Sedimentation in Three Small 5 Forested Drainage Basins in the Alsea River Basin, Oregon
'I I
GEOLOGICAL SURVEY CIRCULAR 490
PREPARED IN COOPERATION WITH THE OREGON STATE BOARD OF HIGHER EDUCATION Sedimentation in Three Small Forested Drainage Basins in the Alsea River Basin, Oregon
By R. C. Williams
GEOLOGICAL SURVEY CIRCULAR 490
Prepared in cooperation with the Oregon State Board of Higher Education
Washington 1964 United States Department of the Interior STEWART L. UDALL, SECRETARY
Geological Survey THOMAS B. NOLAN, DIRECTOR
Free on application to the U.S. Geological Survey, Washington, D. C. 20242 CONTENTS
Page Page Ab str act ______1 Introduction Continued Introduction, ______1 Water and sediment data______6 Purpose and scope______1 Fluvial sediment______6 General description of the drainage Relations to rainfall and runoff _____ 6 basins.______2 A freshet period______11 Methods of measurement ______4 Flow and concentration Rainfall ______5 duration ______14 Water discharge.______5 Water temperature.______14 Water temperature ______5 Summary ______16 Suspended-sediment discharge ____ 5 Literature cited ______16
ILLUSTRATIONS
Page Figure 1. Map showing location of the study basins______3 2. Profiles of stream channels ______4 3. Comparison by drainage basin of precipitation, runoff, and suspended-sediment yield for 1960 water year ______10 4. Distribution by month for precipitation, runoff, and suspended-sediment load for 1960 water year ______12 5. Comparison of hydrologic factors for the Deer Creek basin for the period January 7-13, 1959 ______13 6. Streamflow and suspended-sediment concentration duration curves for the strearns ______15
TABLES
Page Table 1. Monthly rainfall of basins.______5 2. Monthly streamflow and runoff of basins______. 7 3. Average monthly maximum and minimum water temperatures __ 8 4. Monthly suspended-sediment load______8 5. Annual rainfall, runoff, and suspended-sediment.______9
III Sedimentation in Three Small Forested Drainage Basins in the Alsea River Basin, Oregon By R. C. Williams
ABSTRACT the sedimentation of forested drainage ba A multidiscipline investigation to determine the effects of sins under natural conditions, under different logging on the ecology of three small forested tributary ba timber harvesting methods, and during the sins is a part of an overall study of the Alsea River basin in recovery phase after the timber harvest. the Coast Range of Oregon. The investigation of these small basins will be to (1) establish pre-logging conditions, (2) de This report is the first in a series of data termine the effects of different logging methods, and (3) study analyses which will follow the progress of the rate of recovery after the timber harvest. This report presents results of sedimentation in the basins, Deer and the sedimentation investigation. It deals with Flynn Creeks and Needle Branch, for the first 2 years of the first 2 years of the prelogging phase study (1959 and 1960 water years). which will last approximately 5 years. The Rainfall, runoff, and sediment discharge are seasonal for study of all aspects of watershed ecology will the Coast Range of western Oregon. About 95 percent of the span a period of 10 to 15 years. rainfall and rnnoff occurs during the period October to May, but nearly 100 percent of the suspended-sediment discharge occurs during the same period. For Deer Creek, in the I960 This investigation is concerned with the water year, 23 percent of the annual suspended-sediment sedimentation in three small drainage basins lis charge occurred on 1 day, 58 percent during the 10 days in the Alsea River basin in Oregon. The first of greatest discharge, and 78 percent during the 38 days of greatest discharge. phase will be a definition of the undisturbed conditions in each of the three small basins. Rainfall is practically qual for all three of the basins. The runoff of the Deer and Flynn Creek basins is about The second phase will measure the changes equal, but that of the Needle Branch basin averaged 8 per in sediment yield as logging progresses in cent less. the Deer Creek and Needle Branch basins. Sediment yield varies considerably for the three basins. The Needle Branch basin will be clear-cut The suspended-sediment yield of the Deer Creek basin is al of all timber, whereas the Deer Creek basin most twice that of the Needle Branch basin and almost 1% times that of the Flynn Creek basin. will be logged in a staggered cutting pattern. The third phase will cover the rate and ex Water temperature of the three streams varied only 22*22 Fr tent of recovery of the basins. Sediment during the'' 2" water' years.fears. The greatest variation between streams was 3°F in the minimums. Water temperature effect yield from these two basins will be com can be neglected in comparing the sediment yields of the pared with that of the Flynn Creek basin, basins. which will remain undistrubed for the entire The aquifers of the basins have low storage capacities as study as the control or calibration basin. illustrated by the very low, late summer flow. A study of a The