Wildfire as a Catalyst for Hydrologic and Geomorphic Change

2019 ◽  
Author(s):  
Francis K. Rengers
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Overland Flow ◽  
Special Focus ◽  
Soil Erodibility ◽  
Erosion Rates ◽  
Current State ◽  
Order Of Magnitude ◽  
Fundamental Research ◽  
Recurrence Intervals

Wildfire has been a constant presence on the Earth since at least the Silurian period, and is a landscape-scale catalyst that results in a step-change perturbation for hydrologic systems, which ripples across burned terrain, shaping the geomorphic legacy of watersheds. Specifically, wildfire alters two key landscape properties: (1) overland flow, and (2) soil erodibility. Overland flow and soil erodibility have both been seen to increase after wildfires, resulting in order-of-magnitude increases in erosion rates during rainstorms with relatively frequent recurrence intervals. On short timescales, wildfire increases erosion and leads to natural hazards that are costly and threatening to society. Over longer timescales, wildfire-induced erosion can account for the majority of total denudation in certain settings with long-term implications for landscape evolution. There is a special focus on debris flows in this document because they are the most destructive geomorphic processes observed to follow wildfires after high severity burns. To date, research on post-wildfire debris flows has focused on: the provenance of sediment moved in debris flows, the hydrologic and soil properties required to produce debris flows, and debris flow initiation mechanisms. Herein we highlight the relevant research articles showing the current state of progress in debris flow research as well as pointing to the fundamental research on post-wildfire hydrology and erosion necessary for understanding how water and sediment behave after wildfires.

Terrestrial record of rapid mass movements in the Sawtooth Range, Ellesmere Island, Northwest Territories, Canada

1998 ◽  
Vol 35 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Antoni G Lewkowicz ◽  
James Hartshorn
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Growth Curves ◽  
Mass Movements ◽  
Mountain Front ◽  
Order Of Magnitude ◽  
Ice Wedge ◽  
Recurrence Intervals ◽  
Rapid Mass ◽  
Lichen Growth

Widespread clastic deposits, 80-1800 m long, on the eastern side of the Sawtooth Range are the result of debris flow and slushflow. Small hillslope debris flows (10-103 m3), originating on talus slopes at the mountain front and not associated with preexisting gullies, and large channelized debris flows (103-104 m3), debouching from basins within the mountains, are comparable morphologically to those in other high-latitude and high-altitude environments. Channelized deposits are often modified by the effects of slushflow and fluvial activity. Provisional lichen growth curves for the area were produced by correlation of thallus size with the enlargement of ice-wedge polygon troughs. Lichenometry and aerial photograph interpretation were used to estimate the age of deposits so that event frequencies and rates of geomorphic work could be calculated. Vertical transport by rapid mass movements during the 20th Century averaged 17 x 103 Mg ·m ·a-1 ·km-2 ( ± half an order of magnitude), corresponding to a rock denudation rate of 0.05 mm ·a-1 for the basins and peaks feeding the east-facing slopes. Channelized debris flow produced more than 70% of this transport. Several of these large flows occurred in each of the three periods of 30-35 years examined, so their recurrence intervals are substantially shorter than values reported from locations in northern Scandinavia and Spitzbergen.

scholarly journals The Development of a 1-D Integrated Hydro-Mechanical Model Based on Flume Tests to Unravel Different Hydrological Triggering Processes of Debris Flows

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 950 ◽  
Author(s):  
Theo van Asch ◽  
Bin Yu ◽  
Wei Hu
Keyword(s):  
Debris Flow ◽  
Mechanical Model ◽  
Debris Flows ◽  
Overland Flow ◽  
Slope Angle ◽  
Great Influence ◽  
Flume Experiments ◽  
Triggering Mechanisms ◽  
Bed Material ◽  
Triggering Process

