role of
chemical weathering in the warm, humid climate of
Oahu has been stressed (Wentworth, 1928; Scott and
Street, 1976). Stream piracy (Wentworth, 1928; Stearns
and Vaksvik, 1935), rapid weathering at the water table
(Wentworth, 1928), and plunge-pool erosion and
ground-water sapping (Stearns and Vaksvik, 1935)
have been suggested as causes of the unique amphithe-
ater-shaped valleys of the Koolau Range. The most
obvious process of physical erosion is mass wasting of
shallow soil and saprolite on steep hillslopes in areas of

Introduction 5


basins (table 7). Studies in areas where rainfall is the
most important form of precipitation have reported that
effects of roadbuilding on peak flows were detectable
only when 12 percent or more of drainage basin area
was affected (Ziemer, 1981). The H-3 highway affected
between 3 and 11 percent of drainage basin areas
upstream of the stream-gaging stations used for this
study, and the apparent lack of any major effects of H-
3 construction on high flows may have resulted in part
from the relatively small areas affected by the highway.

SUSPENDED-SEDIMENT LOADS BEFORE
AND DURING CONSTRUCTION

Annual suspended-sediment loads were generally
low during 1983-86 (table 8), when rainfall and stream-
flow were low. Suspended-sediment loads were high
during 1988-91 when rainfall and streamflow were
high and after construction had begun upstream of all
stations. The highest annual load at stream-gaging sta-
tion 272200 was in 1982 (table 8).

Suspended-sediment yields were computed for
pre-construction and construction periods by dividing
daily loads by drainage basin areas. Mean daily sus-
pended-sediment yields were higher before construc-
tion at stream-gaging stations 270900 and 272200, and
higher during construction at stream-gaging stations
226200 and 275000 (fig. 7).

Sediment duration.--Sediment-duration curves
(Searcy, 1959) are analogous to flow-duration curves;
each value of daily mean suspended-sediment load is
plotted against the percentage of time that the load is
equalled or exceeded. Sediment-duration curves (fig. 8)
indicate increased and more persistent suspended-sedi-
ment transport during construction at stream-gaging
stations 226200, 270900, and 275000, although the
highest daily suspended-sediment load at station
270900 was during the pre-construction period. The
sediment-duration curve for station 272200 indicates
decreased suspended-sediment transport during con-
struction.

Relations Between Streamflow and
Suspended-Sediment Loads

The analysis of covariance procedure requires that
the covariate, streamflow, be independent of the factor
represented by the dummy variable, in this case con-

Table 8. Annual suspended-sediment loads at stream-gaging
Stations in the H-3 highway study area, Oahu, Hawaii

[All values are in tons; --, no data; station numbers are abbreviated, complete
numbers are preceded by 16]

Water Station number

year 226200 265600 270900 272200 275000
1981 - - - 723 -
1982 ~ - - 3,210 -
1983 - ~ - 173 -
1984 31 24 ~ 77 -
1985, 314 S41 43 336 -
1986 362 472 OL 322 -
1987 615 631 402 1,190 -
1988 3,500 1,730 485 2,240 1,310
1989 16,600 1,220 180 1,290 3,400
1990 2,260 1,160 53 593 1,660
1991 5,220 512 333 1,270 2,970

struction. The lack of any significant effects on high
flows at stream-gaging stations indicates that this con-
dition was reasonably fulfilled.

Analysis of covariance results indicate that rela-
tions between streamflow and suspended-sediment
loads changed significantly during construction at
stream-gaging stations 226200, 270900, and 275000
(table 9; fig. 9). Regression slopes increased during
construction at all three stations. The regression inter-
cept increased during construction at station 226200,
and intercepts decreased during construction at stations
270900 and 275000 (table 9).

Changes in regression coefficients indicate how
streamflow-sediment relations were affected during
construction. The increases in both slope and intercept
at station 226200 indicate that suspended-sediment
loads increased relative to streamflow during construc-
tion. This increase affected the entire range of stream-
flow at this station except for flows below 0.21 ft/s. As
a result of the increase in slope, the construction regres-
sion line is actually below the pre-construction regres-
sion line for flows less than 0.21 ft/s. Because very
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.
At station 270900, the increased slope and decreased
intercept (fig. 9) cause the pre-construction and con-
struction regression lines to intersect; the intersection
point, in units of log-transformed streamflow, can be
determined by dividing the absolute value of the coeffi-
cient for Z by the coefficient for W. The two regressions
estimate the same suspended-sediment load for a
streamflow of 1.25 ft°/s. Suspended-sediment loads are

Suspended-Sediment Loads Before and During Construction 21


STREAMFLOW AND SUSPENDED-SEDIMENT LOADS
BEFORE AND DURING HIGHWAY CONSTRUCTION,
NORTH HALAWA, HAIKU, AND KAMOOALII DRAINAGE
BASINS, OAHU, HAWAII, 1983-91

By Barry R. Hill

U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 96-4259

Prepared in cooperation with the

STATE OF HAWAII DEPARTMENT OF TRANSPORTATION

Honolulu, Hawaii
1996



basins had suspended-sediment yields ranging from 8.6
to 960 (vmi?)/yr (Jones and others, 1971; Doty and oth-
ers, 1981). No clear distinctions are apparent on the
basis of location (leeward or windward) or land use
(undisturbed or mixed use).

Highway Construction Effects in Other Areas

No previous studies of the hydrologic effects of
highway construction are available for Oahu or similar
central Pacific islands. Investigations in other locations,
however, provide some indications of potential effects
of road building.

A number of studies have documented streamflow
changes attributable to construction of logging roads in
the Pacific Northwest region of the United States. These
studies showed that significant increases in peak flows
resulted from road building in areas where rainfall is the
dominant form of precipitation only if roads and other
compacted surfaces constituted at least 12 percent of
drainage basin area (Harr and others, 1975; Ziemer,
1981, King and Tennyson, 1984).

Several studies have evaluated changes in sedi-
ment loads following construction of highways in the
eastern United States (table 2). The drainage basins
used in these studies included areas previously affected
by farming and mining, and do not represent changes
from pristine conditions. Results of these studies indi-
cate that the percentage of the annual sediment loads
attributable to highway construction ranged from 29 to
85 percent (table 2).

