Hydrology of Some Tidal Channels in Estuarine Marshland ...eps.berkeley.edu/people/lunaleopold/(154)...

CATENA V O ~ . 20, p. 469-493 Cremlingen 1993

Hydrology of Some Tidal Channels in Estuarine Marshland Near San Francisco

L.B. Leopold, J.N. Collins & L.M. Collins

Abstract

Measurements of velocity, depth, discharge, and slope were simultaneously made at ten gages along a natural estuarine channel 19,000 feet in length in Petaluma Marsh, California. Along the study reach the channel decreases from a width of 47 feet at its mouth to nearly zero at its headward extent, with accom- panying decrease in depth. Though gage height varies with time in a smooth sinusoidal manner a t all stations, this is not true for velocity, discharge, or slope. Velocity is rather constant for long peri- ods in the ebb cycle and differs but little along the length of the channel. It is somewhat higher on ebb than on flood tide.

At most gage sites, velocity continues one-half to one hour after the gage height has reached its maximum or minimum value and reversed.

In this channel water surface slope is considerably greater in the midreach of channel than in either the mouthward or headward reaches. Slopes vary from less than .0001 to about .0005 through much of a tidal cycle. At some stages of both ebb and flood, the upper end of the channel has a positive slope while the lower end a negative or adverse slope.

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At those times the longitudinal profile of water surface is bow shaped or V shaped.

1 Introduction

Despite the interest in wetland preser- vation and the recognition of the role of marshes in the biologic and chemi- cal cycling, few details have been published on the role of tidal marsh channels. These channels are those whose origin and maintenance depend on tidal inflow and outflow with but little contribution of runoff from terrestrial sources.

The water surface elevation in estuaries rises and falls as a function of time in a nearly sinusoidal relation twice in each lunar day. Along the western mar- gin of the United States there are usually two unequal high tides and two unequal low tides in a day, which give rise to the terms ”mean lower low water” (MLLW) and “mean higher high water” (MHHW). These are the arithmetic average of the elevation of the daily minimum and daily maximum height of the tide computed over the tidal epoch, a period of 19 years.

Because the tide rises and falls with time as a neat sinusoidal curve, it is often supposed that mean velocity and probably mean water surface slope also are sinusoidal with time. Our data show this supposition to be incorrect. Few di-

CATENA-All Interdisc ip l inary J o u r n a l of SOIL SCIENCE-HYDROLOGY-GEOMORPHOLOGY

470 Leopold, Collins & Collins

rect measurements of either are available MLLW 0.0 ft (0.0 I

Mean low water (MLW) 0.91 ft ( .28 I

1.26ft (.38 1

Mean high water (MHW) 5.81 ft (1.77

in the abundant literature on estuaries. Mean tide (MSL) Wishing to understand better the role of channels of different sizes in the development and maintenance of marsh lands,

Mean higher hkh'water (MHHW) 6.33 ft (1.93

a study was made of one major channel and some of its minor tributaries in Petaluma Marsh.

2 Location and general description

The great estuary that opens to the Pa- cific Ocean through the Golden Gate was once a broad flood plain of several major and minor rivers draining the Sierra Nevada and the San Joaquin Valley. With the rise of sea level in Holocene time the early river valley was drowned and many areas bordering the flooded valley became tidal marshlands. Most of them have been diked or drained for urban development, for agriculture, or for evaporation ponds in salt pro- duction. One of the few such marshes of any size remains near the mouth of the Petaluma River that flows south into San Pablo Bay, the northernmost arm of the Golden Gate Estuary. The Petaluma Marsh is natural except for a network of very small ditches dug for the purpose of mosquito abatement. These mosquito control ditches were cut in the 1970s and many have since partly filled in with sediment or partially overgrown with marsh vegetation.

One of the major natural channels in Petaluma Marsh is Tule Slough, which enters Petaluma River across from the village of Lakeville, California.

The statistics for the NOAA tide gage at Lakeville, California, on the Petaluma River (gage number 9415423) for the tidal epoch ending 1978 are as follows:

The study section of the slough is 19,007 feet in length (3.60 mi or 5.80 km). In this length the width decreases from 47 feet near the mouth to about 4 feet at the Railroad gage. A planimetric map is shown in fig. 1.

The earliest topographic map of the marsh was published by the U.S. Coast Survey in 1860. It is surprising that the mainstream channel has changed only infinitesimally in a century, though the smaller tributaries and unvegetated turf pans on the marsh surface have changed somewhat in that period. Their charac- ter and origin have been described by us in a separate paper (Collins, Collins & Leopold 1987).

The marsh is comprised of peat and clay that contact ancient mudflat sediments at an average depth of 2.5 me- ters. The vegetation is dominated by pickleweed (Saiicornia virginica L.). Near the mouth of the main channel low natural levees occur that support coyote brush (Bacharris pilularis) and gum plant (Grendi l ia humi l i s ) . Slump blocks in the channel grow cordgrass (Spartzna joliosa). That the marsh is mostly Salicornia agrees with the find- ing of Stevenson & Emery (1958) that in Newport Bay, California, Salicornia was mostly confined to the narrow range of elevation 3.2 to 3.5 feet above MLW (p. 36) when the tidal range is 3.4 feet. That is, they found Salicornia to lie in the zone 0.2 feet below MHW to 0.1 feet above MHW.

C A T E N A -A 11 1x1 t c I d i I c ip I i 81 a ry J o II r i i R I 0 f 5 0 IL S C I E N C E -- H Y D R O L 0 G Y - G E OM 0 R P H 0 L 0 G Y

Hydrology of tidal channels, California 471

Fig. 1: Map of Petaluma marsh area

3 Channel Measurements

Along Tule Slough seven staff gages were installed and two in confluent tributaries. At a later time three additional measuring points were established to ex- tend the network farther headward. The zero reading of each was determined by spirit levelling - connecting a series of local benchmarks. All benchmark elevations were later tied to a common datum at the NOAA benchmark at Lakeville, just 0.5 miles from the mouth of the Tule Slough. The established net of benchmarks were tied together with a maximum elevation error of 3.5 mm, each leg of the level line being rerun until the required closure was attained. This

with station locations o n Tule Slough.

closure was required to measure water surface slopes. The soft surface of the marsh made level set-ups typically un- stable so some level lines were run several times before the closure was satis- factory.

We found that important errors in water surface elevation can be caused if the staff gage is not perfectly vertical. At a gage where the change in water level was six feet, a deviation of five degrees from vertical could cause an error in water surface elevation of .023 feet (7 mm), twice the allowable value.

Channel cross section was surveyed at each staff gage as well as at other locations. The cross sections are somewhat

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Photo 1: t Photograph looking up the channel of Tule Slough at the Head gage.

Photo 2: t Tule Slough at head ward end showing Railroad gag( ow.

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triangular near the mouth of the slough and get progressively more U-shaped upstream. The bank material exposed to view at low tide is a dark grey mud, with much clay. One sinks in to the hips if one steps out of a boat into the channel at low tide. Many large slump blocks slip from the channel banks in the downstream reaches. Photographs of the channel are shown in photos 1 and 2.

