scholarly journals Aquatic Biological Diversity Responses to Flood Disturbance and Forest Management in Small, Forested Watersheds

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2793
Author(s):  
Robert J. Danehy ◽  
Robert E. Bilby ◽  
Tiffany E. Justice ◽  
Gary T. Lester ◽  
Jay E. Jones ◽  
...  
Keyword(s):  
Debris Flow ◽  
Biological Diversity ◽  
Extreme Rainfall ◽  
Common Species ◽  
Extreme Rainfall Event ◽  
Macroinvertebrate Communities ◽  
Small Watersheds ◽  
High Flood ◽  
Riparian System ◽  
Overbank Flows

We examined riparian system responses to an extreme rainfall event on 1–4 December 2007, in eleven small watersheds (mean area—13.2 km2) from 2008–2016 at debris flow, high flood, and low flood reaches (all extended overbank flows). Macroinvertebrate responses followed expected outcomes after extreme disturbance including increasing chironomids and other multi-voltine species. A core assemblage of twenty abundant and common species-maintained populations even after debris flow (likely by recolonizing quickly) with total richness during project of 253 including 183 rare species (<0.01 total abundance) supporting an annual turnover of species from 22 to 33%. Primary disturbance changes to habitat were declines in shade and in-channel wood at all reaches, more strongly at debris flow reaches. Macroinvertebrate communities across disturbance intensities became increasingly similar after the storm. Combined effects of the flood reducing channel complexity and previous logging decreasing in-channel wood recruitment from riparian systems, limits habitat complexity. Until this feature of forested watershed streams returns, there appears to be a ceiling on reach scale aquatic biological diversity.

scholarly journals Evaluation of Rainfall-Triggered Debris Flows under the Impact of Extreme Events: A Chenyulan Watershed Case Study, Taiwan

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2201
Author(s):  
Jinn-Chyi Chen ◽  
Wen-Shun Huang
Keyword(s):  
Debris Flow ◽  
Extreme Events ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Extreme Rainfall Event ◽  
Extreme Rainfall Events ◽  
Hourly Rainfall ◽  
Central Taiwan ◽  
The Impact

This study examined the conditions that lead to debris flows, and their association with the rainfall return period (T) and the probability of debris flow occurrence (P) in the Chenyulan watershed, central Taiwan. Several extreme events have occurred in the Chenyulan watershed in the past, including the Chi-Chi earthquake and extreme rainfall events. The T for three rainfall indexes (i.e., the maximum hourly rainfall depth (Im), the maximum 24-h rainfall amount (Rd), and RI (RI = Im× Rd)) were analyzed, and the T associated with the triggering of debris flows is presented. The P–T relationship can be determined using three indexes, Im, Rd, and RI; how it is affected and unaffected by extreme events was developed. Models for evaluating P using the three rainfall indexes were proposed and used to evaluate P between 2009 and 2020 (i.e., after the extreme rainfall event of Typhoon Morakot in 2009). The results of this study showed that the P‒T relationship, using the RI or Rd index, was reasonable for predicting the probability of debris flow occurrence.

scholarly journals Susceptibility assessment of landslides under extreme-rainfall events using hydro-geotechnical model; a case study of Umyeonsan (Mt.), Korea

2014 ◽  
Vol 2 (8) ◽  
pp. 5575-5601 ◽  
Author(s):  
S. S. Jeong ◽  
J. H. Kim ◽  
Y. M. Kim ◽  
D. H. Bae
Keyword(s):  
Debris Flow ◽  
Groundwater Flow ◽  
Extreme Rainfall ◽  
Saturated Soil ◽  
Extreme Rainfall Event ◽  
Wetting Front ◽  
Partially Saturated ◽  
Soil Slopes ◽  
Partially Saturated Soil

Abstract. The influence of climate change on patterns has the potential to alter stability of partially saturated soil slopes. Changes in rainfall patterns have a strong influence on stability of partially saturated soil slopes, which recently have resulted in shallow landslides. In this paper, a comprehensive case study on the 2011 Umyeonsan (Mt.) landslides was highlighted. The incident involves the collapse of a soil slope and the debris flow under extreme-rainfall event, causing 16 fatalities and serious damaged to 146 housings. A fundamental study was carried out on the cause and mechanism of landslide/debris flow. An analytical method is developed for determining the failure mechanism of unsaturated soil slopes under extreme-rainfall, the effect of groundwater flow; the downward velocity of wetting front, and the upward velocity of groundwater level. Based on this, we propose the conceptual methodology of landslide design based on experimental tests and numerical analyses which consider the important mechanism of the combined effects of both groundwater flow and rainfall infiltration into the slope.