Many studies which try to analyze conditions for debris flow development ignore the type of initiation. Therefore, this paper deals with the following questions: What type of hydro-mechanical triggering mechanisms for debris flows can we distinguish in upstream channels of debris flow prone gullies? Which are the main parameters controlling the type and temporal sequence of these triggering processes, and what is their influence on the meteorological thresholds for debris flow initiation? A series of laboratory experiments were carried out in a flume 8 m long and with a width of 0.3 m to detect the conditions for different types of triggering mechanisms. The flume experiments show a sequence of hydrological processes triggering debris flows, namely erosion and transport by intensive overland flow and by infiltrating water causing failure of channel bed material. On the basis of these experiments, an integrated hydro-mechanical model was developed, which describes Hortonian and saturation overland flow, maximum sediment transport, through flow and failure of bed material. The model was calibrated and validated using process indicator values measured during the experiments in the flume. Virtual model simulations carried out in a schematic hypothetical source area of a catchment show that slope angle and hydraulic conductivity of the bed material determine the type and sequence of these triggering processes. It was also clearly demonstrated that the type of hydrological triggering process and the influencing geometrical and hydro-mechanical parameters may have a great influence on rainfall intensity-duration threshold curves for the start of debris flows.

scholarly journals Debris flows on forested cones – reconstruction and comparison of frequencies in two catchments in Val Ferret, Switzerland

2007 ◽  
Vol 7 (2) ◽  
pp. 207-218 ◽  
Author(s):  
M. Bollschweiler ◽  
M. Stoffel
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Historical Knowledge ◽  
Study Region ◽  
Sampling Height ◽  
The Alps ◽  
Recurrence Intervals ◽  
Study Sites ◽  
Flow Activity ◽  
Different Characteristics

Abstract. Debris flows represent a major threat to infrastructure in many regions of the Alps. Since systematic acquisition of data on debris-flow events in Switzerland only started after the events of 1987, there is a lack of historical knowledge on earlier debris-flow events for most torrents. It is therefore the aim of this study to reconstruct the debris-flow activity for the Reuse de Saleinaz and the La Fouly torrents in Val Ferret (Valais, Switzerland). In total, 556 increment cores from 278 heavily affected Larix decidua Mill., Picea abies (L.) Karst. and Pinus sylvestris L. trees were sampled. Trees on the cone of Reuse de Saleinaz show an average age of 123 years at sampling height, with the oldest tree aged 325 years. Two periods of intense colonization (the 1850s–1880s and the 1930s–1950s) are observed, probably following high-magnitude events that would have eliminated the former forest stand. Trees on the cone of Torrent de la Fouly indicate an average age of 119 years. As a whole, tree-ring analyses allowed assessment of 333 growth disturbances belonging to 69 debris-flow events. While the frequency for the Reuse de Saleinaz study site comprises 39 events between AD 1743 and 2003, 30 events could be reconstructed at the Torrent de la Fouly for the period 1862–2003. Even though the two study sites evince considerably different characteristics in geology, debris-flow material and catchment morphology, they apparently produce debris flows at similar recurrence intervals. We suppose that, in the study region, the triggering and occurrence of events is transport-limited rather than weathering-limited.

scholarly journals Augmentation and Use of WRF-Hydro to Simulate Overland Flow- and Streamflow-Generated Debris Flow Hazards in Burn Scars

2021 ◽  
Author(s):  
Chuxuan Li ◽  
Alexander L. Handwerger ◽  
Jiali Wang ◽  
Wei Yu ◽  
Xiang Li ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Hydrological Modeling ◽  
Overland Flow ◽  
New Physics ◽  
Reanalysis Data ◽  
Peak Discharge ◽  
Burn Scar ◽  
Big Sur ◽  
Discharge Volume

