Dynamic interactions between lahars and stream flow: A case study from Ruapehu volcano, New Zealand

Abstract

Research Article| January 01, 1999 Dynamic interactions between lahars and stream flow: A case study from Ruapehu volcano, New Zealand Shane J. Cronin; Shane J. Cronin 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand Search for other works by this author on: GSW Google Scholar V. E. Neall; V. E. Neall 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand Search for other works by this author on: GSW Google Scholar J. A. Lecointre; J. A. Lecointre 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand Search for other works by this author on: GSW Google Scholar A. S. Palmer A. S. Palmer 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information Shane J. Cronin 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand V. E. Neall 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand J. A. Lecointre 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand A. S. Palmer 1Department of Soil Science, Massey University, Private Bag 11222, Palmerston North, New Zealand Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1999) 111 (1): 28–38. https://doi.org/10.1130/0016-7606(1999)111<0028:DIBLAS>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Shane J. Cronin, V. E. Neall, J. A. Lecointre, A. S. Palmer; Dynamic interactions between lahars and stream flow: A case study from Ruapehu volcano, New Zealand. GSA Bulletin 1999;; 111 (1): 28–38. doi: https://doi.org/10.1130/0016-7606(1999)111<0028:DIBLAS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Three lahars were sampled in the Whan-gaehu River on the eastern flank of Ruapehu volcano, New Zealand, at 23.5 and 42 km from the source as they were flowing on September 27 and 29 and October 6, 1995. The lahars were generated by water explosively ejected from the highly mineralized Crater Lake. We used the chemical contrast between the lahars and resident stream water in their paths to describe a four-phase model of a noncohesive lahar wave in a river channel: (1) ambient stream water pushed ahead of the lahar in a process of miscible displacement due to hydrodynamic dispersion; (2) a zone of mixing between the stream water and the lahar that increases in length with distance from source; (3) a remnant of the original lahar, least diluted by stream water, that decreases in length and dilutes downstream; (4) the tail of the lahar surge. Peak discharge occurs at the end of phase 1 as water is pushed ahead of the lahar. Peak sediment concentration occurs at the end of phase 2, where debris entrainment by the flow is at its greatest (i.e., in front of the lahar proper). Deposits record only phases 2 and 3 of the lahar wave, phase 1 flow left only a tide line of organic debris, and phase 4 deposits were rapidly eroded by later streamflow. Downstream dilution by stream water eventually caused transformation of phases 2 and 3 of the lahars from debris flow to hyperconcentrated streamflow and then to normal streamflow as the flows became progressively finer grained and more turbulent. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.