Channel Changes of the Gila River in Safford Valley, Arizona 1846-1970

GEOLOGICAL SURVEY PROFESSIONAL PAPER 655-G

Channel Changes of the Gila River in Safford Valley, Arizona 1846-1970

By D. E. BURKHAM

GILA RIVER PHREATOPHYTE PROJECT

GEOLOGICAL SURVEY PROFESSIONAL PAPER 655-G

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972 UNITED STATES DEPARTMENT OF THE INTERIOR

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 2401-2065 CONTENTS

Page Abstract.______Gl Flood-plain reconstruction, 1918-70_-______-__--_--___ G12 Introduction.___--_____-----_-______-_-______-_ 1 Sediment inflow.______--_-______---____---__ 12 Development process______13 Characteristics of the study reach___-_-______---___ 3 Stream-channel development ______13 Data sources. ______4 Alluvial-fan development-______14 Gila River before 1875__------_------_-----_ 4 Rates of sediment accretion.______15 Gila River from 1875 to 1970 ____-__--___.-_-_-_-__-_ 5 Influence of wide flood channel and low-flow Stream-channel widening, 1905-17-______7 rates.___-_-___--___------__------_- 19 Influence of stream-channel treatment practices Factors and mechanics involved._-_--_____-__-__- 7 and flood-plain vegetation.______19 Major floods and grazing-______7 Influence of flood-plain cultivation.______21 Flood-plain vegetation and cultivation ______Changes in stream-channel length and slope.______21 Hydrologic implications.______22 Effects of stream-channel widening on stream Summary. ______22 gradients.______12 References cited.______24

ILLUSTRATIONS

[Plates in pocket] PLATE 1. Map showing extent of study reach and location of cross sections, alluvial fans, and photograph sites. 2. Maps and aerial photographs showing channel changes of the Gila River near Pima. 3. Graphs showing annual streamflow volumes, annual floods, and average stream-channel width, Gila River in Safford Valley. 4. Photographs showing development of the alluvial fan at the mouth of a tributary to the Gila River near Calva. 5. Photographs and profiles showing horizontal and vertical changes in the Gila River near Fort Thomas. Page FIGURE 1. Map showing area of report____---______-..______-___-_------___-_-_-_-____.--- G2 2-4. Photographs showing the Gila River 2. Near Fort Thomas in the 1880's____--______.______._.__-_-_-_---_- 6 3. In 1916 __---_--____-______._.____._-______--__--_-______-______- 8 4. In 1909 and 1969------_- _-_-._---__._..______-_-___.-__-__._. ._._- - - 10 5. Diagrams showing historical changes in the bottom land in subreaches A, B, and D__-_-_--____-___-_-____-__ 11 6. Photographs showing saltcedar encroachment along the Gila River between 1932 and 1964______-__--_-___ 14 7. Graph showing net average change in the altitude of the bottom land, 1935-70, at cross sections in subreaches A and B of the Gila River.__-______._.______-______------_-___--_-___-__---_ 18 8. Photographs showing erosion controls established in the 1930's by the U.S. Soil Conservation Service______20 9. Graphs showing sinuosity of the stream channel of the Gila River in Safford Valley, 1875-1970.______21

TABLES

Page TABLE 1. Characteristics of subreaches A, B, and D of the Gila River, Safford Valley------G5 2. Average change in the altitude of the bottom land at cross sections along the Gila River, Safford Valley..--.------15 3. Estimated volume of sediment accretion for subreaches in Safford Valley, 1935-70.______-______---_------.-- 19

in

GILA RIVER PHREATOPHYTE PROJECT

CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970

Br D. E. BURKHAM

ABSTRACT INTRODUCTION The stream channel of the Gila River in Safford Valley, Flood plains and streams are of prime interest to Ariz., changed significantly from 1846 to 1970. The stream channel was fairly stable and narrow from 1846 to 1904 and inhabitants of arid and semiarid regions in the United meandered through a flood plain covered with willow, cotton- States because they offer, respectively, fertile level land wood, and mesquite. The average width of the stream channel and a water supply. Traditionally, development in these was less than 150 feet in 1875 and less than 300 feet in 1903. regions has centered along the flood plains, and changes During 1905-17 major destruction of the flood plain took place, in the flood plains and stream channels often result in and the average stream-channel width increased to about 2,000 feet. Reconstruction of the flood plain was underway during loss of life, property, and water supply. 1918-70; the stream channel narrowed, and the average width The natural processes involved when changes occur was less than 200 feet in 1964. The flood plain became densely in flood plains and stream channels generally are com­ covered with saltcedar during 1918-70. Minor widening of the plex and varied. Furthermore, data are seldom avail­ stream channel occurred in 1965 and in 1967, and the average able to determine the influence of each of the many width of the channel was about 400 feet in 1968. The major widening of the stream channel during 1905-17 variables involved; the Gila Kiver in the Safford Valley was caused mainly by large floods, which carried small sedi­ in southeastern Arizona (fig. 1) is an exception in that ment loads. The period of flood-plain reconstruction was charac­ large quantities of historical data pertinent to the terized by floods having relatively low peak discharges and large changes are available. sediment concentrations. Primarily, the large sediment loads The present report gives a description of the natural carried by these floods were the result of the erosion of alluvial deposits in the low-altitude drainage basins tributary to the flow-regime~ modification of the flood *-plain and strer.m Gila River. The small floods that originated in these tributary channel of the Gila Kiver in Safford Valley from basins spread over the wide channel of the Gila River, lost 1846 to 1970. The spatial and temporal changes in kinetic energy, and sediment deposition resulted. During 1935- stream-channel width, length, and sinuosity and in the 70 the average rates of sediment accretion along the bottom areal extent of natural vegetation and cultivated land land in two reaches of the river were 0.03 and 0.08 foot per year. The dense cover of saltcedar and the cultivation of the in the flood plain are described. The factors and condi­ bottom land may have been significant contributing factors to tions that influence these changes also are described. the rapid reconstruction of the flood plain. Finally, the hydrologic implications that pertain to The temporal distribution of flow and the average annual aggradation and degradation in alluvial valleys, nor­ flow about 260,000 acre-feet at the head of Safford Valley mal flows and frequencies of floods, hydraulics of flow, during 1920-64 probably were about the same as those during 1800-1904. Based on this premise, the statement can be made and the use of water by flood-plain vegetation are dis­ that the flood of November 1905, which had a peak flow rate cussed. The present report: is the result of studies of of about 150.000 cubic feet per second, probably was the largest environmental factors that affect evapotranspiration in flood in more than 170 years. The preceding statements are the Gila Kiver Phreatophyte Project area (Culler and based on the fact that the channel width is governed mainly others, 1970). The studies are under the direct super­ by rates of streamflow and that, even with the help of man, it took 50 years for the flood-plain development to approach vision of R. C. Culler, project chief, and the report was that prior to 1905. prepared under the general supervision of H. M.

