per cent (765 square miles) is in unimproved land and has a rating of 60; and 29 per cent (715 square miles) is in cultivated land rated at 70. The average cover rating for the type is 73, which indicates a detrimental influence on this critical area.

(e) Wolf River.-The Wolf River rises in northern Mississippi and flows north and west through southwestern Tennessee to the Mississippi River. Its drainage lies between that of the Hatchie on the north and east and the Yazoo Highlands on the south. The total area is 1,888 square miles, of which 23 per cent (432 square miles) is within the boundaries of the bottom-land hardwoods type and 77 per cent (1,456 square miles) is in the upland hardwoods type. Agriculture is the chief industry and 70 per cent of the area is in farms.

Within the boundaries of the bottom-land hardwoods type, 36 per cent (156 square miles) of the area, with a rating of 100, is in forest consisting of gums, oaks, and some cypress. An additional 36 per cent (155 square miles), rated at 80, is in unimproved land, and 28 per cent (121 square miles), with a rating of 90, is in cultivation. The total cover rating for the type is 90, but the location makes this cover of little effect in flood control.

Twenty-eight per cent (408 square miles) of the more extensive area within the boundaries of the upland hardwoods type is in forest consisting mainly of oak and hickory with a little shortleaf pine in mixture. Some fires occur here. The rating is 85. The 33 per cent (480 square miles) of unimproved land, much of it abandoned farm land, rates 60, and the 39 per cent (568 square miles) of cultivated land rates 70. The average rating for all cover in this type is 71, indicating a detrimental influence for this critical area.

(f) Tensas River.--The Tensas River rises in northeastern Louisiana and flows south through northeastern Louisiana. The Bayou Macon, the main tributary of the Tensas, rises in southeastern Arkansas, near the mouth of the Arkansas River. The Ouachita joins the Tensas a short distance above the Red River; the two form the Black River which enters the Red just above its mouth. The Tensas might more properly be included in the Red River drainage, but for the purposes of this study, it has been assigned to the lower Mississippi direct. The Tensas drainage, which has an area of 4,180 square miles, is level, subject to overflow, and, on the whole, well forested, and contributes little to the load of silt in the Mississippi. The Tensas receives a portion of the flood waters from the Arkansas and from the Mississippi itself, thus acting as a safety valve and storage reservoir for the latter stream.

Practically all of the Tensas drainage falls within the boundaries of the bottom land hardwood type, consisting of red gum, various oaks, pecan, and ash, with small amounts of cypress and tupelo gum. Only 34 per cent of the land is in farm ownership, most of the rest belongs to large lumber companies. Of the total area, 41 per cent (1,714 square miles), rated at 100, is in forest; 43 per cent (1,797 square miles), rated at 85, is in unimproved land; and 16 per cent (669 square miles), rated at 95, is in cultivated land. The total cover rating for the entire type and basin is 93.

(g) Atchafalaya River.-Because its drainage is indeterminate, and because it empties into the Gulf of Mexico instead of into the Mississippi, the Atchafalaya River has been omitted from this study.

(h) Miscellaneous smaller tributaries draining directly into the Mississippi.-Included in the lower Mississippi direct, but not mentioned in the discussion above, are five small areas; (1) in eastern Missouri above the Little River drainage; (2) in southwestern Kentucky and northwestern Tennessee; (3) between the Bayou Tallahala and Homochitto River drainages in southern Mississippi; (4) between the Homochitto drainage and the Missippi-Louisiana line; and (5) lying east of the Mississippi River in Louisiana. The largest (2) has an area of 1,414 square miles and the two smallest, (3) and (4), contain about 525 square miles each. All contain critical or near-critical areas; all except (5) lie more in pine or upland hardwood types than in bottom land hardwoods, and exhibit a detrimental influence in respect to floods. Their size, location, and relatively small drainage basins, however, make them of much less importance than the adjacent drainages discussed in detail in this and other minor drainage reports; and it seems sufficient to dismiss them. with a reference to these adjacent drainages for general description. Their areas, by types and conditions, together with the ratings assigned them, are given in the appropriate tables in the major tributary report for the Lower Mississippi Basin.