area studied comprises only a small midwinter freshet period for the Deer Creek basin showed part of the Alsea River basin, but the findings that virtually all the rainfall left the basin as runoff within 4 days; the period of significant sediment transport was should have application in other parts of this thus very short. basin and some application to other forested drainage basins. INTRODUCTION Runoff, suspended-sediment discharge, and PURPOSE AND SCOPE water temperature are readily measured and provide good indices of drainage-basin en The purpose of the overall study is to de vironment. This report summarizes the hy- termine the effects of man's use on the en drologic data collected during the first 2 vironment of forested drainage basins. The years of the study and points out some of the scope of this part of the study is to investi relationships between basin environment and gate the effects of environmental changes on climate. SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON
The overall study in the Alsea River basin the flow of the streams. Little meandering is a multidiscipline examination of drainage occurs, and the streambeds are generally basin ecology. The major parts of this com well armored with fine to coarse gravel. prehensive study are: (1) a soil-vegetation survey designed to inventory the soils and The area is underlain by the Burpee For vegetation of the entire Alsea River basin and mation of middle Eocene age, which may be to provide a base for research in drainage- contemporary with the Tyee Formation to the basin management, (2) a water resource sur south (Yokes and others, 1949). The Burpee vey of the major tributaries of the Alsea Formation consists of a thick sequence of River designed to provide abase for research micaceous sandstones interbedded with mud- in drainage-basin management and water use, stones and siltstones. It is characterized in (3) a study of the effect of lagging upon the the study area by moderate dip slopes and physical and biotic resources of small heavy soil mantle, and by steep slopes and a streams, and (4) the study of the migration shallow, sandy, soil cover where beds of and production of salmonoid fish in selected sandstone are exposed. The variability of streams of the basin. The overall study is the slopes and soils causes much of the vari coordinated by the Oregon Agricultural Ex ability in the sediment yield from these ba periment Station under the Oregon State sins. Board of Higher Education. The participants in this study include the U.S. Geological Sur The mild humid climate of the area is typ vey, U.S. Forest Service, Bureau of Land ical of the coastal region of western Oregon. Management, Soil Conservation Service, the About 90 inches of rainfall is recorded an Soils Department and School of Forestry of nually, and most of it occurs during the Oregon State University, Georgia-Pacific months from October to May. Temperatures Corp., and the Oregon State Game Commis generally range between 20°F and 90°F, with sion. a mean of about 51°F.
GENERAL DESCRIPTION OF THE DRAINAGE BASINS The environments of the three basins ap pear to be very similar because all three are The Alsea River rises on Marys Peak characterized by dense, virgin forest. The (elev. 4,097 feet) and drains about 473 square communities formed by the principal under- miles of the timber-covered Coast Range of story vegetation such as sword ferns, sal- Oregon before emptying into the Pacific monberry, and vine maple vary greatly from Ocean at Waldport. The drainage basins be place to place, but the density of growth ing used for the sedimentation study com varies little from basin to basin. However, prise a very small part of the Alsea River the proportions of the Douglas fir and alder basin. Deer Creek has a drainage area of overstory vary appreciably. About 60 per 1.20 square miles; Flynn Creek has a drain cent of the overstory in the Deer and Flynn age area of 0.84 square mile; Needle Branch, Creek basins is alder, whereas the overstory the smallest of the three streams, has a of the Needle Branch basin is only about 20 drainage area of only 0.32 square mile. (See percent alder. fig. 1.) There are some differences in the geomor- The altitude of these three small basins phology of the three basins. Surveys made by ranges from about 1,600 feet at the highest Oregon Agricultural Experiment Station per point of the Deer Creek hydrographic divide sonnel using an altimeter show that the ba to about 430 feet at the Needle Branch con sins have dissimilar gradients. The data fluence with Drift Creek. The drainage val from these surveys are plotted in figure 2. leys are V-shaped and have moderate to steep side slopes. A canopy of Douglas fir inter Deer Creek basin has drainage slopes mixed with alder covers almost all of the averaging about 40 percent and characteris area and intercepts much of the rainfall. A tically thinner mantles of sandy soil (C. T. very heavy growth of under story vegetation Dyrness, U.S. Forest Service, written com covers virtually all of the drainage basins, munication, 1962). The drainage pattern of giving good natural protection against erosion this basin is more fully developed than that of the fine-grained surface soils. Much tim for the other two basins; thus the runoff col ber debris in the valley bottoms forms natur lects more rapidly and creates a greater al settling basins in places where it retards sediment erosion potential in Deer Creek INTRODUCTION