Acknowledgments

Stream-gaging stations 226000, 229000, and
275000 are operated in cooperation with the Honolulu
Board of Water Supply. Stream-gaging station 272200
is operated in cooperation with the U.S. Army Corps of
Engineers. Stream-gaging station 274499 is operated in
cooperation with the Honolulu Department of Public
Works. Start and end dates for construction activities
were provided by Dennis Higa of the State of Hawaii
Department of Transportation. Ground-water with-
drawal data were provided by Chester Lao of the City
and County of Honolulu Board of Water Supply and
Neal Fujii of the State of Hawaii Commission on Water
Resource Management.

Table 2. Sediment-load results from previous studies on
effects of highway construction effects in the eastern United
States

‘Annual sediment load Type of
from highway sediment
Reference construction (percent) data

Vice and others, 1969 85 total
Eckhardt, 1976 50 suspended
Reed, 1978 29-54 suspended
Helm, 1978 50 suspended
Reed, 1980 63-79 suspended
Ward and Appel, 1988 49 suspended
APPROACH

The approach used in this study is a statistical com-
parison of data collected before construction with data
collected during construction. 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 con-
struction (tables 1 and 3). These periods are not the
same at all stations because start dates for data collec-
tion and for construction varied. Stream-gaging stations
226200, 270900, 272200, and 275000 have reasonably
long periods of data before and during construction
(table 3). Stream-gaging station 265600 has only a few
days of pre-construction data, and this short period is
not sufficient for the analyses described below. Instead,
data collected at stream-gaging station 265600 were
compared with data collected before construction at
nearby stream-gaging station 270900. Suspended-sedi-
ment data are available only for 1991 at stream-gaging
stations 225800 and 273950, and cannot be used to
assess effects of construction at this time. Data for these
stations therefore were not considered in this report.

A simple comparison of data collected before and
during construction is not adequate because rainfall var-
ied during the study. 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 peri-
ods of low rainfall, even in the absence of any construc-
tion or other land-use effects.

Statistical procedures used in data analysis were
designed to remove the variations in streamflow and
suspended-sediment loads that resulted from changes in
rainfall. The remaining variability could then be attrib-

8 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


an altitude of 120 ft, has an area of 0.40 mi2 (fig. 2). The
drainage basin consists of residential and agricultural
lands. H-3 highway construction began in June, 1989
(table 1). Although streamflow data have been collected
since 1987, suspended-sediment data are available only
for 1991.

Kamooalii.--The Kamooalii drainage basin
upstream of stream-gaging station 272200, at an alti-
tude of 115 ft, is 3.81 mi2 (fig. 2). This area includes the
1.11 mi? Right Branch Kamooalii drainage basin
upstream of stream-gaging station 265600 and the 0.44
mi? Luluku drainage basin upstream of stream-gaging
station 270900. Streamflow is perennial at all three sta-
tions. Kamooalii Stream joins Kapunahala Stream
downstream of station 272200 to form Kaneohe Stream,
which flows into Kaneohe Bay. Waimaluhia Reservoir,
a flood-control reservoir, was constructed in 1980
upstream of the confluence of Luluku and Kamooalii
Streams. Streamflow at station 272200 includes water
flowing through Waimaluhia Reservoir and water from
Luluku Stream that does not pass through the reservoir.
Overall stream gradient at station 272200 is 0.095 ft/ft.
The channels within the drainage basin are cut between
2 and 20 ft into alluvium, and are composed mainly of
cobbles and gravel intermixed with finer sediment.

The Hoomaluhia Botanical Garden surrounding
Waimaluhia Reservoir is a public park operated by the
City and County of Honolulu (fig. 2). Below the park,
most of the drainage basin has been developed for resi-
dential use. Above the park, most of the drainage basin
consists of banana plantations or undeveloped land. The
Likelike highway crosses the drainage basin above the
H-3 highway. The Minami golf course was constructed
above the park in 1989-91.

Several municipal wells and water tunnels 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 for golf
course irrigation also were drilled above station 265600
during the construction period. Water is sometimes
pumped from Luluku Stream above station 270900 to
irrigate banana plantations.

Highway construction in the drainage basin began
in 1983 (table 1). The H-3 highway constitutes about 4
percent of the drainage area for station 272200. The
area affected by the H-3 includes about 11 percent of the

drainage area for station 270900 and 5 percent of the
drainage area for station 265600.

Streamflow and suspended-sediment data collec-
tion at station 272200 began in 1976. Data from Octo-
ber, 1980 (after dam closure) through September, 1991
are used in this report. Streamflow and suspended-sedi-
ment data collection began in February, 1983 at station
265600 and in April, 1984, at station 270900. Stream-
flow data previously were collected at station 270900
from 1960-63 (low flow only), 1965-71, and 1971-84
(annual maximum only).

Suspended-Sediment Yields in the Koolau
Range

Sediment data are sparse for the islands of Hawaii,
but some previously collected sediment data are avail-
able for streams in and near the H-3 highway study area.
These data can be usefully compared with data col-
lected for the H-3 study by converting annual sus-
pended-sediment loads to annual suspended-sediment
yields. Annual suspended-sediment loads are quantities
of suspended sediment, in mass units, transported dur-
ing a year. Suspended-sediment loads usually are
reported in tons. Annual suspended-sediment yields are
suspended-sediment loads per unit of drainage area, and
usually are expressed in tons per square mile, or tons per
square mile per year. Sediment data for drainage basins
with drainage areas similar to those of H-3 study drain-
age basins were collected for a 3-year period at eight
stream-gaging stations in the central Koolau Range and
in nearby areas (Jones and others, 1971), for 5 years at
five stations in the same general area (Doty and others,
1981), and for 5 years at two stations in the Moanalua
Valley (Shade, 1984). These data give some indication
of the range of annual suspended-sediment yields for
drainage basins both in undisturbed conditions and
under mixed land use consisting of urban, agricultural,
and conservation uses. Suspended-sediment yields for
undisturbed drainage basins on the leeward side of the
Koolau Range ranged from 24 to 1,770 (Umi2)/yr (Jones
and others, 1971; Doty and others, 1981; Shade, 1984).
The single leeward drainage basin under mixed land use
had a suspended-sediment yield of 970 (vmi2)/yr (Jones
and others, 1971). Undisturbed windward drainage
basins had suspended-sediment yields ranging from 710
to 1,400 (wmi2)/yr, and mixed-use windward drainage

