Magnitude and frequency of debris flows

doi:10.1016/0022-1694(91)90069-T

Journal of Hydrology

Volume 123, Issues 1–2, February 1991, Pages 69-82

https://doi.org/10.1016/0022-1694(91)90069-T Get rights and content

Abstract

Debris flows periodically result in the loss of lives and property. Engineering structures designed to control debris flows are often inadequate because of lack of knowledge of the magnitude of debris events. The objective of this study was to develop a method that could be used to estimate the magnitude and frequency of debris flows. The data base for the study included 29 watersheds in the Los Angeles area, with drainage areas < 3 mile². Assuming a log-normal distribution, prediction equations for 2-, 5-, 10-, 25-, 50-, and 100-year return periods were developed as a function of relief ratio, hypsometric index, the interval between burns, and drainage area. Principal components and correlation analyses were used to select the predictor variables. Numerical optimization was used to calibrate the model. The prediction equations can be used to estimate the magnitude of debris flows for ungaged watersheds where estimates are required for debris basin and channel design, protection of culverts and roads, land use planning, and zoning and establishing insurance rates.

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Cited by (47)

Evaluating the post-earthquake landslides sediment supply capacity for debris flows
2023, Catena
Citation Excerpt :
Current research on the sediment supply capacity (SSC) of debris flow sources generally focuses on assessment using a series of geomorphic indexes, which reflect the landform evolution of catchment erosion and geomorphology in the Davis Geographical Circle (Davis, 1899; Davis, 1922; Strahler, 1950). Several indicators have been used in assessment of the SSC of debris flows and a series of relative indexes were developed, e.g., the Hypsometry Index (Johnson et al., 1991; Bovis and Jakob, 1999; Chen and Yu, 2011; Heiser et al., 2015; Bhushan et al., 2018), Melton Index (Bertrand et al., 2013; Hürlimann et al., 2019), geomorphological information entropy method (Wang et al., 2014; Lombardo et al., 2016), and Sediment Connectivity Index based on geomorphological considerations (Cucchiaro et al., 2019; Schopper et al., 2019; Zanandrea et al., 2021). The development of high-resolution topographic data (Li and Wong, 2010; Wang et al., 2012; Jarihani et al., 2015) and the application of geomorphological indexes provided solutions to evaluate the potential SSC for debris flows.
Earthquake-triggered landslides provide sufficient loose material for the formation of subsequent debris flow events in earthquake-affected catchments. The landslides sediment supply capacity (SSC) for debris flows plays an important role in post-earthquake sediment transportation, which is influenced by landslide location during different post-earthquake periods. In this study, the logarithmic slope–area diagram was used to distinguish hillslope and channel processes in catchments affected by the Wenchuan earthquake, adopting a threshold between hillslopes and channels set at 1 km². In comparison with the existing structural sediment delivery ratio (SDR), it was found that the SSC assessed using the SDR showed a decreasing trend of power exponent as distance increased, effectively eliminating the impact of earthquake-triggered sediment supply. To efficiently assess the SSC of post-earthquake landslides for debris flows, we proposed a novel dimensionless index, namely Mean Landslide Sediment Delivery Ratio (MLSDR), by considering the impact of earthquakes and eliminating the impact of catchment area. It was found that, the SSC of coseismic landslides assessed by the MLSDR in catchments affected by the Wenchuan earthquake could better reflect seismic impact, with higher values concentrated along the seismogenic fault of the earthquake, thereby highlighting the satisfactory applicability of the method in the Wenchuan earthquake-affected area. Moreover, it was found that the proposed index had a reasonable corresponding relationship with debris flow development in Wenchuan earthquake-affected catchments, mainly for values of 0.2 ≤ MLSDR_out ≤ 2.25 and 0.3 ≤ MLSDR_channel ≤ 4.5, which could help identify potential debris flow development. The controlling factors of long-term changes in coseismic and post-earthquake SSC in the Wenchuan earthquake-affected region were assessed. It was found that SSC was controlled by earthquakes during first three years and subsequently controlled by precipitation and grain composition. This study will strengthen the understandings of the long-term evolution of post-earthquake debris flow.
AI-based identification of low-frequency debris flow catchments in the Bailong River basin, China
2020, Geomorphology
Citation Excerpt :
Catchment area (CA), channel length (CL) (Wilford et al., 2004) and catchment perimeter (CP) can reflect the basic morphometric information of a catchment. Average slope (AS) was obtained using the Spatial Analyst function in ArcGIS; Catchment relief (CR) is the difference in elevation between the top and the outlet of the catchment (Zhou et al., 2016); Relief ratio (RR) indicates the overall steepness of a catchment and is found by dividing the CR by the longest horizontal distance of the catchment measured parallel to the major stream (Johnson et al., 1991), i.e., the CL. AS, CR and RR are important impact factors, which can afford enough energy for debris flow initiation and transportation (Zhou et al., 2016).