Waldpo;
9 10 ^ 20 30 MILES
2 MILES I
Figure 1. Map showing location of the study basins in the Alsea River basin, Oregon. SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON
140
120
£ 100
cc CO Is
1000 2000 3000 4000 5000 6000 7000 DISTANCE UPSTREAM FROM STREAM-GAGING STATION, IN FEET
Figure 2. Profile of stream channels. Q, sediment sampling site. basin. Some of the tributary channels in the tent that prelogging conditions seem to pre basin show signs of active erosion; probably vail as indicated by runoff and sediment yield. much of the sediment yield of the basin is * derived from these tributaries. The environment of the basins to date (1961) has been altered only by the structures and The drainage slopes of Flynn Creek basin trails made for this study. Minor adjust average about 34 percent. Much of the basin ments in the stream gradient in the vicinity is on a moderate dip slope of the Burpee of the concrete control weirs and fish traps sandstone beds where there is generally a will continue for sometime, but these changes thick layer of fine soil. Water is temporarily are local in nature and should have little ef stored in surface depressions and as soil fect on the overall environment. moisture on the relatively flat dip slopes during freshet periods. The drainage pattern The various environmental factors affect is not well defined, and the moderate runoff ing sediment yield are complicated and in from these areas lacks the energy for large- separable. A change in one will produce a scale erosion of the tributary channels. change in the others. When logging or other uses of these basins begins, the Needle Branch The Needle Branch basin has drainage basin could have a higher sediment yield than slopes averaging about 37 percent. The heavy the Deer Creek basin. Douglas fir canopy and the relatively flat stream gradient combine to limit the runoff METHODS OF MEASUREMENT and sediment yield from the watershed. Thirty-two acres in the headwaters were Often long-term sediment data must be ob logged off 7 to 10 years ago. The understory tained or a statistical approach must be used vegetation, however, has regrown to the ex to establish relationships of sediment yield INTRODUCTION to the other hydrologic and environmental WATER DISCHARGE parameters. It is intended, during this study, to collect and use comprehensive hydrologic Stream-gaging stations near the mouth of data to analyze these relationships. The ma the streams are used to determine water dis terial presented in this preliminary report is charge from the basins. These stations con based on water and suspended-sediment data sist of a conventional gage house and well that collected during the 1959 and 1960 water are equipped with continuous water-stage years. Terms used herein are those used by recorders. Controls for stabilizing ratings the U.S. Geological Survey in the annual se of water discharge to gage height are pro ries of Water-Supply Papers "Quality of Sur vided by a concrete weir at each station. face Waters of the United States." WATER TEMPERATURES Field surveys of the sediment deposits be hind the concrete control weirs have been A continuous record of water temperature made to determine the amount and character for each stream is obtained by an attachment of these sediments. The results of the sur on the water-stage recorders. The sensing veys and particle-size analyses are incom element is located at the end of the gage- plete at this time; they will be included in house well intake pipe in the pool behind the subsequent reports. weir. Daily maximum and minimum temper atures are determined from these records*, RAINFALL SUSPENDED-SEDIMENT DISCHARGE Continuous records of rainfall are avail During the period of record included in this able for sites just downstream from the gag report, the suspended-sediment load was ing stations in each of the three basins by the measured at sites just upstream from the Oregon Agricultural Experiment Station at stream-gaging stations. Oregon State University. The gages, USWB 8-inch recording types, are so located as to The streambed at the Deer Creek sampling be affected as little as possible by wind cur site consists of angular rock fragments, rents and vegetal cover. A summary of whereas the beds at the Flynn Creek and monthly rainfall for the period January 1959 Needle Branch sites consist of sand and fine to September 1960 for these three sites is gravel. Higher velocities at the Deer Creek given in table 1. The records for these and site cause greater turbulence which probably other sites in the Alsea River basin have been results in a larger load of suspended sand published by Chapman and others (1961).
