Characteristics Of Debris Flow Research Articles

Characteristics of Debris Flow at the Mizunashi River in Mt. Unzen

Unzen volcano began to erupt in November 1990 after 198 years of dormancy and was in violent activity. Continuous growth of lava dome and falls of lava rocks resulted in frequent pyroclastic flows. As a great volume of volcanic material deposited and scattered by the pyroclastic flows, debris flows frequently occurred along the Mizunashi River and damaged many houses in 1991-93. In 1995, the volcanic activity has become calm and no pyloclastic flow has been observed from March, 1995.With the change of the volcanic activity, the occurrence condition of debris flow is expected to change. The result of the data analysis indicates the abrupt change in the critical rainfall for occurrence of debris flow in July, 1993. The relation between rainfall and runoff of debris flow is also changed in the same period of the time.

Flow characteristics of large eruption-triggered debris flows at snow-clad volcanoes: constraints for debris-flow models

Theoretical modelling is not yet adequate to predict the behavior of debris flows, which can be an extremely hazardous hydrologic process commonly associated with volcanic eruptions, particularly at snow-clad stratovolcanoes. To provide a realistic basis for modelling the behavior of large (> 1000 m 3/s) debris flows, this paper summarizes kinematic, volumetric and hydraulic characteristics of ten large historic volcanic debris flows from four different volcanoes. Although debris flows larger than these are known to have occurred in the past, the ten summarized here define a practical upper range in magnitude of more typical flows to be considered for future hazard prediction. Peak flow velocities of the ten debris flows studied were indirectly measured to be between about 5 and 20 m/s on gradients of 0.005 to 0.25 m/m, but locally they were as great as 40 m/s. Hydraulic (average) depths were as great as 25 m, but were more commonly between 5 and 15 m in channels up to 400 m wide. Computed peak discharges (volumetric flow rates) were as high as 10 5 m 3/s, and total volumes were as much as 10 8 m 3. Total flow volumes increased by as much as four times in relatively steep channels as eroded sediment was incorporated into the debris flows. Flows generally achieved supercritical flow and deposited minimal volumes of sediment on gradients steeper than 0.02 m/m. Subcritical flow and active deposition predominated on gradients less than 0.01 m/m, although flows travelled tens of kilometers on such low gradients while laying down deposits. Total distances travelled (as debris flows) were as far as 120 km.

パプアニューギニア北東部のサンゴ礁段丘の総合研究 パプアニューギニア，ヒュオン半島の古崩壊地の年代・分布・形成過程に関する研究

Landsides occur widely on the coral terraces of the tectonically active Huon Peninsula, Papua New Guinea. Large historic earthquakes in Papua New Guinea have frequently triggered large landslides. Landslide that disrupt the coral terraces at Huon Peninsula have a variety of forms including ; 1) large translational block slide features that carry essentially intact coral terrace remnants along, without large debris flows ; 2) complex slides that may begin as rockslide or deep-seated rotational slide features that continue downslope as debris flow features. In addition, small rockfall and rockslide features that commonly occur on steep valley walls and headwall (type III). Large scale landslides of types I and II occur more frequently in the southeast of the study area where uplift rate is high, up to 3.5 m/ka.Approximate ages of 26 large, late Quaternary landslides of types I and II have been obtained by radiocarbon dating of corals from immediately above or below the debris flow units that have extended and across the Holocene reef sequence, or by U-series ages of older coral terraces that have been disrupted by landslides or where terrace have developed on older landslide debris. The youngest debris flow (type I) directly overlies a coseismically uplifted terrace dated at ca. 1, 250 yr BP. At three sites, at least, an older debris flow is intercalated with reef material that was forming during a late stage of the post-glacial transgression about 7-8 ka. More than 10 large blockslides without debris flow (type I) disrupt ca. 33 ka terrace, but these are trimmed at outer edge by the ca. 6.5 ka Holocene terrace, thus providing bracketing ages.Historic precedent of large landslides generated by major earthquakes, and the close association of debris flow deposits with coseismically uplifted terraces of Holocene age lead us to propose that many, and perhaps most, o f the large scale landslides on Huon Peninsula are earthquakegenerated.

