Field measurements of the energy delivered to the channel bed by moving bed load and links to bedrock erosion

Forcing functions and sediment response were measured during two comprehensive surf zone experiments. The experiments included simultaneous measurements of waves and currents, and the movement of sediment as bed and suspended load. The longshore transport of suspended load was found to be about 10 to 20% of the tracer-measured load. Results from tracer measurements of the longshore transport of bed load indicate that previous measurements may have misestimated the effective "tracer layer thickness," and a more rigorous method is proposed.

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Transient bottom topography changes in alluvial streams

Canadian Journal of Civil Engineering ◽

10.1139/l99-063 ◽

2000 ◽

Vol 27 (2) ◽

pp. 309-318

Author(s):

Y R Fares

Keyword(s):

Bottom Topography ◽

Computational Modelling ◽

Field Measurements ◽

Computational Procedure ◽

Bed Load ◽

River Channels ◽

Total Load ◽

Secondary Currents ◽

Sediment Bed ◽

Transient Variations

The development of a quasi two-dimensional computational model for simulating the transient variations of bed topography profiles in alluvial river channels is reported. The formulation of the model is based on combining the longitudinal flow momentum with the continuity principle of the sediment bed load. The Engelund-Hansen formula is employed in estimating the total sediment bed load along the reach of a river channel. The lateral bed load contribution from the total load is calculated in the same way as in calculating the lateral secondary currents from the main flow velocities. The numerical scheme and the computational procedure used in the study are described in detail. The simulated bed level profiles are verified through comparisons with experimental and field measurements taken from case studies in the literature for different flow conditions, channel characteristics, and sediment properties. The correlation between flow discharge, bed load, boundary friction, and channel slope is discussed. On the basis of the reasonably good comparisons with field data, it may be deduced that the model can be used for predicting the bottom topography variations in river channels.Key words: meandering rivers, bottom topography, sediment transport, bed load, boundary roughness, field measurements, experimental data, computational modelling, finite difference method.

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Geophysics - Field Measurements

10.1016/s0076-695x(08)x6035-1 ◽

1987 ◽

Keyword(s):

Field Measurements

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NUMERICAL MODEL TO SIMULATE THE EROSION ON THE SLOPE DUE TO OVERTOPPING

Science and Technology Development Journal ◽

10.32508/stdj.v13i3.2156 ◽

2010 ◽

Vol 13 (3) ◽

pp. 78-87

Author(s):

Hoai Cong Huynh

Keyword(s):

Numerical Model ◽

Flow Model ◽

Bed Load ◽

Experiment Data ◽

Step Method ◽

Morphological Model ◽

Load Transport ◽

Bed Load Transport ◽

The Finite Difference Method ◽

Good Agreement

The numerical model is developed consisting of a 1D flow model and the morphological model to simulate the erosion due to the water overtopping. The step method is applied to solve the water surface on the slope and the finite difference method of the modified Lax Scheme is applied for bed change equation. The Meyer-Peter and Muller formulae is used to determine the bed load transport rate. The model is calibrated and verified based on the data in experiment. It is found that the computed results and experiment data are good agreement.

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79. Comparison of Benzene-Specific Field Measurements at Oil Refineries

10.3320/1.2762859 ◽

1999 ◽

Author(s):

W.R. Haag ◽

P. Owens ◽

D. Mayszak ◽

J. Katona ◽

B. Mangilin ◽

...

