scholarly journals Reconnaissance sediment budgets for Lynn Valley, British Columbia: Holocene and contemporary time scales

2003 ◽  
Vol 40 (5) ◽  
pp. 701-713 ◽  
Author(s):  
David Campbell ◽  
Michael Church
Keyword(s):  
British Columbia ◽  
Drainage Basin ◽  
Mass Movement ◽  
Alluvial Fan ◽  
Stream Channel ◽  
Sediment Sources ◽  
Stream Channels ◽  
Photographic Analysis ◽  
Sediment Transfer ◽  
Channel Degradation

Volumes of erosional and depositional landforms were estimated by reconnaissance methods in a steep, forested drainage basin in the Coast Mountains, British Columbia, to examine what insight might be gained into the sediment budget in the absence of direct measurements of sediment transfer processes. Sediment transfers in postglacial and contemporary time were inferred on hillslopes, from hillslopes to stream channels, and within stream channels. Data were collected by aerial photographic analysis and field observation. Postglacial sediment sources are major gullies created by debris slides and flows, failures in glaciolacustrine terraces, and stream channel degradation. Depositional landforms consist of talus slopes and colluvial and alluvial fans. Contemporary sediment sources include debris slides and flows in established gullies and minor processes on hillslopes. Debris slide and debris flow volumes were calculated, and other processes were estimated from regional values. Erosion rate averaged over postglacial time is 276 t·km–2·a–1 (0.15 mm·a–1 surface lowering), with gullies and stream channel degradation contributing 170 and 82 t·km–2·a–1, respectively. A terminal alluvial fan provides an independent check of the results. In contemporary time, erosion rates are calculated to be 350 t·km–2·a–1, with debris flows and slides contributing nearly all of this sediment. The contemporary rate is probably perturbed by recent land use history. Mass-movement processes appear to be the dominant mechanism of sediment transfer and, contributions from Pleistocene valley deposits have declined significantly during Holocene time.

scholarly journals Determining contemporary and historical sediment sources in a large drainage basin impacted by cumulative effects: the regulated Nechako River, British Columbia, Canada

2019 ◽  
Vol 19 (9) ◽  
pp. 3357-3373 ◽  
Author(s):  
David Gateuille ◽  
Philip N. Owens ◽  
Ellen L. Petticrew ◽  
Barry P. Booth ◽  
Todd D. French ◽  
...  
Keyword(s):  
British Columbia ◽  
Drainage Basin ◽  
Cumulative Effects ◽  
Sediment Sources

Influence of Wildfire on Earth Surface Processes and Geomorphology

2021 ◽  
Author(s):  
Paul Santi ◽  
Francis Rengers
Keyword(s):  
Debris Flows ◽  
Management Practices ◽  
Mass Movement ◽  
Soil Formation ◽  
Alluvial Fan ◽  
Water Repellent ◽  
Alluvial Fans ◽  
Stream Channels ◽  
Sediment Delivery ◽  
Recurrence Intervals

<p>Wildfire is a global phenomenon that is expected to increase in extent and severity due to shifting land management practices and climate change. It removes vegetation, deposits ash, influences water-repellent soil formation, and physically weathers rock. These changes typically lead to increased erosion through sheetwash, rilling, rock spalling, and dry ravel, as well as increased mass movement in the form of floods, debris flows, rockfall, and landslides. Post-wildfire changes in these processes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Research has documented increases in erosion after wildfire ranging from 2-1000 times the pre-fire rates. Post-wildfire landscape lowering by erosion has been measured in the western U.S. at magnitudes of 2 mm per year, with sediment delivery at the mouths of canyons increased in the range of 160-1000% during the post-wildfire window of disturbance. Furthermore, post-wildfire sediment transport enhances the development of alluvial fans, debris fans, and talus cones. Debris-flow likelihood is increased following wildfire, such that modest rainstorms with <2 year recurrence intervals are typically sufficient to trigger debris flows with volumes much larger (270-540%) than at unburned sites. In the western U.S., as much as 25-50% of alluvial fan accumulation can be attributed to post-wildfire debris flows and other post-wildfire fluvial transport. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.  Consequently, wildfire is an important agent of geomorphic change.</p>