In many places along the channel, especially on the slump blocks, bivalve mussels including Geukensia, Isacha- dium, and Macoma attach themselves to stems and roofs of vegetation and from the rough appearance, these colonies must add appreciably to the hydraulic resistance.

At each station a distance of 30 feet along the channel was marked by stakes at each end. For velocity measurements orange peels were used as floats. Sur- face velocity near the channel center line was computed as the time in seconds for the float to travel 30 feet. These velocities were multiplied by 0.8 to give an approximate value of mean velocity in the cross section. Float measurements were made at approximately five to three minute intervals as required to account for brief velocity pulses (Reed 1987). Gage height readings were taken every two minutes. Runs were made on several days in 1984 and 1988.

The data on gage height at each station were reduced to the same datum, MLLW at the Lakeville (NOAA) gage. Cross section data were related to water stage, and with the measured velocity, discharge was computed as a function of time.

4 Channel size parameters along the slough

In fig. 2 several aspects of channel size are plotted as a function of distance along the main slough. The width decreases upstream in an irregular fashion from 47 feet at mouth gage to nearly zero feet at Railroad gage. Local nar- rowing at sections A and D is caused by slump blocks on both banks. Mean bed elevation increases upstream and is equal to MLLW at a distance of about 6,000 feet upstream of the mouth of the channel.

Cross-sectional area and volume of the total prism are both measured at 1400 hours March 17, 1984, where the water surface was at 6.7 feet above MLLW or slightly above bankfull stage.

Cross-sectional area reflects closely the channel width. The tidal prism equals about 3,100,000 cubic feet (71 acre feet) at this near-bankfull condition between the mouth and the upstream gage. Thus, this volume would be filled if an average of 142 cfs flowed past the mouth gage for six hours of flood tide.

The bed of the channel is soft mud. The only visually obvious sources of hydraulic roughness are the mussel colonies in the shallows of the channel, and the slump blocks along the banks that support Spartina. Slump blocks as described make the banks randomly irregular. One must merely guess at the major cause of hydraulic resistance. But the muddy bed is not smooth. In the relatively straight reach between mouth and A gages, a distance of 1,240 feet, depth measurements were taken about five feet apart. More or less regular un- dulations of the bed were observed with an average spacing between successive high points of 96 feet with a standard

CATENA-An Interdisciplinary Journal of S O I L SCIENCE-HYDROLOGY-GEOMORPHOLOGY

&- LL

3 0

W I 3 -1 0 >

I D I S T A N C E T H O U S A N D S OF F E E T

t I I I 4 I

2 6 14 8 I O 1 2 I 1 0

‘1

V O L U M E

li b- \ LL

r

I I- 3 O 0 4 -

E w I A c D M I D

I 1 1 1 1 1 G A G E S 1

Fig. 2: Channel size parameters as func t ion o j distance along Tule Slough, cross sectional area, channel width, mean bed elevation, and cumulative volume of tidal pr i sm. Volume i s computed f o r March 17, 1984, 1400 hr., a t ws elevation of 6.7 f t above MLLW.

+- U.

0

4 W a 4

200 *

0

deviation of 32 feet. The average width of the reach is 36 feet so the mounds are spaced at 2.7 widths. Their amplitude was 1.3 feet, standard deviation 0.4 feet.

As can be seen 011 any tide chart, gage height (water surface elevation) usually varies through time in a smooth nearly sinusoidal curve. Velocity does riot follow this pattern but tends to remain rather constant for much of a tidal period as can be seen in fig. 3. For most of

both ebb and flood flow, the stations at the lower and upper ends of the tliree- niile reach experienced lower velocities than the five interinedia.te stations. This results from the higher values of water surface slope in the mid reach of the channel length as will be shown lat,er.

Another aspect of velocity is its relation to stage. On fig. 4 velocity is plotted vs. water surface elevation for three stations, Mouth, E, and Head, on April

C A T E N A - An I II t e rrl i I c ip 1 i n ary .I I> II I 1 8 a I II t S 0 I L S C I E N C: E- H Y D R 0 L 0 G Y -G E OM 0 R F H 0 L 0 G Y


Fig. 3: Surface velocity at each s tat ion and gage height at M o u t h gage as func t ion of time. The data f o r Apri l 22 and f o r March 17 are plotted together to approximate a full tidal cycle.

6

' ; 5 LL

3 -I -I

z 1 4

m a > w W

W 0

LL

1 3

a

5 2 (0

n W + a 3 1

0

- I

- M H W I K.x,

'X M O U T H

A -

\ *

Fig. 4: Mean velocity ut three stations is plotted against ele- vat ion of the water surface expressed as f e e t above MLLW, f o r Apr i l 22, 1984. Arrows indicate

- M L L W

I I I I I the sequence through time. - I F L O O D E B B + I

V E L O C I T Y F T . PER S E C .

CATENA-An I n t e r d i s c i y i i i i a r y J o u r a a l of SOIL SCIENCE-HYDROLOGY-GEOMORPHOLOGY

- D I S C H A R G E H E A D

-

-

M A R C H 17. 1 3 0 4

0800 I O 0 0 1200 1 4 0 0 I 6 0 0

A P R I L 22. 1 9 8 4

-400 - 1 0 0 0 1200 1 4 0 0 1600

Fig. 5: Discharge as a func t ion of t ime for three stations, Mouth , Mid , and Head. The relation i s shown f o r dates of Apri l 2.2 and March 17, 1984. Note that o n the latter date the discharge was higher because the m a x i m u m water surface elevation was higher o n the March I7 date.

7

6

3 1 3

a > m ‘a

z

c ‘a > W _1

3 0

2 w

I

0


E 0 4 W r

n E A C D - 3 H 0 > I I I I I I

4 6 8 I O 12 1 4

D I S T A N C E T H O U S . O F F E E T

Fig. 6: T i m e of slack water (velocity equals zero) Apr i l 22, 1984, in comparison t o the t ime of minimum gage height f o r stations located a t diflerent distances along the channel. Velocity i s zero one half to one hour after the water surface fal l has reversed.

22, 1984. On April 22 the Head station experienced ebb slack water at an ab- solute elevation about 2-1/2 feet higher than that of the Mouth gage. On this graph, also, it can be seen that the middle reach of the channel exemplified by the E gage has a higher velocity than either end of the three-mile long channel.

Discharge is greater near the mouth than upstream primarily because of the downstream increase in cross sectional area. Magnitude of the discharge is more dependent on the maximum height to which the water rises than on the range of stage of a particular tidal cycle. The range at the mouth gage on April 22 was 5.61 feet and on March 17, 4.16 feet, but on the latter date the maximum elevation reached was 1.4 feet higher than on April 22. As a result, the maximum discharge on March 17 was nearly twice that of April 22 as can be seen on fig. 5.

The rise and fall of the tide tends to be sinusoidal on the average, but at times deviates significantly from a smooth wave-like curve. Fig. 5 shows that on the ebb tide of April 22, both the Mouth gage and the Mid gage experienced a receding water level that smoothly lowered from 0600 to 1400 when a sharp rise in water level began at Mouth and at 1530 a similarly sharp rise began at Mid gage. At both locations discharge changed from ebb to flood nearly simultaneously with the reversal of water surface change.

