Geomorphic change and biogeomorphic feedbacks in a dryland river: The Little Colorado River, Arizona, USA

2019 ◽  
Vol 131 (11-12) ◽  
pp. 1920-1942 ◽  
Author(s):  
D.J. Dean ◽  
D.J. Topping
Keyword(s):  
Colorado River ◽  
Peak Flow ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Water Development ◽  
Spatial And Temporal Scales ◽  
Long Duration ◽  
Hydrologic Change ◽  
Dryland River ◽  
Channel Slope

Abstract The Little Colorado River in Arizona, United States, has undergone substantial geomorphic change since the late 1800s and early 1900s, consisting of sediment accumulation following an earlier period of likely widespread sediment evacuation. We analyzed hydrologic and geomorphic data at different spatial and temporal scales to determine the primary mechanisms responsible for these changes, and to provide context for periods of sediment evacuation and accumulation in other rivers. Peak-flow magnitude has progressively declined since the 1920s despite the occurrence of four alternating periods of high and low total annual flow. Largely coincident with this hydrologic change, the channel has narrowed between 72% and 88% in some reaches since the 1930s, with increases in sinuosity in wide alluvial valleys causing ∼21%–32% reductions in channel slope. Dense stands of vegetation colonized, and thus stabilized, the newly deposited floodplains. Although large, long-duration floods caused some channel widening, these floods have been too infrequent to offset the progressive narrowing. Channel narrowing, increases in sinuosity, decreases in slope, and increases in vegetative roughness appear to have caused biogeomorphic feedbacks, thereby exacerbating sediment deposition, disrupting flood conveyance, and contributing to decreases in peak-flow magnitude and in sediment transport. The progressive increase in water development in parts of the basin has also likely contributed to progressive declines in peak flow. These results show that biogeomorphic feedback processes combined with human water development may be as important as, if not more important than, changes in climate in driving hydrologic, geomorphic, and sediment-load change in dryland river environments.

scholarly journals Spatial and temporal patterns of sediment storage and erosion following a wildfire and extreme flood

2019 ◽  
Vol 7 (2) ◽  
pp. 563-590 ◽  
Author(s):  
Daniel J. Brogan ◽  
Peter A. Nelson ◽  
Lee H. MacDonald
Keyword(s):  
Laser Scanning ◽  
Sediment Accumulation ◽  
Burn Severity ◽  
Spatial And Temporal Patterns ◽  
Channel Network ◽  
Erosion And Deposition ◽  
Long Duration ◽  
Extreme Flood ◽  
Changes Over Time ◽  
Over Time

Abstract. Post-wildfire landscapes are highly susceptible to rapid geomorphic changes, and the resulting downstream effects, at both the hillslope and watershed scales due to increases in hillslope runoff and erosion. Numerous studies have documented these changes at the hillslope scale, but relatively few studies have documented larger-scale post-fire geomorphic changes over time. In this study we used five airborne laser scanning (ALS) datasets collected over 4 years to quantify erosion and deposition throughout the channel network in two ∼15 km2 watersheds, Skin Gulch and Hill Gulch, in northern Colorado after a wildfire followed by a large, long-duration flood 15 months later. The objectives were to (1) quantify the volumes, spatial patterns, and temporal changes over time of erosion and deposition over a nearly 4-year period, and (2) evaluate the extent to which these spatially and temporally explicit changes are correlated to precipitation metrics, burn severity, and morphologic variables. The volumetric changes were calculated from a differencing of DEMs for 50 m long segments of the channel network and associated valley bottoms. The results showed net sediment accumulation after the wildfire in the valley bottoms of both watersheds, with greater accumulations in the wider and flatter valley bottoms in the first 2 years after burning. In contrast, the mesoscale flood caused large amounts of erosion, with higher erosion in those areas with more post-fire deposition. Only minor changes occurred over the 2 years following the mesoscale flood. Volume changes for the different time periods were weakly but significantly correlated to, in order of decreasing correlation, contributing area, channel width, percent burned at high and/or moderate severity, channel slope, confinement ratio, maximum 30 min precipitation, and total precipitation. These results suggest that morphometric characteristics, when combined with burn severity and a specified storm, can indicate the relative likelihood and locations for post-fire erosion and deposition. This information can help assess downstream risks and prioritize areas for post-fire hillslope rehabilitation treatments.