Late Quaternary sediments and geomorphic history of northern Vancouver Island, British Columbia

1983 ◽  
Vol 20 (1) ◽  
pp. 57-65 ◽  
Author(s):  
D. E. Howes
Keyword(s):  
British Columbia ◽  
Late Quaternary ◽  
Mass Movement ◽  
Vancouver Island ◽  
Alluvial Fan ◽  
Eastern Coast ◽  
Sedimentary Environments ◽  
History Of ◽  
Floodplain Deposits ◽  
Organic Deposits

Materials from two glacial intervals and one nonglacial interval have been identified on northern Vancouver Island, British Columbia. The oldest Pleistocene unit, termed "older drift," consists of glaciomarine silt and clay >38 000 years BP in age that overlie a till that has only been recorded in well logs. "Older drift" is tentatively correlated with Dashwood drift of the Semiahmoo Glaciation (early Wisconsin or older). No sediments of the succeeding Olympia nonglacial interval (mid-Wisconsin) have been found in the area. It is thought that this interval was characterized by a period of degradation in which Olympia-age sediments were deposited in transient sedimentary environments and subsequently eroded, in part during the Fraser Glaciation (late Wisconsin). The youngest Pleistocene unit, termed Port McNeill drift, includes advance deposits, till, and deglacial sediments, all deposited during Fraser Glaciation. Ice of this glaciation did not cover most of northern Vancouver Island until after 20 600 ± 330 years BP. At the maximum, which probably occurred about 15 000 years ago, Coast Mountain ice coalesced with and overrode Vancouver Island ice, and flowed in a westerly to northwesterly direction across northern Vancouver Island. Deglaciation commenced prior to 12 930 ± 160 years BP and possibly as early as 13 630 years ago on the eastern coast. Maximum sea level during and immediately following deglaciation was about 92 and 20 m elevation on the east and west coasts, respectively. This suggests that ice thickness at the Fraser maximum decreased westward across the study area. Deposits of Recent time include colluvial sediments formed by weathering and mass movement processes, alluvial fan and floodplain deposits, eolian sands associated with active beaches on the west coast, and organic deposits.

Reconsidering the sediment connectivity and sediment transfer under the influence of hydraulic structures and coal mining in the Jiu river basin

2021 ◽  
Author(s):  
Gabriela Adina Morosanu ◽  
Marta Cristina Jurchescu
Keyword(s):  
Coal Mining ◽  
River Basin ◽  
Spatial Scales ◽  
Sediment Supply ◽  
Anthropogenic Factors ◽  
Hydraulic Structures ◽  
Water Runoff ◽  
Sediment Sources ◽  
Sediment Transfer ◽  
The Impact

<p>The key to an efficient basin management, taking into account both the liquid (river water runoff and its quality) and the solid (sediment sources and delivery) components lies in the way we approach the complex problem of sediment-generating areas in a river basin. This complexity is manifested both through the primary geomorphological processes that contribute to the mobilization of significant amounts of alluvia from the slopes and along the river valleys, and the various environmental and anthropogenic factors that act as restrictors or catalysts of sediment transfer.</p><p>In the present study, we aim to analyze the various categories of anthropogenic factors, operating at different spatial scales (local or at subcatchment/river sector level), which contribute, together with the intrinsic geomorphological potential, to the sediment supply or, conversely, to the inhibition of erosion, transport and accumulation processes.</p><p>Tracking sediment mobilization, transfer, intermediate storage and final delivery in a lithologically and geomorphologically complex environment, such as the Jiu River Basin (10,070 km<sup>2</sup>), located in SW Romania, is a difficult task which can become even more challenging when we factor in the contribution of some additional elements of an anthropic nature. In our study area, represented by a Carpathian and Danubian river basin, some of the most significant issues impacting the research include, on the one hand, the existence of reservoirs and dams, the strengthening of anti-flood embankments or the presence of water diversions, to cite only hydrotechnical interventions, or the impact of coal mining on landforms, slope processes and sediment sources, on the other hand.  All these factors can act locally or regionally and they can surpass the influence exerted by the natural factors, thus being responsible for the reduction, storage, or, on the contrary, for the acceleration of specific hydro-sedimentary fluxes on certain paths.</p><p>In order to connect these two categories of potential factors regulating sediment generation and transfer, the methodological approach consists in evaluating the internal – geomorphic upstream-downstream connectivity in relation/contrast with the disruptive anthropogenic factors. The proposed workflow can be divided in two steps: 1) the identification of the upstream sediment generating areas which are most connected to the downstream delivery/ storage/ accumulation areas (river network and river mouth) by applying the connectivity index (IC) proposed by Cavalli et al. (2013); and 2) the evaluation of potential hotspot areas exhibiting the highest degree of connectivity, as seen through the lens of the additional coupling or decoupling effects induced by the anthropic activities specific to the Jiu river basin: hydraulic structures and coal mining.</p><p>Outcome discussions will focus on mapping problematic sediment production, storage and transfer sectors, as evidenced by the impact of hydrotechnical works and artificial landforms from coal mining on the connectivity potential of the Jiu river basin.</p>