On March 17 the flood discharge became zero and changed to ebb at 1420 at both Mouth and Mid gages, but both had experienced maximum water elevation at 1330. This is an example of how discharge reversal lags reversal in slope. At both locations the stage had been falling for 50 minutes before the

CATENA-An Interd i sc ip l inary Journal of S O I L SCIENCE-HYDROLOGY-GEOMORPHOLOGY


discharge reversed from flood to ebb di- rection.

The time relation among the parameters slack water, gage height, and slope is somewhat unexpected. Velocity does not become zero when the water surface elevation changes from rising to falling or vice versa. Velocity continues for one- half to one hour after gage height has reached its maximum or minimum and has reversed. This is shown in fig. 6 which shows the time relation of slack water to minimum water surface eleva- t ion.

On April 22 at Mouth gage, the minimum gage height occurred at 1348 hours and reversed, but the velocity did not become zero until 1430. On the same day the most upstream gage, Head, reached minimum gage height at 1700 hours, but velocity did not become zero until 1742. On March 17, at Mouth gage maximum gage height was at 1324, but velocity became zero at 1448.

The reason for this lag is apparently related to the inertia of the flowing water. Water flowing upstream during flood flow keeps moving upstream until after the slope has reversed and the adverse gradient brings the velocity to zero.

In the present study, the water surface elevation was measured with sufficient precision that water surface slope may be computed between pairs of stations through a portion of the tidal cycle. The elevation differences are small, but they are generally larger than the precision of the leveling. These differences range between 0.10 and 0.45 feet and the distance between stations are mostly in the order of 1,200 feet so slopes are in the magnitude of 1 x

Fig. 7 is a plot of water surface slope computed between adjacent gages as a

to 40 x

function of times for April 22, 1984 observations. The slope values for the two dates are similar in that the middle reach of the three mile-long channel is steeper than either the upstream or downstream reach. In figures 8 and 9, the water surface is plotted as profiles.

On April 22 the water surface was falling, but sloped mouthward more or less uniformly from 0800 to 1000 hours a t which time the midreach steepened and the most mouthward 3,000 feet was very nearly level. This steepening re- sulted from the fact at the Head and E stations the rate of water surface fall was much less than at the stations nearer the mouth. Between 1400 and 1600 hours the water was rising near the mouth but continuing to fall upstream of Sta- tion D, but in the next hour all stations except Head were rising and slope was headward through all reaches. At 1600 hours the profile is V shaped, in that the mouthward half of the channel had a slope headward while the headward half had a slope mouthward.

5 Hydraulic resistance

In most computations of tidal flow it is necessary to use a measure of flow resistance or hydraulic roughness. Without direct measurements of hydraulic gradient (water surface slope), the roughness must be estimated. In the present study the parameters necessary for computing roughness, depth, slope, and velocity, were measured in the field. Computed values of roughness from these measurements also give at least some indica- tion why the central reach of the channel has a consistently steeper water surface slope than either the upper or the lower end.

Slope measurements are available for

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5 - I- LL

0 T O M I 0 E c T O 0,

. 0 0 0 6

. I 9 0 0 ----

Fig. 7: Water surface slope computed between adjacent gages as a func t ion of t ime during Apri l 2$ 1984 observation period. Slope i s considered positive during e b b p o w ,

0800

0900

IO00

I 1 0 0

I300 I500

I

D U W I

Fig. 8: Longitudinal profiles of the water surface along the channel of Tule Slough each hour during the observation period of Apri l A'gJ 1984. The stage falls (ebb t ide) and then rises during the period.

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7

I- LI

B -16 I > m a

0

_I

z

2 5 > W _I W

W 0 4 b.

3 67

a W I-

a 4

a 3

3

- - - -:-- l40o -- - - - - - - - - - - - ___z

-

/ / / /

/

/ / / /

/ /

/

- H

0

W I

a

Fig. 9: Longitudinal profiles f o r the observation period o n March 17, 1984. stage rises (flood t ide) and falls during this period.

Station

Mouth A C D Mid E Head

0900 April 22 Depth along channel

3-4 feet Resistance Value

Manning’s u/u, n

,046 4.9 .028 11.7 ,032 9.8 ,033 9.9 ,050 6.4 .062 5.1 ,032 9.1

1600 March 17 Depth along channel


Manning’s u/u, n

,055 6.5 ,042 8.5 ,039 8.6 ,042 8.4 ,062 5.6 -048 7.2 ,051 6.5

1200 March 17 Depth along channel


Manning’s u fu, n

,034 11.0 ,038 9.8 .036 9.9 .029 12.3 ,036 9.9 ,063 5.6 ,044 7.6

Tab. 1: Hydraulic resistance a t three chosen t imes .

The

C A T EN A-A n I n t e rd i II c ip I i II &cy J o u rn a I D f S 0 I L S C I E N C E- HY D R O L 0 G Y -G EO M 0 RP H 0 L 0 G Y

. -

Hydrology of tidal channels, California 48 1

the full measurement period on each of the days when several stations were manned. However, hydraulic theory specifies that computation of resistance, either Manning n or the ratio u/u,, applies only in steady, uniform flow. Therefore, to sample resistance values along the length of the channel, three times were chosen which appear to sat- isfy the requirement. At 0900 hours April 22, when the flow was ebb, the water surface profile was neither extremely broken nor flat as it would be at maximum tide. Depths along the channel from mouth to head at this time were from three to four feet. Distances used for computation of slope were from mid- points between gage locations.

Another example is 1600 March 17 when the flow was ebb, the depths along the channel were from four to six feet. The third example is 1200 March 17 when the flow was in flood, the depths were from six to eight feet. Tab. 1 shows the hydraulic resistance expressed as Mannings n and u/u,, for each station along the length of Tule Slough.

These values confirm the interpreta- tion of the water surface profiles in that the steep slope in the middle reach of channel is caused in part by higher values for resistance. The roughness values are scattered and not very consistent, but it appears that the steep slope in the reach from Stations E to Mid is related to high roughness, high values of n and low values of u/u,.

The computed values of roughness re- flect all the types of resistance, bank as well as bed irregularities and channel alignment. We believe that the major part of the resistance comes from bed irregularities. As previously noted, the bed protuberance in the mouthward reach had an average amplitude

of 1.3 feet. Using an often-observed depth of six feet, the relative roughness, (depth/roughness height) is 4.5 which would be typical for a channel of mod- erate roughness.

Roughness at each station was great- est for intermediate stage (4-6 ft.). This range of elevation generally corresponds to the vegetated surfaces of the slump blocks. More data are needed to as- certain if this observation is repeated in other examples.

6 Hydraulic geometry

An attempt to describe the relations among width, depth, velocity, and discharge in a tidal channel has previously been made only by Myrick & Leopold (1963) in a Potomac estuary marsh. This is more complicated than in rivers because discharge and velocity become zero both at large depth (flood revers- ing to ebb) and at low depth (ebb re- versing to flood). Myrick and Leopold concluded (p. B15) that “the principal difference in the at-a-station hydraulic characteritics of estuarine and terrestrial streams is that the former have a much more rapidly changing velocity with discharge than do terrestrial rivers. This is compensated by a less rapidly changing depth and width with discharge.”

