Terrain, Vegetation, and Drainage
Physiographically, Somalia is a land of limited contrast. In the north, a maritime plain parallels the Gulf of Aden coast, varying in width from roughly twelve kilometers in the west to as little as two kilometers in the east. Scrub-covered, semiarid, and generally drab, this plain, known as the guban (scrub land), is crossed by broad, shallow watercourses that are beds of dry sand except in the rainy seasons. When the rains arrive, the vegetation, which is a combination of low bushes and grass clumps, is quickly renewed, and for a time the guban provides some grazing for nomad livestock.
Inland from the gulf coast, the plain rises to the precipitous northward-facing cliffs of the dissected highlands. These form the rugged Karkaar mountain ranges that extend from the northwestern border with Ethiopia eastward to the tip of the Horn of Africa, where they end in sheer cliffs at Caseyr. The general elevation along the crest of these mountains averages about 1,800 meters above sea level south of the port town of Berbera, and eastward from that area it continues at 1,800 to 2,100 meters almost to Caseyr. The country's highest point, Shimber Berris, which rises to 2,407 meters, is located near the town of Erigavo.
Southward the mountains descend, often in scarped ledges, to an elevated plateau devoid of perennial rivers. This region of broken mountain terrain, shallow plateau valleys, and usually dry watercourses is known to the Somalis as the Ogo.
In the Ogo's especially arid eastern part, the plateau-- broken by several isolated mountain ranges--gradually slopes toward the Indian Ocean and in central Somalia constitutes the Mudug Plain. A major feature of this eastern section is the long and broad Nugaal Valley, with its extensive network of intermittent seasonal watercourses. The eastern area's population consists mainly of pastoral nomads. In a zone of low and erratic rainfall, this region was a major disaster area during the great drought of 1974 and early 1975.
The western part of the Ogo plateau region is crossed by numerous shallow valleys and dry watercourses. Annual rainfall is greater than in the east, and there are flat areas of arable land that provide a home for dryland cultivators. Most important, the western area has permanent wells to which the predominantly nomadic population returns during the dry seasons. The western plateau slopes gently southward and merges imperceptibly into an area known as the Haud, a broad, undulating terrain that constitutes some of the best grazing lands for Somali nomads, despite the lack of appreciable rainfall more than half the year. Enhancing the value of the Haud are the natural depressions that during periods of rain become temporary lakes and ponds.
The Haud zone continues for more than sixty kilometers into Ethiopia, and the vast Somali Plateau, which lies between the northern Somali mountains and the highlands of southeast Ethiopia, extends south and eastward through Ethiopia into central and southwest Somalia. The portion of the Haud lying within Ethiopia was the subject of an agreement made during the colonial era permitting nomads from British Somaliland to pasture their herds there. After Somali independence in 1960, it became the subject of Somali claims and a source of considerable regional strife.
Southwestern Somalia is dominated by the country's only two permanent rivers, the Jubba and the Shabeelle. With their sources in the Ethiopian highlands, these rivers flow in a generally southerly direction, cutting wide valleys in the Somali Plateau as it descends toward the sea; the plateau's elevation falls off rapidly in this area. The adjacent coastal zone, which includes the lower reaches of the rivers and extends from the Mudug Plain to the Kenyan border, averages 180 meters above sea level.
The Jubba River enters the Indian Ocean at Chisimayu. Although the Shabeelle River at one time apparently also reached the sea near Merca, its course is thought to have changed in prehistoric times. The Shabeelle now turns southwestward near Balcad (about thirty kilometers north of Mogadishu) and parallels the coast for more than eighty-five kilometers. The river is perennial only to a point southwest of Mogadishu; thereafter it consists of swampy areas and dry reaches and is finally lost in the sand east of Jilib, not far from the Jubba River. During the flood seasons, the Shabeelle River may fill its bed to a point near Jilib and occasionally may even break through to the Jubba River farther south. Favorable rainfall and soil conditions make the entire riverine region a fertile agricultural area and the center of the country's largest sedentary population.
In most of northern, northeastern, and north-central Somalia, where rainfall is low, the vegetation consists of scattered low trees, including various acacias, and widely scattered patches of grass. This vegetation gives way to a combination of low bushes and grass clumps in the highly arid areas of the northeast and along the Gulf of Aden.
As elevations and rainfall increase in the maritime ranges of the north, the vegetation becomes denser. Aloes are common, and on the higher plateau areas of the Ogo are woodlands. At a few places above 1,500 meters, the remnants of juniper forests (protected by the state) and areas of candelabra euphorbia (a chandelier-type cactus) occur. In the more arid highlands of the northeast, boswellia and commiphora trees are sources, respectively, of the frankincense and myrrh for which Somalia has been known since ancient times.
A broad plateau encompassing the northern city of Hargeysa, which receives comparatively heavy rainfall, is covered naturally by woodland (much of which has been degraded by overgrazing) and in places by extensive grasslands. Parts of this area have been under cultivation since the 1930s, producing sorghum and corn; in the 1990s it constituted the only significant region of sedentary cultivation outside southwestern Somalia.
The Haud south of Hargeysa is covered mostly by a semiarid woodland of scattered trees, mainly acacias, underlain by grasses that include species especially favored by livestock as forage. As the Haud merges into the Mudug Plain in central Somalia, the aridity increases and the vegetation takes on a subdesert character. Farther southward the terrain gradually changes to semiarid woodlands and grasslands as the annual precipitation increases.
The region encompassing the Shabeelle and Jubba rivers is relatively well watered and constitutes the country's most arable zone. The lowland between the rivers supports rich pasturage. It features arid to subarid savanna, open woodland, and thickets that include frequently abundant underlying grasses. There are areas of grassland, and in the far southwest, near the Kenyan border, some dry evergreen forests are found.
Along the Indian Ocean from Mereeg, about 150 kilometers northeast of Mogadishu, southwestward to near Chisimayu lies a stretch of coastal sand dunes. This area is covered with scattered scrub and grass clumps where rainfall is sufficient. Overgrazing, particularly in the area between Mogadishu and Chisimayu, has resulted in the destruction of the protective vegetation cover and the gradual movement of the once-stationary dunes inland. Beginning in the early 1970s, efforts were made to stabilize these dunes by replanting.
Other vegetation includes plants and grasses found in the swamps into which the Shabeelle River empties most of the year and in other large swamps in the course of the lower Jubba River. Mangrove forests are found at points along the coast, particularly from Chisimayu to near the Kenyan border. Uncontrolled exploitation appears to have caused some damage to forests in that area. Other mangrove forests are located near Mogadishu and at a number of places along the northeastern and northern coasts.
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