Accelerated Erosion and Sedimentation in Southeast Asia

2005 ◽  
Author(s):  
Avijit Gupta
Keyword(s):  
Southeast Asia ◽  
Sediment Yield ◽  
Large Scale ◽  
Drainage Basin ◽  
High Rate ◽  
Annual Rainfall ◽  
Sediment Yields ◽  
Erosion Rates ◽  
Sediment Transfer ◽  
Very High

Periodic attempts to plot global distribution of erosion and sedimentation usually attribute most of Southeast Asia with a very high sediment yield (Milliman and Meade 1983). The erosion rates and sediment yield figures are especially high for maritime Southeast Asia. Milliman and Syvitski (1992), for example, listed 3000 t km−2 yr−1 for the archipelagos and peninsulas of Southeast Asia. They provided a number of natural explanations for the high erosion rate: location near active plate margins, pyroclastic eruptions, steep slopes, and mass movements. This is also a region with considerable annual rainfall, a very substantial percentage of which tends to be concentrated in a few months and falls with high intensity. Part of Southeast Asia (the Philippines, Viet Nam, Timor) is visited by tropical cyclones with heavy, intense rainfall and possible associated wind damage to existing vegetation. The fans at the foot of slopes, the large volume of sediment stored in the channel and floodplain of the rivers, and the size of deltas all indicate a high rate of erosion and episodic sediment transfer. This episodic erosion and sediment transfer used to be controlled for most of the region by the thick cover of vegetation that once masked the slopes. When vegetation is removed soil and regolith de-structured, and natural slopes altered, the erosion rates and sediment yield reach high figures. Parts of Southeast Asia display striking anthropogenic alteration of the landscape, although the resulting accelerated erosion may be only temporary, operating on a scale of several years. Over time the affected zones shift, and slugs of sediment continue to arrive in a river but from different parts of its drainage basin. The combination of anthropogenic alteration and fragile landforms may give rise to very high local yields. Sediment yields of more than 15 000 t km−2 yr−1 have been estimated from such areas (Ruslan and Menam, cited in Lal 1987). This is undoubtedly towards the upper extreme, but current destruction of the vegetation cover due to deforestation, expansion of agriculture, mining, urbanization, and implementation of large-scale resettlement schemes has increased the sediment yield from < 102 to > 103 t km−2 yr−1.

scholarly journals Over 16,000 Years of Fire Frequency Determined from AMS Radiocarbon Dating of Soil Charcoal in an Alluvial Fan at Bear Flat, Northeastern British Columbia

Radiocarbon ◽  
2006 ◽  
Vol 48 (3) ◽  
pp. 435-450 ◽  
Author(s):  
A J Timothy Jull ◽  
Marten Geertsema
Keyword(s):  
British Columbia ◽  
Radiocarbon Dating ◽  
Large Scale ◽  
Fire Frequency ◽  
Alluvial Fan ◽  
Before Present ◽  
Ams Radiocarbon Dating ◽  
Soil Charcoal ◽  
Large Fires ◽  
Millennial Time Scale

