matl.). By 1804 (Rennell, 1804; see suppl. matl.), the Nasirpur course (called the Dimtadee River on the map) flowed immediately to the north of the town of Nasirpur. The map of Arrowsmith (1804; see suppl. matl.) notes that the Indus flood season over the delta was in April, May and June, two months earlier than today, possibly indicating a greater contribution from the Himalaya. Pinkerton (1811; see suppl. matl.)

states that the Indus River is navigable for 900 km upstream. Steamships continued this website to ply the river as a cargo transport to Attock until replaced by railways in 1862 (Aitkin, 1907). The Baghar channel (Fig. 1) began to silt up in circa 1819. The Indus River then forged its main channel down its former Sattah Branch, but turned west, reaching the sea via the Ochito Branch (Fig. 1; Holmes, 1968). Through the period 1830–1865 (SDUK, 1833 and Johnston, 1861; see suppl.

matl.) the main Indus Delta channel was located along the modern Indus course, and numerous distributary channels were maintained both to the west and to the southeast (Fig. 7). On an 1833 map (SDUK, 1833; see suppl. matl.) the tide is stated as reaching inland 111 km. By 1870–1910 (Letts, 1883; see suppl. matl.), the main Indus had shifted further south and east while still maintaining flow to the western distributary channels (Fig. 7; also see Johnston and Johnston, 1897 in the suppl. matl.). By check details 1922 (Bartholomew, 1922; suppl. matl. and Fig. 7), the Ochito River channel was the main branch,

but this had largely been abandoned by 1944 (Fig. 7). The Indus channel is reduced to a single thread in its deltaplain, and the number of delta distributary channels has decreased during the 19th century, from ∼16 to 1 (Table 1 and Fig. 6). The modern delta does not receive much fluvial water or sediment. There were zero no-flow days prior to the Kotri Barrage construction in 1955. After construction (c. 1975), up to 250 no-flow days per year occur. The average annual water and sediment discharges during 1931–1954 were 107 km3 and 193 Mt, respectively. During the 1993–2003 period these rates dropped an order-of-magnitude to 10 km3 and 13 Mt (Inam et al., 2007). The Indus discharge downstream of the Kotri Barrage is usually limited to only not 2 months: August–September, with the sea now intruding the delta up to 225 km (Inam et al., 2007). Abandoned Indus Delta channels have been tidally reworked all along the coast (Fig. 8 and Fig. 9). We mapped this evolution of delta channels using high-resolution imagery: (1) the 1944 topographic maps (USACE, 1944; RMS location error ±196 m), (2) the 2000 SRTM/SWDB database (see suppl. matl.; RMS error ±55 m), and (3) LANDSAT imagery from 1978, 1989, 1990, 1991, 2000 (RMS location error between ±32 m and 196 m). Imagery was selected to be representative of being part of the same astronomic tidal stage.