Quartz-grain surfaces of debris flow material in the marginal mountains of Tibet

Debris flow is a natural phenomenon which occurs on steep slopes of mountain regions. Very often morainic material and nonmorainic sediments, such as debris flow material, fluvial and other sediments, are mixed in the marginal mountain systems of the Tibetan Plateau. The study of quartz-grain surface features of debris flow has an important significance for differentiating between different origins of Quaternary sediments. Features of quartz-grain in debris flow will be described as below: 1. The predominant shapes of quartz grains are irregular. 2. The degree of roundness of grains is in general are angular to subangular in shape. 3. The textures of quartz-grains in debris flows are conchoidal fractures, parallel steps and mechanical V-marks. Parallel steps are especially abundant. Their presence is the most characteristic indicator of debris flow sand, aiding in the differentiation between debris flow and glacial sand. 4. Fresh cleavage planes are extremely flat.

Debris flow characteristics in an area of continuous permafrost, St. Elias Range, Yukon Territory

Debris flow characteristics in an area of continuous permafrost, St. Elias Range, Yukon Territory

An Analysis of Eocene Mass Movements in the Wadi Athrun, Cyrenaica

AbstractThis study examines the evidence for mass movement activity in the Eocene deposits of Wadi Al Athrun. Slump and debris flow features were identified and analysed using fold orientation, slip plane separation and angles and mean vector methods. Results indicate that the palaeoslope of the Eocene continental slope was N20W, with a palaeostrike of N70E. Mass movements are separated into two units according to deformation intensity. The lower unit is primarily composed of slumped Bathyal Realm sediments of the Apollonia Formation, while the upper unit evidences slump and debris flow features incorporating nummulite-rich Neritic Realm deposits of the Darnah Formation. These observations represent further insight into the sedimentary history of the continental margins of North Africa.

Characteristics of Debris Flow Caused by Denser Fluid

Sediment discharge and concentration are experimentally investigated for debris flows caused by denser fluid and by plain water, respectively. Denser fluid is represented by the mixture flow of sand and water. The former debris flow is found to carry more gravels than the latter. Gravel discharge and concentration increase with the decrease in the sand grain diameter. This can be explained by critical fluid velocity for gravel movement in the mixture flow. For the estimate of the critical velocity the drag force is also investigated. The value of the drag force in the mixture flow of very fine sand is close to that in plain water. Therefore, such mixture flow is found to behave like a single fluid.

Characteristics of debris flow caused by outburst of glacial lake in Boqu river, Xizang, China, 1981

A catastrophic outburst of a moraine dammed lake at the head of a tributary of Boqu river on the S-flank of the Tibetan Himalayas took place in 1981. The flood with a peak discharge of 15920 m3/s at the breach and 2316 m3/s at Bharabise, more than 50 km downstream, was 16 times larger than the average annual flood of the river, and caused a large scale sediment morement. Spreading over 50 km or more along Boqu river, the debris flow involved a total of about 4 mio. m3 of solid material. The debris flow valley may be divided into three sections according to erosion and deposition: the section of vertical erosion, the section of lateral erosion-flow passage, and the section of lateral erosion-deposition. Half of the total solid materials was derived from the vertical erosion in the first section and the other half from the lateral erosion in the latter two sections. This debris flow was a sediment-laminated movement under the conditions of an extraordinary flood. The moving layer of sediment may be estimated as being 4 to 10 m in thickness. Debris flow deposits with well developed morphologies are chiefly scattered along the last section of the debris flow valley. The most significant morphologies include the levee (a leteral deposit), the stone pile (a flow surge deposit) and the residual terrace (the residue of the flow). The sedimentology of these deposits is characteristicly coarse grain and of mixed composition with a lack of bedding and sorting, the presence of inverse grading, parallelism of long axes and imbrication. All these features imply an accordance with the “grain flow” concept developed by R. A. Bagnold in the mechanics of sediment movement.