scholarly journals The human impact on North American erosion, sediment transfer, and storage in a geologic context

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
David B. Kemp ◽  
Peter M. Sadler ◽  
Veerle Vanacker
Keyword(s):  
Mass Transfer ◽  
North American ◽  
Sediment Accumulation ◽  
River System ◽  
Rapid Expansion ◽  
Past Century ◽  
Spatial And Temporal Scales ◽  
Alluvial Sediment ◽  
European Colonization ◽  
The Impact

AbstractHumans are primary agents of geomorphic change, and rates of anthropogenic landscape change likely far exceed the pace of change expected from natural geologic processes. Nevertheless, our understanding of the impact of humans on the natural landscape is limited by difficulties in accurately comparing past and present rates of change across wide spatial and temporal scales. Here, we present a compilation of  >4000 rates of alluvial sediment accumulation that provide an indirect record of North American erosion, mass transfer and sediment storage from the late Pleistocene to the present day. Continent-wide rates of alluvium accumulation were broadly stable for ~40,000 years, but increased 10-fold during the rapid expansion of agriculture and river system modification associated with European colonization. Interpreted in terms of mass transfer, humans have moved as much sediment in North America in the past century as natural processes can transfer in 700–3000 years.

BEDFLOW: integrating river morphodynamics in the Sillaro River across spatial and temporal scales

2020 ◽  
Author(s):  
Francesco Brardinoni ◽  
Anna Rita Bernardi ◽  
Federico Bonazzi ◽  
Giuseppe Caputo ◽  
Marwan Hassan ◽  
...  
Keyword(s):  
Vertical Channel ◽  
Channel Width ◽  
Topographic Maps ◽  
Event Scale ◽  
Channel Changes ◽  
Spatial And Temporal Scales ◽  
Gravel Mining ◽  
Basin Scale ◽  
Channel Slope ◽  
Active Channel

<p>Anthropogenic disturbance is one of the main drivers of contemporary river adjustment. In mountain streams, information and prior work on post-disturbance recovery rates is limited, compared to lowland counterparts. The BEDFLOW initiative aims to investigate fluvial morphodynamics along the mountain portion of the Sillaro River (138 km<sup>2</sup>), Northern Apennines, to guide local strategies of sediment management at the basin scale and improve environmental quality of this fluvial system. Of particular interest is the understanding of the historical and contemporary response of the Sillaro River to gravel mining activities, which focused in the mid-to-lower portions of the river between the mid-1940s and the early 1980s. To this end, BEDFLOW adopts a multi-scale approach that integrates: (1) historical analysis of planform channel changes across the entire montane channel main stem over the past 100 years; (2) hydraulic and bed texture characterization of 14 representative reaches that encompass drainage areas comprised between 2.7 and 113 km<sup>2</sup>; and (3) flood-event scale, RFID bedload monitoring in two reaches, complemented by topo-photogrammetric surveys of the subaerial and submerged channel bed.</p><p>Analysis of historical channel changes was conducted by mapping active channel width on historical topographic maps (1928) and across 11 sequential aerial photo sets (1954, 1969, 1976, 1988, 1996, 2000, 2008, 2011, 2014, 2016 and 2018), along a valley segment of about 26 kilometers (i.e., 35 homogeneous reaches). Vertical channel adjustment was assessed by comparison of long profiles extracted from 1928 and 1976 topographic maps.</p><p>Preliminary results indicate that the river has experienced intense channel narrowing between 1969 and 1996. This pattern has progressively slowed down, even though narrowing continues until today. Cumulatively, reduction in active channel width has been highest in the distal most unconfined reaches, where median width has decreased from >120 m in 1954 to about 20 m in 2018, intermediate in semi-confined reaches (from 99 m to 28 m), and least in the upper confined reaches (from 30 m to 15 m). In the semi-confined and unconfined reaches, where most of the gravel mining took place, channel pattern has changed from braided to wandering and/or from wandering to single-thread. Today, after about 35 years since in-channel gravel mining became interdicted, the river still exhibits signs of incomplete recovery, as bedrock sporadically outcrops amidst mid channel bars, formerly occupied by braided plains.</p><p>The two monitoring reaches, which are active since February 2020, have contrasting morphology and degree of hillslope coupling. The upper one (drainage area = 35 km<sup>2</sup>) is a riffle-pool, uncoupled reach, characterized by a fine-to-coarse gravel texture and a channel slope of 0.8 %. The lower one (50 km<sup>2</sup>) is a transitional reach with dominantly plane-bed morphology and lesser riffle-pool and step-pool stretches; it is characterized by fine gravel to boulder texture, and by a channel slope of 1.5 %. The b-axis of deployed tracer stones spans from 36 to 180 mm.</p><p>The Sillaro River basin functions also as a training site for students. This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.</p><p>https://site.unibo.it/bedflow/en</p><p>https://site.unibo.it/bedflow/it</p>