To sum up, the lower Mississippi direct drainage, with a gross area of 27,561 square miles (excluding the basin of the Atchafalaya, which does not empty into the Mississippi), has 4 per cent of its area, 1,008 square miles, within the boundaries of the pine type; 14,915 square miles, or 54 per cent, within the bottom land hardwoods types; and 11,638 square miles, or 42 per cent within the upland hardwoods type. Within this area as a whole all the critical areas except Crowley's Ridge and the eastern Missouri hills lie to the east of the Mississippi. Most of the land on the west side is of relatively small importance in flood control, though much of it suffers directly from floods originating elsewhere.

The upland hardwood type, lying as it does on the higher lands which constitute the critical areas, is of most importance from the standpoint of flood control and erosion. It includes 34 per cent (3,900 square miles) of woodland and forest, much of it burned at intervals, but with an average rating of 85; 29 per cent (3,424 square miles) of unimproved land, much of which is washed and gullied almost beyond reclamation, with an average rating of 61; and 37 per cent (4,314 square miles) of cultivated land, as a whole insufficiently protected against erosion, and rated at 70. The total cover rating for the type is 72. Next in importance is the pine type, which occurs on three critical areas-two in Mississippi and one in Louisiana. Fire is more common on the 35 per cent (348 square miles) of woods and forests than in the corresponding cover in the upland hardwood forests, and the pine forests are rated at 82; unimproved land occupies 50 per cent (504 square miles) of the area, and is rated at 64; and cultivated land, rated at 74, occupies 15 per cent of the area, or 156 square miles. The total rating for the type is 71.

Because of its location the bottom land hardwood type, with a total cover rating of 90, is of practically no importance in the study of run-off and erosion.

CRITICAL AREAS

Within this series of direct drainages the following areas appear critical from the standpoint of flood control:

(1) The region in southeastern Missouri belonging to the northern Ozark soil province where, mainly because of the hilly topography, soil erosion must be guarded against.

(2) Crowleys Ridge in southeastern Missouri and northeastern Arkansas, which is similar, as regards soil formation, to the Mississippi bluff lands on the opposite side of the Mississippi River. Here soil erosion is serious mainly on cultivated land, and this can be overcome by improved agricultural practices and by keeping the steepest slopes in forest cover. Such forest cover can be maintained by fire protection and conservative cutting practices.

(3) Practically all of the lands which occur in the Mississippi bluffs and silt loam uplands soil province lie east of the Mississippi River and adjoin similar areas to the north and south. Together these areas in several different drainages from a belt stretching from the western tip of Kentucky to eastern Louisiana, bounded on the west by the flood plains of the Mississippi River and on the east by an irregular line which marks the eastern termination of the rough, easily eroded hill country of the silt loam uplands where they merge with the more level coastal plain soils. It is here that soil erosion is at its worst, with practically no steps being taken to improve conditions. Typical of this region is the Yazoo highlands, concerning which Dr. E. N. Lowe, the State geologist of Mississippi, has made the following statement: 1

The interrelation of deforestation of the uplands, rapid erosion of the soils, extensive stream filling, and destructive flooding of lowlands, seems evident in the Yazoo drainage basin. It seems equally evident that these distressing conditions are yearly growing worse instead of better, calling for immediate and effective remedial treatment. But no remedy will be effective which does not strike at the root of the evil. The rapid erosion of the uplands must be stopped. In the more broken areas forests or other protective growth will be necessary, and in the less broken parts seeding the soil with Bermuda grass and other forage plants may be used effectively. Where great chasms have developed and are yearly cutting deeper into the hillslopes, damming would be too expensive to attempt in this stage of agricultural development. But an effective remedy consists of seeding the bottoms of these washes in black locust and honeysuckle. In a few years these begin to mat the washing surface so thickly as to stop the washing and promote filling. Usually at this stage these may be reinforced in the open spaces with Bermuda grass.

These methods are proving satisfactory in many places and within a few years will produce notable results.

The rating given to these scattered drainages has been put at 76.

RECOMMENDATIONS

Most of the critical areas occurring in these widely scattered minor drainages of the lower Mississippi River can best be handled in conjunction with the adjoining areas which have been discussed in detail under recommendations for the Bayou Tallahala, Yazoo Highlands, Homochitto, and Big Black River Basins in Mississippi. The solution of the soil-conservation problem in this region hinges on Gov

'Lowe, Dr. E. N. Lumber World Review. Feb. 25, 1922.

ernment control because little or nothing is being done by-or can be anticipated from-the districts affected. The establishment of either National or State forests, or both, would assure the quickest and most effective remedy at the present time, especially in the area lying within the boundaries of the States of Mississippi, Louisiana, and Missouri. Probably State action alone would be sufficient in Kentucky and Tennessee; but in all of the districts included in these drainages past damage can be repaired and future mistakes avoided only through maintaining or replacing a forest cover on such slopes as are subject to excessive erosion and in limiting cultivation to the more level areas. The forest land must be protected from fire and the cutting practices regulated so that the forest cover is never entirely removed; barren or severely eroded places must be replanted to trees. The introduction of improved agricultural practice such as contour plowing and terracing is essential and will necessitate the closest cooperation between county agricultural agents, extension foresters, and State departments of forestry.

