[ghsc-seminars] FW: LHP Seminar, this Wed. (Nov. 18th): Dr. Colton Conroy presenting "Modeling entrainment of bed sediment by debris flows and water floods"

Mon Nov 16 16:31:17 UTC 2020

Hi Everyone,

See details below for a seminar this week about debris flows and sediment entrainment modeling!

Best,

Francis

Francis Kevin Rengers, Ph.D. | Geomorphologist
U.S. Geological Survey | Research Geologist
1711 Illinois St. Golden, CO 80401
office: 303-273-8637 | cell: 720-618-0351
https://www.usgs.gov/staff-profiles/francis-rengers

From: Thomas, Matthew A <matthewthomas at usgs.gov>
Date: Monday, November 16, 2020 at 9:29 AM
To:
Subject: LHP Seminar, this Wed. (Nov. 18th): Dr. Colton Conroy presenting "Modeling entrainment of bed sediment by debris flows and water floods"

Hi Folks,

The last LHP Seminar of CY 2020 will meet (virtually, via Microsoft Teams) this week on Wednesday, November 18th @ 1500 Mountain (MST).

Dr. Colton Conroy<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> from Southern Methodist/Columbia University will be presenting, “Modeling entrainment of bed sediment by debris flows and water floods”:

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.

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.

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.

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.

Hope you can join us!

Seminar Connection Instructions:

-- Turn your VPN services off.

-- Join in via Microsoft Teams by clicking here<https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fteams.microsoft.com%2Fdl%2Flauncher%2Flauncher.html%3Furl%3D%252f_%2523%252fl%252fmeetup-join%252f19%253ameeting_NmU4M2E3ZDktNmIwOS00Y2NkLWEyZmMtNGM3YTQwYjQxYTFm%2540thread.v2%252f0%253fcontext%253d%25257b%252522Tid%252522%25253a%2525220693b5ba-4b18-4d7b-9341-f32f400a5494%252522%25252c%252522Oid%252522%25253a%25252282b4c0ea-89e9-402c-8d2a-8f68ffac5319%252522%25257d%2526anon%253dtrue%26type%3Dmeetup-join%26deeplinkId%3D354c7d10-e11c-4bfa-9af2-9aee09c70a3f%26directDl%3Dtrue%26msLaunch%3Dtrue%26enableMobilePage%3Dfalse%26suppressPrompt%3Dtrue%23&data=04%7C01%7C%7Cdc3db7c74e654638cf4e08d88a4d0afb%7C0693b5ba4b184d7b9341f32f400a5494%7C0%7C0%7C637411410780961195%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=AzLgLl2hYzGghlA001rbgEDa8Gpo6CMxC82vUCu22bw%3D&reserved=0>.

Take care,

matt

Matthew A. Thomas
Research Hydrologist (Mendenhall Fellow)
1711 Illinois Street, Golden, CO 80401
office: 303-273-8588
cell: 720-417-9021

USGS<https://www.usgs.gov/staff-profiles/matthew-a-thomas> | ResearchGate<https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.researchgate.net%2Fprofile%2FMatthew_Thomas27&data=04%7C01%7C%7Cdc3db7c74e654638cf4e08d88a4d0afb%7C0693b5ba4b184d7b9341f32f400a5494%7C0%7C0%7C637411410780961195%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=pRVdV8oa%2FzcZZd%2BWiGij11967ngDNX%2B9IbhbxRVPmNc%3D&reserved=0> | Google Scholar<https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fscholar.google.com%2Fcitations%3Fuser%3DHg7I2YcAAAAJ%26hl%3Den&data=04%7C01%7C%7Cdc3db7c74e654638cf4e08d88a4d0afb%7C0693b5ba4b184d7b9341f32f400a5494%7C0%7C0%7C637411410780971153%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=SZMq9lDiEoHtbCzrTqkeIouFOIiKSa0pz38S6TMoQxg%3D&reserved=0>
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