Gl G2 GILA RIVER PHREATOPHYTE PROJECT

APACHE MOHAVE

N A V A J O

MARICOP A PHOENIX

GRAHAM

J JSANTA CRUZ J V

FIGURE 1. Area of report. CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G3 cock, district chief of the Water Eesources Division of is eroded easily at higher flows; the riffles are fairly the U.S. Geological Survey in Arizona. stable gravel bars. The flood plain is densely covered The cooperation of the many people who supplied with saltcedar, willow, and mesquite, except in arets historical data vital to this investigation is gratefully where the vegetation has been removed by man. acknowledged. Special thanks are due B. H. Eupkey, The depth to ground water in the alluvium along J. H. Jones, Jr., and Harold Johnson of the U.S. Bu­ the Gila Eiver is less than about 20 feet below the land reau of Indian Affairs; D. M. Marshall of the U.S. surface, and during flows of long duration, the water Department of Justice; J. J. Turner of the U.S. Soil table intercepts the streambed. About 69,000 acres of Conservation Service; and J. A. Lentz of the Phelps land is under cultivation in the Gila Eiver basin above Dodge Corp. for assistance in furnishing data. The au­ Coolidge Dam; about 33,000 acres of the cultivated thor appreciates the help of E. W. Scott of the U.S. land is in Safford Valley (Barr, 1954, p. 14-17). Th?, Bureau of Land Management, who located the 1937 principal crops are cotton and alfalfa. Part of the irri­ U.S. Soil Conservation Service cross sections in the gation water is diverted from the Gila Eiver, and the field; Thomas Macldock, Sr., furnished profile data for rest is obtained from wells. the 19-il resurveys of the cross sections established by Climatically, the semiarid Safford Valley is in th°. the Soil Conservation Service. Sonoran Border zone (Thomas, 1962, p. 13). The ten- perature extremes recorded at Safford, which is at CHARACTERISTICS OF THE STUDY REACH an altitude of 2,900 feet above mean sea level in ths The Safford Valley, which extends from the conflu­ upstream end of the valley, are 7° and 114° F (Sellers, ence of the Gila Eiver and Bonita Creek to Cooliclge 1960). The annual precipitation at Safford ranges from Dam, trends northwestward between the Gila Moun­ 3.0 to 17.5 inches and averages about 8.7 inches (Seller^ tains on the northeast and the Pinaleno and Santa Te­ 1960). resa Mountains on the southwest (fig. 1). The valley An area of about 7,900 square miles contributes run­ is about 12 miles wide and 75 miles long and is filled off to the Gila Eiver at the head of Safford Valley. TH with more than 1,000 feet of silt, sand, and gravel. drainage basin ranges in altitude from about 3,000 to The deposits have been classified informally as terrace 11,000 feet above mean sea level and extends eastward gravel and alluvium, deformed conglomerate or gravel, into the mountains in New Mexico. and basin fill (Davidson, 1961, p. 151). Troughs incised The area tributary to the Gila Eiver adjacent to tH in the basin fill are from 2,000 to 10,000 feet wide and Safford Valley contains about 3,570 square miles ard are filled with as much as 100 feet of terrace gravel and is drained by many ephemeral streams. The tributary alluvium. The Gila Eiver enters the valley a few miles basins typically are long and narrow, and the drainage northeast of Safford and drains the area. areas are from less than 1 square mile to about 2,200 The study reach is about 45 miles long and extends square miles. The altitudes of the basins range frcm from the confluence of the Gila and San Simon Eivers about 2,500 to 11,000 feet above mean sea level. In to Calva, Ariz. (pi. 1). The present report is concerned general, the slopes of streams tributary to the stuc'y with the part of the alluvial area along the Gila Eiver reach downstream from Fort Thomas are steep to tl Q, that underwent major changes from 1846 to 1970; in bottom land; in the bottom land the slopes of tH general, the area is included in the 1914-15 flood chan­ streams abruptly decrease. The slopes of most of tl °, nel (pi. 1) as described by Olmstead (1919) and cor­ tributaries upstream from Fort Thomas are relatively responds approximately to bottom land as defined by gentle to the bottom land. Gatewood, Eobinson, Colby, Hem, and Halpenny (1950, Streamflow in the Gila Eiver is classified as winter p. 10). As herein used, the term "bottom land" refers flow and as summer flow. Winter flow takes place fro^n to the area in the 1914-15 flood channel, and the term November through June, and summer flow takes place "flood plain" refers to the part of the bottom land not from July through October. occupied by the stream channel. The term "stream chan­ Winter flow is mainly from precipitation durirg nel" refers to the area that is generally void of vege­ frontal storms, snowmelt, or outflow from ground-water tation and that has a definite bed in which flowing storage and often is a combination of the three. The flow water is confined by banks. rate may be fairly constant for several days, and tlx°- The bottom-land area of the Gila Eiver is from 1,000 sediment concentrations are low. The causes of major to 5,000 feet wide, and the present (1970) stream chan­ winter floods are widespread heavy rainfall of long nel is from 60 to 500 feet wide. The stream channel has duration, warm weather after a large snow accumula­ an average slope of about 0.002 and is a pool-and-riflle tion, or widespread rainfall on snow. type. During flows of less than about 500 cfs (cubic feet The main source of summer streamflow is hxnl per second), the pools generally are full of sand, which thunderstorms, which are especially prevalent in July G4 GILA RIVER PHREATOPHYTE PROJECT and August. Individual summer thunderstorms char­ channel meander, and vegetation along the stream. The acteristically produce high unit rates and unit volumes cadastral surveys extended upstream from the east of flow from small watersheds, but only rarely do they boundary of the San Carlos Indian Reservation to above produce high unit rates or unit volumes of flow from the confluence of the Gila and San Simon Rivers. large watersheds. The crest of a flood from a thunder­ The basic data for 1903 through 1917 are mainly from storm typically is very sharp near the site of the four sources a soil survey made by Lapham. s nd Neill thunderstorm, but it may become rounded or flattened (1904), photographs and topographic maps furnished downstream because of the dampening effects of tem­ by the U.S. Bureau of Indian Affairs (data in files of porary storage in the conveyance channels. During U.S. Bur. Indian Affairs, Phoenix, Ariz., and YTashing- September and October, occasional frontal activity ton, D.C.), Senate Document 436 (Olmstead, 1C19), and causes precipitation that produces widespread runoff. U.S. Geological Survey Water-Supply Paper 450-A The combined runoff from the frontal storms and con­ (Schwennesen, 1921). The soil-survey report ccvers a 2- current local thunderstorms is the most common cause to 6-mile-wide tract that extends from Solomon to Fort of large flows of the summer season. Sediment concen­ Thomas (pi. 1) and includes general descriptions of the trations generally are high during summer flows. Gila River and the vegetation along the bottom land in The annual surface-water inflow for the period 1903 (Lapham and Neill, 1904). The topographic maps 1938-61 averaged about 255,000 acre-feet for the reach of Safford Valley were compiled in 1914-15, and the that extends from the head of Safford Valley to Calva photographs showing views along the Gila River in the (Burkham, 1970, table 4). The inflow includes 230,000 San Carlos Indian Reservation were taken during acre-feet for the Gila River at the head of Safford Val­ 1909-17 (data in files of U.S. Bur. of Indian Affairs, ley, 11,000 acre-feet for the San Simon River, and 14,000 Phoenix, Ariz., and Washington, D.C.). The topo­ acre-feet for ungaged tributaries. About 70 percent of graphic maps, which are at a scale of 1:12,010, show the flow in the Gila River at the head of Safford Valley altitude contours at 5-foot intervals, both banks of the occurs in the winter, whereas the flows in the San Simon Gila River, irrigation canals, diversion points, irrigated River and in the ungaged tributaries occur mainly in land, and land that could be supplied with water from the summer. the ditches in 1914-15. The study reach is divided, in downstream order, Data for 1918-70 were obtained mainly from aerial into four subreaches (pi. 1) A, from the confluence of photographs, topographic maps, and cross-sectional the San Simon and Gila Rivers to the bridge at Pima; profiles. The aerial photographs were taken in 1935, B, from the bridge at Pima to the east boundary of the 1942, 1947, 1954, 1957, 1964, 1966, 1967, and 19^8. Data San Carlos Indian Reservation; C, from the east bound­ were taken from two sets of topographic maps One set ary of the San Carlos Indian Reservation to the bridge was prepared by the U.S. Soil Conservation Service on U.S. Highway 70 near Bylas; and D, from the bridge in 1935 at a scale of 1: 7,200; the contours are at 2-foot on U.S. Highway 70 near Bylas to the railroad bridge intervals. The other set was prepared by the U.S. Geo­ that spans the Gila River near Calva. Only a small logical Survey in 1960 at a scale of 1: 62,500; the con­ amount of topographic data is available for subreach C. tours are at 40-foot intervals. Cross-sectional profiles are and data for this subreach are not included in the tables available for many sites along the study reach; most in this report. Subreach D is the same as subreach 1 in of the cross sections were established by the U.S. Soil the Gila River Phreatophyte Project area (Culler and Conservation Service in 1937 and by the Phelps Dodge others, 1970). Spatial and temporal changes in the flood Corp. in 1943. The cross sections used in the, present plain and stream channel are described for each sub- report (pi. 1) were resurveyed by the author during reach and for the entire study reach for the periods for 1965-70. which data are available. GILA RIVER BEFORE 1875

DATA SOURCES Francisco Vasquez de Coronado, in ques*: of the "Seven Cities of Gold," crossed the Gila River near Diaries and journals written from 1846 to 1874 con­ the present town of Geronimo in 1540. According to tain the first known descriptions of the Gila River in Calvin (1946, p. 135), Coronado described the Gila Safford Valley. A few of the diaries and journals, River as " 'a deep and reedy stream'." The nert known written by people in transit through the valley, include reference to the Gila River is by Emory (1848, p. 67), descriptions of the vegetation along the travel routes. a U.S. Army topographical engineer, who described the Cadastral surveys (data in files of U.S. Bur. Land Gila River near Bonita Creek as having a croes section Management, Phoenix, Ariz.) made during 1875-94 give of "about 70 feet by 4" on October 27, 1846. Emory detailed descriptions of stream-channel width, stream- (1848, p. 68) found cottonwood and willow clcse to the CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G5

Gila River near its confluence with the San Simon In summary, before 1875 the Gila River probably River, and farther downstream away from the Gila he was less than 150 feet wide and 10 feet deep at bankfull noted that "the dust was knee deep in the rear of our stage. The river meandered through a flood plain cov­ trail; the soil appeared good, but, for whole acres, not ered with willow, cottonwood, and mesquite. the sign of vegetation was to be seen. Grass was at long intervals, and, when found, burned to cinder." GILA RIVER FROM 1875 TO 1970 Johnston, who traveled in the same military expedi­ The channel changes of the Gila River in Safford tion as Emory, substantiates Emory's description of Valley may be grouped into three distinct periods the vegetation. Johnston (in Emory, 1848, p. 588) re­ 1846-1904,1905-17, and 1918-70. The size of the stream ported that channel and the vegetation in the flood plain apparently the grass along the edge of the water on the river grows in a were about the same in 1875 as they were during the pre­ thin stripe very luxuriantly; there is usually a thicket of wil­ vious few decades. In 1875 the average width of the lows, about 10 yards deep, along the borders of the stream; stream channel, determined from maps made during then in the bottom, which is subject to overflow, cottonwoods the cadastral surveys, was about 150 feet for subreaches grow of two and three feet in diameter; this strip is usually 200 or 300 yards wide. A and B (table 1) ; however, the width ranged from about 70 to 220 feet. The average stream-channel width Johnston implies that the banks of the Gila River in the was obtained by dividing the plan area of the channel Safford Valley were not high and related that the party by the length measured along the axis of the channel. crossed the Gila River several times without much The sinuosity of the stream channel in subreach A was difficulty. about 1.20.(table 1). Sinuosity is the ratio between On October 28, 1846, Dr. Griffin (1953, p. 27), en stream-channel length and valley length, in which val­ route to California, wrote that the Gila River near ley length is taken as the flood-channel length in Mount Graham was "some 60 yards broad and very 1914-15. rapid and quite deep." Evidently, the river was at flood TABLE 1. Characteristics of subreaches A, B, and D of the Gila stage at this time and had received runoff from tribu­ River, Safford Valley taries as a result of storms on the previous day (Clarke, [Location and extent of subreaches shown on pi. l] 1966, p. 94). In 1849 the Gila River probably was much the same History of the bottom Stream channel landi as it was in 1846. Chamberlin (1945, p. 164) described Area the bottom land near the base of Mount Graham on Year Vege­ Culti­ eroded tated vated Stream beyond Total Length Average Sinuosity July 15, 1849, as follows: "The bank of the river is so area channel the area width bottom beset with underbrush and drift that we cannot get a land supply of water without extreme difficulty." He reported Acres Acres Acres Miles Feet Foot/foot that the sand and dust along the trail in the valley were Subreach A very deep. 1875. 2,760 0 220 70 290 15.34 160 1.20 1903. 2,540 0 370 71 441 14.30 260 1.12 According to Chapin (copies of correspondence be­ 1914. 0 0 0 2,980 12.74 1,930 1.00 1935. 2,050 253 673 163 836 13.82 500 1.08 tween Chapin, Commander of Camp Goodwin in 1867, 1957. 1,440 1,220 320 240 560 14.42 320 1.13 1966. 870 1,320 790 280 1,070 12.84 690 1.01 and his superiors in files of U.S. Bur. Land Manage­ 1967. 790 1,180 1,000 160 1,160 12.90 740 1.01 ment, Phoenix, Ariz.), in 1867 the Gila River near 1968- 970 1,200 810 20 830 12.80 530 1.01 Geronimo was "sandy under smooth stretches of water Subreach B 1875- 4,550 0 380 0 380 222.90 137 while slight rapids occur at intervals of one or two 1894. 3795 0 M50 0 3450 37.44 3500 1.12 1903. »1,740 0 3448 0 3448 3 13. a 3270 1.16 miles no rocks in place are found in the river, the chan­ 1914. 0 0 4,900 0 4,900 20.2 2,000 1.00 1935. 3,340 330 1,230 220 1,450 22.6 530 1.12 nel of water being 50 feet broad with an average depth 1942. 3,420 470 1,000 290 1,290 23.1 460 1.14 1957- 3,500 1,090 310 280 590 24.1 200 1.19 of 2 feet," He also stated: "The mesquite trees are 1966. 2,290 2,070 540 270 810 22.9 290 1.13 1967. 2,390 1,170 1,340 240 1,580 23.0 570 1.13 found in the low grounds, and the cottonwoods upon 1968- 3,040 1,030 830 70 900 22.8 330 1.13 the banks of the Gila." Weech (1931, p..23) related that Subreach D the Gila River "was fringed on both sides with cotton- 1914. 827 503 503 6.09 907 1.09 1935. 1,010 320 320 6.29 420 1.12 woods and willow trees" in 1867. On crossing the river 1942. 1,100 225 225 6.56 280 1.17 1947. 1,210 70 70 6.91 80 1.24 at a point near Fort Thomas, Weech stated: "The river 1954. 1,270 59 59 7.05 70 1.26 1964. 1,260 70 70 7.32 80 1.31 was swollen by the melting snow and to cross it we had 1967. 122 122 150 1.22 to swim our horses. The Gila then was a stream with 1968. 238 238 290 1.22 well defined banks and sloping graveled bottom. It 1 The term "bottom land" refers to the area in the 1914-15 flood channel (pi. 1). 2 Stream length was not measured in 1875; the length was "sketched in" by the was about four to six rods wide." field party. 3 Map covered only part of reach.