Introduction 7


Table 10. Evaluation of State water-quality standards for selected stream-gaging stations, Oahu, Hawaii--Continued

Concentration (mg/L) exceeded Percentage of time
30 mg/L (ary) 55 mg/L (dry)
Water Geometrig rpean' 10 percent 2 percent 50 mg/L (wet) 80 mg/L (wet)
year Season m: of time of time exceeded exceeded
Station 270900—Continued
wet 5 22 167* 0 5
1989 dry 5 7 80* 0 >2
wet 10 50 222* 0 7
1990 dry 7 10 50 0 0
wet 7 20 46 0 0
1991 dry 20* 43* 175* 22 6
wet 19 88* 250* 20 12
Station 272200
1983 dry 6 10 17 0 0
wet 8 15 31 0 0
1984 dry 10 23 33 0 0
wet 10 18 64 0 0
1985 dry 11* 27 60* 0 >2
wet 16 29 53 0 0
1986 dry 8 14 40 0 0
wet 8 12 15 0 0
1987 dry 7 16 109* 0 S
wet 7 13 39 0 0
1988 dry 3 7 19 0 0
wet 8 42 197* 0 5
1989 dry 21* 58* 130* 31 ll
wet 19 35 189* 0 6
1990 dry 14* 141* 237* 21 15
wet 12 43 115* 0 3
1991 dry 8 18 33 0 0
wet 17 45 139* 0 4
Station 275000
19845 dry 3 5 12 0 0
wet 6 14 21 0 0
1985 dry a - ~ - -
wet - - ~ - -
1986 dry - ~ - - ~
wet ~ - - - -
19876 dry 7 18 120* 0 3
wet - - ~ ~ -
1988 dry 3 8 21 0 0
wet 9 6l* 257* 1 8
1989 dry 9 19 160* 0 3
wet 15 89* 637* 13 10
1990 dry 6 16 153* 0 4
wet 10 68* 595* 11 8
1991 dry 2 8 74* 0 >2
wet 6 99* 687* 13 1

1 computed using log-probability regression to estimate values for data reported as zero

data for water year 1983 from February | through September 30; all wet season concentrations were zero, and the geometric mean could not be computed
data for water year 1983 from February 1 through September 30
data for water year 1984 from April | through September 30

5 data for water year 1984 from December 1 through September 30
data for water year 1987 from July 20 through September 30; no wet season data

28 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


Table 10. Evaluation of State water-quality standards for selected stream-gaging stations, Oahu, Hawaii

[Suspended-sediment concentrations were used in place of total nonfilterable residue, and results therefore can only indicate possible exceedance
of the standards; * indicates possible exceedance of standard; > indicates that the computed percentage of time was greater than the value indicated
by less than 0.5 percent; station numbers are abbreviated, complete numbers are preceded by 16]

Concentration (mg/L) exceeded

Percentage of time

Water Geometric mean’ 10 percent 2 percent 50 mL (re) 30 mor (wey
year Season (mg/L) of time of time exceeded exceeded
Station 226200
1983 dry 1 6 16 0 0
wet - 0 0 0 0
1984 dry 0 2 10 0 0
wet 1 4 16 0 0
1985 dry 1 4 20 0 0
wet 2 8 50 0 0
1986 dry 2 7 38 0 0
wet 1 6 28 0 0
1987 dry 2 9 37 0 0
wet 2 10 39 0 0
1988 dry 3 37 307* i 8
wet 7 59% 309* ul 8
1989 dry 12" 64* 523* 14 10
wet 44x 668* 1,336* 38 35
1990 dry 5 26 169* 0 6
wet 5 19 i71* 0 3
1991 dry 10 44* 180* 13 8
wet 9 itt 430* 15 ul
Station 265600
1983) dry Be 45* lis* n 5
wet 9 21 43 0 0
1984 dry i 24 51 0 0
wet 9 34 o1* 0 3
1985 dry 13* 34x 99% 12 6
wet 10 32 126* 0 3
1986 dry 10 19 106* 0 4
wet 9 u n 0 0
1987 dry 14* 28 77* 0 7
wet 18 26 118* 0 5
1988 dry o* 26 103* 0 5
wet 10* 52* 207* >10 7
1989 dry 22 42* 74* 14 6
wet 30* 95+ 257* 14 12
1990 dry 13* 34s 110* 1B 7
wet 18 m1 419* 12 9
1991 dry 7 20 39 0 0
wet 16 61* 133* 14 5
Station 270900
1984 dry 4 8 ul 0 0
wet 6 14 44 0 0
1985 dry 4 5 7 0 0
wet 5 Wl 46 0 0
1986 dry 6 8 48 0 0
wet 6 8 2 0 0
1987 dry 5 5 64* 0 >2
wet 5 6 194* 0 3
1988 dry 4 5 7 0 0

Suspended-Sediment Loads Before and During Construction 27


21°26"

2te24' Fe

21°22"

ans f i

EXPLANATION 0 1 2MILES

—-+- DRAINAGE DIVIDE ° 1 2 KILOMETERS

267500, STREAM-GAGING STATION AND ABBREVIATED
STATION NUMBER--Complete number is 16275000

265700 5 = MISCELLANEOUS SITE AND ABBREVIATED
SITE NUMBER--Complete number is 16265700

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

4 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


tend to eliminate natural sources of streamflow variabil-
ity. The Luluku drainage basin upstream of station
270900, however, is entirely within the marginal dike
zone where large quantities of high-level ground water
are discharged to streams. In contrast, the drainage
basin upstream of station 265600 is mostly within the
dike complex where ground-water discharge is gener-
ally low (Takasaki and Mink, 1985). Base flows could
be expected to be higher at station 270900 than at sta-
tion 265600 because of this difference in geology.
Although comparison of streamflow data for these two
stations is of limited value, it is useful to the extent that
large increases in streamflow at station 265600 during
highway construction might be detected if streamflow
at station 265600 was found to be higher than stream-
flow at station 270900.