The same general conclusion is reached from the present study except that the difference between the estuarine and terrestrial channel is not as marked as found in the Potomac estuary study. Fig. 10 presents plots of width, depth, and velocity vs. discharge for the Mouth location. Our present data appear more scattered or less consistent than the similar data of Myrick and Loepold for rea- sons that can be only conjectured. The velocities of the present study are all

CATENA-An Interd i sc ip l inary Journal of SOIL SCIENCE-HYDROLOGY-GEOMORPHOLOGY


x E B B

o F L O O D A P R I L 22

.I I I I I I I l l

+ E B B * F L O O D

M A R C H 1 7

'1 I '

& O H

Fig. 10: Hydraulic geometry relations at M o u t h gage: m e a n

I O I O 0 I 000 ted us. discharge. D I S C H A R G E C F S

measurements by float, multiplied by 0.8 to approximate mean velocity for the cross section. The Potomac study measured velocity by current meter. The cross sections in Tule Slough are less uniform than those of the Potomac study owing to the prevalence of slump blocks that fall irregularly into the channel. An advantage of the present study is that for each of the two days of intensive observation, all seven sections were measured simultaneously and by the same meth- ods. In our 1988 data, four sections were measured simultaneously.

The value of exponents in the hy-

draulic geometry at-a-station is tabulated here, w a: Q6, d a: Q f , v aQm:

b f 'hle Slough

Mouth gage . l l .35 E gage .ll .35 Head gage .17 .40

Wrecked Recorder Slough' .04 .18 Old Mill Creek' .OB .14 Ravenswood Slough' .14 .OB Terrestrial rivers, average2 .26 .40

From Myrick & Leopold (1963). Leopold, Wolman & Miller (1964).

m

.55

.55

.25

.78

.78

.78

.34

As in rivers, width increases downstream faster than depth, so width/ depth ratio increases downstream. As mentioned earlier, bed elevation intersects the level

CATENA-An l n t c r d i n c i p l i n a r y J o u r n a l of SOIL SCIENCE-HY DROLOGY--GEOMORPHOLOGY


of MLLW near Mid gage, so at low flow, reaches upstream continue to drain through the whole ebb tide and become dry when water level falls to or below MLLW. Upstream of the intersec- tion, channels are narrow, deep, and U- shaped. In the downstream reaches the channels are more triangular or rounded in shape. The meaning of these shape relations to tide level cannot be ascer- tained from the few examples studied but appear to be distinctive enough to warrant further study.

In Wrecked Recorder Slough the highest values of discharge, considered to be the effective discharge, tended to occur at bankfull, for the channel was regu- larly overtopped at high tide. Not so in Tule Slough, where bankfull is equalled or exceeded in only one of three high tides. The effective discharge is believed to be within banks, but at this time we are unsure how effective discharge should be defined in Tule Slough.

7 Suspended sediment concentrat ion

Observation in the field demonstrates that the water is more clear - less tur- bid - in upstream reaches of the tidal channels than near the mouth. Quan- titative data were needed to determine how large are the differences and what controls them.

In part to obtain suspended sediment samples over a wide range of channel size, two additional observation locations were established on the headward portion of the main Tule channel, and one on a tributary. These are called, re- spectively, Railroad (RR), (CAN), and Tule Tributary West (TTW).

On September 7, 1988, simultaneous

measurements of suspended load and velocity were made at locations C, Head, TTW, CAN and RR during a six hour period of flood tide. The headward stations were dry during the first part of the tidal cycle and measurements began when water reached each measurement point. Fig. 2 shows that the mean bed elevation at MLLW is near station E or about 7,000 feet from the mouth. There- fore, on the average, all of the channel upstream of that point is drained of water during ebb tide.

Suspended load was measured at intervals of 5 to 15 minutes at five locations using a D64 sampler while at the same time water surface elevation was recorded and velocity was measured by surface floats. The data are plotted in fig. 11. Sediment concentration increases markedly with discharge at most stations, but there are unexplained devi- ations from this simple relation. There is a definite progression of decreasing values of maximum sediment concentration from the large downstream channel sections to the smaller upstream stations. The peak concentrations of 200 mg/l at section C is ten times larger than the maximum concentration at the upper- most location RR.

The temporal variability in sediment concentration at station C reflects the turbulent flow there. Rising and falling clouds of sediment were visible passing through the downstream section as samples were taken, especially during the period of high velocity. The variability at TTW, a tributary confluent to Tule Slough near station C, also reflects this turbulent vertical mixing in the main channel, because flow at TTW was not turbulent. In general, turbulence de- creased with distance upstream.

The sediment concentration is not di-

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- .5

- I

J

2 2 0 0

-. ,,.Q -- i -.e.--\_ L// +--- '4' /'-. / - - A

- .e A

- I I I- I I I I

s z

I- 2 a a I- z W 0 z 0 0

I- z W z n W 0 n W n z W a (I) 3 (0

0 W (I) \ I- LI. > 0 0 J W 7

t

I50

I O 0

50

0

,/.', R R

1 I I I i

I 3 0 0 I400 I 5 0 0 I600 I 1 0 0 I 2 0 0

H O U R

Fig. 11: Suspended sediment concentration as a function of time during flood tide at five stations on September 7, 1988. Below are plotted curves of mean velocity during the same observation period.

rectly related to velocity of flow, as can be seen by the data for station C in fig. 11. Similarly, at the headwater station RR, the maximum velocity occurred at 1435, but concentration con- tinued to increase until 1610. Nor does it correlate with water surface slope. Concentration most closely follows discharge, which is more dependent on stage (cross sectional area of flowing wa-

ter) than on either slope or velocity. These observations pose interesting

questions about both source and dis- position of sediments, and about processes of marsh history. The most obvious areas of sediment accumulation that could be the source of suspended load in Tule Slough are the broad mud flats bordering many shorelines of San b a n - cisco Bay. Much of the material in these

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mud flats was derived from hydraulic mining of river valleys near the end of the 19th century. To provide passage of barge traffic, the outlet of Petaluma River is extensively dredged through the mud flats of the north border of San Pablo Bay.

The time of high tide at section C was about 1358 and low tides at 0753 and at 2004. Section C experienced a gradual increase in mean velocity to about 1130, from which time it remained nearly steady at 0.9 feet per second for 2 1/2 hours. Sediment concentration remained low until about the time velocity reached 0.9 ft/sec and then rapidly increased from 40 to 200 mg/l. Concen- tration peaked at 1315, probably coin- ciding with maximum flood discharge.

We conjecture that sediment is not en- trained in quantity until some volume of discharge is reached and thereafter tends to follow the discharge curve. At upstream locations both the discharge and sediment concentrations are lower. Be- cause these upstream channels are without water during part of the ebb cycle, they are progressively filled during the flood cycle. This filling must be by water of relatively high velocity, or surface water. Perhaps this skimming of surface water leaves behind the water near the bed where concentrations are highest.