450-345 O - 72 - 2 G6 GILA RIVER PHREATOPHYTE PROJECT

The average width of the stream channel probably neers in files of U.S. Bur. Land Management, Phoenix, increased from 1875 to 1894 and decreased from 1894 to Ariz.), and 1903 (Lapham and Neill, 1904). 1903. The average width for the section of the river Widening of the Gila River streajn channel began in from Fort Thomas to the boundary of the San Carlos 1905 and continued intermittently through 1917. The Indian Reservation an area that includes about a third average width of stream channel in subreaches A and of subreach B was about 140 feet in 1875, 500 feet in B increased from about 260 feet in 1903 to nearly 2,000 1894, and 260 feet in 1903. feet in 1914-15 (table 1; pi. 2). In 1914 the average The vegetation along the Gila River from 1875 to stream-channel width in subreach C was about '1,600 feet and was about 900 feet in subreach D. Although it 1904 probably was about the same as it was in previous is known that the average width of stream channel in years (fig. 2). The banks of the Gila River were densely the study reach continued to increase during 1915-17 covered with willow, cottonwood, and mesquite in 1875, (Olmstead, 1919, p. 9), the amount of increase is un­ 1883, 1894 (vegetation notes made by cadastral engi­ known.

FIGURE 2. Gila River near Fort Thomas in the 1880's. A, Cavalry camp on the flood plain in 1881. B, Stream channel in 1885. The trees in the two photographs are mainly willow and cottonwood. Photographs1 furnished by the Arizona Pioneers' Historical Society. CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G7

Most of the dense stands of willow and cottonwood produced stresses greater than the banks could with­ that grew along the Gila River prior to 1905 were de­ stand. The effects of major floods and grazing and of stroyed during 1905-17 (fig. 3). The stream channel flood-plain vegetation and cultivation are discussed was relatively barren in 1909 (fig. 4); therefore, most of below. the destruction probably occurred during 1905-9. MAJOR FLOODS AND GRAZING Redevelopment of the flood plain in the Safford Val­ Major floods were a primary cause of the widening ley occurred during 1918-70; the stream channel be­ of the stream channel of the Gila River; the widening came narrower, the meander of the stream channel be­ events in 1891, 1905-17, 1941, and 1965-67 were coinci­ came progressively greater, and the vegetative cover in dent with major floods (pi. 3; Burkham, 1970, p. 20-30). the flood plain became more dense. The rate of redevel­ Most of the floods originated in the mountainous part opment varied, and there were definite breaks in 1941 of the headwaters area as a result of frontal storms, and during 1965-67, when minor stream-channel widen­ which moved into the area from the southern Pacific ing occurred. The average stream-channel width in sub- Ocean. Except for the flood of August 1967, the major reaches A and B had decreased to about 500 feet by 1935; floods occurred from September through February. The in subreach D the width had decreased to about 420 feet peak discharges ranged from about 30,000 to 150,000 (table 1). By 1964, the average stream-channel width in cfs. Eight major floods occurred during 1905-17, which the study reach had decreased to less than 200 feet. Dur­ is the "wettest" period in Safford Valley since the begin­ ing two major floods one in December 1965 and one in ning of record. According to Stockton and Fritts (1968, August 1967 the average width of the stream channel p. 18-20), 1905-17 may have been the wettest period in the study reach increased to about 400 feet. since 1650. The sinuosity of the stream channel in Safford Valley Major floodflows exert great force on the stream- increased from about 1.0 in 1918 to about 1.1 in 1957 channel banks and on objects in the main-flow path and was about 1.2 in 1964. During the December 1965 and cause channels to enlarge. During a major flood, the and August 1967 floods, however, the sinuosity decreased main-flow path generally is straight down the valley, to about 1.1. and, in many places, the banks of the meandering Saltcedar became the dominant tree type in the bot­ stream channel constitute objects in the main-flow path. tom land during 1920-30. The saltcedar, a plant brought While the meander pattern is intact, part of the flow is into Texas and New Mexico from the Mediterranean directed along the meandering stream, and large turbu­ region, apparently was introduced into the Safford Val­ lence is developed along the streambaiiks. Eventually, ley in the second decade of the 20th century (Gatewood as a result of the stresses produced by the turbulent and others, 1950, p. 11). Conditions for the growth of forces along the streambanks and around other station­ the saltcedar were ideal, and it spread rapidly along the ary objects, changes take place stream-channel banks flood plain. The saltcedar, which consumes large erode, trees are uprooted and flushed downstream, pro­ amounts of water, reached its maximum areal extent tective grasses are removed, alluvial fans at the mouths in the study reach during 1945-55; after 1955, farmers of the tributaries are destroyed, and dikes protecting began to clear large areas of saltcedar for the cultiva­ cropland are breached. The result of these changes is tion of crops (fig. 5). additional debris in the flowing water. Most, but apparently not all, of the stream-channel STREAM-CHANNEL WIDENING, 1905-17 widening during 1905-17 occurred in 1905 and 1906. As indicated in a foregoing section, widening of the According to Olmstead (1919, p. 9) : "From October, stream channel of the Gila River in Safford Valley oc­ 1915, to September, 1916, by actual plane table sur­ curred during 1905-17. The following discussion of the vey, * * *, there was washed away by the Gila River, 1,155 acres in Safford Valley and 990 acres in the San stream-channel widening is based primarily on compar­ Carlos Reservation, or 2,145 acres in all." Olmstead isons between the different topographic maps, on analy­ (1919, p. 10) further stated that the flood in October sis of streamflow data, on comparisons between the maps 1916 washed out "perhaps some 400 acres more along and the photographs that were taken before and after this Safford Valley reach." widening, and on observations by the author during the The high flows during 1905-17 probably carried rela­ major floods of December 1965 and August 1967. tively small sediment loads at the head of Safford Val­ ley, which may have been a significant factor in causing FACTORS AND MECHANICS INVOLVED the widening of the stream channel of the Gila River. The widening of the stream channel occurred because Studies based on the meager data available prior to the forces applied along the stream-channel boundary 1905 (U.S. Army Corps Engineers, 1914, p. 30) and on G8 GILA RIVER PHREATOPHYTE PROJECT

^. r?^ --.

x^ B

FIGURE 3. Gila River in 1916. A, Looking upstream at the bridge at Pima ; the drift in the foreground probably is cottonwood. B, Looking downstream at Black Point near Bylas; the trees in the background across the river probably are cottonwood. C, Erosion on the left bank of the river at Bylas; the alluvial fan on the right side of the river at the mouth of Salt Creek (not shown in photo-

data for 1965-70 (U.S. Geol. Survey, issued annually) the lack of transportable material. Large flows having indicate that the sediment concentration for a given flow relatively low sediment yields are conducive to erosion. rate in the winter in the Gila River at the head of Grazing apparently did not have a significant influ­ Safford Valley is less than 20 percent of the average ence on the major floods during 1905-17 and, therefore, concentration for the same flow rate in the summer. probably had no effect on the widening of the stream Most of the winter flow originates in mountainous ter­ channel. Large-scale grazing began in about 1872 in the rain, which does not erode easily. The sediment load Gila River drainage (Calvin, 1946, p. 136), and, by does not increase with increasing discharge because of 1890, the area apparently was "overstocked." A few CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G9

graph; see pi. 1) is causing a realinement of the river. D, Gila River near Bylas; debris in the left background is uprooted cottonwood. Photograph A is from Olmstead (1919, pi. 11) ; photographs B, C, and D furnished by the U.S. Bureau of Indian Affairs, Phoenix, Ariz. years later, many of the cattle starved or were shipped areas. If there had been large areas of grass in the flood- to eastern markets (Calvin, 1946, p. 139; Rowalt, 1939, producing area, the floods probably would have been p. 7). Since about 1905, the number of cattle in the area slightly more severe. has been small compared to the number in 1890. The parts of the Gila River drainage that were overstocked FLOOD-PLAIN VEGETATION AND CULTIVATION in 1890 were in the valleys below the shaded mountain Although the trees along the river contributed to the forests and belowT the area that produced most of the stability of the flood plain during small and moderate floodwater; grass was the dominant vegetation in these floods, the trees may have had a minor influence on the

450-345 O - 72 - 3 G10 GILA RIVER PHREATOPHYTE PROJECT

FIGURE 4. Gila River in 1909 and 1969. A, Looking downstream near Geronimo in May 1909. B, Looking downstream near the railroad siding at Calva in 1909. C, Looking downstream near the railroad siding at Calva in 1969 (arrow indicates location of railroad bridge) ; the bottom-land vegetation was eradicated in 1966 to control evapotranspiration. and the photograph in figure 6 shows the same area before eradication. Photographs A and B furnished by the U.S. Bureau of Indian Affairs, Phoenix, Ariz. Photograph C furnished by Mr. R. M. Turner, Tucson, Ariz. CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 Gil

3000 Vegetation Hi

2000 -

+ 1000 -

0 -

Stream channel outside the bottom land

-1000 I T I I I I SUBREACH A 5000 -i

4000 - LLJ cc CJ 3000 - cc < 2000 -

+ 1000 -

0 - Stream channel outside the bottom land

-1000 1 I I I I I T I SUBREACH B 2000 -i Vegetation removed to control evapotranspiration