Debris flow is a major geohazard in mountainous regions and poses a significant threat to life and property. The damage caused by debris flows have increased with the expansion of human settlements and activity into the mountainous regions of China. In regards to risks from debris flows, previously unrecognized low-frequency debris flow catchments constitute an especially significant threat. According to our investigation, only about 500 catchments have debris flow records in >2000 catchments of Bailong River basin. The main purpose of this paper is to introduce a new methodology using Artificial Intelligence (AI) that can simultaneously input parameters related to geomorphological conditions and material conditions to better distinguish low-frequency debris flow catchments (LFDs) from medium-high frequency debris flow catchments (MHFDs). A total of 449 prototypical debris flow catchments, 15 parameters, and 9 commonly used learning machines were used to build identification models. Debris flow catchments are divided into 4 cases (LO1-LO4) based on different sample ratios of LFDs and MHFDs, which are input into each classifier one by one. Based on model evaluation, the CHAID model in the case LO2 performs best, which only uses five parameters (formation lithology index, land use index, vegetation coverage index, drainage density and landslide density index) to predict LFDs. The results indicate that LFDs are mainly distributed in areas with less landslide distribution and better vegetation coverage compared with MHFDs. However, the distribution of LFDs is concentrated on FLI (formation lithology index) =4, which is the weak lithology area. The tree classifier seems to be better at classifying fluvial processes. The model developed in this paper can help us quickly find LFDs in similar areas, and help to assess the risk of debris flows.
Magnitude-frequency relationships of debris flows - A case study based on field surveys and tree-ring records
2010, Geomorphology
Debris-flow activity in a watershed is usually defined in terms of magnitude and frequency. While magnitude–frequency (M–F) relations have long formed the basis for risk assessment and engineering design in hydrology and fluvial hydraulics, only fragmentary and insufficiently specified data for debris flows exists. This paper reconstructs M–F relationships of 62 debris flows for an aggradational cone of a small (< 5 km²), high elevation watershed in the Swiss Alps since A.D. 1863. The frequency of debris flows is obtained from tree-ring records. The magnitude of individual events is given as S, M, L, XL, and derived from volumetric data of deposits, grain size distributions of boulders, and a series of surrogates (snout elevations, tree survival, lateral spread of surges). Class S and M debris flows (< 5 × 10³ m³) encompass a typical size of events and have mean recurrence intervals of 5.4 (SD: 3.2) and 7.4 years (SD: 6.7), respectively. Class XL events (10⁴–5 ×10⁴ m³) are, in contrast, only identified three times over the past 150 years, and major erosional activity on the cone was restricted to two of these events in 1948 and 1993. A comparison of results with hydrometeorological records shows that class L and XL events are typically triggered by advective storms (rainfall > 50 mm) in August and September, when the active layer of the rock glacier in the source area of debris flows is largest. Over the past ∼ 150 years, climate has exerted control on material released from the source area and prevented triggering of class XL events before 1922. With the projected climatic change, permafrost degradation and the potential increase in storm intensity are likely to produce “class XXL” events in the future with volumes surpassing 5 × 10⁴ m³ at the level of the debris-flow cone.
Sediment transfer processes in two Alpine catchments of contrasting morphological settings
2009, Journal of Hydrology
Coarse sediment transport processes in steep headwater streams may vary between bedload and debris flows events, depending on basin geomorphology and sediment supply. This paper compares two small catchments (drainage area 4–5 km²) located in the Eastern Italian Alps where the dominant sediment transport processes differ substantially, i.e., debris flows in the Moscardo Torrent and bedload events in the Rio Cordon. The two basins were selected because they provided the unique opportunity to analyze long-term data of debris flow and bedload volumes, respectively. The two basins are compared in terms of peak discharge, event duration, and magnitude–frequency characteristics of transported sediment volumes. Additional bedload data from two more Alpine experimental basins are also considered. The results show that, for comparable recurrence intervals, debris flow volumes are 2–3 orders of magnitude larger than bedload volumes. This contrasting sediment transfer activity can be attributed to different basin and channel morphologies, which are analyzed in terms of sediment supply conditions, longitudinal profiles and slope–area curves.
The morphometric and stratigraphic framework for estimates of debris flow incidence in the North Cascades foothills, Washington State, USA