This skimming does not mean that the sediment is deposited. It may remain in suspension and be carried with the water in ebb flow. It is observed that the channel configuration remains amazingly constant for decades. Only the occasional tide is overbank, and such tides contribute to the natural levee seen bordering the channel in downstream reaches. But on the whole, the suspended load is washed upstream and downstream with very little deposition

in any short period of years.

Acknowledgements

Several colleagues and students manned the staff gages to read gage heights and measure velocities over long hours. Dr. Kirk Vincent was most helpful both in instrumentation and in making observations.

Dr. W.W. Emmett, of the U.S. Geo- logical Survey, provided many forms of assistance, including the analysis of suspended load samples in the laboratory.

Dr. Kent G. Dedrick arranged for a levelling survey by the California State Lands Commission to connect our level network to the NOAA gage at Lakeville. This was an important contribution to the study.

References

COLLINS, L.M., COLLINS, J.N. & LEOPOLD, L.B. (1987): Geomorphic processes of an estuarine marsh: Preliminary results and hypotheses. Internat. Geomor- phology 1986, Part I . John Wiley & Sons Ltd., 1049-1071.

LEOPOLD, L.B., WOLMAN, M.G. & MILLER, J.P. (1964): Fluvial Processes in Geomorpholigy. W . Freeman Co., San Francisco.

MYRICK, R.M. & LEOPOLD, L.B. (1963): Hydraulic geometry of a small tidal estuary. U.S. Geological Survey Prof. Paper 422B, 18 pp.

REED, D.J. (1987): Temporal sampling and discharge asymmetry in salt marsh creeks. Estuarine, Coastal and Shelf Sciences 25, 459-466.

S T E V E N S O N , R.E. & EMERY, K.O. (1958): Marshlands at Newport Bay, Cal- ifornia. Allan Hancock Foundation Occa- sional Paper No. 20.

CATENA-An I n t e r d i s c i p l i n a r y Journal of S O I L SCIENCE-HYDROLOGY-GEOMORPHOLOGY


Explanation of tables in Appendices

Elevation:

Velocity:

Width:

Area:

Depth: Discharge: Slope:

Observed gage heights adjusted to datum of MLLW at Lakeville tide gage near mouth of Tule Slough. Mean velocity is float velocity observed multiplied by 0.8 to approximate mean for section. Water surface width excluding shallow water overflowing slump blocks at high stage. Planimetered cross sectional area of flowing water excluding overflow as in width described. Area defined above divided by width as defined above. Product of area defined above and mean velocity as defined above. For a given station computed as water surface elevation difference between the station upstream and the one downstream divided by distance along channel between those gages.

Positive values refer to ebb tide. Negative values refer to flood tide.

Throughout this paper MHW is the arithmetic mean elevation of all high tides, two per lunar day, for the tidal epoch ending in 1978. MHHW is the arithmetic elevation of the highest of the two tides in a day. MLLW is the mean of the lower of two tides in each day. All elevations are referred to the datum of MLLW at the NOAA tide gage at Lakeville, California (gage no. 9415423), which is the near the mouth of Tule Slough.

The data in these appendices have been tabulated for intervals of one half hour though the original data include observations made at intervals of a few minutes and thus show many details. But for general purposes the uniform time intervals give an uncluttered sense of relationship. For some purposes those details may be important and are on file.

From T o Distance C Distance ( f t ) ( f t )

Petalunia River Mouth 800 800 Mouth A 1240 2040 A C 1390 3430 C D 1155 4585 D Mid 1165 5750 Mid E 1970 7720 E Head 6405 14125 Head Railroad 4882 19007

Appendix 1: Distance between gages, Petalurna Marsh along centerline of channel, feet .

CATENA-An Interd i sc ip l inary J o u r n a l of SOIL SCIENCE-HYDROLOGY-GEOMORPHOLOGY


Hour Elevation Velocity Width Area Depth Discharge Slope

MLLW ( f t ) ( f t / w c ) ( f t ) (ft2) ( f t ) ( f t3 /s ) XIOs above V W A d Q 5

0530 5.25 0600 5.15 0630 4.93 0700 4.58 0730 4.04 0800 3.49 0830 2.91 0900 2.37 0930 1.88 1000 1.50 1030 1.16 1100 0.81 1130 0.54 1200 0.26 1230 -0.02 1300 -0.20 1330 -0.36 1400 -0.36 1430 -0.70 1500 0.12 1530 0.67 1600 1.35 1630 2.03 1700 2.69 1730 3.32 1800 3.90 1830 4.37 1900 4.65

0.00 47 336 0.24 47 333 0.4G 47 322 0.64 47 304 0.49 47 280 0.51 46 254 0.56 46 227 0.42 45 205 0.53 43 181 0.45 42 166 0.44 4 1 151 0.42 39 137 0.34 38 1 Z G 0.24 36 117 0.20 35 106 0.36 34 101 0.24 34 94 0.18 34 94 0.00 34 101

-0.18 35 111 -0.33 39 131 -0.43 42 158 -0.52 44 188 -0.64 46 216 -0.56 46 246 -0.56 46 273 -0.53 47 294 -0.49 47 308

7.1 7.1 6.8 6.5 6.0 5.5 5.0 4.6 4.2 3.8 3.7 3.5 3.3 3.2 3.0 3.0 2.8 2.8 3.0 3.1 3.4 3.8 4.3 4.7 5.3

0 80

148 195 137 130 127

86 96 75 66 58 43 28 21 36 23 17 0

-20 -39 -68 -98

-138 -138

4.0 3.2 4.0 5.6 4.8 4.8 3.2

-0.80 2.4 1.6 4.8 4.8 2.4 2.4 1.4

-1.G 0 0.8

-2.4 -0.8

5.9 -153 1.6 6.3 -156 -2.4 6.6 -151 -3.2

Appendix 2: Mouth gage, Petalurna Marsh, April 22, 1984. Slope: Mouth to A .

Hour Elevatioii Velocity Width Area Depth Discharge Slope above V W A d Q 5

MLLW (f t ) ( f t / sec) ( f t ) (ft’) ( f t ) (ft3/s) x105

0800 3.54 1.06 26 143 5.5 152 6.5 0830 2.95 1.09 26 128 4.9 140 5.7 0900 2.42 1.06 26 115 4.4 122 5.7 0930 1.95 0.92 26 101 3.9 93 5.3 1000 1.56 0.77 24 92 3.8 71 3.8 1030 1.22 0.74 22 85 3.8 63 3.4 1100 0.85 0.64 2 1 77 3.6 49 1.9 1130 0.53 0.64 2 1 70 3.4 45 1.5 1200 0.29 0.56 20 66 3.3 37 1.2 1230 0.04 0.52 20 60 3.1 3 1 1.1 1300 -0.14 0.50 19 57 3.0 29 2.3 1330 -0.30 0.40 19 54 2.8 22 2.3 1400 -0.33 0.30 19 53 2.7 16 0.4 1430 -0.17 0.08 19 57 2.9 5 1.2 1500 -0.14 -0.10 20 63 3.2 -G -0.4 1530 0.65 -0.41 21 73 3.5 -30 -2.7 1600 1.35 -0.56 23 87 3.8 -49 -2.2 1630 2.04 -0.66 2G 103 4.0 -68 -2.2 1700 2.66 -0.62 26 120 4.6 -74 -2.7 1730 3.31 -0.74 26 137 5.3 -101 -3.4 1800 3.88 -0.8G 26 152 5.8 -131 -1.1 1830 4.34 -0.84 26 164 6.3 -138 -1.2 1900 4.69 -0.79 2G 172 6.6 -136 -2.7

Appendix 3: A gage, Petaluma Marsh, April 22, 1984. Slope: Mouth to C.


