THE NILE DELTA
Delta ID # 27.
Contributed by Huh et al, 2004.
Nile River Delta, Egypt, Africa
LOCATION LAT. 31°44’N, LONG. 30°42’E
LANDMASS DRAINED AFRICA.
BASIN OF DEPOSITION MEDITERRANEAN SEA
CLIMATE DESERT (Bwh)
AIR TEMP RANGE 14°C TO 37°C,
TIDAL AMPLITUDE 0.4 M
DISCHARGE WATER 28000M3/S, SEDIMENT 111X106 TONS/YR,
DRAINAGE BASIN AREA 2.715X106 KM2
Delta type: Classic delta shape.
Contributed by Professor James Coleman, LSU. From: Coleman and Huh, 2004.
The Nile River system is the largest river system in Africa and the drainage basin covers an area of 3,038,100 sq km. From its major source, Lake Victoria (Figure 67) in east central Africa, the White Nile flows generally north through Uganda and into Sudan where it meets the Blue Nile at Khartoum, which rises in the Ethiopian highlands. From the confluence of the White and Blue Nile, the river continues to flow northwards into Egypt and on to the Mediterranean Sea. The southern part of the drainage basin consists of Pre-Cambrian rocks (East African Rift) and the remainder of the basin consists of a variety of Mesozoic, Tertiary and Quaternary sediments comprising the Amhara and Khartoum Plateaus. The southern and central basin is sparsely vegetated, consisting of subtropical savannas and grasslands, while the northern part of the basin consists mainly of xeric shrubs and deserts. The tributary density in the in the drainage basin is quite dense (0.20 km stream length per 500 sq km) and Lake Victoria is well displayed in this figure. From its headwaters, the main channel is some 3,878 km long. The average elevation in the basin is 737 m while the maximum is 2,900 m and the minimum is only 40 m. Average annual rainfall is 664 mm with a maximum of 2,703 mm and a minimum of 1 mm. Rainy months occupy the months of April through October and the dry months are November through March, during which the monthly rainfall rarely exceeds 20 mm per month. Surrounded by the Sahara Desert, with the Sinai Peninsular and Red Sea to East the Nile River system is an oasis of life within a highly arid environment [27-i06].
The alluvial valley of the main river channel is well-defined in the space shuttle photograph showing the relationship of the Nile River to the surrounding desert landscape (27-i07); and, is approximately 1,100 miles long and has an average width of 50 km. The average annual river discharge is 2,778 cu m/sec with a maximum of 7,692 cu m/sec in the month of September and a minimum of 979 cu m/sec in the month of April. The image adequately displays the narrow strip of green vegetation in the alluvial valley totally surrounded by the harsh desert conditions. The river is predominantly meandering in nature [27-i01] and numerous abandoned meander loops are found within the valley. Population within the alluvial valley is quite high, average density being 30 people per square kilometer.
The term "delta" was first applied by the Greek historian, Herodotus, approximately 450 B.C., to the triangular alluvial deposits at the mouth of the Nile River (27-i04). The delta displays the classical triangular shape characteristics of numerous large world-wide deltas. The area of the subaerial delta is 12,512 sq km and the abandoned delta is 8.68 times larger than the active delta. Two major distributaries are active today, the Damietta and the Rosetta. In ancient times, the Nile had seven distributaries; the Pelusiac, the Tanitic, the Mendesian, the Phatnitic (Bucolic), the Sebennytic, the Bolbitine and the Canopic. There are only two today; the Damietta and the Rosetta (27-i03). Tides offshore are extremely low, averaging only 0.43 m range. Wave energy is relatively high, with an average wave power at the shoreline of 10.25 x 107 ergs/sec/m coast.
The shoreline wave energy is highest during the months from November through April [27-g01]. Note that the highest wave energy is concentrated at the protruding mouths of the two distributaries. The root mean square wave height is 1.53 m. Subsidence is relatively high in the delta region, averaging 1.2 mm/yr. A considerable part of the delta coast lies below 1m elevation and some parts are below sea level and with continued eustatic sea level rise and continued subsidence, much of the delta will be inundated in the next century. Severe beach erosion is occurring along the coast and will continue and increase in future especially at the Rosetta and Damietta headlands. The delta was continuing to prograde at the mouth of the two main distributaries until construction of the Aswan High Dam, when severe coastal erosion commenced.
The delta area is heavily populated, with population densities of 3,000 per sq km being common in some parts of the delta. The region is under heavy agricultural use and the dark green colors on 27-i05 show the density of this agricultural use. Although heavily modified by man, the remnants of the former distributaries can still be discerned on the image. Saline salt and algal flats are common behind broad coastal barrier islands and dune fields.