2008, Geomorphology
Active debris flow fans in the North Cascade Foothills of Washington State constitute a natural hazard of importance to land managers, private property owners and personal security. In the absence of measurements of the sediment fluxes involved in debris flow events, a morphological-evolutionary systems approach, emphasizing stratigraphy, dating, fan morphology and debris flow basin morphometry, was used. Using the stratigraphic framework and 47 radiocarbon dates, frequency of occurrence and relative magnitudes of debris flow events have been estimated for three spatial scales of debris flow systems: the within-fan site scale (84 observations); the fan meso-scale (six observations) and the lumped fan, regional or macro-scale (one fan average and adjacent lake sediments). In order to characterize the morphometric framework, plots of basin area v. fan area, basin area v. fan gradient and the Melton ruggedness number v. fan gradient for the 12 debris flow basins were compared with those documented for semi-arid and paraglacial fans. Basin area to fan area ratios were generally consistent with the estimated level of debris flow activity during the Holocene as reported below. Terrain analysis of three of the most active debris flow basins revealed the variety of modes of slope failure and sediment production in the region.
Micro-scale debris flow event systems indicated a range of recurrence intervals for large debris flows from 106−3645 years. The spatial variation of these rates across the fans was generally consistent with previously mapped hazard zones. At the fan meso-scale, the range of recurrence intervals for large debris flows was 273−1566 years and at the regional scale, the estimated recurrence interval of large debris flows was 874 years (with undetermined error bands) during the past 7290 years. Dated lake sediments from the adjacent Lake Whatcom gave recurrence intervals for large sediment producing events ranging from 481−557 years over the past 3900 years and clearly discernible sedimentation events in the lacustrine sediments had a recurrence interval of 67−78 years over that same period.
Empirical models to predict the volumes of debris flows generated by recently burned basins in the western U.S.
2008, Geomorphology
Recently burned basins frequently produce debris flows in response to moderate-to-severe rainfall. Post-fire hazard assessments of debris flows are most useful when they predict the volume of material that may flow out of a burned basin. This study develops a set of empirically-based models that predict potential volumes of wildfire-related debris flows in different regions and geologic settings.
The models were developed using data from 53 recently burned basins in Colorado, Utah and California. The volumes of debris flows in these basins were determined by either measuring the volume of material eroded from the channels, or by estimating the amount of material removed from debris retention basins. For each basin, independent variables thought to affect the volume of the debris flow were determined. These variables include measures of basin morphology, basin areas burned at different severities, soil material properties, rock type, and rainfall amounts and intensities for storms triggering debris flows. Using these data, multiple regression analyses were used to create separate predictive models for volumes of debris flows generated by burned basins in six separate regions or settings, including the western U.S., southern California, the Rocky Mountain region, and basins underlain by sedimentary, metamorphic and granitic rocks.
An evaluation of these models indicated that the best model (the Western U.S. model) explains 83% of the variability in the volumes of the debris flows, and includes variables that describe the basin area with slopes greater than or equal to 30%, the basin area burned at moderate and high severity, and total storm rainfall. This model was independently validated by comparing volumes of debris flows reported in the literature, to volumes estimated using the model. Eighty-seven percent of the reported volumes were within two residual standard errors of the volumes predicted using the model. This model is an improvement over previous models in that it includes a measure of burn severity and an estimate of modeling errors. The application of this model, in conjunction with models for the probability of debris flows, will enable more complete and rapid assessments of debris flow hazards following wildfire.

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Research paperMagnitude and frequency of debris flows

Abstract

Flow of cohesionless grains in fluids

Philos. Trans., R. Soc. London

Soil slips, debris flows, and rainstorms in the Santa Monica Mountains and vicinity, Southern California

USGS Prof. Pap.

On ratio correlation in petrography

J. Geol.

Generalized viscoplastic modeling of debris flow

Debris flows in small mountain stream channels of Colorado and their hydrologic implications

Bull. Assoc. Eng. Geol.

Water In Environmental Planning

Effects of a North Central Washington Wildfire on runoff and sediment production

Water Resourc. Bull.

Soil slumps and debris flows: Prediction and Protection

Bull. Assoc. Eng. Geol.

Research paper
Magnitude and frequency of debris flows