Near-Bed Cohesive Sediment Processes: Development of a Self-Contained System for Long-Term Field Measurements

Near-Bed Cohesive Sediment Processes: Development of a Self-Contained System for Long-Term Field Measurements

Atkins, R.
Ockenden, M.C.

TU Delft

1993-09-30

This report describes the development of a self-contained system for making long-term field measurements of bed elevation changes and the associated near-bed hydrodynamics and cohesive sedimentary parameters in estuarine environments. These measurements are required to ensure the understanding of these parameters and their interaction with bed elevation changes. In particular, more information is sought on the relative contributions of each tide in a spring-neap cycle and on the effect of waves. This knowledge is necessary to refine and verify the algorithms used in numerical models of the erosion and deposition processes. This should lead to improved confidence in these models, in particular when .making long-term predictions of bed elevation changes. The measurement system will be capable of unattended deployment for a complete spring-neap cycle (15 days) and measures the following: (1) Turbulent velocities in 3 orthogonal directions close to the bed. (2) Turbidity levels at 3 heights in the bottom 1m of the water column. (3) Water depths. (4) Wave characteristics. (5) Bed elevation changes. The system has integral signal conditioning, data logging facilities and power supplies. The basic calibrations of all the instruments in the measurement system have been established during laboratory tests. The instruments included in the measurement system have been selected not only on the grounds of the nature and range of the data required but also to minimise the system's power consumption. The choice of annular electromagnetic current meters ensures the system is suitable for use in wave or current only conditions or combined waves and currents. All the underwater components of the system have been pressure tested to a depth equivalent to approximately 10m of water column. A suite of data analysis computer programs has been developed to process the data collected by the measurement system efficiently.

bed elavation
field measurements
measurement equipment
measurement system
cohesive sediment
sediment transport
sediment transport measurement

TLE500100
TLN100335
TLN450200

http://resolver.tudelft.nl/uuid:df26f116-9488-433c-947e-814b758160e0

HR Wallingford

SR 341

Hydraulic Engineering Reports

report

(c) 1993 HR Wallingford