Daily mean streamflows per unit area at station
265600 were significantly (p<0.0001) lower than those
at station 270900 under pre-construction conditions.
Average streamflow per unit area at station 265600 was
1.37 (ft3/s)/mi2 and average streamflow per unit area at
station 270900 was 1.78 (fP/syimi2. The significant dif-
ference between streamflow per unit area at these sta-
tions was likely the result of differences in geology.
Large increases in streamflow during construction at
station 265600 appear unlikely because construction
period streamflow at station 265600 was lower than
pre-construction streamflow at station 270900. Any
streamflow decreases resulting from construction can-
not be detected with this procedure.

Land-Use Effects on Streamflow

Changes in streamflow during highway construc-
tion resulting from factors other than changes in rainfall
were significant at stations 270900 and 272200 (tables
6 and 7). These changes are unlikely to have occurred as
a result of random streamflow variations, and are prob-
ably the result of changes in drainage-basin conditions
because of land-use activities. H-3 highway construc-
tion is a possible cause of the changes in streamflow,
but other activities that coincided with construction may
have also affected streamflow.

Low Flows

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

Izuka, 1992). Any alterations of the ground-water flow
system could have affected low flows (Hirashima,
1963; 1965; 1971), which changed significantly during
construction at stream-gaging stations 270900 and
272200. The most likely activities that could have
affected ground-water flow during construction of the
H-3 highway include municipal ground-water with-
drawals and H-3 construction.

Municipal ground-water withdrawals.--Munici-
pal 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 significantly (p<0.05) during
highway construction in the drainage basins upstream
of stream-gaging stations 270900 and 272200 (fig. 6).
These increased withdrawals could be expected to
reduce low flows at these stations (Takasaki and Mink,
1985).

Stepwise multiple regression analyses (Helsel and
Hirsch, 1992) using monthly average streamflow at
stream-gaging station 229000, monthly precipitation
(from Wong and Hill, 1992, and U.S. Geological Sur-
vey unpublished data), and monthly average municipal
ground-water withdrawals (Honolulu Board of Water
Supply, 1981-92) as independent variables failed to
detect any significant effects of withdrawals on monthly
average streamflow at station 272200. Withdrawals
were a significant explanatory variable at station
270900, but were positively correlated with streamflow.
A negative correlation would be expected if withdraw-
als were depleting streamflow. On the basis of these
analyses, no clear link between municipal withdrawals
and streamflow is apparent.

A simple comparison of withdrawals and stream-
flow, however, could fail to detect effects of withdraw-
als on streamflow if interrelations are complicated by
seasonal or other variations. For example, the propor-
tion of ground water currently withdrawn from wells
and tunnels that would be discharged to streams under
natural conditions might change from month to month,
or from wet season to dry season. In such a case, total
withdrawals would be poorly correlated with stream-
flow even if streamflow was affected by withdrawals.

Although the true proportion of the ground water
withdrawn for municipal uses that would otherwise
have supplied streamflow cannot be determined with
any certainty, a rough estimate of the maximum poten-
tial effect of increased withdrawals during highway

18 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


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24 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


7. Mean daily suspended-sediment yields before and during H-3 highway construction

at selected stream-gaging stations, Oahu, Hawaii ...............0 eee cece eee eee eee ee 22
8. Sediment-duration curves of daily mean sediment load at selected stream-gaging stations,
Oahu, Hawaii .... 02.2.6 e teen 23
9. Pre-construction and construction-period relations between streamflow and suspended-
sediment loads at selected stream-gaging stations, Oahu, Hawaii................ 000s eee 24
10. Annual streamflow and suspended-sediment yields for leeward and windward areas,
Oahu, Hawaii .... 6.6... 30
TABLES
1. Chronology of construction activities, H-3 highway project, 1983-92, Oahu, Hawaii.................+++ 5
2. Sediment-load results from previous studies on effects of highway construction in the
eastern United States ..
3. Pre-construction and construction periods at stream-gaging stations in the H-3
highway study area, Oahu, Hawaii
4. Annual rainfall at stream-gaging stations in the H-3 highway study area, Oahu, Hawaii,
water years 1983-91... 0... 0. een cnet ett enter eee e nent eee 13
5. Annual streamflow at stream-gaging stations in the H-3 highway study area, Oahu,
Hawaii, water years 1981-91... 2.0... cnn een eee ene n tenes 13
6. Analysis of covariance relating streamflow at index station to streamflow at stream-gaging
stations in the H-3 highway study area, Oahu, Hawaii ........... 200-20 e cece eee eee een eee 16
7. Estimated changes in streamflow resulting from altered drainage-basin conditions during
H-3 highway construction, Oahu, Hawaii .... 0.0.0... cece eee eee ete tenet eee eee 17
8. Annual suspended-sediment loads at stream-gaging stations in the H-3 highway study
area, Oahu, Hawaii... 2.20.6... 6c cee ccc ete ete t etre etree tee ener eee 21
9. Analysis of covariance for suspended-sediment loads at stream-gaging stations in the H-3
highway study area, Oahu Hawaii +. 22
10. Evaluation of State water-quality standards for selected stream-gaging stations, Oahu, Hawai . 27
11. Observed and estimated annual suspended-sediment yields at selected stream-gaging stations
during H-3 highway construction, Oahu, Hawaii .3l
iv Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


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

Qu.3 = A +B X Qy29000) + (C XZ), 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 229000. This third
equation was expressed as

Qu.3 = A + (B X Qor9000) + (C x Z) + (Dx W), (3)

or as
Qy.3 = A + (BX Qy29000) + (C x Z) +(D XZ x

QW 29000)» (4)

where D was a regression coefficient. The interaction
term was zero for all dates before construction 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 sin-
gle intercept and slope would adequately describe the
relation throughout the study. In such a case, the coeffi-
cients 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
beginning of construction, however, either the intercept
or the slope or both should differ for the two time peri-
ods, and coefficients for Z and/or W would be signifi-
cantly different from zero.

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 com-
puted 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 consid-
ered 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 deter-
mined with F-tests (for example, Helsel and Hirsch,
1992). F-tests 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 correspond-
ing 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.