Table 1. Monthly rainfall of basins, in inches by water year Deer Creek Flynn Creek Needle Branch Month 1959 1960 1959 1960 1959 1960
October. ______8.73 7.77 9.43 November ______6.59 5.95 6.96 December ______9.26 8.16 8.95 January ______23.00 9.81 21.27 10.29 25.19 11.00 February ______12.00 18.16 10.46 18.16 12.17 17.71 March ______10.47 12.77 9.82 12.77 11.33 13.65 April ______4.83 9.04 4.70 8.32 4.95 9.24 May _ _ _ _ 5.70 10.53 5.22 9.84 6.30 9.19 June. ______3.62 1.20 3.37 1.08 3.90 .95 July. ______. . . ______.65 .03 .69 .00 .78 .00 August. ______.60 2.37 .56 2.14 .52 2.21 September ______11.49 .36 11.26 .29 13.12 .41
Total ______72.36 88.85 67..S5 84.77 78.26 89.70 SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE RASINS IN THE ALSEA RIVER RASIN, OREGON than that carried by the other two streams. flow data for the period covered have been Some sand and gravel move past the sampling published in Water-Supply Papers 1638 and sites as bedload. A major part of the bed- 1718* These data are summarized in table load and some of the suspended sediment 2. Data on daily extremes of water temper have been deposited in the backwater pools ature, daily suspended-sediment loads, and of the concrete control weirs. The rate of sediment particle-size analyses will be pub deposition gradually diminished until the end lished in Water-Supply Papers 1745 and of the 1960 water year when the amount of 1815. Monthly averages of the daily water sediment being retained in the pools behind temperature extremes are summarized in the weirs was only a small part of the total table 3. A summary of monthly suspended- sediment load. All the sampling sites were sediment loads is given in table 4. subsequently moved to the control weirs where virtually the total sediment load can FLUVIAL SEDIMENT be sampled and the yield of the basins can be compared more accurately. RELATIONS TO RAINFALL AND RUNOFF
Surveys were made at selected transects Data on rainfall, runoff, and suspended- of the channel upstream from the weirs to sediment transport collected during the 1959 determine the volume of the deposits. Ran and 1960 water years are summarized in dom core samples were obtained to deter table 5. The recorded rainfall data are for mine the specific weight and the particle-size the period January 1, 1959, to September 30, distribution of the material in the deposits. 1960. All other data are for November 20, This procedure will be repeated yearly to 1958, to September 30, 1960. The data were evaluate the amount and character of this tabulated in this form to compare individual part of the sediment load. These values will items for corresponding periods of time. then be reported in yearly increments to The true relation of the rainfall to runoff permit the determination of the annual total may not actually be so close as the table in load. dicates because rainfall was recorded at only one point near the mouths of the streams. The suspended-sediment samples were col The relation might be different if rainfall lected at midstream with DH-48 depth-inte had also been recorded at upstream sites. grating samplers at time intervals ranging from one or two times a week during periods Table 5 suggests that the rainfall for the of low flow to as often as four times a day Needle Branch drainage basin is greater than during periods of high flow. These mid that for Deer and Flynn Creek basins. Short- stream samples were considered to be rep term precipitation records may be mislead resentative of stream concentration because ing, however, because studies have shown of the narrow, turbulent nature of the streams. that considerable differences are sometimes recorded even by adjacent gages (Court, 1960; For some periods when no samples were Mead, 1950). No significant difference in the collected, daily loads of suspended sediment average annual rainfall of the three basins is were estimated on the basis of water dis expected because of the close proximity of charge, sediment concentrations observed the basins, their alinement, and their similar immediately preceding and following the pe altitudes. During the short period of record riods, and suspended-sediment loads for no large differences have occurred in the other periods of similar discharge. Sedi amount and distribution of the rainfall at the ment loads from one or both of the other two three rain gages used during this study. stations and weather conditions were used to make these estimates. As table 5 shows, the runoff for Deer and Flynn Creek basins was nearly equal for WATER AND SEDIMENT DATA each of the 2 years of study, but that for Needle Branch basin averaged only 92 per Complete tables of water and sediment data cent of the average for the other two. Part summarized for this report are published in of the difference can probably be explained U.S. Geological Survey Water-Supply Papers. by the difference in the overstory vegetation These reports also contain discussions of of the basins. As pointed out earlier, the 'standard methods and terms used but not Needle Branch basin has about 80 percent fully defined in this report. Daily stream- Douglas fir in the overstory compared to FLUVIAL SEDIMENT