Hour Elevation Velocity Width Area Depth Discharge Slope above V W A d Q 5

MLLW ( f t ) ( f t / sec) ( f t ) (r t2) ( f t ) (r t3 /s ) x105

0900 2 . G 5 1.19 28 93 3.4 111 13.3 0930 2.14 0.92 27 79 2.9 73 16.8 1000 1.76 0.82 26 70 2.6 57 19.4 1030 1.44 0.76 25 61 2.5 46 19.4 1100 1.10 0.68 24 63 2.3 36 24.2 1130 0.88 0.55 23 47 2.1 26 29.3 1200 0.56 0.68 22 40 1.8 27 37.0 1230 0.34 0.52 21 35 1.7 18 40.5 1300 0.20 0.48 20 32 1.6 15 46.1 1330 0.10 0.45 20 30 1.5 14 49.5 1400 0.04 0.26 20 28 1.4 7 50.0 1430 -0.02 0.26 20 27 1.4 7 40.4 1500 0.13 0.00 20 3 1 1.5 0 39.3 1530 0.53 -0.10 22 39 1.8 - 4 -3.1 1600 1.20 -0.40 24 55 2.3 -22 -9.1 1630 1.95 -0.76 27 73 2.8 -55 -6.1 1700 2.60 -0.80 28 92 3.3 -74 -5.6 1730 3.19 -0.72 28 107 3.8 -77 -6.9 1800 3.65 -0.78 28 121 4.3 -94 -10.0 1830 4.33 -0.79 28 140 5.0 -111 -4.7 1900 4.65 -0.67 28 149 5.3 -100 -1.8

L


MLLW ( f t ) ( f t / sec) ( t t ) (ft2) (ft) ( f t3 / s ) x105

0800 3.66 0.82 40 153 3.8 126 0830 3.06 0.84 39 129 3.3 108 0900 2.52 0.92 36 104 3.0 96 9.2 0930 2.02 1.18 35 92 2.6 108 7.7 1000 1.60 0.75 34 77 2.3 58 8.4 1030 1.25 0.76 32 62 2.1 49 9.4 1100 0.86 0.87 30 58 1.8 46 10.8 1130 0.57 0.84 29 47 1.6 38 13.9 1200 0.28 0.78 27 36 1.3 29 12.1 1230 0.05 0.68 26 26 1.1 2 1 12.9 1300 -0.14 0.54 25 26 1.0 14 14.7 1330 -0.30 0.56 24 22 0.9 12 17.3 1400 -0.35 0.44 24 19 0.8 8 16.9 1430 -0.19 0.20 25 24 1.0 5 7.4 1500 0.13 0.0 27 33 1.2 0 -0.4 1530 0.60 -0.28 29 46 1.6 -12 -4.9 1600 1.29 -0.58 32 67 2.1 -39 -6.1 1630 1.98 -0.58 34 90 2.6 -53 -3.9 1700 2.62 -0.74 37 113 3.0 -84 -2.3 1730 3.23 -0.82 39 135 3.5 -111 -4.7 1800 3.85 -0.90 40 160 4.0 -145 -9.8 1830 4.35 -0.84 40 181 4.5 -152 0.4 1900 4.66 -0.64 40 192 4.8 -123 -1.6

Appendix 4: C gage, Petaluma Marsh, April 22, 1984. Slope: A to D.

Appendix 5: D gage, Petaluma Marsh, April 22, 1984. Slope: C to Mid.

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Hydrology of t idal channels, California 489


MLLW ( f t ) ( f t /sec) ( f t ) ( f t2) ( f t ) ( f t3 /s ) x105

0900 2.83 0.84 37 121 3.2 102 16.6 0930 2.41 0.80 35 107 3.0 86 18.5 1000 2.05 0.79 34 93 2.7 73 19.8 1030 1.70 0.66 33 81 2.4 53 21.3 1100 1.42 0.GO 32 72 2.2 43 25.5 1130 1.25 0.48 3 1 66 2.1 32 27.9 1200 1.09 0.42 30 62 2.0 26 24.7 1230 0.99 0.28 29 59 2.0 17 40.9 1300 0.93 0.24 29 56 1.9 13 43.8 1330 0.85 0.16 28 55 1.9 9 45.7 1400 0.81 0.21 28 53 1.9 11 46.0 1430 0.74 0.23 28 52 1.8 12 46.8 1500 0.70 0.20 28 51 1.8 10 38.7 1530 0.69 0.12 28 5 1 1.8 6 20.3 1600 1.08 -0.36 30 62 2.0 -22 -6.2 1630 1.84 -0.80 34 87 2.5 -70 -14.5 1700 2.49 -1.00 36 109 3.0 - 109 -17.7 1730 3.07 -1.12 38 129 3.4 -144 -14.8 1800 3.68 -1.34 39 153 3.9 -205 -8.4 1830 4.24 -1.10 43 176 4.4 -194 -10.0 1900 4.62 -0.76 44 191 4.7 -143 -4.9

Appendix 6: Mid gage, Petaluma Marsh, April 22, 1984. Slope: D to E.

Hour Elevation Vclocity Width Area Depth Disrhargr Slope above V W A d Q 5

MLLW (ft) ( f t /sec) ( f t ) (rt2) ( f t ) ( f t3/s) x 1 0 5

0800 3.98 0.30 36 133 3.7 40 0830 3.53 0.GG 35 117 3.4 76 0900 3.18 0.08 34 106 3.1 72 17.8 0930 2.68 0.68 32 89 2.8 6 1 13.7 1000 2.34 0.68 3 1 78 2.5 53 14.7 1030 2.10 0.68 30 72 2.3 49 20.3 1100 1.88 0.60 30 65 2.2 39 23.4 1130 1.72 0.59 29 GO 2.0 35 23.9 1200 1.56 0.60 28 55 1.9 33 23.9 1230 1.50 0.57 28 53 1.9 30 25.9 1300 1.42 0.42 28 52 1.8 22 24.9 1330 1.38 0.34 28 50 1.8 17 26.9 1400 1.32 0.29 27 48 1.8 14 25.9 1430 1.28 0.33 27 47 1.7 16 27.4 1500 1.26 0.40 27 47 1.7 19 28.4 1530 1.22 0.30 27 45 1.7 14 26.9 1600 1.18 0.20 27 44 1.7 11 5.1 1630 1.44 -0.04 28 52 1.9 -2 -20.3 1700 2.00 -0.90 30 68 2.2 -61 -25.9 1730 2.74 -1.22 33 92 2.8 -112 -19.3 1800 3.40 -1.20 34 113 3.3 -13G -14.2 1830 4.00 -1.08 36 134 3.7 -145 -12.2 1900 4.48 -0.94 36 151 4.2 -142 -7.1

Appendix 7: E gage, Petaluma Marsh, April 22, 1984. Slope: Mid to E.

