汶川地震后四川省绵竹市清平乡文家沟泥石流灾害调查研究

在2008年5月12日汶川地震后的地震灾区暴发了许多泥石流灾害,其中以四川省绵竹市清平乡文家沟泥石流最为显著。文家沟原来不是泥石流沟,在汶川地震时由于滑坡形成的巨大的滑坡-碎屑流堆积体改变了文家沟的泥石流形成条件,在此后的3个雨季内,文家沟先后暴发了5次大规模和特大规模的泥石流灾害,其中以8.13文家沟泥石流规模和危害最大。8.13文家沟泥石流暴发时的总降雨量为227mm,泥石流持续时间约2.5h,泥石流总量约310×104m3;泥石流造成7人死亡,5人失踪,39人受伤,479户农房被掩埋,直接经济损失4.3亿元。5次大规模和特大规模的泥石流以及洪水仅带走了16%的可以很容易形成泥石流的滑坡-碎屑流堆积物,文家沟如再遭遇较大降雨还会暴发泥石流。即使在今后的雨季中暴发几次规模如8.13泥石流一样大的特大规模泥石流,文家沟在较大降雨下仍然可能暴发泥石流灾害,因此对文家沟泥石流的防治工作将是一个长期的工作。     

九寨沟泥石流预测

以泥石流起动条件为基础,建立了泥石流的判断预测法和计算预测法。据此对九寨沟泥石流加以预测,预测结果与实际情况基本一致。     

甘肃省文县关家沟泥石流综合治理

关家沟是一条活动频繁、危害较大的泥石流沟 .对其需采用工程措施稳沟、拦挡泥沙、排导和封山育林、植树造林等生物措施相结合的综合治理方案     

甘肃省武都县马槽沟泥石流特征

马槽沟是一条典型的灾害性泥石流沟。沟内不良地质现象发育。降水是该泥石发生的条件,十分钟雨强是暴发泥石流的关键。列出了泥石流特征值,这为泥石流防治提供了有实用价值的参数。     

Gully systems under undisturbed indigenous forest, East Coast Region, New Zealand

Gully erosion is commonly associated with agricultural landscapes where vegetation clearance and farming practices increase runoff, leading to fluvial incision. However, gully erosion can also occur in forests that have undergone some form of disturbance, either natural or resulting from human impacts. This paper reports on recent gully development within areas of undisturbed indigenous forest as a result of a high magnitude rainfall event on the East Coast of New Zealand's North Island. This region, through a combination of crushed and sheared rock types, steep topography, and tectonic and climatic setting, has high natural rates of erosion, exacerbated by European deforestation in the late 19th and early 20th centuries.Sequential air photographs, spanning a 58 year period between 1939 and 1997 were used to classify and document the growth and recovery of gully systems in the 14.1 km² headwaters of the Mangaoporo catchment. Following a severe cyclone in 1988, with a rainfall of 535 mm, there were 21 active gully systems within the indigenous forest. On photography prior to 1988 only four gully systems were present. During this period there were 8 major rainfall events (150–250 mm). Despite further 5 rainfall events of 150–250 mm between 1988 and 1997 all gully systems showed signs of recovery, with a combined reduction in active area of 37%. The nature and location of these features is strongly influenced by lithology (orientation of jointing and bedding), and to a topographic threshold defined by catchment slope and catchment area.     

SPATIAL DISTRIBUTION AND MORPHOLOGICAL FEATURES OF GULLIES IN AN AGROPASTORAL AREA IN SARDINIA, ITALY

1 INTRODUCTION Many studies on soil erosion by water have been carried out in the Mediterranean area, since erosion is considered as one of the most important land degradation processes in these environments (UNEP, 1994). Those studies mainly focused on r…     

INITIATION AND DEVELOPMENT PROCESSES OF TUNNEL SYSTEMS IN THE HILLY LOESS REGION OF NORTHERN CHINA

1 INTRODUCTION Tunnel erosion or piping is very common in semi-arid areas. It is often associated with gully system development (e.g., Parker, 1965; Heede, 1971; Harvey, 1982; Crouch, 1983; Gutierrez et al., 1997). It may also become a severe soil conserv…     