Keyword(s):

Field Measurements ◽

Oil Refineries ◽

Specific Field

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GLOBAL LEAF AREA INDEX DATA FROM FIELD MEASUREMENTS, 1932-2000

ORNL Distributed Active Archive Center Datasets ◽

10.3334/ornldaac/584 ◽

2001 ◽

Cited By ~ 2

Author(s):

G. P. ASNER ◽

S. T. GOWER ◽

J. M. O. SCURLOCK

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Field Measurements ◽

Area Index ◽

Index Data

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An evaluation of a strategic de-stocking regime for dairying to improve nitrogen efficiency and reduce nitrate leaching from dairy farms in nitrate-sensitive areas

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.2000.62.2401 ◽

2000 ◽

pp. 105-110

Author(s):

Cecile De Klein ◽

Jim Paton ◽

Stewart Ledgard

Keyword(s):

New Zealand ◽

Nitrate Leaching ◽

Management Practice ◽

Field Measurements ◽

Dairy Farms ◽

Nitrogen Efficiency ◽

Management Tool ◽

Pasture Production ◽

Leaching Losses ◽

Sensitive Areas

Strategic de-stocking in winter is a common management practice on dairy farms in Southland, New Zealand, to protect the soil against pugging damage. This paper examines whether this practice can also be used to reduce nitrate leaching losses. Model analyses and field measurements were used to estimate nitrate leaching losses and pasture production under two strategic de-stocking regimes: 3 months off-farm or 5 months on a feed pad with effluent collected and applied back to the land. The model analyses, based on the results of a long-term farmlet study under conventional grazing and on information for an average New Zealand farm, suggested that the 3- or 5-month de-stocking could reduce nitrate leaching losses by about 20% or 35-50%, respectively compared to a conventional grazing system. Field measurements on the Taieri Plain in Otago support these findings, although the results to date are confounded by drought conditions during the 1998 and 1999 seasons. The average nitrate concentration of the drainage water of a 5-month strategic de-stocking treatment was about 60% lower than under conventional grazing. Pasture production of the 5-month strategic de-stocking regime with effluent return was estimated based on data for apparent N efficiency of excreta patches versus uniformlyspread farm dairy effluent N. The results suggested that a strategic de-stocking regime could increase pasture production by about 2 to 8%. A cost/ benefit analysis of the 5-month de-stocking system using a feed pad, comparing additional capital and operational costs with additional income from a 5% increase in DM production, show a positive return on capital for an average New Zealand dairy farm. This suggests that a strategic destocking system has good potential as a management tool to reduce nitrate leaching losses in nitrate sensitive areas whilst being economically viable, particularly on farms where an effluent application system or a feed pad are already in place. Keywords: dairying, feed pads, nitrate leaching, nitrogen efficiency, productivity, strategic de-stocking

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A protocol for sampling pastures in hill country

Journal of New Zealand Grasslands ◽

10.33584/jnzg.2016.78.511 ◽

2016 ◽

Vol 78 ◽

pp. 203-209 ◽

Cited By ~ 2

Author(s):

K.J. Hutchinson ◽

D.R. Scobie ◽

J. Beautrais ◽

A.D. Mackay ◽

G.M. Rennie ◽

...

Keyword(s):

Random Sampling ◽

Geographical Information Systems ◽

Field Measurements ◽

Decision Support Tool ◽

Accurate Estimate ◽

Ease Of Use ◽

Geographical Information ◽

Support Tool ◽

Topographic Complexity ◽

Hill Country

To develop a protocol to guide pasture sampling for estimation of paddock pasture mass in hill country, a range of pasture sampling strategies, including random sampling, transects and stratification based on slope and aspect, were evaluated using simulations in a Geographical Information Systems computer environment. The accuracy and efficiency of each strategy was tested by sampling data obtained from intensive field measurements across several farms, regions and seasons. The number of measurements required to obtain an accurate estimate was related to the overall pasture mass and the topographic complexity of a paddock, with more variable paddocks requiring more samples. Random sampling from average slopes provided the best balance between simplicity and reliability. A draft protocol was developed from the simulations, in the form of a decision support tool, where visual determination of the topographic complexity of the paddock, along with the required accuracy, were used to guide the number of measurements recommended. The protocol was field tested and evaluated by groups of users for efficacy and ease of use. This sampling protocol will offer farmers, consultants and researchers an efficient, reliable and simple way to determine pasture mass in New Zealand hill country settings. Keywords: hill country, feed budgeting, protocol pasture mass, slope

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