We present results of radiocarbon dating of charcoal from paleosols and buried charcoal horizons in a unique sequence, which potentially records the last 36,000 yr, from a fan at Bear Flat, British Columbia (BC) (56°16'51’N, 121°13'39”W). Evidence for forest-fire charcoal is found over the last 13,500 ± 110 14C yr before present (BP) or 16,250 ± 700 cal BP. The study area is located east of the Rocky Mountains in an area that was ice-free at least 13,970 ± 170 14C yr BP (17,450–16,150 cal BP) ago. The latest evidence of fire is during the Medieval Warm Period (MWP). The charcoal ages show a periodicity in large fires on a millennial scale through the Holocene—an average of 4 fires per thousand years. Higher fire frequencies are observed between 2200 to 2800 cal BP, ∼5500 and ∼6000 cal BP, ∼7500 to 8200 cal BP, and 9000 to 10,000 cal BP. These intervals also appear to be times of above-average aggradation of the fan. We conclude that fire frequency is related to large-scale climatic events on a millennial time scale.

Response Time of Forested Mountainous Watersheds in Humid Regions

2000 ◽  
Vol 31 (3) ◽  
pp. 149-168 ◽  
Author(s):  
A. Loukas ◽  
N. R. Dalezios
Keyword(s):  
Field Experiments ◽  
Time Lag ◽  
Wave Theory ◽  
Roughness Coefficient ◽  
Stream Channel ◽  
Stream Channels ◽  
Mountainous Watersheds ◽  
Two Phases ◽  
Comparison Of The Results ◽  
Estimation Of Time

This study proposes an analytical method for the estimation of time lag for forested mountainous watersheds. The water flow in a watershed is separated and analyzed in two phases, the land or hillslope phase and the stream channel phase. In many areas around the globe the flow in a forested high gradient watershed is generated through subsurface pathways as several field experiments have shown. The kinematic wave theory is used to describe the generation of flow from steep forested hillslopes. This hillslope runoff is, then, used as input to the stream channels. The equations were developed by assuming kinematic conditions in the stream channel and that the stream slope and the roughness coefficient i) vary according to a second order polynomial with the distance from the mouth of the watershed, ii) vary linearly with the distance from the outlet of the watershed, and iii) are constant throughout the watershed. Comparison of the results of the proposed equation with data from two experimental watersheds in Coastal British Columbia indicates that the three expressions of the proposed equation, even the simplest one assuming constant stream slope and roughness coefficient, are reliable and give good approximation of the observed time lag.

Modern Alluvial History of the Paria Rver Drainage Basin, Southern Utah

1986 ◽  
Vol 25 (3) ◽  
pp. 293-311 ◽  
Author(s):  
Richard Hereford
Keyword(s):  
Sediment Yield ◽  
Drainage Basin ◽  
River Channel ◽  
High Flow ◽  
Low Flow ◽  
Vertical Accretion ◽  
Important Process ◽  
Stream Channels ◽  
History Of ◽  
Peak Flood

Stream channels in the Paria River basin were eroded and partially refilled between 1883 and 1980. Basin-wide erosion began in 1883; channels were fully entrenched and widened by 1890. This erosion occurred during the well-documented period of arroyo cutting in the Southwest. Photographs of the Paria River channel taken between 1918 and 1940 show that the channel did not have a floodplain and remained wide and deep until the early 1940s. A thin bar (<50 cm), now reworked and locally preserved, was deposited at that time. Basin-wide aggradation, which began in the early 1940s, developed floodplains by vertical accretion. The floodplain alluvium, 1.3–3 m thick. consists of two units recognizable throughout the studied area. An older unit was deposited during a time of low flow and sediment yield whereas the younger unit was deposited during times of high flow, sediment yield, and precipitation. Tree-ring dating suggests that the older unit was deposited between the early 1940s and 1956, and the younger between 1956 and 1980. The units are not time transgressive, suggesting that deposition by knickpoint recession was not an important process. High peak-flood discharges were associated with crosion and low flood discharges with aggradation. The erosional or aggradational mode of the streams was determined principally by peak-flood discharge, which in turn was controlled by precipitation.

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