scholarly journals Catastrophic debris flow triggered by an extreme rainfall event in the Volcán village, January 2017. Cordillera Oriental of Argentina

2018 ◽  
Author(s):  
María Yanina Esper Angillieri ◽  
Laura Perucca ◽  
Nicolás Vargas
Keyword(s):  
Debris Flow ◽  
River Basin ◽  
Large Scale ◽  
Extreme Rainfall ◽  
Economic Losses ◽  
Low Grade ◽  
Extreme Rainfall Event ◽  
Conditioning Factors ◽  
Mountainous Regions ◽  
Slow Moving

Abstract. Slides, rockfalls, debris floods and debris flows are periodical events in the dry mountainous regions of Argentina, during times of torrential rainfalls. In the Grande River basin, Jujuy Province, these processes take place almost every summer. Extreme rainfall on January 10, 2017 caused the seasonal acceleration of large-scale and slow-moving landslides in the Los Filtros River basin. These slides broke down into a disaggregated mass, triggering a debris flow which transformed progressively downstream into a debris flood, producing widespread damage along a narrow valley (named Quebrada de Humahuaca), with the Volcán village withstanding the worst of the disaster. The event caused four fatalities and great economic losses, mainly destroying infrastructure and buildings. In order to document this catastrophic event and to explore its causes, a morphometric analysis of the Los Filtros river basin, tributary of the western margin of the Grande River and located on the Cordillera Oriental area, was carried out. The drainage network was derived from digital elevation models. In addition, some landslides were mapped using high-resolution satellite data acquired before and after the event. Of a total landslide area of 2.39 km2, 0.60 km2 was considered as active and 0.089 km2 as new sliding area (from 2015 to 2017) associated to the large-scale and slow-moving landslides. The geological characteristics of the study basin are very favourable conditioning factors in landslide generation. Precambrian-age low grade metaclastics shatter in the frost climate of the higher mountains and poorly consolidated Quaternary deposits along the sides of the gully erode readily and become source material for landslide that damage or bury roads, railroads, and houses. Finally, this study aims to increase knowledge of all the above-mentioned events in order to provide several methods of analysis for landslide prevention and control.

scholarly journals Debris flow initiation characteristics and occurrence probability after extreme rainfalls: case study in the Chenyulan watershed, Taiwan

2017 ◽  
Author(s):  
Jinn-Chyi Chen ◽  
Jiang-Guao Jiang ◽  
Wien-Shun Huang ◽  
Yuan-Fan Tsai
Keyword(s):  
Debris Flow ◽  
Empirical Relationship ◽  
Recovery Period ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Rainfall Index ◽  
Central Taiwan ◽  
Time Required ◽  
Debris Flow Initiation

Abstract. Rainfall and other extreme events often trigger debris flows. This study examines the debris flow initiation characteristics and probability of debris flow occurrence after extreme rainfalls. The Chenyulan watershed, central Taiwan, which has suffered from the Chi-Chi earthquake (CCE) and extreme rainfalls, was selected as a study area. The rainfall index (RI) was used to analyze the return period (T) and characteristics of debris flow occurrence after extreme rainfalls. The characteristics of debris flow occurrence included the variation in critical RI, threshold of RI for debris flow initiation, and recovery period (t0), the time required for the lowered threshold to return to the original threshold. The variations in critical RI after extreme rainfall and t0 associated with RI were presented. The critical RI threshold was reduced in the years following an extreme rainfall event. The reduction in RI as well as t0 were influenced by the RI. Reduced RI values showed an increasing trend over time, and it gradually return to initial RI. The empirical relationship between the probability of debris flow occurrence (P) and corresponding T of the rainfall characteristics for areas affected by extreme rainfalls and affected by the CCE were developed. Finally, a method for determining the P of a rainfall event was proposed based on the relationship between P and T. This method was successfully applied to evaluate the probability of debris flow occurrence after extreme rainfalls.