Characteristics, controlling factors and importance of deep gullies under cropland on loess-derived soils

Several studies describe the formation and importance of shallow ephemeral gullies under cropland (depth<0.8 m). Some of these gullies may develop into channels with a depth of more than 0.8 m (up to 4 m). Despite their spectacular nature, these deep gullies have not yet been studied in detail. Therefore, the objectives of this study are to analyze the characteristics and the controlling factors of these deep gullies, as well as their importance in terms of sediment production.Comparison of a dataset with 28 deep gullies, formed in the period 1985–2003 and 123 shallow ephemeral gullies formed in the period 1994–1999 in central Belgium indicates that the deep gullies have clearly different morphological characteristics compared to shallow ephemeral gullies. Several factors were analyzed to understand the formation of deep gullies. Plotting runoff contributing area versus slope of the soil surface at the gully head indicates that the topographical threshold for deep gully formation is significantly larger compared to ephemeral gully formation. Deep gullies form on short, steep valley sides and their position is strongly affected by the presence of linear landscape elements. All deep gullies incised on landscape positions with a very erodible soil horizon at shallow depth. Analysis of causative rainfall showed no significant differences in incision thresholds between rills and shallow ephemeral gullies on the one hand and deep gullies on the other hand.The relation between area-specific sediment yield in central Belgium and drainage area, indicates that the development of deep gullies contributes significantly to the sediment output of small rural catchments and causes peaks in the mean area-specific sediment yield that are up to a factor of three higher compared with catchments where shallow ephemeral gullying occurs.     

云南蒋家沟泥石流运动要素观测数据整编

根据中国科学院东川泥石流观测研究站所在地蒋家沟的多年观测数据,利用成熟的计算和分析方法,按建立数据库的要求对泥石流运动要素的原始观测数据进行了计算机处理,提出了建立泥石流运动要素数据库的内容及其指标和计算公式,并对数据库的编建原则、特点及结果表达进行了讨论。     

Medium-term evolution of a gully developed in a loess-derived soil

Field surveys in the Belgian loess belt revealed the presence in many forested areas of large, permanent gully systems, most of which are currently inactive. In cultivated areas, such gullies can only be observed in cross-sectional soil profiles through hollows, as virtually all such large gullies are currently infilled with colluvium. Little is known about the spatial distribution, initiation and temporal evolution of these large, permanent gully systems on loess-derived soils. Therefore, the medium-term evolution of a gully initiated in a cultivated area on loess-derived soils southwest of Leuven (Belgium) in May–June 1986, was studied over 13 years. Two intense rainfall events created this (ephemeral) gully, which was not erased by subsequent tillage. Between June 1986 and the December 1999, eight field surveys were conducted to measure gully dimensions. During two surveys, topographic indices (e.g., slope and drainage area) were also measured. Daily rainfall for the measuring period were obtained from a rainfall station located some 10 km southwest of the gully. Analysis of rainfall data showed that no extreme rainfall event was required to initiate such large (permanent) gullies, as observed in forested areas and through cross-sectional profiles in cultivated fields in the Belgian loess belt. Return periods of the event that caused the gully varied between <1 year and 25 years, depending on the assumptions used for defining event rain intensity. Once established, length, surface area and volume of the studied gully evolved with time, cumulative rainfall or cumulative runoff, following a negative exponential relation. This accords with observations reported for gullies in Australia and the USA. This study shows that a degressive increase of gully extension, can be largely explained by the evolution of a “slope–drainage area” factor (S×A, which is proportional to stream power) with time. While gully length and gully surface area asymptotically evolve towards a final value, gully volume decreased at a given point in time. From this, it is inferred that sediment deposition will potentially infill the gully to such an extent that the farmer can drive across it. From this moment on, the combined effect of water and tillage erosion in the gully drainage area, will lead towards rapid infilling. This expected evolution of a gully in cultivated fields accords with observations of large infilled gully systems in cultivated areas in eastern Belgium. The permanent gullies observed under forest are attributed to the fact that after severe gully erosion, this area was reforested or abandoned. Therefore, the sediment source was cut off and the gully was not filled in by sediment deposition.