Failure and flow on a 35° slope: Causes and three‐dimensional observations

AbstractA well‐vegetated 35° slope in upland Wales, U.K., failed during a winter flood event. Failure was linked to high magnitude rainfall and diversion of flowing water onto the slope. Mass movement began with gravitational slumping, which was transformed rapidly into a debris flow. Three‐dimensional characteristics of the active debris flow are reconstructed from mudlines on 58 trees still standing in the flow path. Mudline formation only on the up‐flow side of trees indicates the relatively high viscosity of the debris flow. Mudline height is a function of the maximum thickness and velocity of the flow at any tree.

１９８４年長野県西部地震による斜面崩壊とその特徴

１９８４年長野県西部地震による斜面崩壊とその特徴

Characteristics of debris flow with a plug : Hashimoto, H; Tsubaki, T Mem Fac Engng Kyushu UnivV44, N3, Sept 1984, P273–289

Characteristics of debris flow with a plug : Hashimoto, H; Tsubaki, T Mem Fac Engng Kyushu UnivV44, N3, Sept 1984, P273–289

Subaerial Debris-Flow Deposition in the Upper Paleozoic Cutler Formation, Western Colorado

ABSTRACT Outcrops of the lower part of the Cutler Formation near Gateway, Colorado, contain proximal alluvial-fan deposits of two principal lithofacies. The diamictite lithofacies (D) consists of a variety of sharply bounded, massive, muddy beds which are interpreted as deposits of subaerial debris flows. The gravelly sandstone lithofacies (S) consists of amalgamated beds of laminated and cross-bedded conglomeratic sandstones which are interpreted as water-deposited sediments. Clasts in S are rarely larger than 0.5 m in maximum diameter, but clasts in D are commonly much larger (up to 8 m). Both normal and inverse grading are visible in D, but grading is generally not well developed in either lithofacies. Imbrication of clasts, although more pronounced and more consistent in S, is fairly commo in both lithofacies. Four subfacies of diamictite are distinguishable on the basis of clast packing and grading: massive matrix-supported (Dram), graded matrix-supported (Dmg), inversely graded clast-supported (Dci), and massive clast-supported (Dcm). Given the hydrodynamic and rheologic properties of debris flows as reported by previous workers, four debris-flow regimes are postulated on the basis of varying water content and clast interaction. Subfacies Dram and Drag typify deposits of flows having viscous clast interactions; subfacies Dci represents deposits of flows having inertial or colliding clast interactions. Subfacies Dram comprises deposits of flows with demonstrably high yield strengths. Subfacies Dcm represents deposits of flows in which yield strength was insufficient to support most clasts. This classification specifically recognizes turbulence, selective deposition, and bedload transport of clasts as essential characteristics of certain dilute debris flows. It also accommodates as debris-flow deposits some beds which have features usually associated with aqueous deposition, including clast frameworks, channelization, imbrication, and normal grading.

Erratum for “Mechanical Characteristics of Debris Flow”

Erratum for “Mechanical Characteristics of Debris Flow”

Mechanical Characteristics of Debris Flow

A mechanism of occurrence of bore-like debris flow due to the appearance of overland flow on the debris accumulation is considered using the applying shear stress and resisting stress relationship in the bed. The criteria for the occurence of the nonstationary bed flow and the partly stationary bed flow are made clear. The partly stationary bed flow approaches a quasi-steady state, whose depth, velocity and concentration are predictive applying the concept of dilatant fluid introduced by Bagnold. Although the front height of the nonstationary bed flow increases versus distance, the translation velocity and concentration are nearly constant and flow characteristics are theoretically predictive by some appropriate assumptions.