The critical area in southeastern Missouri should be included in any plans leading toward improvement of conditions in the Ozark region as a whole, most of which lies in adjoining drainages. The Crowley's ridge region is too valuable as agricultural land to be kept in forests (excepting the steeper slopes); and improved agricultural practices will be sufficient to prevent further erosion in this region.

Detailed investigations of each of the regions considered critical will be necessary before estimates of the area of forest land needed for protection purposes can be made. Development of methods of erosion prevention and study of the measures needed to stop erosion which has already started will be necessary also and should be undertaken immediately by the agencies best equipped to handle such investigations.

YAZOO BOTTOM LANDS

(Area 41)

LOCATION AND AREA

The Yazoo bottom lands, covering a gross area of 7.324 square miles, are located in northwestern Mississippi. The boundary of this region extends from the Mississippi River near the Tennessee line southwards nearly to Vicksburg. The Mississippi River forms the entire western boundary of these bottom lands. The rugged line of the Mississippi Bluffs on the east divides the bottom lands from the Yazoo Highlands, and to the southeast lies the Big Black watershed.

TOPOGRAPHY

This drainage basin is about 180 miles long and 60 miles wide at its widest part, tapering gradually to a point at both northern and

southern extremities.

Ninety-two per cent of this entire region, known as the Yazoo Delta, consists of a flat, alluvial plain which slopes gently southward. Portions of the Mississippi Bluff lands occur in the southeast corner of this watershed, composing the remaining 8 per cent of the area.

At the Tennessee line near the northern tip of the bottom lands, the elevation is 217 feet above sea level. Vicksburg, near the southern extremity, has an elevation of 97 feet. Due to this lack of topographic relief, drainage is poor and the streams are sluggish and inclined to meander. Long, narrow, crooked lakes and bayous formed by the abandonment of old stream channels, are of common

occurrence.

Clays form the predominating soil type and occupy the lower, more poorly drained lands, farther from the streams. The silt deposits from the periodic overflow of the streams have formed ridges, the highest portions of which are always found nearest the water courses because of the immediate deposition of the heavier soil particles whenever the stream overflows its banks. As the velocity of the overflow decreases with increased distance from the main stream bed, due to the obstruction of vegetation, the carrying power of the water also decreases, causing further deposition of sediment.

Although this whole area was originally heavily timbered, most of it is now in a high state of cultivation, the land having been rapidly converted into farms after the timber had been cut off.

GEOLOGY AND SOILS

The soils of the Yazoo bottom lands are almost entirely made up of alluvial deposits, the single exception occurring in the comparatively small area of wind-blown, or loess, soil of the Mississippi bluff region in the southeast corner of the watershed.

Along the eastern border of the bottom lands adjacent to the Mississippi Bluffs there is a soil type composed of material which has been washed down from the hill land of the upper Yazoo. This area is but a few miles wide at most and, being somewhat higher than the adjacent bottom lands, is well drained, and makes up an extremely fertile agricultural region. Stiff, impervious clays predominate over the remaining portion of the bottoms. Narrow belts of loam occur along the streams.

The composition of these soils is such as to make them very susceptible to erosion, but the complete lack of topographic relief removes this danger. Erosion in the Yazoo bottom lands is limited entirely to the small area of loess soils in the southeast corner. Here, as in adjacent watersheds containing loess deposits, gullying of unprotected and uncared-for lands is proceeding rapidly.

CLIMATE

The mean annual precipitation is 50 inches, half of which falls during the warm season. About 15 inches of rain normally falls during March, April, and May, but in 1927 the rainfall amounted to 21 inches during March and April. As compared with other areas in the lower Mississippi region the normal precipitation is medium. in amount.

The mean temperature is about 64° F. for the year, 40° to 45° for January, and 80° for July. Snow covers the ground for two or three days per year.