Abstract. In steep wildfire-burned terrains, intense rainfall can produce large volumes of runoff that can trigger highly destructive debris flows. The ability to accurately characterize and forecast debris-flow hazards in burned terrains, however, remains limited. Here, we augment the Weather Research and Forecasting Hydrological modeling system (WRF-Hydro) to simulate both overland and channelized flows and assess postfire debris-flow hazards over a regional domain. We perform hindcast simulations using high-resolution weather radar-derived precipitation and reanalysis data to drive non-burned baseline and burn scar sensitivity experiments. Our simulations focus on January 2021 when an atmospheric river triggered numerous debris flows within a wildfire burn scar in Big Sur – one of which destroyed California’s famous Highway 1. Compared to the baseline, our burn scar simulation yields dramatic increases in total and peak discharge, and shorter lags between rainfall onset and peak discharge. At Rat Creek, where Highway 1 was destroyed, discharge volume increases eight-fold and peak discharge triples relative to the baseline. For all catchments within the burn scar, we find that the median catchment-area normalized discharge volume increases nine-fold after incorporating burn scar characteristics, while the 95th percentile volume increases 13-fold. Catchments with anomalously high hazard levels correspond well with post-event debris flow observations. Our results demonstrate that WRF-Hydro provides a compelling new physics-based tool to investigate and potentially forecast postfire hydrologic hazards at regional scales.

Why are some alpine catchments debris-flow active and others not? - the influence of geomorphology on debris-flow initiation

2020 ◽  
Author(s):  
Philipp Aigner ◽  
Leonard Sklar ◽  
Markus Hrachowitz ◽  
Roland Kaitna
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Regional Scale ◽  
Alpine Regions ◽  
Order Of Magnitude ◽  
Elevation Changes ◽  
Alpine Catchments ◽  
Flow Activity ◽  
The Impact ◽  
Debris Flow Susceptibility

<p>Processes like flash floods or debris flows, which typically occur in small headwater catchments, represent a substantial natural hazard in alpine regions. Due to the entrainment of sediment, the discharge of debris flows can be up to an order of magnitude larger compared to 100-year fluvial flood events in the same channel, which poses a great threat to affected communities. Besides the triggering rainfall, the initiation of debris flows depends on the watershed’s hydrological and geomorphological susceptibility, which makes it hard to predict and understand where and when debris flows occur.</p><p>In this study we aim to quantify the influence of geomorphologic characteristics and long-term sediment dynamics on debris flow activity in the Austrian Alps. Based on a database of debris-flow events within the last 60+ years, a geomorphological assessment of active and non-active sub-catchments in different study regions is carried out. In a first step, we derive geomorphological characteristics, such as terrain roughness, Melton number as well as weathering potential of geological units found within the watersheds. Based on the findings of the terrain shape analysis, a set of representative watersheds will be selected for systematic monitoring of surface elevation changes over the project period of three years. This will be achieved by comparing digital surface models based on photogrammetric UAV surveys and monitoring of channel reaches with cameras.</p><p>In order to project these findings onto a larger regional scale, the derived terrain parameters will be used to integrate and extend a previously designed hydro-meteorological debris-flow susceptibility model (Prenner et al., 2018) with a sediment-disposition-model. This will form the basis for an advanced debris flow forecasting tool and help to better assess the impact of climate change on the magnitude and frequency of future debris flows.</p><p> </p><div><span>References:</span></div><div><span>Prenner, D.</span>, <span>Kaitna, R.</span>, <span>Mostbauer, K.</span>, & <span>Hrachowitz, M.</span> ( <span>2018</span>). <span>The value of using multiple hydrometeorological variables to predict temporal debris flow susceptibility in an Alpine environment</span>. <em>Water Resources Research</em>, <span>54</span>, <span>6822</span>– <span>6843</span>. </div><p> </p>

scholarly journals Erosion after an extreme storm event in an arid fluvial system of the southern Atacama Desert: an assessment of the magnitude, return time, and conditioning factors of erosion and debris flow generation

2020 ◽  
Vol 20 (5) ◽  
pp. 1247-1265 ◽  
Author(s):  
Germán Aguilar ◽  
Albert Cabré ◽  
Victor Fredes ◽  
Bruno Villela
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Atacama Desert ◽  
Storm Event ◽  
Alluvial Fans ◽  
Sediment Discharge ◽  
Stream Networks ◽  
Erosion Rates ◽  
Extreme Storm ◽  
High Sediment