1000 -

1 I I I I 1 I I I 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 YEAR SUBREACH D

FIGURE 5. Historical changes in the bottom land in subreaches A, B, and D. The increases in channel width are the result of the major floods in 1891, 1905-17, 1941, 1965, and 1967 (pi. 3). Data plotted from table 1. G12 GILA RIVER PHREATOPHYTE PROJECT widening of the stream channel during the major floods The widening of the stream channel of the river de­ of 1905-17. The trees restricted the flow of water onto creased the length of most of the tributary streams and the flood plain and concentrated flow in the stream resulted in an increase in the stream gradients at their channel. The concentrated flow increased stresses along confluence with the Gila River. the stream-channel banks, which may have influenced erosion of the original stream channel. The cotton wood FLOOD-PLAIN RECONSTRUCTION, 1918-70 trees may have contributed to the widening in another The reconstruction of the Gila River flood plain ap­ way. During the major floods, floating debris hung on parently began soon after the major flood of October 14, the trees, which resulted in an increase in turbulence 1916; however, erosion continued in places along the and erosion. Because the trunks of cottoiiwood trees are flood channel through the fourth decade of the 20th very rigid, the forces applied to the trees created torsion century. High flows could take any one of several at the ground. The combination of torsion and erosion paths in the wide flood channel, causing local damage caused the trees to overturn; the trees usually took large to canals, dikes, and cultivated land along the banks chunks of alluvium with them, which left the easily of the flood channel. Generally, however, erosion of the erodible material exposed. The unanchored trees be­ bank in one area made more sediment available for came a part of the floating debris and may have hung on deposition in the flood channel in another area, and the other trees farther downstream, which caused them to rate of reconstruction of the flood plain was rapid. The be uprooted. reconstruction was accomplished almost entirely by the Cultivation of the flood plain probably was not an accretion of sediment. Conditions favoring the rapid important factor in causing the widening of the stream accretion of sediment were a large sediment inflow and channel during 1905-17 because only a small amount of the inability of the Gila River to move the sediment, land was cleared for farming. Lapham and Neill (1904, through the valley. p. 1059) stated that only "a small proportion of the Pecos sand is at present cultivated, mainly because of SEDIMENT INFLOW the difficulty and expense of clearing off the willow, cotton wood, and mesquite, and leveling the land In the third and fourth decades of the 20th century, for irrigation. Small tracts are, however, being the floods in the Gila River in Safford Valley carried cleared * * *." The areal extent of the Pecos sand and large sediment concentrations (Rowralt, 1939, p. 45; the areal extent of the flood plain were about the same Calvin, 1946, p. 135). The large sediment loads origi­ in 1903. nated mainly from the erosion of 'alluvium in the lower The small dams and canals used to divert irrigation altitudes of the watersheds tributary to the Gila River water from the Gila River probably did not influence above Coolidge Dam. The erosion was triggered mainly the stream-channel widening greatly because of their by the major floods of 1905-17, although the lack of pre­ temporary nature. The diversion dams and canals gen­ cipitation and extensive grazing in earlier periods may erally were cheagly built and readily failed during have contributed to the erosion. The high flows in the floods. Gila River drainage during 1905-17 accelerated erosion The author concludes that the large floods having low in the tributaries of the Gila River by increasing the sediment concentrations were the main cause of the gradient of most of the tributaries at their confluence with the Gi'la River and by providing the motive power widening of the stream channel. Flood-plain vegetation, however, may have been a minor contributing factor. necessary to start the erosion. Generally, the areal extent of the channel erosion in EFFECTS OF STREAM-CHANNEL WIDENING ON the steep streams that drain the mountainous terrain STREAM GRADIENTS near the Gila River was small because of the small areal As the stream channel of the Gila River widened, it extent of the easily erodible alluvium that underlies straightened, and the channel length decreased and its these streams (pis. 4, 5). Man's use of the steep water­ gradient increased. Before the floods of 1905-17, the sheds was insignificant. However, the alluvial valleys stream channel was about 20 percent longer than the drained by gently sloping streams apparently were very valley; following the floods, however, the stream channel vulnerable to erosion, and erosion in some of the valleys was only slightly longer than the valley (table 1). Avail­ was severe. able data indicate that the altitude of the stream- The lack of precipitation and the extensive grazing channel floor did not change appreciably during the prior to 1905 may have contributed to the susceptibility periods of major stream-channel widening and flood- of the alluvial valleys to erosion during high flows. The plain reconstruction. Therefore, the straightening of the period 1870-89 was one of the driest periods of compa­ stream channel increased the gradient about 20 percent. rable length since 1650 (Stockton and Fritts, 1968, p. CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G13 20-21), and 1895-1904 was another period having very posit in the field. Nevertheless, the methods are dif­ little precipitation. The years having small amounts of ferent, and examples of each are found in the study precipitation coincided with the years in which large reach. The characteristics of methods 1-4 are described numbers of cattle were brought into the area. The com­ in the section "Stream-Channel Development," and the bination of little precipitation and extensive grazing characteristics of method 5 are described in the section caused a deterioration in the vegetation of the valley, "Alluvial-Fan Development." which may have made the alluvium more susceptible to erosion. STREAM-CHANNEL DEVELOPMENT The San Simon River (pi. 1) is an example of a Low-flow channels that developed'during the floods gently sloping stream that has undergone severe chan­ of 1905-6 and 1915-17 were the beginning of the present nel erosion since 1905. The San Simon River drains an (1970) stream channel. The small channels meandered area of about 2,200 square miles, and its valley covers between sediment islands that were formed during the most of the watershed. Apparently, debris from side floods. The sediment islands were remnants of the. old tributaries had been collecting in the alluvial-filled flood plain and sandbars and dunes that formed in the valley for centuries, and in 1905 it was poorly drained areas of low velocity. At first, the sediment islands were and relatively unstable. In 1903 the San Simon River small, but they increased in size as a result of successive was an insignificant and poorly defined watercourse additions of sediment, mainly at the downstream ends. (Lapham and Neill, 1904, p. 1050). When severe erosion In time, vegetation became established, and the islands began, probably during the major floods of 1905, deep became fairly stable (fig. 6). channels were cut and eventually became large; erosion The development of the islands reduced the width of then spread to the side tributaries. According to Olm- the surrounding channels, and deposition often occurred stead (1919, p. 79), there was 60 miles of eroded channel in one of the channels. One channel generally will carry along the San Simon River in about 1919; by 1960, a larger part of the sediment load than the other channel there was more than 100 miles of gullied channel from (Lindner, 1952); in this instance, the channel that car­ 10 to 40 feet deep (Peterson, Dejulio, and Rupkey, writ­ ries the largest part of the load generally will aggrade ten commun., 1960) and from 20 to 500 feet wide. The until it carries only a small percentage of the gullied channels captured runoff that, prior to the streamflow, and eventually the channel is abandoned, erosion, would have spread over the valley and replen­ except during floods (Schumm and Lichty, 1963, p. 82- ished soil moisture necessary for plant growth. As the 84). The islands were united by this process and formed water flowed into the deep channels, additional erosion a flood plain paralleling a low-flow channel. In the occurred; however, the eroded material, generally of beginning, almost all the flows overtopped the low-flow small size, was easily moved downstream because the channel and deposited sediment on the flood plain. Be­ flow was confined. cause of the absence of large floods, vegetation became According to Olmstead (1919, p. 79), a ditch dug at fairly permanent. Successive depositional events have the mouth of the San Simon River may have influenced resulted in a flood plain at a level several feet above channel erosion in that stream. The ditch was dug by the present (1970) streambed. settlers prior to 1900 to divert floods in the San Simon The deposition along the banks in the stream channel River away from the cultivated land. Because severe may be described as lateral deposition. This type of erosion took place at the same time in other gently slop­ deposition occurs in places where stream velocities are ing streams, the author assumes that the erosion in the relatively low; along the inside banks at bends; at down­ San Simon River basin would have occurred even if stream ends of objects protruding into the flow; and, the ditch had not been dug. in some instances, in straight channels without pro­ DEVELOPMENT PROCESS truding objects. Lateral deposits generally occur at Sediment accretion in alluvial flood plains may occur all levels below the top of the channel banks. If lateral in five general ways: (1) by the development of islands deposits are not disturbed by floods, they increase in in the stream channel and their subsequent attachment thickness with each successive addition of sediment to one bank by channel abandonment, (2) by direct until the top level reaches that of the original banks. deposition on the flood plain. (3) by deposition in the The higher deposits are more stable, owing to less fre­ stream channel along the banks, (4) by formation of quent disturbance by floods and to the protective natural levees, and (5) by deposition on alluvial fans vegetation. at the mouths of tributary streams. The processes of When flow overtops the banks, deposition often takes deposition overlap, and it is often difficult to determine place just outside the stream channel and forms natural the method of deposition by observing a sediment de­ levees. As the flow leaves the stream channel, the veloc- G14 GILA RIVER PHREATOPHYTE PROJECT