scholarly journals Characteristics of rainfall triggering of debris flows in the Chenyulan watershed, Taiwan

2013 ◽  
Vol 13 (4) ◽  
pp. 1015-1023 ◽  
Author(s):  
J. C. Chen ◽  
C. D. Jan ◽  
W. S. Huang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Field Investigation ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Rainfall Index ◽  
Hourly Rainfall ◽  
Central Taiwan ◽  
Debris Flow Initiation

Abstract. This paper reports the variation in rainfall characteristics associated with debris flows in the Chenyulan watershed, central Taiwan, between 1963 and 2009. The maximum hourly rainfall Im, the maximum 24 h rainfall Rd, and the rainfall index RI (defined as the product RdIm) were analysed for each rainfall event that triggered a debris flow within the watershed. The corresponding number of debris flows initiated by each rainfall event (N) was also investigated via image analysis and/or field investigation. The relationship between N and RI was analysed. Higher RI of a rainfall event would trigger a larger number of debris flows. This paper also discusses the effects of the Chi-Chi earthquake (CCE) on this relationship and on debris flow initiation. The results showed that the critical RI for debris flow initiation had significant variations and was significantly lower in the years immediately following the CCE of 1999, but appeared to revert to the pre-earthquake condition about five years later. Under the same extreme rainfall event of RI = 365 cm2 h−1, the value of N in the CCE-affected period could be six times larger than that in the non-CCE-affected periods.

scholarly journals Extreme rainfall impacts on soil CO2 efflux in an urban forest ecosystem in Beijing, China

2016 ◽  
Vol 96 (4) ◽  
pp. 504-514 ◽  
Author(s):  
Wenjing Chen ◽  
Xin Jia ◽  
Chunyi Li ◽  
Haiqun Yu ◽  
Jing Xie ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Forest Ecosystem ◽  
Urban Forest ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Co2 Efflux ◽  
Abrupt Decrease ◽  
Environmental Controls ◽  
Beijing China

Extreme rainfall events are infrequent disturbances that affect urban environments and soil respiration (Rs). Using data measured in an urban forest ecosystem in Beijing, China, we examined the link between gross primary production (GPP) and soil respiration on a diurnal scale during an extreme rainfall event (i.e., the “21 July 2012 event”), and we examined diel and seasonal environmental controls on Rs. Over the seasonal cycle, Rs increased exponentially with soil temperature (Ts). In addition, Rs was hyperbolically related to soil volumetric water content (VWC), increasing with VWC below a threshold of 0.17 m3 m−3, and then decreasing with further increases in VWC. Following the extreme rainfall event (177 mm), Rs showed an abrupt decrease and then maintained a low value of ∼0.3 μmol m−2 s−1 for about 8 h as soil VWC reached the field capacity (0.34 m3 m−3). Rs became decoupled from Ts and increased very slowly, while GPP showed a greater increase. A bivariate Q10-hyperbolical model, which incorporates both Ts and VWC effects, better fits Rs than the Q10 model in summer but not for whole year.

scholarly journals Trends in the Frequency of Intense Precipitation Events in Southern and Southeastern Brazil during 1960–2004

2011 ◽  
Vol 24 (7) ◽  
pp. 1913-1921 ◽  
Author(s):  
Mateus da Silva Teixeira ◽  
Prakki Satyamurty
Keyword(s):  
Extreme Rainfall ◽  
Southeastern Brazil ◽  
Extreme Rainfall Event ◽  
Southern Brazil ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Annual Frequency ◽  
Long Term Trends ◽  
Increasing Trends

Abstract A new approach to define heavy and extreme rainfall events based on cluster analysis and area-average rainfall series is presented. The annual frequency of the heavy and extreme rainfall events is obtained for the southeastern and southern Brazil regions. In the 1960–2004 period, 510 (98) and 466 (77) heavy (extreme) rainfall events are identified in the two regions. Monthly distributions of the events closely follow the monthly climatological rainfall in the two regions. In both regions, annual heavy and extreme rainfall event frequencies present increasing trends in the 45-yr period. However, only in southern Brazil is the trend statistically significant. Although longer time series are necessary to ensure the existence of long-term trends, the positive trends are somewhat alarming since they indicate that climate changes, in terms of rainfall regimes, are possibly under way in Brazil.

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