PANCREATIC DIABETES AND HYPOPHYSECTOMY IN THE SNAKE XENODON MERREMII

1960 ◽  
Vol XXXV (III) ◽  
pp. 313-323 ◽  
Author(s):  
B. A. Houssay ◽  
J. C. Penhos
Keyword(s):  
Blood Sugar ◽  
Blood Sugar Level ◽  
Total Pancreatectomy ◽  
Progressive Increase ◽  
List Type ◽  
Progressive Decrease ◽  
Pancreatic Diabetes ◽  
Long Duration ◽  
Glucose Tolerance Curve ◽  
Tolerance Curve

ABSTRACT 1. – Total pancreatectomy in Xenodon merremii produces a slight decrease in blood sugar for 1–3 days, and later on a progressive increase until a diabetic level (5–6 times higher than the normal was reached). 2. – Removal of 83–88 % of the pancreatic mass produces no changes in the blood sugar level. 3. – Hypophysectomy in fasting snakes produces: progressive decrease of glycaemia, adynamia and death. 4. – Preventive hypophysectomy diminishes the increase in blood sugar after pancreatectomy. Hypophysectomy in diabetic pancreatectomized animals brings about a decrease of the glycaemia. 5. – This snake is sensitive to insulin, the effect being greater in pancreatectomized than in normal animals. 6. – Alloxan produces an initial transitory increase of glycaemia, followed by a marked and lasting hypoglycaemia. Diabetes was not observed. 7. – Carbutamide and tolbutamide produced a decrease in the blood sugar level in normal snakes, but did not diminish it in the pancreatectomized animals. 8. – Glucagon has a powerful and very lasting hyperglycaemic action in the snakes. 9. – The glucose tolerance curve has a long duration in normal snakes and is even more prolonged in the pancreatectomized snakes. 10. – Cortisol had a transitory hyperglycaemic action in normal and totally pancreatectomized snakes. Somatotrophin only has this action in the pancreatectomized animals.

scholarly journals Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Vol 12 (7) ◽  
pp. 1539-1553 ◽  
Author(s):  
Maria-Angela Bassetti ◽  
Serge Berné ◽  
Marie-Alexandrine Sicre ◽  
Bernard Dennielou ◽  
Yoann Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are the most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea–land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m long sediment core from the Rhône mud belt in the Gulf of Lions in an area where the average accumulation rate is ca. 0.70 m 1000 yr−1. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multiproxy dataset (XRF core scan, 14C dates, grain size and organic-matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes in the Rhône hydrological activity. Our results show that (1) the early Holocene was characterized by high sediment delivery likely indicative of local intense (but short-duration) rainfall events, (2) important sediment delivery around 7 ka cal BP presumably related to increased river flux, (3) a progressive increase in continental/marine input during the mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, (4) multidecadal to centennial humid events took place in the late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Ages Cold Period) and also coincide with time intervals of major floods in the northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

scholarly journals Effects of Underlay on Hill-Slope Surface Runoff Process of Cupressus funebris Endl. Plantations in Southwestern China

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 644
Author(s):  
Bingchen Wu ◽  
Shi Qi
Keyword(s):  
Spatial Pattern ◽  
Surface Runoff ◽  
Peak Flow ◽  
Pearson Correlation ◽  
Composite Index ◽  
Southwestern China ◽  
Near Surface ◽  
Long Duration ◽  
The Impact ◽  
Micro Topography