FIGURE 6. Saltcedar encroachment along the Gila River between 1932 and 1964. A, Looking upstream from the railroad bridge near Calva in 1982; the braided stream probably is typical of the Gila River in most of the Safford Valley in the third and early fourth decades of the 20th century. B, Looking upstream from the railroiad bridge near Calva in 1964. Leaders indicate: a, location of railroad siding at Calva (fig. 4B, C) ; 6, location of alluvial fan shown on plate 4; c, location of stream channel in 1964. ity is reduced and sediment is deposited adjacent to the The development of an alluvial fan is depicted on banks. The deposition is aided by the retarding action plate 4. The floods of 1905-6 in the Gila Eiver appar­ of the vegetation along the banks. Natural levees occupy ently washed out the alluvial fan at the mouth of a only a small part of the flood plain at present (1970); tributary stream near Calva and eroded a low-flow however, in places, the levees are more than 3 feet channel. Removal of the fan caused an increase in the high. The natural levees and the retaining dikes con­ gradient at the mouth of the tributary channel and aug­ structed by farmers keep median flows flows below mented erosion. Subsequently, another fan developed about 5,000 cfs from spreading over the flood plain. at the site, forcing the Gila River stream channel to­ Conversely, during high flows, water that flows over ward the opposite side of the flood plain. Development the levees and water from the tributary streams often of the fan has caused a progressive aggradation in the are retained in basins formed by flood-channel banks, tributary stream; the deposit is about 17 feet thick at alluvial fans, and the natural levees, which results in the mouth and about 5 feet thick at the railroad bridge deposition of sediment. spanning the tributary (pi. 4). The alluvial fan and the tributary stream apparently are reverting to a ALLUVIAL-FAN DEVELOPMENT natural state similar to that existing prior to 1905. In the bottom land, alluvial fans generally are lim­ Alluvial fans at the mouths of a few tributary streams ited to the reach downstream from Fort Thomas (pi. 1). have caused striking shifts in the course of the Gila Because of the steep slopes, flows in streams tributary to River. For example, at the mouth of Salt Creek at this part of Safford Valley usually travel at relatively Bylas (pi. 1), the fan, which probably developed after high velocities, carry large sediment loads, and move the floods of 1905-6, shifted the Gila River channel large amounts of coarse material along the channel bed. Upon reaching the wide flat bottom land along the Gila southward during the major flood of December 1914 Eiver, the material carried by the tributary flows is (Burkham, 1970, p. 25), causing flood damage in Bylas. deposited as alluvial fans. According to C. R. Oldberg (written commun., January CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G15 1916, in files of U.S. Bur. Indian Affairs, Phoenix, The average change in the altitude of the bottom Ariz.) : land at each cross section for a given time increment was obtained as follows: (1) The measured profiles at For several years previous to 1914, however, the stream channel seemed to hug the north bank of the river * * *. In December each cross section were plotted on graphs; (2) the ver­ 1914, the river attacked the south bank in three places * * *. tical area between plotted profiles was obtained from In July 1915, another flood, although not so great as the one the graph; and (3) the change in altitude was obtained in December 1914, eroded the [south] river bank for about 6,600 by dividing the vertical area by the horizontal length feet * * * at the same time cutting the channel deeper on the of the cross section. These data are for the bottom land south side of the river and building up on the north side. * * * The channel is now headed directly towards the school [in within the end points of the cross sections as initially Bylas] * * *. established (table 2). The profile data were obtained In February 1920, H. V. Clotts (written commun., from field surveys, except the data for 191^-15 and March 1920, in files of U.S. Bur. Indian Affairs, 1935, which were scaled from contour maps. A positive Phoenix, Ariz.) found that "the wide detour of the change in altitude for a time increment indicates a [Gila River] channel * * * has been gradually ap­ larger area of fill than of scour in the section. In many proaching the school [in Bylas] * * *. While the river places there is fill in part of a cross section and scour has been cutting in the Southside, it has been deposit­ in the rest (pl. 5A). ing a bar on the Northside on the inside of the curve." The meager topographic data indicate that the alluvial fan at the mouth of Salt Creek at Bylas re­ TABLE 2. Changes in the altitude of the bottom land at cross sections tarded flow in the Gila River and caused the deposition along the Gila River, Safford Valley of sediment in the backwater areas during the major Cross section No.: See plate 1 for locations of cross sections. Change in altitude: Change in altitude for a cross section is averaged by dividing the floods of 1905-17. Some of the sediment deposited dur­ change in vertical area by the horizontal width of the section. Rate of change in altitude: Total change in altitude divided by the number of years ing the floods was removed later by smaller flows. between the first survey and the last, but data for 1914-35,1914-37, and 1914-43 were Plate 5 shows the horizontal and vertical changes in not used in calculating the rate of change. the Gila River near Foit Thomas as a result of two Rate of alluvial fans and high flows. The fans, which formed Change in change in Cross section No. Period between surveys altitude altitude at the mouths of two tributaries, apparently were re­ (feet) (feet per moved during the floods of 1905-17; however, a deep year) channel did not erode in the smaller tributary until SCS 18------July 1937 »to July 1965 -1. 22 subsequent years (pi. 1). As the alluvial fans re-formed, -0.03 July 1965 to July 1966-- + .27 there was keen competition for the space occupied by the flood plain between the alluvial fans on the north 17-.-___-_ July 1937'to July 1965. -1. 60 -.04 and the cultivated land on the south. The alluvial fans July 1965 to July 1966-- +. 44 caused a bend to develop in the Gila River and caused the erosion of the cultivated land during the floods of 16------July 1937 > to July 1965. -.98 -.03 1965-67. July 1965 to July 1966.- +. 24 In summary, the alluvial fans that formed at the mouths of the steep streams have affected the recon­ 15---.---- July 1937 »to July 1965. -0. 78l -.09 struction of the Gila River flood plain in several ways. July 1965 to July 1966- _ -1. 80] The fans occupy space and, therefore, retard floodflow, which results in the deposition of sediment in the back­ 14----.-- July 1937 Ho July 1965. + 1. 37 -.31 +.04 water areas. The fans furnish a supply of easily erodible July 1965 to July 1966-. material that is redistributed to other parts of the flood -.07 13.------July 1937 »to July 1965. -.02 plain by floods. The fans also have forced the Gila River -.79 into a meandering course through the bottom land. July 1965 to July 1966-.

RATES OF SEDIMENT ACCRETION 12--._---_ July 1937 l to July 1941 -. 28 July 1941 to July 1965-- +.21 -.03 The amount of sediment accreted for each of the five July 1965 to July 1966-. -. 79 processes of deposition is unknown. In subreaches A and B, however, the composite accumulation as a result ll--.--__- July 1937 ' to July 1941 -1. 00 of all processes is well documented through the periodic July 1941 to July 1965-. -.71 -.06 surveys that have been made at several cross sections July 1965 to July 1966-. -.02 (pl. 1). 1 Date that the cross section was established. G16 GILA RIVER PHREATOPHYTE PROJECT

TABLE 2. Changes in the altitude of the bottom land at cross sections TABLE 2. Changes in the altitude of the bottom land at crtss sections along the Gila River, Safford Valley Continued along the Gila River, Safford Valley Continued

Rate of Rate of Change in change in Change in change in Cross section No. Period between surveys altitude altitude Cross section No. Period between surveys altitude altitude (feet) (feet per (feet) (feet per year) year)

SCS 10. ..__-_- July 1937 Ho July 1941. _ __ +0.04] PD 222___-___ Oct. 1914 to July 1935. ___. +. 8S July 1935 to June 1943 l _ . _ _ +.531 July 1941 to July 1965-_--_ +. 09> +0.03 . 01 July 1965 to July 1966-.--- +. 77J June 1943 Ho Oct 1969. .... -.971

9-..--_-_- July 1937 Ho July 1941. _ _. +. 15\ 216----.-- Oct. 1914 to July 1935__. __ .49 July 1935 to June 1943 L . _ _ -. 3f 1 July 1941 to July 1965----. +. 07l +. 05 July 1965 to July 1966- _ . _ . +. 46 [ June 19431 to Sept. 1969 . +1. 92l July 1966 to Dec. 1968..--. -. 67j 215.-_-.--. Oct. 1914 to July 1935 .__. 2.11 July 1935 to June 1943 !_.__ +1. 101 8------July 19371 to July 1941.-.- +.49] +. 03 June 19431 to Sept. 1969... . +. Oil July 1941 to July 1965-__-_ +1. 61> +.05 July 1965 to July 1966. .... -. 59J 214 _-__- Oct. 1914 to July 1935 .._ +.15 July 1935 to June 1943i____ +1. 60l 7-..------July 1937 l to July 1941. ._. -.05] +. 04 June 19431 to Sept. 1969 - -. 2li July 1941 to July 1965----. +. 81> +.02 July 1965 to July 1966.---- -. 09J 209 -- - July 1935 to June 1943 ! _ +. 93J +. 07 June 19431 to Dec. 1969. _ __ +1.371 6. .-_.-._ July 1914 to July 19371.-.. +.60 July 19371 to July 1941...- +. 48| 208 .- _- July 1935 to June 1943 J.--- +1. 07] July 1941 to July 1965_ -___ +. 56> +.02 + . 07 June 1943 Ho Dec. 1969._._ +1. 28J July 1965 to July 1966. _.__ -. 50j 207 July 1 935 to June 1 943 » _ _ _ . + . 20| +. 04 5. .-_*____ July 1914 to July 1937 !.___ -1.30 June 1943 Ho Dec. 1969.. ._ +1. 23J +. 04 July 19371 to July 1941. -__ +.95] July 1941 to July 1965.--- _ +.92^ +.01 196 July 1914 to July 1935. ____ -0. 32 July 1965 to July 1966-_-_- -1. 60J July 1935 to June 1943i_ _ +- JQ +. 10 June 1943 Ho July 1966_._- +2. 73 4...-----_ July 1914 to July 19371.--. -.77 July 19371 to July 1941.-.- +. 10] GS (Pima Oct. 1914 to July 1935. ____ -. 16] July 1941 to July 1965_ -_-_ +1. 11> +.03 + . 08 bridge) . July 1935 to Feb. 1968 »_ _ _ . + 2. 57 July 1965 to July 1966_ _ _ _ _ - . 42J PD 185 - _ Mar. 1915 to July 1935____ -.18 3. .._._--. July 1914 to July 19371.--. +.94 July 1935 to June 19431. _ +1 Q-) July 1937 ! to July 1941.___ +. 541 +. 06 July 1943 Ho Jan. 1970.... _ +. 90 July 1941 to July 1965. _-_. -.05] + 184 Mar. 1915 to July 1935... __ +1. 12 2. ..__._._ July 1914 to July 1937i._ __ +.85 July 1935 to June 1943 »_ _ +. 8^ July 1937 i to July 1965._-_ +. 62l + .04 June 1943 Ho Jan. 1970____ +. 62 July 1965 to July 1966.---- -.60] + 183 _ Mar. 1915 to July 1935____ +1.65 1. .._--___ July 1914 to July 19371.. __ +.31 July 1935 to June 1943 1___. +.H} , Q3 July 1937 i to July 1965 .___ T. 40] July 1965 to July 1966--.-- -. 17> +.01 June 1943 Ho Jan. 1970. _-_ +.27] "*"' July 1966 to Dec. 1968... __ -. 26 j 177..---.- Mar. 1915 to July 1935___- -1.3* July 1935 to June 1943 »_ _ _ -.43 GS (Safford Dec. 1942 Ho Nov. 1967- _. +1. 80l + . 03 June 1943 » to Dec. 1966--- +1. 42 bridge). Nov. 1967 to Jan. 1969.- .. -. 25J + 176.- __ Mar. 1915 to July 1935..... -2.22 PD 224-.__.__ Oct. 1914 to July 1935_ _.-_ +3.56 July 1935 to June 1943 ».... +1. 84 July 1935 to June 1943i____ -.78} +.07 June 1943 * to Dec. 1966. . _ +.23 June 1943 1 to Oct. 1969. - _ _ - 1. 70J 175-..._- _. Mar. 1915 to July 1935..... -1.25 223_ _ Oct. 1914 to July 1935. __ +2. 51 July 1935 to June 1943 i .... - 1. 74 July 1935 to June 1943i_ _ -1. 87} June 1943 J to Dec. 1966___ -. £9 -.07 June 19431 to Oct. 1969____ -. 541 ' Dec. 1966 to Dec. 1968_ __- .12 1 Date that the cross section was established. CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G17

