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The layout and elevation design of the lava barriers on the Reykjanes Peninsula, Iceland

Hörn Hrafnsdóttir, Emilía Sól Guðgeirsdóttir

Abstract

In March 2021, the Department of Civil Protection and Emergency Management in Iceland, appointed a group of specialists (engineers and volcanologists) to look into ways to protect important infrastructure on the Reykjanes Peninsula, which had been dormant for about 800 years. The work started immediately. During the Fagradalsfjall eruption in 2021, barriers were tested. The real test came in late 2023 when land started to rise underneath Svartsengi Geothermal Power Plant (SGPP) and the town of Grindavík. Work on the lava barriers for the SGPP started early November 2023 and early January for Grindavík. On 19th of December 2023 the Sundhnúkur fissure erupted, with six additional eruptions in 2024. The barriers are now 13 km in length with height up to 25 m. They have so far protected the infrastructure as intended, even though a fissure in January 2024 opened through the barrier and another one at the very edge of Grindavík. The talk will focus on the design of the barriers which include. 1) The main tool: lava flow modelling using the Bingham fluid option in HEC-RAS; 2) Calibration of parameters; 3) The design lavas and their evolution/re-evaluation between events; 4) How well did the simulations fit with reality; 5) How the simulations have been used for the layout and elevation design of the barriers; 6) How a re-evaluation of the barriers is needed after each eruption; 7) How the simulations have been used to estimate minimum time before lava might reach important locations.