Clarifying the impact of underlay (i.e., the combination of near-surface vegetation and surface micro-topography) on the surface runoff process would provide a significant theoretical basis for the adjustment of vegetation patterns and the control of soil erosion on steep slopes in mountainous areas of southwestern China. In the current study, the runoff process under different rainfall characteristics was observed based on 10 natural runoff plots, and the correlation between the spatial pattern of cypress (Cupressus funebris), micro-topography, and runoff characteristic parameters was tested using the Pearson correlation coefficient method. The coupling effects of the spatial pattern of cypress and micro-topography on surface runoff also were analyzed using the Response Surface Method (RSM). The results showed that (1) under the conditions of long-duration moderate rainfall or long-duration rainstorm, topographic relief, surface roughness, runoff path density, contagion index of cypress, and stand density of cypress were the main reasons for the difference in the peak flow of each runoff plot, while under the condition of the short-duration rainstorm, the factors previously mentioned were no longer the dominant factors; (2) under the conditions of long-duration heavy rainfall or long-duration rainstorm, the common laws reflected by the response of the peak flow to the composite index of the spatial pattern of cypress and micro-topography were that (1) when the composite index of the spatial pattern of cypress (V) was below 21 and the composite index of micro-topography (U) was below 10.5, the peak flow would not be significantly affected; (2) when U > 10.5, increasing the composite index of the spatial pattern of cypress within a certain range would promote peak flow; (3) when U < 7.5 and V > 18, the increase of V value could significantly reduce the peak flow, and on this basis, adjusting the V value to 41, the reduction rate of peak flow could reach 84%.

scholarly journals Holocene hydrological changes of the Rhone River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Author(s):  
M. A. Bassetti ◽  
S. Berné ◽  
M. A. Sicre ◽  
B. Dennielou ◽  
Y. Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea-land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m-long sediment core from the Rhone mud belt in the Gulf of Lions in an area where the average accumulation rate is of ca. 0.70 m/1000 years. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multi-proxy dataset (XRF-core scan, 14C dates, grain size and organic matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes of the Rhone hydrological activity. Our results show that 1) the Early Holocene was characterized by high sediment delivery likely indicative of local intense (but short duration) rainfall events , 2) important sediment delivery around 7 ka cal BP roughly presumably related to increased river flux, 3) a progressive increase of continental/marine input during the Mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, 4) multi-decadal to centennial humid events in the Late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Age) and also coincide with time intervals of major floods a in the Northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

scholarly journals Effect of Air Pollutants on Peak Expiratory Flow Rate of Public Bus Drivers in Bhaktapur, Nepal

2019 ◽  
Vol 15 (1) ◽  
pp. 30-33
Author(s):  
Prabin Kumar Karki ◽  
Sushil Kharel ◽  
Gita Khakurel ◽  
Nripendra Tiwari
Keyword(s):  
Air Pollution ◽  
Air Pollutants ◽  
Matched Control ◽  
Peak Flow ◽  
Control Group ◽  
Kathmandu Valley ◽  
Outdoor Air ◽  
Bus Drivers ◽  
Long Period ◽  
Long Duration

Background: Rapid increase in number of vehicles in Kathmandu valley over past decade and never ending road expansion projects has aggravated air pollution. People involved in transportation jobs for long duration like bus drivers, conductors are more vulnerable to ill effects of air pollutants. The purpose of the present study was to assess lung function of public bus drivers exposed to outdoor air pollution by means of PEFR. Methods: Fifty healthy, non smoking bus drivers were selected randomly from bus parks of Bhaktapur district. Anthropological records were taken. PEFR value was obtained by Mini Wright’s peak flow meter. Their mean PEFR was compared with 50, age matched control group involved in other office works. Results: The PEFR value was significantly lower among bus drivers than the control group (p<0.001). Mean PEFR decreased with increasing age and increased duration of bus driving. Conclusions: Our study concluded that PEFR value among bus drivers who are exposed to air pollutants for long period of time was significantly reduced.

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