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 229000), the dummy variable (Z), and the inter-
action term (W) to those of regressions computed using
the covariate and Z as independent variables. F-statis-
tics 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 free-
dom, to the mean-square error of the regression that
included all three independent variables. If the magni-
tude of the F-statistic exceeded the appropriate critical
value of the F distribution (for example, 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 (stream-
flow at station 229000), the dummy variable (Z), and
the interaction term (W) with those of regressions com-
puted using only the covariate as an independent vari-
able. If the magnitude of the F-statistic exceeded the
appropriate critical value of the F distribution (for
example, Iman and Conover, 1983), 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.

Approach 11


STREAMFLOW BEFORE AND DURING
CONSTRUCTION

Hydrologic Conditions During the Study

Rainfall.--Annual rainfall totals were highest at
all stations in 1988 and 1989 (table 4). Rainfall at
stream-gaging stations 226000, 226200, and 265600
also was high in 1991 (table 4). For much of the H-3
highway study area, therefore, the period of highest
rainfall coincided with the construction period (table 3).

Flow duration.--Annual streamflow at all sta-
tions was higher in water years 1988, 1989, and 1991
than during the other years of the 1983-91 study period
(table 5). Records available for stream-gaging stations
226000 and 272200 show that annual streamflow was
higher in 1982 than for any year during the study period.
The years of highest streamflow during the study period
coincided with years of high rainfall (table 4) and with
highway construction at stream-gaging stations 226200,
265600, 270900, and 275000 (tables 1 and 3). Average
streamflow per unit area was higher during the pre-con-
struction period than during the construction period at
stations 272200 and 275000, and higher during con-
struction at stations 226200 and 270900 (fig. 4).

Flow-duration curves (Searcy, 1959; fig. 5) show
the temporal distribution of streamflow for periods
before and during construction. Flow-duration curves
indicate the percentage of time that values of daily mean
streamflow were equalled or exceeded. These curves
cannot be used to assess effects of highway construc-
tion, because the time periods are not of equal lengths
and because rainfall differed during the two periods;
however, the curves are useful for evaluating the nature
of differences in streamflow during the two periods. At
station 226200, low flows persisted longer and peak
flows were higher during construction than before con-
struction (fig. 5). At station 270900, the highest daily
mean streamflow was during the pre-construction
period, but otherwise streamflow was higher during
construction. The highest daily mean streamflow at sta-
tion 272200 was during the construction period, but
streamflow was otherwise higher during the pre-con-
struction period. At station 275000, streamflow was
greater during the construction period for both low and
high flows.

Table 4. Annual rainfall at stream-gaging stations in the H-3
highway study area, Oahu, Hawaii, water years 1983-91

[All values in inches; --, no data; station numbers are abbreviated, complete
numbers are preceded by 16]

Water Station

year 226000 226200 265600 270900 275000
1983 65.4 = - - ~
1984 44.1 23.5 38.9 - -
1985 61.6 40.7 63.9 66.8

1986 60.9 32.9 59.2 66.2 -
1987 68.3 33.8 67.2 66.7 75.4
1988 90.6 56.5 86.8 95.1 113
1989 191.2 55.5 84.1 87.2 105
1990 66.5 35.3 62.4 62.8 92.0
1991 80.2 41.2 68.5 59.9 -

| includes estimated values for period of missing data based on comparison
with data at station 226200

Table 5. Annual streamflow at stream-gaging stations in the
H-3 highway study area, Oahu, Hawaii, water years 1981-91

[All values are in cubic feet per second-days; --, no data; station numbers are
abbreviated, complete numbers are preceded by 16]

Water Station

year 226000 226200 265600 270900 272200 275000
1981 918 - = = 3,140 =
1982 4,300 - - -- 8,040 -
1983 964 - - -- 4,090 877
1984 S17 525 122 - 1,600 520
1985 827 969 284 152 2,290 604
1986 1,590 1,580 406 150 2,940 674
1987 1,440 1,540 612 327 3,760 790
1988 3,140 3,690 988 509 6,070 1,270
1989 3,040 3,640 1,040 532 5,930 1,420
1990 1,670 «1,840 = 532 488 4,280 888
1991 2,740 3,440 762 737 5,000 1,230

Flood frequency.--Recurrence intervals for
annual instantaneous peak flows were computed using
methods of the Interagency Advisory Committee on
Water Data (1981) for two gaging stations in the study
area with long (more than 30 years) periods of record:
stream-gaging station 226000 in North Halawa Valley
(fig. 1) and stream-gaging station 275000 in Haiku Val-
ley (fig. 2). Recurrence intervals for both pre-construc-
tion and construction-period annual peak flows at
station 226000 ranged from 1 to 2 years. At station
275000, pre-construction recurrence intervals ranged
from | to 2 years, and all construction-period recurrence
intervals were about 2 years. Peak flows during the

Streamflow Before and During Construction 13


CONTENTS

Abstract
Introduction
H-3 Highway Construction .
Study Drainage Basins . .
Suspended-Sediment Yields in the Koolau Range . .
Highway Construction Effects in Other Areas .
Acknowledgments
Approach
Data Collection . . :
Streamflow Analysis... .

Suspended-Sediment Analysis
Streamflow Before and During Construction. .
Hydrologic Conditions During the Study
Streamflow Changes During Construction .
Land-Use Effects on Streamflow .. .

Low Flows
High Flows :
Suspended-Sediment Loads Before and During Construction . . 21
Relations Between Streamflow and Suspended-Sediment Loads. .............00 2 cece cece ence eee 21
Suspended-Sediment Yields at Stream-Gaging Station 265600. . . 25
Evaluation of State Water-Quality Standards - 26
Estimated Magnitude of Highway-Construction Effects on Suspended-Sediment Loads ............... 26

Regional Comparison of Suspended-Sediment Yields .
Exceedance of State Water-Quality Standards
Comparison With Highway Construction Effects in Other Areas . .
Conclusions ... .

References Cited ..

