The Indus River plain is a vast expanse of fertile land, covering about 200,000 square miles (518,000 square km), with a gentle slope from the Himalayan piedmont in the north to the Arabian Sea in the south. The average gradient of the slope is no more than 1 foot per mile (1 metre per 5 km). Except for the micro relief, the plain is featureless. It is divisible into two sections, the upper and lower Indus plains, on account of their differing physiographic features. The upper Indus plain is drained by the Indus together with its tributaries, the Jhelum, Chenab, Ravi, Beas, and Sutlej rivers, forming a developed system of interfluves, known locally as doabs, in Punjab province (Persian panj āb, “five waters,” in reference to the five rivers). In the lower plain the Indus River has a Nilotic character; i.e., it forms a single large river with no significant tributaries. The plain narrows to form a corridor near Mithankot, where the Sulaiman Range comes close to the plain and the Indus merges with its last major tributary, the Panjnad River (which is itself merely the confluence of the five Punjab rivers). Flooding is a perennial problem, especially along the Indus, as a consequence of heavy rains (usually in July and August).
The upper Indus plain consists of three subdivisions: the Himalayan piedmont, the doabs, and the Sulaiman piedmont (referred to locally as the Derajat). The Himalayan piedmont, or the sub-Shiwalik zone, is a narrow strip of land where the rivers enter into the plain from their mountain stage, thereby giving each a somewhat steeper gradient. The zone is characterized by numerous rivulets, which have produced a broken topography in parts of the zone. These streams remain dry except in the rainy season, when they swell into gushing streams with considerable erosive power.
The doabs between the various rivers display similar micro relief, which comprises four distinct landforms—active floodplains, meander floodplains, cover floodplains, and scalloped interfluves. An active floodplain (known locally as a khaddar or bet), which lies adjacent to a river, is often called “the summer bed of rivers,” as it is inundated almost every rainy season. It is the scene of changing river channels, though protective bunds (levees) have been built at many places on the outer margin of the bet to contain the river water in the rainy season. Adjoining the active floodplain is the meander floodplain, which occupies higher ground away from the river and is littered with bars, oxbow lakes, extinct channels, and levees. The cover floodplain is an expanse of geologically recent alluvium, the result of sheet flooding, in which alluvium covers the former riverine features. The scalloped interfluves, or bars, are the central, higher parts of the doab, with old alluvium of relatively uniform texture. The boundaries of the scalloped features are formed by river-cut scarps at places over 20 feet (6 metres) high. The generally level surface of this section of the plain is broken into small pockets in Chiniot and at Sangla Hill, near the much denuded Kirana Hills, which stand out in jagged pinnacles. These hills are considered to be the outliers of the Aravali Range of India.