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<p class="MsoNormal">Hi Everyone,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">See details below for a seminar this week about debris flows and sediment entrainment modeling!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Francis <o:p></o:p></p>
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<p class="MsoNormal" style="background:white;vertical-align:baseline"><b><span style="font-size:8.0pt;font-family:"Palatino Linotype",serif;color:#174E86;border:none windowtext 1.0pt;padding:0in">Francis Kevin Rengers, Ph.D. | Geomorphologist </span></b><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><b><span style="font-size:8.0pt;font-family:"Palatino Linotype",serif;color:#174E86">U.S. Geological Survey | Research Geologist </span></b><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><b><span style="font-size:8.0pt;font-family:"Palatino Linotype",serif;color:#174E86">1711 Illinois St. Golden, CO 80401 </span></b><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
<p class="MsoNormal" style="background:white;vertical-align:baseline"><b><span style="font-size:8.0pt;font-family:"Palatino Linotype",serif;color:#174E86">office: 303-273-8637 | cell: 720-618-0351</span></b><span style="font-size:8.0pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:8.0pt;font-family:"Palatino Linotype",serif;color:#174E86"><a href="https://www.usgs.gov/staff-profiles/francis-rengers"><span style="color:#0563C1">https://www.usgs.gov/staff-profiles/francis-rengers</span></a></span></b><o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Thomas, Matthew A <matthewthomas@usgs.gov><br>
<b>Date: </b>Monday, November 16, 2020 at 9:29 AM<br>
<b>To: </b><br>
<b>Subject: </b>LHP Seminar, this Wed. (Nov. 18th): Dr. Colton Conroy presenting "Modeling entrainment of bed sediment by debris flows and water floods"<o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black">Hi Folks,</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black"> </span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black;background:white">The
<b>last <span class="markr5pzcgmfz">LHP</span> <span class="mark3u6ljn0fn">Seminar of CY 2020</span></b> will meet (virtually, via Microsoft Teams) this week on<b> Wednesday, November 18th @ 1500</b> <b>Mountain </b>(MST).</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
<p style="background:white"><span style="font-size:12.0pt;color:#201F1E"> </span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:#201F1E"><a href="https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcoltonjconroy.squarespace.com%2Fabout-me&data=04%7C01%7C%7Cdc3db7c74e654638cf4e08d88a4d0afb%7C0693b5ba4b184d7b9341f32f400a5494%7C0%7C0%7C637411410780951239%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Ry4Y%2BTXmoX2DoXaeyyTpvW7FWLAtLVPd6EyfXJmYn68%3D&reserved=0" originalsrc="https://coltonjconroy.squarespace.com/about-me" shash="A/0ZTM9+X2ZmRdVI8U1BOe0XD2W05xBpxR8d4J/FZAwPBf3BldrWYKvyjUgC22vnv7/cNllqIlJBat+7912tLlFfARkvaP8zCSLAtPleP182r18tJCHTYFL0X3obW2/w2pMTX6djRRKy329Tnt+fCpdanEMmYMCIV5V5vFTmoG8=" title="https://coltonjconroy.squarespace.com/about-me">Dr.
Colton Conroy</a> from Southern Methodist/Columbia University will be presenting, “Modeling entrainment of bed sediment by debris flows and water floods”:</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:black">Wildfires drastically change the hydrological properties of a watershed by burning vegetation and the underlying soil creating low-permeability surfaces. When intense precipitation
falls on these surfaces, a reduced hydraulic conductivity leads to reduced infiltration making the catchment susceptible to run-off. As this run-off collects and moves downstream, then at some critical threshold it begins to entrain loose sediment and mobilize
debris, including boulders and tree stumps, creating a two-phase mixture. Pore-pressure feedback within the two-phase mixture can cause the flow to contract and run away interacting with topography and gaining enough momentum to damage structures in its path.
When these debris flows occur on alluvial fans in populated areas the results can be catastrophic.</span><span style="font-size:10.0pt;color:#201F1E"> </span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:black">In an effort to measure the resilience of human communities to run-off generated debris flows and design robust protocols to predict probable inundation in post wildfire
scenarios, we develop a new sediment entrainment model that can be used in geophysical flow models to initiate and propagate run-off generated debris flows.</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:black">The model extends the mathematical model of Iverson and George (2014) to account for an erodible bed and assumes that the transfer of momentum from the bed to the flow
is due to a change in the pressure gradient at the flow/bed interface. More specifically, the jump in the pressure gradient at the flow/bed interface is a function of the shear stress on the bed created by the overlying flow and the resistance of the bed to
the shear stress, which consists of Coulomb friction and pore-pressure suction.</span><span style="font-size:10.0pt;color:#201F1E"> </span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:10.0pt;color:#201F1E">We evaluate the new entrainment model against large-scale experiments performed at the USGS experimental flume in Blue River, Oregon. We compare model results to gate-release
experiments that consist of saturated debris flows and water floods traveling over a 47 m long, and approximately 12 cm thick, bed of partially saturated sediment lining the 31◦flume. We highlight the model’s ability to reproduce experimental results for varying
degrees of saturation of the bed sediment and present initial qualitative results from application of the model to entrainment scenarios at Spirit Lake in Washington.</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black;background:white">Hope you can join us!</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span class="mark3u6ljn0fn"><b><span style="font-size:10.0pt;color:#201F1E">Seminar</span></b></span><b><span style="font-size:10.0pt;color:#201F1E"> Connection Instructions:</span></b><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:10.0pt;color:#201F1E">-- Turn your VPN services off.</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black">Take care,</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p style="background:white"><span style="font-size:12.0pt;color:black">matt</span><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#201F1E"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt">Matthew A. Thomas</span></b><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt">Research Hydrologist (Mendenhall Fellow)</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;color:black;background:white">1711 Illinois Street, Golden, CO 80401</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;color:black;background:white">office: 303-273-8588 </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;color:black;background:white">cell: 720-417-9021<br>
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</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"><a href="https://www.usgs.gov/staff-profiles/matthew-a-thomas" title="https://www.usgs.gov/staff-profiles/matthew-a-thomas"><span style="font-size:10.0pt;background:white">USGS</span></a></span><span style="font-size:10.0pt"> |
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