«w «t- CO OOOOO5 sfin-tfocoaicococo C35 O5CMCO CO'-HC-CO'^CMCMOO CO o o> ^fC35CD CO-^fiOC-^t-iOCOin CO CDCOO 'stl CO'-ICO'5tl CO'*COi-< CD K o O(NOO OOOCDCO-^i-t COC-OO OOOCOOOt-H-^OO'-lO t-H OCMO5 CO'-l|>CO'5tl '5tl CDCDC35 05 1-H -~» rt CQ co ^Ht-H-^H C-OCD'-IOOin-^fCOlM 0 O5t-i-l lOt-t-HOOlOi-HCOCM * X! -f-> CM >~. t-ic- mojiococot-H CM t-H ^HCOUO lOt-HCDiOiO'-l 0 O t-H c H£>B ^ -arf t-H ^M CD m rt ^ Cfl i-l O5i~l x*£^ CO -^f OOOOC-t-OCOt-ICO OCMCO CO t-HCOiOcOCMCM'-l M -< «w t-H(N|lO OOt-^COCOi-H Uf5 00 ^HiOCO ^OOiO'^'*1 CO iS rt 0 t-H i 1 t-H -H t-H f% 13 *" t CQ t-t-HC5 CO cot-oo -tf-tfcomcviajococo * C-CMiO CMCOCOCMCOO-^funO t-H Cti CQ CQ OCD(N ^ M ^-U t-H X ^ ""^ CO -< TJ Water1959______year 0) O >1 CO 05 n3 t-H C CX3 CTl CTI O IO IO in vo M TJ O1 CTI CTI CTI -H « cd r.Gj 0> H >^ Q>M MQ> p^ S« Q> « h § M fe M xi xi >> b fJ (= M xi xi >* b fJ Q> ,saa ^-g^ ts g 13 -§Q>0) §^^^>>, Table 3. Average monthly maximum and minimum water temperatures, in degrees Fahrenheit by water year Deer Creek Flynn Creek Needle Branch Month 1959 1960 1959 1960 1959 1960 Max. Min. Max. Min. Max.1 Min. Max. Min. Max. Min. Max. Min. October ______54 52 50 49 52 51 51 50 53 52 51 51 November ______49 48 46 45 49 48 48 47 49 48 48 46 December ______48 47 46 46 48 48 48 47 48 47 46 45 January ______47 46 43 43 47 47 46 45 47 46 44 43 February ______47 46 46 45 47 46 47 47 47 46 46 46 March.. ______48 47 46 45 48 47 48 46 46 46 47 46 April ______50 48 49 47 49 47 49 48 49 47 49 48 May. ______49 48 49 48 50 48 50 49 49 48 49 49 June______51 50 53 50 52 51 53 51 51 50 53 51 July______55 54 56 52 56 54 55 52 55 54 56 54 August. ______55 54 56 54 55 53 56 53 55 54 57 55 September ______52 51 54 52 52 51 54 52 54 53 56 54 Average ______50 49 50 48 50 49 50 49 50 49 50 49 Table 4. Monthly suspended-sediment loads, in tons ]L959 Water year 1960 Water ye;ar Month Deer Creek Flynn Creek Needle Branch Deer Creek Flynn Creek Needle Branch October______1.7 0.7 0.2 November _____ ltl.l *2.4 *1.4 4.9 .9 .3 December...... 5.2 3.2 .9 5.6 1.2 .2 January. ______62.0 39.1 10.3 7.0 3.3 .5 February _____ 7.1 4.3 1.3 53.3 27.0 8.1 March.. _ .___ 2.8 1.4 .7 6.6 2.9 .6 April ______1.5 1.1 .2 7.3 2.3 .4 May _ _.__.__. 1.7 .8 .3 3.3 .3 .3 June.. ______.8 .2 ty\ .4 /9\ *9\ ^) W July ... _ .3 i9\ fy\ v-t \^l (2) (2) W August. _ _ _ _. t Total ____ _ 3 89.7 3 53.1 3 15.5 90.1 38.7 10.6 " Does not include sediment load for Nov. 1 19. 2 Less than 0.050 ton. 3 Does not include sediment load for October 1 to November 19, 1958. FLUVIAL SEDIMENT 9 o about 40 percent in the other two basins (C. 10 iH 05 T,. Etyrness, U.S. Forest Service, written com i 2 i-H rH C & m munication, 1961). The fir intercepts more oi a 02 CU ^ VH of the water during the heavy rainfall period ?§ (N because the alder has no leaves then. An 73 "+J 0 other possible explanation of the difference cu oi CO CO Oi 00 TH could be the loss due to subsurface flow from ££ iH rH CU the basin, either through the tilted sandstone m IO CO TH beds or through the alluvium of the valley TH rH rH o iH mouth. The suspended-sediment loads of the three O 00 TH Oi ^^ 3"o m o oo CO streams for November 1958 to September CO 1 s H 1960 vary considerably, as would be ex pected from the relative size of their drain "** 0) o in co co * CO C- -^ CO age basins. The drainage area of Deer Creek g ^ rH 0 CU iH is 3.8 times that of Needle Branch, but the sediment load was 6.9 times as large. Flynn T3 r; CU n m IO CM 00 Creek has 2.6 times the drainage area, but CO +£ C- CO ^ 00 TH iH transported 3.5 times more sediment than Needle Branch. 1 H Oi 00 02 TH 00 8 O* O* CO* CO* A better comparison of the three basins C- Oi (M 73 H ai iH (M canbe made by dividing the annual suspended- 0 r-H » «> iH C- CO "*. sediment load of each stream by the area of 0 CO CD CO O* oi the drainage basin to obtain the suspended- O5 CO rH CO TH sediment yield. These unit area values (table §1 iH 5) show that the suspended-sediment yield t- (M 10 "*. cu CT> for the Deer Creek basin for November 1958 CO m oj c>i in £> oo m TH m to September 1960 was 1.4 times that for the iH rH Flynn Creek basin and 1.9 times that for the CO CO -^ r-H Needle Branch basin. 0} 8 CO M CD* CO CO (M H TH rH rH The 1960 water year was the only full year for which records of rainfall, runoff, and 'o 2 t- LO CO CU 00 o 0 0 CO ,0 m suspended-sediment yield were available. fi "^ CO d o> 3 CJ OJ to t^ CQ 8- The bar graph presented in figure 3 compares 05 .5 iH CO CO LO o « cu ^ the relationships between precipitation, run CO 00 00 Q ^ o * c- off, and suspended-sediment yield for 1960. S For almost equal values of recorded rainfall, i 1 CO CO CO [N the runoff values for Deer and Flynn Creek TH CM CO basins were almost equal, but the runoff for a (M rH Oi the Needle Branch basin was only 88 percent +? iH CM* l> CO LO CO TH TH rH of the average of the other two. The ratios of rH runoff to rainfall are 0.74, 0.79, and 0.65, r-H » >> r-H CQ in t- o O respectively, for the Deer Creek, Flynn Creek, CO 00 t- C- O3 oo" -^i* oi and Needle Branch basins. Sediment yields .5 o TH CTJ C 00 OO OO for the 1-year period reflect