CATENA-An l n t e r d i s c i p l l n a r y Journal of S O I L SCIENCE-HYDROLOGY-GEOMORPHOLOGY


MLLW (ft) ( f t /sec) ( f t ) ( f t2) (ft) ( f t3 /s ) x105

0800 4.20 0.32 14 32 2.3 10 3.4 0830 3.80 0.32 14 26 1.9 8 4.2 0900 3.41 0.43 14 21 1.9 9 3.6 0930 3.07 0.44 13 17 1.3 7 6.1 1000 2.77 0.38 12 13 1.0 5 6.7 1030 2.52 0.42 11 10 0.9 4 6.6 1100 2.32 0.37 10 8 0.7 3 6.9 1130 2.16 0.29 9 6 0.6 2 6.9 1200 2.05 0.30 9 5 0.5 2 7.7 1230 1.96 0.28 8 3 0.5 1 7.2 1300 1.90 0.24 8 3 0.4 1 7.5 1330 1.87 0.21 8 3 0.4 1 7.7 1400 1.84 0.13 8 3 0.4 0 8.1 1430 1.82 0.09 7 2 0.4 0 8.4 1500 1.81 0.09 7 2 0.4 0 8.6 1530 1.80 0.04 7 2 0.4 0 8.7 1600 1.79 0.10 7 2 0.4 0 9.5 1630 1.78 0.08 7 2 0.4 0 5.3 1700 1.78 0.10 7 2 0.4 0 -3.4 1730 1.78 0.08 7 2 0.4 0 -15.0 1800 2.44 -0.89 10 8 0.9 -7 -15.0 1830 3.55 -0.78 14 23 1.7 -18 -7.0

Appendix 8: Head gage, Petaluma Marsh, April 22, 1984. Slope: E to Head.


MLLW (f t ) ( f t / sec) ( f t ) (ft’) ( f t ) ( f t s / s ) x105

1000 3.57 -0.83 46 257 5.6 213 1030 4.63 -1.02 47 307 6.6 -313 -2.4 1100 5.36 -1.14 47 343 7.3 -391 -4.8 1130 5.96 -0.96 47 370 7.9 -355 -2.4 1200 6.36 -0.88 47 388 8.3 -341 -2.4 1230 6.61 -0.60 47 402 8.5 -241 0 1300 6.76 -0.70 47 407 8.7 -285 -0.8 1330 6.79 -0.67 47 409 8.7 -274 0.8 1400 6.72 -0.32 47 406 8.6 -130 1.6 1430 6.37 0.54 47 389 8.3 210 4.8 1500 5.78 1.04 47 361 7.7 375 10.1 1530 4.98 1.29 47 324 7.0 418 15.1 1600 4.19 1.20 47 287 6.1 344 17.3 1630 3.38 1.24 46 250 5.4 310 18.0 1700 2.63 1.08 45 213 4.7 230 10.1

Appendix 9: Mouth gage, Petaluma Marsh, March 17, 1984. Slope: Mouth to A .

CATENA-An I n t e r d i s c i p l i n a r y Journal of SOIL SCIENCE-HYDROLOGY-GEOMORPHOLOGY

Hydrology of tidal channels, California 49 1

Hour Elevation Velocity W i d t h Area Dep th Discharge Slopc abovc V W A d Q 5

MLLW ( f t ) (ft/sec) ( f t ) ( r t 2 ) ( f t ) ( r t3 / s ) x i o 5

Hour Elevatioii Vrlocity W i d t h A r r a Depth Diacliargt Slop(, above V W A d Q 5

MLLW ( f t ) ( f t /scc) ( f t ) (ft2) ( f t ) ( f t3/s) ~ 1 0 "

1030 4.GO -0.88 2 G 1 G G 6.4 -14G -8.7 1100 5.30 -0.80 2G 186 7.1 -148 -5.7 1130 5.93 -0.82 2 G 201 7.7 - 1 G 5 -4.G 1200 G . 3 3 -0.7G 2 G 212 8 . 1 -1G1 -2 .3 1230 G . G l -0.G8 2 G 220 8 . 5 -150 -0.7 1300 6 .75 -0.G1 2 G 225 8 . G -137 -0.8 1330 6.80 -0.54 2 G 228 8.8 -123 -0.3 1400 6.74 -0.36 2G 22.5 8 . G -81 1.1 1430 G.43 0.48 26 214 8.2 103 6.3 1500 5.88 1.18 2 G 200 7.7 23G 9 .1 1630 5.20 1.45 2G 182 7.0 2G4 G . 3 lG00 4.47 1.70 2 G 164 G . 3 279 19.8 1 ~ 3 0 3.G9 1.8G 2G 1 4 5 5 . G 270 21.3 1700 2.92 1.9G 2G 124 4.8 243 13.7

1

Appendix 10: A gage , Petaluma Marsh, March 17, 1984. Slope: Mouth to C.

Hour Elev;rt,ion Velocity Wid th Area Dr1,t.h D i s c l i a r y Slop? >tl>OVC. V W A <1 Q 5

MLLW ( f t . ) ( f t / s cc ) ( f t ) (ft') ( f t , ) ( f t 3 / s ) X105

1030 4.40 1100 6.21 1130 6.84 1200 G.30 1230 G.59 1300 G.74 1330 G . 8 1 1400 G.76 1430 G.51 1500 G . 2 0 1630 5.41 1G00 4.71 1630 3.94 1700 3.60

-0.97 40 182 4.5 -0.93 40 214 5.3 -0.89 40 240 G.O -0.G4 40 267 G.4 -0.G2 40 270 G 7 -0.50 40 274 6.8 -0.48 40 27G G.9 -0.18 40 274 G.9 0.58 40 2GG G.7 1.28 40 247 G . 2 2.24 40 23s 6.6 1.62 40 197 4.8 1.88 40 1 G 3 4 .8 1.48 39 129 3.2

-177 -8.0 -199 -G.3 -214 -4.1 -154 -2.0 -1G7 -l.G -137 -8.0 -132 -1.7

154 5.5 3 1 G 9.0 500 18.2 296 1g.9 30G 15 .1 191 22.4

- 4 9 0.8

Appendix 11: G gage , Petaluma Marsh, March 17, 1984. Slope: A to D.

6.14

1430 1500

5.64

4.18 3.46

-1.20 -1.30 -1.18 -0.92 -0.82 -0.60 -0.66 -0.68 -0.52 0.25 1.12 1.32 1.68 1.83 2.60

28 28 2 8 28 28 28 28 28 28 28 2 8 28 28 28 28

118 4.2

162 5.8 185 G.G 194 G.9 200 7.1

204 7.3

200 7.1 188 G.7 172 (3.1 157 5.6 135 4.8 I15 4.1

140 5.0

203 7.2

203 7.2

-142 -182 -191 -170 -169 -120 -134 -118 -1OG

50 211 227 2G4 247 23G

-9.9 -10.4

-6.G -2.0 -1 .0 -1.3 -1.3 1.8 6.4

12.5 17.7 22.4 24.1 36.G

Appendix 12: D gage, Petaluma Marsh, March 17, 1984. Slope: C to Mad.

