Geomorphic impact and rapid subsequent recovery from the 1996 Skeiðarársandur jökulhlaup, Iceland, measured with multi-year airborne lidar

The November 1996 jökulhlaup that burst from the Vatnajökull ice cap onto Skeiðarársandur was the highest-magnitude flood ever measured on the largest active glacial outwash plain (sandur). Centimeter-scale elevation transects, measured from repeat-pass airborne laser altimetry missions flown in 1996 (pre-flood), 1997, and 2001, show that sediment deposition exceeded erosion across the central Skeiðarársandur and established an average net elevation gain of + 22 cm for the event. Net elevation gains of + 29 and + 24 cm occurred in braided channels of the Gígjukvísl and Skeiðará rivers, respectively. Nearly half of these gains, however, were removed within 4 years, and the two rivers contrast strongly in style of erosional/depositional impact and subsequent recovery. In the Gígjukvísl, the 1996 jökulhlaup caused massive sediment deposition (up to ∼12 m) near the ice margin and intense “mega-forming” of braided channels and bars downstream. Post-jökulhlaup recovery (1997–2001) was characterized by rapid erosion (− 0.5 m) of ice-proximal sediments and their transport to downstream reaches, and eradication of the mega-forms. In contrast, the Skeiðará displays minimal post-jökulhlaup se