Abstract. The contribution of an individual extreme storm event to long-term erosion rates has been estimated for the first time in the Atacama Desert. A mean erosion of 1.3 mm has been calculated for the March 2015 event that impacted the southernmost part of the Atacama Desert. The estimated erosion is consistent with millennial erosion rates and the previously reported return times of high-sediment-discharge events in the study area. This is significant because erosion rates, related to events of high sediment discharge in arid fluvial systems, are difficult to measure with sediment loading due to destruction of gauges by devastating flash floods and therefore have not been directly measured yet. During the March 2015 storm, debris flows were reported as the main sediment transport process, while gullies and channels erosion were the main source of sediments that generated debris flows reaching the tributary junctions and the trunk valleys. Sediment yield at tributary outlets is highly dependent on the ability of catchments to store sediments in stream networks between storms. The largest tributary catchments, the high hydrological hierarchy, the low topographic gradient and the gentle slopes are the most determining factors in generating debris flows capable of reaching alluvial fans in any storm event from large sediment volumes stored in the stream networks. Our findings better assess the susceptibility to debris flow of arid catchments, which is significant for the southernmost valleys of the Atacama Desert because human settlements and industries are mostly established in alluvial fans.

scholarly journals Debris flow characteristics and relationships in the Central Spanish Pyrenees

2003 ◽  
Vol 3 (6) ◽  
pp. 683-691 ◽  
Author(s):  
A. Lorente ◽  
S. Beguería ◽  
J. C. Bathurst ◽  
J. M. García-Ruiz
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Characteristics ◽  
Spatial Prediction ◽  
Runout Distance ◽  
Building Models ◽  
Spanish Pyrenees ◽  
Physically Based ◽  
Order Of Magnitude ◽  
The Difference

Abstract. Unconfined debris flows (i.e. not in incised channels) are one of the most active geomorphic processes in mountainous areas. Since they can threaten settlements and infrastructure, statistical and physically based procedures have been developed to assess the potential for landslide erosion. In this study, information on debris flow characteristics was obtained in the field to define the debris flow runout distance and to establish relationships between debris flow parameters. Such relationships are needed for building models which allow us to improve the spatial prediction of debris flow hazards. In general, unconfined debris flows triggered in the Flysch Sector of the Central Spanish Pyrenees are of the same order of magnitude as others reported in the literature. The deposition of sediment started at 17.8°, and the runout distance represented 60% of the difference in height between the head of the landslide and the point at which deposition started. The runout distance was relatively well correlated with the volume of sediment.

scholarly journals Regional-scale GIS-models for assessment of hazards from glacier lake outbursts: evaluation and application in the Swiss Alps

2003 ◽  
Vol 3 (6) ◽  
pp. 647-662 ◽  
Author(s):  
C. Huggel ◽  
A. Kääb ◽  
W. Haeberli ◽  
B. Krummenacher
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Flow Direction ◽  
Regional Scale ◽  
Satellite Image ◽  
Swiss Alps ◽  
Special Focus ◽  
High Mountain ◽  
Mountain Areas ◽  
Single Flow