differences al p^ ^- co m co CO CO (M Oi ^ O most the same as those for the November m M E> 00* CU 0) 1958 to September 1960 period. Deer Creek t- CO t- 73 73 r 1 basin has 1.6 times the yield of the Flynn 1 1 1 Creek basin and 2.3 times that of Needle 1 1 ^ ' £& CU Branch basin. -* cu cu o o .a ^ £ n 03 ^ r i 1 H CO CO Another comparison can be made of the nj 0 cu 0} PQ 8 sediment-transport characteristics of the oJ |« three basins by using the weighted-mean Q S iS concentration. Values of this index were 10 SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON 90 90 NX 80 XV 80 70 70 I O 60 60 cr LJ Q. 9 50 50 P a: Q Q _J UJ 40 40 O C/) a:UJ 30 30 Q. Q UJ Q. C/) 20 20 10 10 DEER CREEK FLYNN CREEK NEEDLE BRANCH Precipitation Runoff Suspended-sediment yield Figure 3. Comparison by drainage basin of precipitation, runoff, and suspended-sediment yield for 1960 water year. computed (table 5) for the period November were obtained for the other two streams. 20, 1958, to September 30, 1959, for the 1960 Total load computation to be presented in water year, and for November 20, 1958 to future reports will provide adequate data for September 30, 1960. A comparison of these study of this item. values for the three basins again emphasizes the greater amount of sediment transported The weighted-mean concentration is also by Deer Creek. useful for comparing the water discharge- sediment load relationship for a period of A small part of the differences in sediment- years. Because the data for the missing pe transport rates may be due to differences in riod October 1 to November 19 of the 1959 the turbulence at the individual sampling water year would have little effect on the sites. As shown in figure 2, the gradient weighted-mean concentration of the streams, where samples were obtained on Deer Creek values computed for the rest of the year can is steeper than the gradients where samples be compared with the 1960 values. This FLUVIAL SEDIMENT 11 comparison shows that the sediment concen discharge peak closely coincides with the tration of these streams was nearly the same water-discharge peak. During the logging for each of the 2 years of record. Little phase, the concentrations may be higher and change can be expected as long as the streams may thereby have more influence on the remain under virgin-forest conditions, but shape of the suspended-sediment discharge changes in the environment of the basin will graph. most likely be reflected by changes in the weighted-mean concentrations. Figure 5 shows that rainfall intensity has little effect on sediment discharge. In densely The time distribution of precipitation, run forested areas, such as these drainage ba off, and sediment load has vital importance in sins, there is limited opportunity for the the study of the hydrologic environment of raindrops to reach the soil mantle and to these drainage basins. The monthly distribu loosen particles by impact. Sediment dis tion of precipitation, runoff, and suspended- charge is influenced by rainfall intensity in sediment load is given for each drainage basin these small basins to the degree to which the for the 1960 water year in figure 4. About 95 rainfall determines the magnitude and dura precentof the precipitation and runoff occurs tion of the runoff peak. during the period October to May, but nearly 100 percent of the sediment discharge occurs The disposition of the rainfall that leaves during the same period. During the 1960 wa the basin as runoff can be studied by means ter year, almost two-thirds of the total annual of the graphs presented in figure 5. In the suspended-sediment discharge from the three lower half of the figure, water discharge (in drainage basins occurred during February. A cubic feet per second) has been converted to further breakdown for Deer Creek the largest rate of runoff (in inches per hour) for direct carrier shows that 23 percent of the annual comparison with rainfall intensity. On the suspended-sediment discharge occurred dur rate-of-runoff graph a smooth curve was used ing 1 day, 58 percent during the 10 days of between the computed plots, but because of greatest discharge, and 78 percent during the the necessity of computing numerous values 38 days of greatest discharge. Thus almost for definition, a graph of average rainfall in all the sediment discharge of these undis tensity was used. The rainfall intensities turbed forested watersheds occurs during the changed rather suddenly, and a good average relatively few days of freshet activity. value could be obtained between major breaks A FRESHET PERIOD of the mass-rainfall curve. These average values were plotted as straight lines for the Because most of the sediment discharge periods they represent. If a period of time occurs during freshet periods, it is appro is considered, rate of runoff and rainfall in priate to study one such interval. The ab tensity become inches of depth on the drain sence of clear definition of the variations of age area, and therefore, the area under a sediment concentration for freshet periods segment of either graph represents a volume. precludes a comprehensive comparison of Because