TABLE 2. Changes in the altitude of the bottom land at cross sections TABLE 2. Changes in the altitude of the bottom land at cross sections along the Gila River, Safford Valley Continued along the Gila River, Safford Valley Continued

Rate of Rate o* Change in change in Change in change in Cross section No. Period between surveys altitude altitude Cross section No. Period between surveys altitude altitude (feet) (feet per (feet) (feet per year) year)

SCS 145______Mar. 1915 to July 1937 l __. -2.82 PD lll._ _ _ Feb. 1915 to Sept. 1935__-__ -0.13 July 1937 i to July 1965 . . . . + 2. 40} + 0. 09 Sept. 1935 to June 1943 »___ -. 59} June 1943 Ho Dec. 1966---. +3. 05J + 146---____ Mar. 1915 to July 1937 l . -4.68 July 1937 » to July 1965.-- +2. 19} 110______Feb. 1915 to Sept. 1935.---- +.97 July 1965 to Dec. 1968. .... -. 38J Sept. 1935 to June 1943 l.-. -1. 54} June 1943 Ho Dec. 1966_-_- +3. 37J +- Ut) PD 148------Mar. 1915 to Sept. 1935. ._. +1. 66 Sept. 1935 to June 1943 1 ._ . +. 12) 109______Feb. 1915 to Sept. 1935-.- _ +.03 June 1943 l to Dec. 1967__. +2. 25J +> Sept. 1935 to June 1943 L.. -. 66] June 1943 l to Dec. 1966____ +3. 97 > +. 14 147. .._____ Mar. 1915 to Sept. 1935.-- +2.27 Dec. 1966 to Dec. 1968.---- +1. 2oJ Sept. 1935 to June 1943 ».._ -. 15) June 1943 » to Dec. 1967. __ + 2. 54l +> 108 ___--. Feb. 1915 to Sept. 1935__-_- -.56 Sept. 1935 to June 1943 ».___ -.68] , 146.. -- Mar. 1915 to Sept. 1935. _. +2.28 June 1943 Ho Dec. 1966..-- +3. 89J "*"' Sept. 1935 to June 1943 1 .._ +1.331 June 1943 » to Dec. 1967- _. +2. 62] +> 107___-__- Feb. 1915 to Sept. 1935_-_- +1. 52 Sept. 1935 to June 1943 1 .__ 1. 171 , - 144. .._____ Mar. 1915 to Sept. 1935. .__ +1.11 June 1943 l to Jan. 1968...- +4. 45J """ Sept. 1935 to June 1943 »... +1.41' June 1943 1 to Dec. 1967_ _ _ +3. 56 +.15 106_ ___.-- Feb. 1915 to Sept. 1935. ___ +. 17 Dec. 1967 to Dec. 1968. ..._ -. 15 Sept. 1935 to June 1943 ».._ T. 23] , 1? June 1943 l to Jan. 1968.... +5. 23 J 141. ----.__ Mar. 1915 to Aug. 1935_ ___ +1.73 Aug. 1935 to June 1943 l ___ +. 49\ , 105. ___--- Feb. 1915 to Sept. 1935.--- -.81 June 1943 > to Dec. 1967- _ _ + 1. 35l Sept. 1935 to June 1943 ».__ +. 48} , 17 June 1943 » to Jan. 1968...- +4. 83] 118---____ Feb. 1915 to Sept. 1935_ _._ 1.12 Sept. 1935 to June 1943 1 .._ +.821 GS 1. ...___--_ Nov. 1964 l to June 1966___ -.83} , gi June 1943 l to Dec. 1968___ +2. 371 June 1966 to June 1968- ___ +2. 08J 3..-..----- Nov. 1964»to June 1966__- +.94} + 55 117-.-____ Feb. 1915 to Sept. 1935____ -.51 June 1966 to June 1968___- +1. 25J Sept. 1935 to June 1943 ».__ -. 13} . June 1943 l to Jan. 1968.... +2. 2lJ + ' 5. ..._----_ Nov. 1964 Ho June 1966__- -17} _|_ 08 June 1966 to June 1968___- +. 48J 116 -..--___ Feb. 1915 to Sept. 1935_ __ -.37 Sept. 1935 to June 1943 L.. +. 51} , 7--..-_---_ Nov. 1964 Ho June 1966__- -.09} + Q4 June 1943 l to Dec. 1966. __ +2. 37J June 1966 to June 1968.--- +. 21 J 9....-_--__ Nov. 1964 » to June 1966.-- -.09} +20 115.. -...._ Feb. 1915 to Sept. 1935_ ___ -1.23 June 1966 to June 1968.--- +. 89J Sept. 1935 to June 1943 l ... +. 39] June 1943 1 to Dec. 1966_ _._ +2. 29 > +.09 Dec. 1966 to Dec. 1968..... +. 24j The sediment-accretion data for 1914 35, 1914 37, and 1914-43 are of poor quality for two reasons. First, 114______Feb. 1915 to Sept. 1935.____ -2.47 several of the cross sections established in 1937 and 194-3 Sept. 1935 to June 1943 L.. -. 10] June 1943 » to Dec. 1966- _ . _ + 1. 24J + did not extend across the entire bottom land, and tJN amount of fill or scour in the unsurveyed areas could 113...... _ Feb. 1915 to Sept. 1935___-_ -1.46 not be determined ; however, the amount in the unsur­ Sept. 1935 to June 1943 »___ -.09] veyed areas may have been a large part of the fill or June 1943 Ho Dec. 1966-.-- +3. 42J + 1 scour during these periods. Secondly, the small scale 112______Feb. 1915 to Sept. 1935- __._ -.07 (1:12,000) and large contour intervals (5-ft) for tH Sept. 1935 to June 1943 »___ +. 30} _ 1914-15 topographic map resulted in limited accuracy June 1943 l to Dec. 1966..-- +2. 18J +- of the cross-sectional profiles. Although these data may 1 Date that the cross section was established. have limited hydrologic value today, they do indicate G18 GILA RIVER PHREATOPHYTE PROJECT

the areas of aggradation and degradation. The sedi­ shown by 16 of the 22 sets of sediment data for 1965-66 ment-accretion data collected from 1935-70 are of bet­ (table 2), which indicates a net scour of the bottom land ter quality. Since 1935 most of the changes in the alti­ in the valley in 1965-66. tude of the bottom land are assumed to have occurred The volume of coarse material being deposited an­ in the surveyed areas. nually on the bottom land is unknown, but data ob­ From 1935 to 1970, the net change in the altitude of tained from periodic surveys of five alluvial fans (pi. the bottom land has been an increase at 45 of the 57 1) in and near the lower part of the study re^ch indi­ cross sections in subreaches A and B, although data cate that the amount is large. The volumes of the allu­ show short periods of scour at some of the other sec­ vial fans were determined from a topographic map for tions (table 2; fig. 7). The author hypothesizes that the 1914 and from a field survey made in 1968. Th^ sizes of increase in sediment accretion in the downstream direc­ the contributing watersheds and the increases in vol­ tion occurred because more coarse material is deposited umes of the five fans for 1914-68 are given below. in the bottom land in the lower part of the valley than Size of watershed (square Increase in volume in the upper part, and because streamflow is depleted Alluvial fan number miks) of fan (acre-feet) by infiltration and diversion. Coarse material originat­ 0. 31 2. 2 1. 78 5 5 ing in steep watersheds tributary to subreaches D and 2. 37 140 C and part of subreach B is deposited directly in the 10. 2 187 2. 56 36 6 bottom land. In subreach A and in the other part of subreach B, only the fine material makes its way to the The volumes of coarse material moving toward the bottom land, and most of the fine material is carried bottom land from the five tributaries undoubtedly were through the valley and is deposited in the San Carlos greater than those indicated above because sorie of the Keservoir. fan material probably was eroded during major floods The data for cross sections where scour is indicated in subsequent to those of 1914. figure 7 may be grouped for (1) cross sections at bends The data given in tables 1 and 2 were used to estimate in the stream channel where bank erosion is occurring the volume of sediment accretion for the subreaches in and (2) cross sections where the stream channel has the Safford Valley for 1935-70 (table 3). The estimates been enlarged to improve the conveyance capacity. Ex­ of sediment accretion in subreaches A and B were taken amples of the data in group 1 are those for cross sec­ as the product of the average annual change in altitude tions PD 222, PD 223, PD 224, and PD 175. The erosion of the bottom land (0.03 ft. per yr for subreach A and on the outside of the bends in the stream channel at 0.08 ft per yr for subreach B), the average area of these sections apparently has been greater than the fill uncultivated bottom land in 1935-68 (2,390 acres for on the inside. Data for cross sections SCS 11 through subreach A and 4,360 acres for subreach B), and the SCS 18 are examples of group 2 (table 2; pi. 1; fig. 7). number of years in the period (35 yr). Estimates of A decrease in the average altitude of the bottom land is sediment accretion in subreaches C and D were obtained

mcor- m * 10 = co r^oom^ioco N m -t £££ 2592 t« 888s ?; SS3 QQQ QQQ <" Q QQQQQQ QQQ

1- r A f \ _J + 0 20 - 01 innr- t> /->i i n 01 innr A /->i i A < o»_)L)i\i_/-\v^i i u vji_iuni_/-\v^i i f-\ cc z \ f, ''\ < 10 - LU +0 * i _/'" r~J ~~ -f -A __T_Cend line r I LU >- U z CC EXPLANATION \', l ^-=7^ .. __ -~^J^_\ _ LU 0 - < Q. PD105 | . '\ l\ I U LU scs 8 I Sections at bends \ \r \'-" LU GS (pnma bndgei " gtream channel " "i " ' LU LL -0 10 - U Cross section number Stream channel straight-. ' i z cc< see piate i for location of cross section: ened and enlarged to im-^^ LU> -0 20 - dafa plotted from table 2 prOVB Conveyance < 1 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 z DISTANCE, IN MILES