FIGURES

1-2. Maps showing:
1. Selected stream-gaging stations and drainage basins in the H-3 highway study area,

Oahu, Hawaii . 2
2. Selected stream-gaging stations and miscellaneous sites in the windward area of the

H-3 highway study area, Oahu, Hawaii 4

3-10. Graphs showing:

3. Monthly streamflow at stream-gaging station 16229000 and upstream ground-water

withdrawals, Oahu, Hawaili.......... 000. .c eee ccc e eee eect eee eene 10
4. Mean daily streamflow before and during H-3 highway construction at selected

stream-gaging stations, Oahu, Hawaii ....... 2.0.00. 14
5. Flow-duration curves of daily mean streamflow at selected stream-gaging stations,

Oahu, Hawaii... 6.6... nnn nett n teen etn eee 15
6. Monthly ground-water withdrawals upstream of stream-gaging stations 16272200

and 16270900, Oahu, Hawaii... .. 6.2... e eee eee cnet cnet eee 19

Contents


Rantz, S.E., and others, 1982a, Measurement and computa-
tion of streamflow: Volume 1. Measurement of stage and
discharge: U.S. Geological Survey Water-Supply Paper
2175, 284 p.

noteee, , 1982b, Measurement and computation of streamflow:
Volume 2. Computation of discharge: U.S. Geological
Survey Water-Supply Paper 2175, 346 p.

Reed, L.A., 1978, Effectiveness of sediment-control tech-
niques used during highway construction in central
Pennsylvania: U.S. Geological Survey Water-Supply Pa-
per 2054, 57 p.

Reed, L.A., 1980, Suspended-sediment discharge in five
streams near Harrisburg, Pennsylvania, before, during,
and after highway construction: U.S. Geological Survey
Water-Supply Paper 2072, 37 p.

Scott, G.A.J., and Street, J.M., 1976, The role of chemical
weathering in the formation of Hawaiian amphitheatre-
headed valleys: Zietschrift fur Geomorphologie, v. 20,
no. 2, p. 171-189.

Searcy, J.K., 1959, Flow-duration curves: U.S. Geological
Survey Water-Supply Paper 1542-A, Manual of Hydrol-
ogy: Part 2. Low-Flow Techniques, 33 p.

Searcy, J.K., and Hardison, C.H., 1960, Double-mass curves:
U.S. Geological Survey Water-Supply Paper 1541-B,
66p.

Shade, P.J., 1984, Hydrology and sediment transport,
Moanalua Valley, Oahu, Hawaii: U.S. Geological Sur-
vey Water-Resources Investigations Report 84-4156,
54p.

Sherman, G.D., and Ikawa, Haruyoshi, 1967, Soil sequences
in the Hawaiian Islands: Pacific Science, v. 22, p. 458-
464.

State of Hawaii Department of Health, 1990, Administrative
Rules, Title 11, chap. 54, p. 54-21.

State of Hawaii Department of Land and Natural Resources,
1973, Pan evaporation in Hawaii 1894-1970: Honolulu,
Hawaii, Department of Land and Natural Resources Re-
port R51, 82 p.

Stearns, H.T., and Vaksvik, K.N., 1935, Geology and
ground-water resources of the island of Oahu: Territory
of Hawaii Division of Hydrography Bulletin 1, 479 p.

Takasaki, K.J., Hirashima, G.T., and Lubke, E.R., 1969, Wa-
ter resources of windward Oahu, Hawaii: U.S. Geologi-
cal Survey Water-Supply Paper 1894, 119 p.

Takasaki, K.J., and Mink, J.F., 1985, Evaluation of major
dike-impounded ground-water reservoirs, island of
Oahu: U.S. Geological Survey Water-Supply Paper
2217, 77 p.

Tamura, T., M.L. Jackson, and G.D. Sherman, 1953, Mineral
content of low humic, humic, and hydrol humic latosols
of Hawaii: Soil Science Society of America Proceedings,
v. 19, p. 435-439.

U.S. Department of Commerce, Environmental Science Ser-
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waii: Climatography of the United States no. 60-51, 27 p.

U.S. Department of Transportation, Federal Highways Ad-
ministration, and State of Hawaii Department of Trans-
portation, 1987, Final third supplement to the Interstate
Route H-3 Environmental Impact Statement, Interstate
Route H-3 Halawa to Halekou interchange, Report Num-
ber FHWA-HI-EIS-87-01-F(S), variable pagination.

U.S. Geological Survey, 1982, Water resources data, Hawaii
and other Pacific area, water year 1981, volume 1, Ha-
waii: U.S. Geological Survey Water-Data Report HI-81—
1, 266 p.

Vice, R.B., Guy, H.P., and Ferguson, G.E., 1969, Sediment
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Geological Survey Water-Supply Paper 1591-E, 41 p.

Visher, F.N., and Mink, J.F., 1964, Ground-water resources
in Southern Oahu, Hawaii: U.S. Geological Survey Wa-
ter-Supply Paper 1778, 133 p.

Ward, S.M., and Appel, D.H., 1988, Suspended-sediment
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Wentworth, C.K., 1928, Principles of stream erosion in Ha-
waii: Journal of Geology, v. 36, no. 5, p. 385-410.

os , 1943, Soil avalanches on Oahu, Hawaii: Bulletin of the
Geological Society of America, v. 54, p. 53-64.

White, S.E., 1949, Processes of erosion on steep slopes of
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168-186.

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ment of rainfall warning thresholds for debris flows in
the Honolulu District, Oahu: U.S. Geological Survey
Open-File Report 92-521, 44 p.

Wong, M.F., and Hill, B.R., 1992, Statistical summary of hy-
drologic and water-quality data from the North Halawa,
Haiku, and Kamooalii drainage basins, Oahu, Hawaii,
water years 1983-89: U.S. Geological Survey Water-Re-
sources Investigations Report 92-4049, 52 p.

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34 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


PRE-CONSTRUCTION

DURING CONSTRUCTION

MEAN DAILY SUSPENDED-SEDIMENT YIELD,
IN TONS PER SQUARE MILE
-
T

16226200 16270900 16272200 16275000

STREAM-GAGING STATION

Figure 7. Mean daily suspended-sediment yield before and during H-3 highway construction at selected
stream-gaging stations, Oahu, Hawaii.