both are plotted on the same scale, the drainage basins. The period January 7- the runoff- storage budget can be approximated 13, 1959, was selected for a study of a freshet for any period of time by using the lower half in the Deer Creek basin. Definition of the of figure 5. The amount represented by the suspended-sediment concentration for the pe area between the two graphs above the rate- riod was fair, and data on rainfall and runoff of-runoff graph is stored or lost to the at were available. Data on rainfall intensity, mosphere, and the amount represented by the rate of runoff, suspended-sediment concen area between the two graphs below the rate- tration, suspended-sediment discharge, and of-runoff graphs is taken from storage. If a water discharge for the above period are period is chosen between times when surface presented in graphic form in figure 5. For runoff is depleted, the amount of water con general comparison with the hydrologic rela tributed to or taken from storage can be ap tionships of other freshet periods for all proximated for a particular period of time. three basins, all quantities are plotted on a It must be assumed that recorded rainfall per unit area basis. Water discharge is equals actual rainfall and that average rain plotted in cubic feet per second per square fall intensities approximate instantaneous mile in the upper graph for better compari values. The daily rainfall for January 7 13 son with concentration and suspended-sedi was computed by accumulating the products ment discharge. The suspended-sediment of the average rainfall intensity and the 12 SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON 60 25 50 40 20 Suspended-sediment load 15 30 ^ DEER CREEK 10 i 20 10 UJ X^ X o z J ,-n R^L. ; 20 40 u_ O o: ^ 15 30 FLYNN CREEK 20 o i UJ _ a: 5 ^ 10 Q. I N*; S| ^ 0 I^a_ I 20 40 15 30 NEEDLE BRANCH 10 20 X A x\ ^ X?3 ^^1 X^ ^ 10 I 1 OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT Figure 4. Distribution by month for precipitation, runoff, and suspended-sediment yield for 1960 water year. RAINFALL AND RUNOFF, WATER DISCHARGE, IN CUBIC FEET PER IN INCHES PER HOUR SECOND PER SQUARE MILE i\j 8888 CONCENTRATION, IN PARTS PER MILLION IN) O1 8 8 SUSPENDED-SEDIMENT DISCHARGE, IN POUNDS PER HOUR PER SQUARE MILE SI 1N3WKHS TVIAIVH 14 SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON period of time in hours. The values obtained FLOW AND CONCENTRATION DURATION compared closely with values taken directly from the mass-rainfall graphs, and thus in For many water uses, it is desirable to dicate that no great error was introduced. know what percentage of time during a year Losses by evaporation and transpiration can various magnitudes of daily mean flow and be neglected for the purposes of this study suspended-sediment concentration will be ex because these losses are small for freshet ceeded. These values can be predicted with periods of short duration during the winter fair accuracy by the use of the frequency months. duration curves based on the data for the first 2 years of record (fig. 6). Inasmuch as Computation by the procedures described long-term records at nearby Newport, Or eg., above shows that the total rainfall for the (12 miles northwest of the study area) indi January 7 13 period was 10.46 inches; the cate that rainfall during these years was runoff was 7.64 inches; and the remaining slightly higher than normal, the rainfall in 2.82 inches was stored in surface depres these basins was also probably higher than sions or as soil moisture. Thus a volume of normal. Because the flows and concentra water equaling 73 percent of the rainfall ran tions are assumed to have been higher than off before midnight on January 13. At this normal also, the values predicted for a nor time, almost 21 hours after the last shower mal year by these curves should be slightly of the freshet period, the discharge of Deer high. An example of a possible use of these Creek was still 20.6 cfs (cubic feet per sec curves would be to find what percentage of ond). This discharge decreased at an almost time the flow exceeds a known value at which constant rate to 13.1 cfs at 7:00 p.m. on Jan salmon can move upstreamto spawning beds. uary 15, when the next shower began. If the Assume that this value is 6.5 cfs for Flynn rate of decrease in discharge is assumed Creek. Use the flow duration curve for Flynn constant, after only about 3|- days after mid Creek to find where 6.5 cfs on the ordinate night on January 13, the discharge would fall intersects the curve and, by vertical projec to 5.8 cfs, the base-discharge at the begin tion to the abscissa, read 22. This figure is ning of the January 7 13 period. If all sur the percentage of time that a daily mean flow face runoff had ceased by midnight January of 6.5 cfs can be expected to be equalled or 13, the 2.82 inches of water stored during the exceeded at the Flynn Creek gage. It might period would be depleted in less than 4 days be desirable to know for hydrologic or aquatic even if evaporation and transpiration losses studies what value of suspended-sediment were ignored. The above analysis indicates concentration