FIGURE 7. Net average change in the altitude of the bottom land, 1935-70, at cross sections in subreaches A and B of the Gila River. Distance was measured along the eenterline of the stream channel (1960). CHANNEL CHANGES OF THE GILA EIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G19

by multiplying the length of the subreach (7.2 miles for comparison with those of 1905-17 (pi. 3), and the flashy subreach C and 6.1 miles for subreach D), measured sediment-laden summer flows have contributed much along the center of the bottom land, by the per-mile of the total flow. Summer flows about 25 percent of volume of sediment accretion in subreach B (604 acre-ft which come from watersheds tributary to the study per mile). reach spread over the wide flood channel, losing kinetic energy and depositing their sediment loads. Owing to TABLE 3. Estimated volume of sediment accretion for subreaches the absence of the flushing action of the large flows of in Safford Valley, 1936-70 fairly clear water, the accreted sediment becomes rel­ Sediment-accretion volumes Location atively stable. When major floods having low sediment Acre-feet, 1935-70 contents occur, however, extensive erosion results. Subreach: The effects of streamflow depletion on sediment-accre­ A____...______._. 2,500 70 B______._.______12,200 350 tion rates in Safford Valley are unknown. However, the C______.______4,350 120 inflow to the valley is greater than the outflow from the D______._____.______3,680 110 valley (Burkham, 1970, p. 6-10), and streamflow deple­ Total for study reach______22, 730 650 tion is known to influence the rate of deposition. San Carlos Reservoir______» 61, 000 2, 000 Total______83, 730 2,650 INFLUENCE OF STREAM-CHANNEL TREATMENT PRACTICES AND FLOOD-PLAIN VEGETATION 1 Sediment accretion for 1935-66; data furnished by F. P. Kipple (written commun., 1970). Stream-channel treatment practices in the Gila River The value of 2,650 acre-feet per year (table 3) prob­ include those designed to reduce erosion and those de­ ably is a conservative estimate for the amount of sedi­ signed to increase conveyance. The two treatment prac­ ment moving toward the bottom land because the accre­ tices are dynamically opposed the first tends to cause tion of the sediment in the cultivated part of the bottom deposition, and the second tends to cause erosion. land and the amount of sediment moving through the As discussed on page 12, erosion of the farmland San Carlos Reservoir are not included. The accretion was occurring in places along the Gila River in the of sediment in the cultivated area probably is signifi­ second, third, and fourth decades of the 20th century. cant in only a few places; however, the farmers make The U.S. Soil Conservation Service initiated an erosion- no special effort to keep suspended sediment from mov­ control program in the 1930's to stabilize the stream- ing onto the cultivated land during the diversion of banks an;d slow the movement of floodwater in the badly river water for irrigation because the sediment has a eroding areas. According to Rowalt (1939, p. 46): high nutritive value. At times, floodwater is ponded The program is primarily vegetative in character, which is temporarily on the cultivated land and is desilted. The nature's way, with here and there some mechanical reinforce­ amount of sediment that moves through the San Carlos ment to enable nature to work with less interference. * * * The Reservoir is assumed to be small. It is of interest to note native black willow is used. Black willow cuttings about the that about 75 percent of the annual sediment volume size of fence posts are set 4 or 5 feet apart under the banks. * * * that moves onto the bottom land moves through the bot­ In the more vulnerable places the willows are planted behind brush and cable revetments. Mechanical protection is also pro­ tom land and is deposited in the San Carlos Reservoir. vided on the outside banks of curves. Usually this consists of The sediment in the reservoir is mainly of small diame­ cable and log jetties placed across the bow of the channel, or ter, which indicates that most of the material that is cable and brush anchored at both ends under high-cut banks. eroded from the gently sloping alluvial valleys is de­ Rail tetrahedron lines have been used, and these are effective posited in the reservoir and most of the material that but expensive. is eroded from steep streams is deposited in the flood The erosion-control treatment used by the Soil Conserva­ plain. tion Service (fig. 8) undoubtedly had some short-term local effects because it was applied during a period hav­ INFLUENCE OF WIDE FLOOD CHANNEL AND ing few major floods; however, saltcedar became estab­ LOW-FLOW RATES lished naturally, and any reduction in erosion effected The wide flood channel and low-flow rates probably by the willow probably would have occurred later as a were the most important factors influencing the depo­ result of the saltcedar. sition of sediment during 1918-70. The natural devel­ Vegetation was sparse in the flood plain through the opment of the flood channel took place in order to ac­ second and third decades of the 20th century, but, once commodate the large flows of fairly clear water from saltcedar was established, it spread rapidly and became major winter floods that originated in the mountains. the dominant vegetation (Gatewood and others, 1950, Since 1917 the flow rates have been relatively small in p. 11). Saltcedar reached its maximum areal extent G20 GILA RIVER PHREATOPHYTE PROJECT CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G21 during 1945-55 (fig. 5). At present (1970), saltcedar is land was stripped of natural vegetation and leveled, and very dense in most places where the black willow was dikes were built to protect the cropland from flood- planted, and most of the mechanical devices are buried Initially, only the outer edges of the bottom land were under the alluvium. cultivated, but during extended periods of low flow Flood-plain vegetation affects sediment accretion in (pi. 3) in the Gila River and as heavy equipment became three general ways: (1) it retards flow, which results available for vegetation removal, additional bottom in the deposition of sediment in backwater areas; (2) it land was converted to cropland (fig. 5). At the same aids in the stabilization of the deposits; and (3) it con­ time, the stream channel was becoming narrower, and centrates flow in the stream channel, thus increasing the uncultivated part of the flood plain was becoming erosion tendencies in the channel during floods. There­ heavily congested with vegetation. fore, during the periods when there are few major In times of moderate floods, the dikes prevented the floods, the trees in the flood plain aid in flood-plain water from spreading onto the cropland and concen­ building and stream-channel maintenance. During trated flow in the stream Channel. The Concentrate'1 major floods, however, the trees in the flood plain may flow increased stresses along the channel boundary, cause the volume of erosion in the stream channel to which may have led to erosion. The dikes probably exceed the volume of fill deposited on the flood plain; contributed to the erosion in the stream channel during the author believes that this phenomenon is most likely the floods of 1965-67. Once the dikes were breached to occur during floods carrying very small sediment by floodflows, however, the cropland acted as a reli«,f loads. For example, the trees in the flood plain probably valve; large amounts of water flowed into the fields, contributed to the erosion in the Gila River channel where they were temporarily imponded and desilted. during the floods of 1965-66 (fig. 3) and to the major The dams, which were built to divert irrigation water, widening of the stream channel during 1905-17. Unlike may have caused accretion of sediment locally in the the cottonwood, the saltcedar is not a rigid tree and will channel upstream from the dams. The dams usually are bend during large floods, thus releasing hanging debris. built on gravel bars and generally are unstable. In 1969 Saltcedars were not uprooted during the floods of 1965 only three oLthe 14 dams were of a more permanert and 1967, except where bank erosion occurred along the type. The accretions of sediment caused by the dams are stream channel. small and generally are flushed downstream during Since 1950, farmers have altered short sections of the major floods. channel in several places in an attempt to improve its CHANGES IN STREAM-CHANNEL LENGTH AND SLOPP conveyance capacity. The usual alterations are straight­ ening and enlarging of the channel, which create tem­ Since 1917, significant changes have taken place in the porary increases in the sediment-carrying capacity of length and slope of the stream channel of the Gila the flow. Any increase in sediment load in the treated River the length has increased and the slope has de­ section, however, generally leads to additional deposi­ creased. In 1920 the'low-flow channel, which is described tion in the adjoining downstream section; also, some in the section "Stream-Channel Development," ws,s erosion generally takes place in the adjoining upstream slightly longer than the flood channel, and its length section. Eventually, through the process of erosion in increased steadily through 1964 (fig. 9). The length in­ the upstream section and filling in the downstream sec­ creased simultaneously with the development of tita tion, the treated area returns to a fairly stable state sediment islands, the attachment of the islands to the similar to that before the treatment. banks, and the development of the alluvial fans. Further increases in the length of the stream channel occurred INFLUENCE OF FLOOD-PLAIN CULTIVATION as a result of erosion on the outside and filling on the Cultivation of the bottom land is limited almost en­ 1 - 40 ^ EXPLANATION A A tirely to subreaches A and B, where large-scale cultiva­ Subreach A tion began in the fourth decade of the 20th century; the Subreach