Table 9. Analysis of covariance for suspended-sediment loads at stream-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 | for construction; W was set to Z x log-streamflow; tobit regression (Cohn, 1988) was used to compute F-statistics; * indicates sig-
nificant effect of period on the basis of F-test; critical F-values are 3.84 for significance of W and 3.00 for significance of Z and W together; station numbers
are abbreviated, complete numbers are preceded by 16]

Regression coefficients for Likelinood ee
Station Intercept Slope r4 Ww ratio for Z Ww (Z+W)
226200 -1.59 0.656 0.311* 0.456* 26.3* 43.6* 29.8*
270900 -1.62 1.05 —0.175* 1.80* 13.0* 92.2* 46.6*
272200 -1.98 1.43 -0.069 0.140 0.18 1.79 2.96
275000 -2,32 2.69 —0.167* 0.599* 8.57* 12.3* 7.18*

22 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY
Gordon P. Eaton, 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:

District Chief

U.S. Geological Survey

677 Ala Moana Blvd., Suite 415
Honolulu, HI 96813

Copies of this report can be
purchased from:

U.S. Geological Survey
Branch of Information Services
Box 25286

Denver, CO 80225-0286


4,500

4,000

3,500

30,00

2,500

2,000

1,500

1,000

500

4,000

3,500

3,000

2,500

ANNUAL SUSPENDED-SEDIMENT YIELD, IN TONS PER SQUARE MILE

2,000

1,500

1,000

500

0

T T T T T

LEEWARD UNDISTURBED

LEEWARD MIXED USE

STATION 16226200 DURING CONSTRUCTION
STATION 16226200 PRE-CONSTRUCTION

>DrPOe

400 600 800 1,000 1,200

0

oeOomPoe

WINDWARD UNDISTURBED ¢
WINDWARD MIXED USE

STATION 16265600 DURING CONSTRUCTION
STATION 16270900 DURING CONSTRUCTION
STATION 16270900 PRE-CONSTRUCTION
STATION 16275000 DURING CONSTRUCTION
STATION 16275000 PRE-CONSTRUCTION

Po

500 1,000 1,500 2,000 2,500

3,000

ANNUAL STREAMFLOW PER UNIT AREA, IN CUBIC FEET PER SECOND-DAYS PER SQUARE MILE

Figure 10. Annual streamflow and suspended-sediment yields for leeward and windward areas,

Oahu, Hawaii.

30 Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91


estimated to be higher before construction for stream-
flows below 1.25 ft?/s and higher during construction
for streamflows higher than 1.25 ft?/s. This is also the
case at station 275000, where estimated loads corre-
sponding to streamflows less than 1.90 f/s are higher
before construction and loads at streamflows higher
than 1.90 ft3/s are higher during construction (fig. 9).
Because most of the suspended-sediment loads are
transported at flows higher than these intersection
points, the estimated changes in streamflow-sediment
relations at stations 270900 and 275000 would be
expected to indicate that loads increased during con-
struction.

The significance of the changes in regression slope
and intercept detected for station 270900 (table 9; fig.
9), however, are difficult to reconcile with the lower
average suspended-sediment yield observed during
construction, particularly because streamflow was
higher during construction, and higher streamflow
would normally increase sediment loads. Examination
of scatterplots of daily suspended-sediment loads and
corresponding daily mean streamflows revealed that
several low outliers were affecting streamflow-sedi-
ment relations. Analysis of covariance with ordinary
least squares regression using loads of 0.5 t/d or greater
and corresponding streamflows indicated that sus-
pended-sediment loads in this range actually decreased
during construction; this effect was masked by the
inclusion of the loads less than 0.5 t/d in the original
analysis of covariance. The omission of loads below 0.5
t/d eliminates only 4 percent of the suspended-sediment
load for the period of record at station 270900 from the
analysis. The changes in regression coefficients for sta-
tion 270900, although statistically significant, do not
represent substantially increased suspended-sediment
loads for the construction. Daily suspended-sediment
loads at low flows, however, appear to have been
increased during construction, and these increases
resulted in the changes in streamflow-sediment rela-
tions indicated in table 9.

No significant changes in suspended-sediment
transport were detected at station 272200 (table 9; fig.
9). Deposition of sediment in Waimaluhia Reservoir
upstream of the station reduces suspended-sediment
loads at station 272200, and any increase in sediment
mobilization resulting from highway or golf-course
construction might not be detected at the station. Bathy-
metric surveys indicated that volume of the reservoir
decreased by 5.9 acre-ft because of sediment deposition

from 1983 to 1988 (Wong and Hill, 1992). Work is cur-
rently in progress to determine rates of sediment depo-
sition in the reservoir since 1988.

Pre-construction and construction-period regres-
sion equations cannot be used to estimate construction
effects on suspended-sediment loads because of limita-
tions of the statistical techniques used. At all stations
except station 270900, the range of streamflow data
during construction exceeds the range before construc-
tion. Extrapolation beyond the range of data used to
develop the regressions can lead to serious errors
because sediment transport relations commonly change
as streamflow increases (Nolan and others, 1986; Glys-
son, 1987). Also, the use of tobit regression in place of
ordinary least squares regression means that residuals
cannot be used to determine appropriate regression rela-
tions or bias-correction factors (Helsel and Hirsch,
1992). Instead, regional sediment-transport relations
were used to estimate construction effects, as described
later in the section "Regional comparison of suspended-
sediment yields.”

Suspended-Sediment Yields at Stream-Gaging
Station 265600

Construction-period suspended-sediment loads at
stream-gaging station 265600 were compared with pre-
construction loads at stream-gaging station 270900 to
determine whether construction-period loads at station
265600 were significantly different from pre-construc-
tion loads on the same days at nearby station 270900.
Suspended-sediment loads were divided by drainage-
basin areas to allow direct comparison of yields for the
two stations. Differences between daily yields were
tested for significance using the Wilcoxon signed-ranks
test (Iman and Conover, 1983).