for Flynn Creek will be ex that a volume of water equaling the rainfall ceeded 50 percent of the time. To find this for the period made its way to the surface value, project the intersection of the 50-per water courses and left the basin in a short cent line with the concentration duration period of time; little was left to sustain flow curve for Flynn Creek horizontally to the during the late summer months. If the aqui ordinate, and read 2+ ppm (parts per million) fer was not saturated before this freshet pe the daily mean concentration that will be riod, a low recharge rate and a low specific equalled or exceeded 50 percent of the time. yield for the Burpee Formation in this vicin The relationships given by these curves ity are indicated. should not change greatly until the parame ters are changed when logging operations The volume of water discharge (in cubic begin. feet per second-hours per square mile) for any period of time (in hours) is represented WATER TEMPERATURE by the area under the water-discharge graph in the upper half of figure 5. This amount of The variation between the maximum and water was available for flu vial-sediment minimum water temperatures for the three transport for that period. The area under streams during the 1959 and 1960 water years the sediment discharge graph for the same was only 22°F, the maximum was 59°F, and period of time represents the suspended- the minimum was 37°F. The maximums for sediment load (in pounds per square mile) the three streams were identical at 59°F, and that was transported during the period. the minimums ranged from 37°F for Needle FLUVIAL SEDIMENT 15 1000 100 L\ Vv 10 1.0 100 \ \ 10 Nv 1.0 x 0.1 0.01 0.05 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99.5 99.9 99.99 PERCENT OF TIME STEAMFLOW OR CONCENTRATION WAS EQUAL TO OR GREATER THAN THE INDICATED VALUE Figure 6. Streamflow (bottom) and suspended-sediment concentration duration (top) curves for the streams (based on records for 1959 and 1960 water years). 16 SEDIMENTATION IN THREE SMALL FORESTED DRAINAGE BASINS IN THE ALSEA RIVER BASIN, OREGON Branch, the smallest stream, to 40°F for Branch basin and nearly lj times that of the Deer Creek, the largest stream. These Flynn Creek basin. streams are the greatest distance apart and have the greatest difference in average alti A study of the January 7-13, 1959, freshet tude. Table 3 gives a summary of average period in the Deer Creek basin showed that monthly maximum and minimum water tem probably only a small part of the precipita peratures. tion during freshet periods is stored as ground water. The study showed that a vol The differences given above for streams ume of water equal to the rainfall for the pe indicate that the water temperatures of these riod left the basin in less than 4 days. streams vary little from stream to stream and from time to time. The effect of water Water temperature during the 1959 and temperature therefore can be disregarded 1960 water years variedonly 22°F. The max when comparing sediment yields from these imum variation between streams at any one small forested basins during the prelogging time was only about 3°F. period because the small differences shown for the basins would have little effect on On the basis of records for the first 2 flu vial-sediment transport (U.S. Inter-Agency years of study, the Flynn Creek basin was a Committee on Water Resources, 1957). The wise choice as the control or calibration ba turbulence in these streams is more than sin. This drainage most nearly represents sufficient to hold in suspension silt and clay the average of the hydrologic conditions of particles which would otherwise be most af the three study basins. fected by temperature differences. LITERATURE CITED SUMMARY Chapman, D. W., Corliss, J. F., Phillips, R.W., The rainfall, runoff, and sediment yield of and Demory, R. L., 1961, Alsea watershed the three basins are seasonal. A large pro study: Oregon Agr. Exp. Sta. Misc. Paper portion of the rainfall and runoff occur during 110, 52 p., Corvallis. the freshets of the October to May period. Court, Arnold, 1960, Reliability of hourly pre Almost all of the sediment discharge occurs cipitation data: Jour. Geophys. Research, during the relatively few days of freshet ac v. 65, no. 12, p. 4017-4024. tivity. As much as one-fourth of the annual Mead, D. W., 1950, Hydrology: New York and sediment load may occur in 1 day, and over London, McGraw-Hill Book Co. p. 195-208. one-half may occur in the 10 days of greatest U.S. Inter-Agency Committee on Water Re discharge. sources, Subcommittee on Sedimentation 1957, Some fundamentals of particle size For the 2 years of record, the annual pre analysis: Rept. 12, p. 24. cipitation, runoff, and suspended-sediment Vokes, H. E., Norbisrath, H., and Snavely, P. yield for each of the three forested drainage D., Jr., 1949, Geology of the Newport- basins did not vary greatly. However, the Waldport area, Lincoln County, Oregon: suspended-sediment yield of the Deer Creek U.S. Geol..Survey Oil and Gas Inv. Prelim. basin was nearly 2 times that of the Needle Map OM-88. U. S. GOVERNMENT PRINTING OFFICE : 1964 O - 742-302