gl.2CH Subreach

FIGURE 8. Erosion controls established in the 1930's by the U.S. 1.10 - Soil Conservation Service in the stream channel of the Gila River. A, Mechanical device in stream channel near Safford, 1.00 November 1935. Note vegetation staves. B, Willows in stream 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 channel near Fort 'Thomas; the willows were planted in March 1938, and the photograph was taken in June 1938. FIGURE 9. Sinuosity of the stream channel of the Gila River Photographs furnished by the U.S. Soil Conservation Service. in Safford Valley, 1875-1970. G22 GILA RIVER PHREATOPHYTE PROJECT inside of bends. Because the altitude of the streambed 1846-1904; and, subsequent to the channel-widening has not changed significantly, the increase in channel floods of 1905-17, it took 50 years for the flood-plain length has resulted in a decrease in stream-channel development to approach that prior to 1905. Large- slope. The author hypothesizes that an increase in the magnitude floods equal to those that destroyed the Gila number of alluvial-fan deposits and the depletion of River flood plain during 1905-17 apparently did not streamflow in the downstream direction caused the occur in the 19th century. If large-magnitude floods had increase in sinuosity in the downstream direction occurred during 1800-46, the stream channel probably (fig. 9). would have been wider than that described by travelers in 1846. Based on the preceding assumption, the No­ HYDROLOGIC IMPLICATIONS vember 1905 flood of 150,000 cfs (Smith and Heckler, Several interesting hydrologic implications were 1955, p. 61) and the December 1906 flood of 140,000 cfs brought out during this study. The implications are in (Olmstead, 1919, p. 64) may have been the largest floods relation to aggradation and degradation in alluvial val­ for more than 170 years; according to Stcckton and leys, normal flows and frequency of floods, hydraulics of Fritts (1968), the floods may have been the largest for flow in the Gila River, and use of water by bottom-land more than 300 years. vegetation. The major stream-channel widening during 1905-17 Gilbert's theory (in Chorley and others, 1964, p. 562) caused changes in the amounts of surface-water storage of the translation of the effects of variation of erosive available for all subsequent flow events ir the Gila power to all parts of the river system apparently applies River, except perhaps for the large floods anc1 low flows. to the erosion of the alluvium that occurred in the Gila The changes in storage probably resulted in reductions River watershed above Coolidge Dam as a result of the in peak flows as the water moved down the river; how­ major floods of 1905-17 and to the redevelopment of ever, the effects of channel widening on the peak flows the flood plain during periods having no major floods. became less significant as the flood plain was recon­ According to Gilbert (in Chorley and others, 1964, p. structed. 562): A net decrease in evapotranspiration in the bottom Of the 'main conditions which determine the rate of erosion, land along the Gila River may have occurred as a result namely, quantity of running water, vegetation, texture of rock, of cultivation. The amount of water saved annually is and declivity, only the last is reciprocally determined by rate unknown; however, it probably ranged from almost of erosion. * * * Wherever by reason of change in any of the conditions the erosive agents come to have locally exceptional zero in 1920, when only a few acres was cultivated, to power, that power is steadily diminished by the reaction of rate as much as 10,000 acre-feet in 1964, when p.bout 3,700 of erosion upon declivity. Every slope is a member of a series, acres was cultivated (fig. 5). The reduction in evapo­ receiving the water and the waste of the slope above it, and transpiration losses in 1964 was calculated u^ing values discharging its own water and waste upon the slope below. If one of 5 acre-feet per year per acre for evapotrpnspiration member of the series is eroded with exceptional rapidity, two things immediately result: first, the member above has its level by saltcedar (Gatewood and others, 1950) and 2 acre- of discharge lowered, and its rate of erosion is thereby increased; feet per year per acre for evapotranspiration by cotton and second, the member below, being clogged by an exceptional (Blaney and Griddle, 1962). load of detritus, has its rate of erosion diminished. The accelera­ tion above and the retardation below, diminish the declivity of SUMMARY the member in which the disturbance originated; and as the declivity is reduced the rate of erosion is likewise reduced. Changes in the Gila River in Safford Valley were The author believes that the erosion and the subse­ grouped into three periods for this study 1846-1904, quent filling in the lower altitudes of the Gila River 1905-17, and 1918-70. From 1846 to 1904, the stream watershed is a repetitive process that occurs naturally. channel was narrow and meandered through a flood The severity of erosion has not been the same in all the plain covered with willow, cottonwood, and mesquite. alluvial deposits, however, because of anomalies in Only moderate changes occurred in the width and the amounts of flowing water, vegetation, texture of sinuosity of the stream channel in this period; the rock, and declivity. average width of the stream channel was le's than 150 The temporal distribution of flow and the average feet in 1875 and less than 300 feet in 1903. annual flow about 260,000 acre-feet at the head of During 1905-17 the average width of the stream chan­ Safford Valley during 1920-64 probably were about the nel increased to about 2,000 feet, mainly as a result of same as those during 1800-1904. The preceding state­ large winter floods that carried small sediment loads. ment is based on the following: The stream-channel The meander pattern of the stream and the vegetation width is governed mainly by rates of streamflow; the in the flood plain were destroyed completely by the stream channel was narrow and fairly stable during floods. The trees on the flood plain may 1 ave had a CHANNEL CHANGES OF THE GILA RIVER IN SAFFORD VALLEY, ARIZONA, 1846-1970 G23 minor influence on the widening in two ways. First, the nated in the tributary watersheds and spread over th°- trees restricted the flow of water onto the flood plain wide flood channel, losing kinetic energy and depositing during the major floods and concentrated the flows in their sediment loads. The major floods of 1905-17 prob­ the stream channel; the concentrated flow increased ably were the main cause of the rapid-erosion era in th?< stresses along the stream-channel banks, which may have tributary basins; however, periods of drought and ex­ caused erosion. Second, during the major floods, float­ tensive grazing prior to the floods may have been con­ ing debris hung on the fairly rigid cottonwood trees, tributing factors. and the forces applied to the trees created torsion at the The natural vegetation and cultivation in the flood ground; eventually the trees were uprooted, carrying plain may have had a significant influence on the recon­ large chunks of alluvium with them and leaving the struction of the flood plain. The trees retarded flood- easily credible material exposed. flow, which resulted in the deposition of sediment in During 1918-70 the stream channel narrowed, and backwater areas, aided in the stabilization of the de­ the average width was less than 200 feet in 1964. The posits, and concentrated the flow in the stream channel stream channel developed a meander pattern, and the that helped maintain the stream channel. Large-scale flood plain became densely covered with vegetation. cultivation of the bottom land began in the fourtl Saltcedar became well established in the fourth decade decade of the 20th century; the land was stripped of of the 20th century, and it was the dominant vegeta­ natural vegetation and leveled, and dikes were built to tion type. Minor widening of the stream channel oc­ protect the cropland from floods. In times of moderate curred in 1965 and in 1967, and the average width of floods, the dikes prevented the water from spreading the channel was about 400 feet in 1968. onto the cropland and concentrated flow in the stream During 1918-70 reconstruction of the flood plain was channel, which helped maintain the stream channel. accomplished almost entirely by the accretion of sedi­ Once the dikes were breached by floodflows, however, ment, which occurred in five general ways: (1) -by the large amounts of water flowed into the fields, which development of islands in the stream channel and their reduced the stresses in the stream channel. In places, subsequent attachment to one bank by channel aban­ the small unstable dams, which were built to divert donment, (2) by direct deposition on the flood plain, irrigation water, may have influenced sediment accre­ (3) by deposition in the stream channel along the banks, tion. The accretions of sediment caused by these dams (4) by formation of natural levees, and (5) by deposi­ are small, however, and generally are flushed down­ tion on alluvial fans at the mouths of tributary streams. stream during major floods. In subreaches A and B the volume of sediment accre­ The temporal distribution of flow and the average tion by all the different methods is well documented for annual flow about 260,000 acre-feet at the head of 1935-70. The average annual change in altitude of the Safford Valley in 1920-64 probably were about the same bottom land was 0.03 foot per year for subreach A and as those during 1800-1904. Based on this premise, the 0.08 foot per year for subreach B. Much of the sediment flood of November 1905, which had a peak flow rate of accreted in subreach B is coarse material from steep about 150,000 cfs, probably was the largest flood ir side tributaries. For 1935-70 the accretion of sediment more than 170 years. The preceding statements are in the 45-mile-long study reach of the Gila River is esti­ based on the following facts: The stream-channel mated to be about 650 acre-feet per year. width is governed mainly by rates of streamflow; dur­ The most important factors influencing the deposi­ ing 1846-1904 the stream channel was narrow and fairly tion of sediment during 1918-70 were the wide flood channel and the small floods that carried large sediment stable and meandered through a densely vegetated floor1 loads. The large sediment loads resulted mainly from plain; and, subsequent to the channel-widening floods the rapid erosion of the alluvial deposits in the water­ of 1905-17, it took 50 years for the flood-plain develop­ sheds tributary to the Gila River. The small floods origi­ ment to approach that prior to 1905. G24 GILA RIVER PHREATOPHYTE PROJECT REFERENCES CITED

Barr, G. W., 1954, Arizona agriculture 1954: Arizona Univ., Agr. Lapham, M. H., and Neill, N. P., 1904, Soil survey of the Expt. Sta. Bull. 252,18 p. Solomonsville area, Arizona: U.S. Dept. Agriculture, Bur. Blaney, H. F., and Criddle. W. D., 1962, Determining consump­ Soils 5th Rept, p. 1045-1070. tive use and irrigation water requirements: U.S. Dept. Lindner, C. P., 1952, Diversions from alluvial streams: Am. Soc. Agriculture Tech. Bull. 1275. 59 p. Civil Engineers Proc., v. 78, no. 112, 25 p. Burkham, D. E., 1970, Precipitation, streamflow, and major Olmstead, F. H., 1919, Gila River flood control ? report on floods at selected sites in the Gila River drainage basin flood control of the Gila River in Graham County, Arizona: above Coolidge Dam, Arizona: U.S. Geol. Survey Prof. U.S. 65th Cong., 3d sess., S. Doc. 436, 94 p. Paper 655-B, 33 p. Rowalt, E. M., 1939, Soil defense of range and farm lands in the Calvin, Ross, 1946, River of the sun Stories of the storied Gila: Southwest: U.S. Dept. Agriculture Misc. Pub. 338, 51 p. Albuquerque, New Mexico Univ. Press. 153 p. Schumm, S. A., and Lichty, R. W., 1963, Channel widening and Chamberlin, W. H., 1945, From Lewisburg to California in flood-plain construction along Cimarron Rive" in south­ 1849 Notes edited by L. B. Bloom: New Mexico Historical western Kansas: U.S. Geol. Survey Prof. Prper 352-D, Rev., v. 20, no. 2, p. 144-180. p. 71-88. Chorley, R. J., Dunn, A. J., and Beckinsale, R. P., 1964, The Schwennesen, A. T., 1921, Geology and water resources of the history of the study of landforms or the development of Gila and San Carlos Valleys in the San Carlos Irdian Reser­ geomorpliology Volume 1, Geomorphology before Da vis : vation, Arizona: U.S. Geol. Survey Water-Supply Paper Methuen and Co., and John Wiley & Sons, 678 p. 450-A, 27 p. Clarke, D. L., 1966, The original journals of Henry Smith Sellers, W. D., ed., 1960, Arizona climate: Tucson, Arizona Univ. Turner : Norman, Oklahoma Univ. Press, 173 p. Press, 60 p. Culler, R. C.. and others, 1970, Objectives, methods, and environ­ Smith, Winchell. and Heckler. W. L., 1955, Compilation of flood ment Gila River Phreatophyte Project, Graham County, data in Arizona, 1862-1953: U.S. Geol. Survey open-file Arizona : U.S. Geol. Survey Prof. Paper 655-A, 25 p. report, 113 p. Davidson, E. S.. 1961, Facies distribution and hydrology of inter- Stockton, C. W., and Fritts, H. C., 1968, Conditional probability montane basin fill, Safford basin, Arizona, in Geological of occurrence for variations in climate based o*1 widths of Survey research 1961: U.S. Geol. Survey Prof. Paper 424-C, annual tree rings in Arizona: Arizona Univ., Laboratory of p. C151-C153. Tree-ring Research Ann. Rept., 24 p. Emory, W. H., 1848, Notes of a military reconnaissance, from Thomas, H. E., 1962, The meteorologic phenomenon of drought Fort Leavenworth, in Missouri, to San Diego, in California, in the Southwest: U.S. Geol. Survey Prof. P^per 372-A, including part of the Arkansas, Del Norte, and Gila Rivers: 43 p. U.S. 30th Cong., 1st sess. Ex. Doc. 41, 614 p. Gatewood, J. S., Robinson, T. W., Colby. B. R., Hem, J. D., and U.S. Army Corps of Engineers, 1914, San Carlos Irrigation Halpenny. L. C., 1950, Use of water by bottom-land vegeta­ Project, Arizona : U.S. 63d Cong., 2d sess., H. Do-. 791, 168 p. tion in lower Safford Valley, Arizona: U.S. Geol. Survey U.S. Geological Survey, issued annually, Water resources data Water-Supply Paper 1103, 210 p. for Arizona Part 2, Water quality records: U.S. Geol. Griffin, J. S., 1953, A doctor comes to California The diary of Survey open-file reports. John S. Griffin, assistant surgeon with Kearny's Dragoons, Weech, Hiram. 1931, Autobiography: Hollywood, Calif., Lee 1846-1847: San Francisco, California Hist. Soc., 97 p. Printing Co., 46 p.

U. S. GOVERNMENT PRINTING OFFICE : 1972 O - 450-345