HL was commissioned by the EA Southern Region, as sub-consultants to Halcrow Consulting Engineers, to undertake the feasibility and hydrometric design of 6 sites on streams feeding the Romney Marsh. On one of the streams, the Kent Ditch, it was necessary to design a two section/stage gauging station for which a Sarasota 2000 ultrasonic transit-time meter was installed.
One measuring section was upstream of a bridge to measure low to medium flows. The second section was under the bridge to measure medium to high flows.
The data from these gauging stations was required by the Environment Agency to further their understanding of the water resources of the Romney marshes which is a very important eco-system. The Kent ditch was one of six gauging stations designed for sites on streams that feed Romney Marshes for which ultrasonic transit-time meters were selected as the preferred instrument for a variety of hydraulic, other site characteristics, cost and logistic reasons.
This twin flow gauge site arrangement was necessary since the bridge had sufficient capacity to contain all but the most extreme high flows but the depth of flow was too low for the operation of an acoustic gauge at lower discharges. Sufficient depth of flow could be obtained upstream since the bed of the channel was significantly lower than the invert of the bridge. The upstream channel overtops the bank at relatively low discharges so was not suitable for high flow measurement. The Thermo Fisher Scientific Sarasota 2000 system is ideally suited to this type of multi-site gauge because up to 32 paths at 4 different locations can be configured on the system.
Design and installation services were provided by our sister company within the Hydro-Logic Group, Hydro-Logic Services Ltd.