The average daily suspended-sediment yield at sta-
tion 265600 was 2.01 t/mi* during the pre-construction
period for station 270900. The average daily sus-
pended-sediment yield at station 270900 during this
pre-construction period was 1.40 t/mi. These averages
were significantly different (p<0.0001). Construction-
period suspended-sediment yields at station 265600
therefore were significantly higher than pre-construc-
tion yields on the same days at station 270900, indicat-
ing a significant effect of construction at station
265600. Golf course construction upstream of station
265600 probably increased sediment loads at this sta-

Suspended-Sediment Loads Before and During Construction 25


Table 3. Pre-construction and construction periods at stream-
gaging stations in the H-3 highway study area, Oahu, Hawaii
[Construction was continuing upstream of all stations as of September 30,
1991; station numbers are abbreviated, complete numbers are preceded by 16]

Pre-construction During construction

Station Start End Start End

226200 02/01/83 11/01/87 11/02/87 09/30/91
265600 02/01/83 02/21/83 02/22/83 09/30/91
270900 04/01/84 03/05/89 03/06/89 09/30/91
272200 10/01/81 02/21/83 02/22/83 09/30/91
275000' 10/01/82 10/23/88 10/24/88 09/30/91

| Sediment data at station 275000 are discontinuous; sediment data are
available for 12/01/83 to 09/30/83 and from 07/20/87 to 09/30/91

uted to land-use effects. Effects of rainfall were mini-
mized by using analysis of covariance (Helsel and
Hirsch, 1992). Analysis of covariance is a regression-
based procedure that assesses relations between two
hydrologic variables during different time periods. In
this case, the time periods were the periods before and
during construction of the H-3 highway ("time period"
as used in this report refers to the periods before and
during construction listed in table 3). One of the vari-
ables, known as the independent variable or covariate,
represented natural variations resulting from rainfall,
with no effect from highway construction. The other
variable is known as the dependent or 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 con-
struction. If a significant change was detected, it was
considered the result of a change in drainage-basin con-
ditions that coincided with construction. The applica-
tions of this method are described more fully in the
sections on streamflow and suspended-sediment analy-
ses below.

Results of statistical tests were reported as signifi-
cant if the probability of obtaining the results by chance
was less than or equal to 5 percent. This is equivalent to
setting the o level for all hypothesis tests to 0.05.

Data Collection

Rainfall was recorded using two types of rain
gages. At stream-gaging stations 226000, 226200,
265600, and 270900, tipping bucket rain gages were

used. At stream-gaging station 275000, a float-type rain
gage (8-in. diameter) was used.

Stream-gaging stations 226200, 265600, 270900,
272200, and 275000 were equipped with continuous
gage-height recorders. Streamflow was measured peri-
odically at these stations and at miscellaneous sites
265700, 266500, 267500, and 269500 (fig. 2) using
standard practices for current-meter measurements
(Rantz and others, 1982a). Peak flows that could not be
measured with current meters were measured using the
slope-area method (Dalrymple and Benson, 1967).
Streamflow was computed using the streamflow mea-
surements and gage-height records as described by
Rantz and others (1982b).

Suspended-sediment samples were collected at
stream-gaging stations using PS-69 automatic sus-
pended-sediment samplers (Edwards and Glysson,
1988). Samples were collected daily when conditions
permitted, and more frequently during storms. Depth-
integrated cross-sectional samples were collected peri-
odically using the equal-width-increment method
(Edwards and Glysson, 1988) and were used to calibrate
the PS-69 sample data (Porterfield, 1972). At station
265600, a Manning automatic sampler (Edwards and
Glysson, 1988) was used at times in place of the PS-69
because of suspended-sediment deposition near the PS-
69 intake. In 1990, the automatic samplers at station
265600 were replaced by an observer who collected
daily cross-sectional samples. Cross-sectional samples
were collected periodically at miscellaneous sites. Sus-
pended-sediment concentrations were determined at the
U.S. Geological Survey laboratory in Honolulu using
methods described by Guy (1969). Suspended-sediment
loads were computed using suspended-sediment con-
centrations and streamflow records, as described by
Porterfield (1972).

Streamflow Analysis

Streamflow at stream-gaging stations 226200,
270900, 272200, and 275000 was used as the response
variable and streamflow at index stream-gaging station
229000 (fig. 2) was used as the covariate in the analysis
of covariance. Streamflow at station 229000 was unaf-
fected by H-3 highway construction, diversions, or any
major change in land use. Water was withdrawn from
tunnels and wells upstream of the station, but these

Approach 9


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.

Suspended-Sediment Analysis

Analysis of covariance was used to assess changes
in relations between streamflow and suspended-sedi-
ment loads at stream-gaging stations 226200, 270900,
272200, and 275000 during construction of the H-3
highway. The analysis-of-covariance procedure tested
whether time period accounted for variations in sus-
pended-sediment loads, after streamflow variations
were removed, by computing regression equations
relating suspended-sediment load to streamflow. This
analysis relied on the implicit assumption that stream-
flow was not affected by construction. The extent to
which this assumption was justified is discussed in this
report in the section "Streamflow changes during con-
struction." 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.
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 indepen-
dent variable, a second including Z, and a third includ-
ing Z and W.

Streamflow and suspended-sediment data were
transformed to common (base 10) logarithms before
analysis. A number of daily suspended-sediment loads
were reported as 0 tons in two situations: (1) loads were
O tons on many days at station 226200 when streamflow
at that station was 0 ft?/s; (2) loads were reported as 0
tons at all stations when the product of streamflow, sus-
pended-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 cen-

sored 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
(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 ft/s were
assigned an arbitrary value slightly below the reporting
limit of 0.005 t/day. Randomly selected subsamples of
500 suspended-sediment load-streamflow data pairs
were used for the analysis of covariance to avoid serial
correlation of residuals.

The significance of the regression coefficient for Z
was tested using a likelihood ratio (Cohn, 1992), which
is analogous to the T-test used to evaluate the coeffi-
cient for Z in the analysis of streamflow. If the likeli-
hood 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 (for example, Iman and Conover, 1983),
the effect of time period on the slope of the relation
between streamflow and suspended-sediment 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 (stream-
flow), 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 (for example, Iman and Conover,
1983), the overall effect of time period on the relation
between streamflow and suspended-sediment load was
considered to be significant.

12. Streamflow and Suspended-Sediment Loads During Highway Construction, Oahu, Hawaii, 1983-91