492 Leonold. Collins SC Collins

n Hour Elevatioii Velocit,y Width Area Depth Discharge Slope

above V W A d Q 5 MLLW ( f t ) ( f t / m c ) ( f t ) (ft2) ( f t ) ( f t3 / s ) X10’

1200 5.90 -0.50 14 56 4.0 -28 -3.4 1230 G.31 -0.34 14 60 4.2 -20 -2.5 1300 6.53 -0.28 14 65 4.6 -18 -2.0 1330 6.62 -0.31 14 66 4.7 -20 -1.9 1400 6.67 -0.30 14 6 7 4.8 -20 -1.4 1430 6.69 -0.29 14 6 7 4.8 -19 0.3 1500 6.60 0.10 14 6 6 4.7 5 3.3 1530 6.38 0.45 14 62 4.4 22 5.9 I600 5.98 0.62 14 56 4.0 28 7.0 1630 5.48 0.83 14 5 2 3.7 34

Hour Elcvat,ioii Velocity W i d t h Arca Depth Dischirrgc Slopc xbovc V W A d Q 5

MLLW ( r t ) (rt /scc) ( f t ) (r t2) ( f t ) ( r t 3 j s ) ~ 1 0 ~

1030 4.17 -1.29 4 0 180 4.4 -232 -17.3 1100 4.97 -1.26 40 203 5.0 -25G -13.9 1130 6.71 -1.25 40 239 5.9 -299 -9.5 1200 G.23 -1.00 40 254 6.3 -254 -5.0 1230 6 .53 -0.82 4 0 267 6.6 -219 -3.2 1300 (3.71 -0.76 40 274 6.8 -20G -2.1 1330 G.78 -0.70 40 278 6.9 -195 -1.0 1400 (3.79 -0.42 4 0 278 G.9 -117 -0.7 1430 G . G 3 0.18 40 272 6.7 49 3.8 1500 6.31 0.74 40 257 6.3 190 10.7 1530 5.82 0.08 40 237 5.8 232 l G . G lG00 5.23 1.08 40 215 5.3 232 21.8 l G 3 0 4.GO 1.18 40 188 4.0 222 1700 3.91 1.08 4 0 1G2 4.0 175

U -~

Appendix 13: Mid gage, Petaluma Marsh, March 17, 1984. Slope: D to E.

H o u r Elevxtioii Vclocity W i d t h Area Dcptli Discliargc Slo l~e above

1030 3 . 8 4 -0.88 3 5 128 3.6 -113 -1G.8 1100 4.71 -0.99 157 4.3 -155 -13.3 1130 5.52 -0.80 183 5.1 -183 -9.6

G . 1 2 -0.66 -203 -5.G -0.54 -217 -0.52

1330 G.74 -0.41 -226 1400 G.76 -0.2G 227 -227 -1.5 1430 6.G7 0.04 223 2.0 1500 (5.30 0.86 184 4.1 1530 (5.00 1.04 199 5.5 207 9.1 I G O O 5.53 1.14 187 5.2 213 15.2

Appendix 14: E gage, Petaluma Marsh, March 17, 1984. Slope: Mad to E.

Appendix 15: Head gage, Petaluma Marsh, March 17, 1984. Slope: E to Head.

C A T E N A A I I I l i t e l r l i s c i p I I I I bi y . I , , 11 1 11 d l , , t RC) I L S C I E N C E ~- H Y D R O L O G Y -- C EO&! 0 R . P H O L 0 G Y

Hydrology of tidal channels, California 493 ____

- Hoiir Elevetioii V(.locit.y W i d t h A r c ~ a Deptl i Discliary

;rl,ov(* V W A (1 Q MLLW ( f t . ) ( f t / s e c ) ( f t ) ( f t 2 ) ( f t , ) ( f t, 3 / s )

1030 0.89 -0.11 3 0 66 1.8 - G 1100 1.G9 -0.48 34 80 2.4 -38 1130 2.G8 -1.07 37 114 3.1 -121 1200 3.8G -1.20 4 0 1G0 4.0 -192 1230 4.G4 -1.17 40 192 4 .8 -224 1300 5.30 -1.08 40 218 6 .4 -236 1330 5.77 -1.13 40 237 6.9 -2G7 14 00 (7.16 -0.78 40 262 G . 3 - 1 9 G 1430 G.32 -0.68 40 25D G . 6 -160 1600 G.34 -0.15 40 260 G.G -38 1630 G.21 + 0 .4 0 40 266 6.4 + l o 2

Appendix 16: Channel data, C gage, September 7, 1988.

Hour Elc-vat,ioii Vclocity Width Arra Dcptli Discliargv S l o ~ ) c S1o1)c

MLLW ( f t ) ( f t /s<.c) ( f t ) ( f t 2 ) ( f t ) ( f t ,3/s) X 1 0 " X 1 0 "

ii 1 )o ve V W A d Q 5 5

1300 4.03 -0.93 14 32 2 . 3 - 3 0 -11.9 -37 -0.2 C to 1330 5.11 - 0 . 7 9 1 4 47 3.4

1400 5.67 - 0 . G 2 14 6 4 3 .8 -33 -6.4 R.iiilroad 1430 (3.07 - 0 . 4 6 14 G O 4.3 -27 -2.3 - 5 . G 1500 0.20 -0 .27 14 G 3 4 .5 -17 -1.4 -3.2 1630 (3.23 -0.14 14 G 3 4.5 -9

' Flow revcwnl dowiistremi a t C page.

Appendix 17: Channel data , Head gage, September 7, 1988. Slope: C to Head.

Hour Elrvatioir Vclocity Widt Ii Area Dcptli DiscliarKt. Slop(.

MLLW ( f t ) ( f t , /sec) ( f t , ) (ft,') ( f t , ) ( f t ,3/s) ~ 1 0 " abovr W A

1430 6.44 -0.52 4 2.96 0.73 -1.63 -12.9 1600 5.83 -0.37 G 6.39 0.90 -1.99 -7.G 1530 (3.05 -0.30 7 7.75 1.10 -2.32 -3.7 lG00 G . l l -0.20 7 8.00 1.27 -1.78

* Flow rrvrrsel dowustrciriu ;it Hei rd girgc.

Appendix 18: Channel data, RR gage, September 7, 1988. Slope: Head to RE.

Addresses of authors: Dr. Luna B. Leopo ld Department of Geology and Geophysics University of California Berkeley, CA, U.S.A. Dr. Joshua N. Collins Department of Geography University of California Berkeley, CA, U.S.A.

Laurel M. Collins Lawrence Berkeley Laboratory Berkeley, CA, U.S.A.

C A T E N A- A I I I n t e r d i s ci p I i ita L y .I ,.I II I I I d I o f S 0 I L B C: I EN I: E- H Y D R O L 0 G Y - G E O M 0 R P H 0 L 0 C: Y

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