Abstract. Debris flows triggered by glacier lake outbursts have repeatedly caused disasters in various high-mountain regions of the world. Accelerated change of glacial and periglacial environments due to atmospheric warming and increased anthropogenic development in most of these areas raise the need for an adequate hazard assessment and corresponding modelling. The purpose of this paper is to pro-vide a modelling approach which takes into account the current evolution of the glacial environment and satisfies a robust first-order assessment of hazards from glacier-lake outbursts. Two topography-based GIS-models simulating debris flows related to outbursts from glacier lakes are presented and applied for two lake outburst events in the southern Swiss Alps. The models are based on information about glacier lakes derived from remote sensing data, and on digital elevation models (DEM). Hydrological flow routing is used to simulate the debris flow resulting from the lake outburst. Thereby, a multiple- and a single-flow-direction approach are applied. Debris-flow propagation is given in probability-related values indicating the hazard potential of a certain location. The debris flow runout distance is calculated on the basis of empirical data on average slope trajectory. The results show that the multiple-flow-direction approach generally yields a more detailed propagation. The single-flow-direction approach, however, is more robust against DEM artifacts and, hence, more suited for process automation. The model is tested with three differently generated DEMs (including aero-photogrammetry- and satellite image-derived). Potential application of the respective DEMs is discussed with a special focus on satellite-derived DEMs for use in remote high-mountain areas.

scholarly journals The Development of a 1-D Integrated Hydro-Mechanical Model Based on Flume Tests, to Unravel Different Hydrological Triggering Processes of Debris Flows

2018 ◽  
Author(s):  
Theo W.J. van Asch ◽  
Bin Yu ◽  
Wei Hu
Keyword(s):  
Debris Flow ◽  
Mechanical Model ◽  
Debris Flows ◽  
Overland Flow ◽  
Slope Angle ◽  
Great Influence ◽  
Flume Experiments ◽  
Triggering Mechanisms ◽  
Bed Material ◽  
Triggering Process

Many studies, which try to analyze conditions for debris flow development, ignore the type of initiation. Therefore this paper deals with the following questions: What type of hydro-mechanical triggering mechanisms for debris flows can we distinguish in upstream channels of debris flow prone gullies? Which are the main parameters controlling the type and temporal sequence of these triggering processes and what is their influence on the meteorological thresholds for debris flow initiation? A series of laboratory experiments were carried out in a flume, 8 m long and with a width of 0.3 m. to detect the conditions for different types of triggering mechanisms. The flume experiments show a sequence of hydrological processes triggering debris flows, namely erosion and transport by intensive overland flow and by infiltrating water causing failure of channel bed material. On the basis of these experiments an integrated hydro-mechanical model was developed, which describes Hortonian and Saturation overland flow, maximum sediment transport, through flow and failure of bed material. The model was calibrated and validated using process indicator values measured during the experiments in the flume. Virtual model simulations, carried out in a schematic hypothetical source area of a catchment show that slope angle and hydraulic conductivity of the bed material determine the type and sequence of these triggering processes. It was also clearly demonstrated that the type of hydrological triggering process and the influencing geometrical and hydro-mechanical parameters may have a great influence on rainfall intensity-duration threshold curves for the start of debris flows.

Short Review and opinion: New matter properties and applications based on Hybrids Graphene based Metamaterials

2020 ◽  
Vol 04 ◽  
Author(s):  
A. Guillermo Bracamonte
Keyword(s):  
Short Review ◽  
New Materials ◽  
Design And Synthesis ◽  
Chemical Structures ◽  
Current State ◽  
Potential Applications ◽  
Fundamental Research ◽  
Miniaturized Instrumentation ◽  
And Control ◽  
Conductive Properties

: Graphene as Organic material showed special attention due to their electronic and conductive properties. Moreover, its highly conjugated chemical structures and relative easy modification permitted varied design and control of targeted properties and applications. In addition, this Nanomaterial accompanied with pseudo Electromagnetic fields permitted photonics, electronics and Quantum interactions with their surrounding that generated new materials properties. In this context, this short Review, intends to discuss many of these studies related with new materials based on graphene for light and electronic interactions, conductions, and new modes of non-classical light generation. It should be highlighted that these new materials and metamaterials are currently in progress. For this reason it was showed and discussed some representative examples from Fundamental Research with Potential Applications as well as for their incorporations to real Advanced devices and miniaturized instrumentation. In this way, it was proposed this Special issue entitled “Design and synthesis of Hybrids Graphene based Metamaterials”, in order to open and share the knowledge of the Current State of the Art in this Multidisciplinary field.

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