Andy Steele (on the right) in this picture of the Maplin Model from 1973 still works as an engineer in HR Wallingford's Coastal Structures Group
One of the major projects carried out by the Hydraulics Research Station at Howbery Park in the 1970s was the construction of an extensive model of the then planned third airport for London - the proposed Maplin airport and seaport, which was to be built on 30 square miles of reclaimed land in the Thames Estuary.
A new steel-framed building was custom-built on a green field at Howbery Park to house this one model. At that time, the roof span of this enormous building could claim the title of being the widest single span steel structure in Europe. From when building work started, to being a working model, took about one year which was impressively quick. The building came to be known as the Maplin Building.
Andy Steele started work at the Hydraulics Research Station in 1973 to work on the Maplin Model. Andy is still with HR Wallingford today, working on physical models for the Coastal Structures Group.
The model used a distorted scale 1:1,000 horizontal, 1:100 vertical, so extra roughness was needed.
A particular feature of the model was the many cylinders placed in the model of the Thames river bed which were used to create hydraulic turbulence. Andy remembers how these cylinders had to be moved around many times, using trial and error, to create just the right amount of resistance in the flow.
The model of the Thames river bed featured cylinders to create hydraulic turbulence.
Flow pumps, and a tide tank were used to simulate the tidal flow from the Channel to the North Kent coast, reproducing the tide in the model. Andy remembers that the tidal cycle was 7.5 minutes. Water level followers monitored the rise and fall of the tide. Tidal velocities in the channels approaching the airport were also measured.
A larger-scale section of the Maplin Seaport was built in a separate building, to simulate and test navigation, using radio-controlled boats. Bill Biggs, who was the Chief Photographer, is holding the clipboard, standing next to John Broster who managed the Maplin seaport project.
Within the model, was the 30 square mile reclamation area which was being considered as the site for the new London airport, surrounded by a sea wall. The model also included landmarks such as Southend Pier. The Maplin model was manned by staff who worked in a shift pattern, in one of two teams, working either from 7.30am to 1.30pm or from 1pm to 10pm.
When the tide was run, the output results were produced as numbers on a printout and on a punched paper tape. These numbers were used to plot several of the tide curves, such as at Southend and Bawdsey, by hand on graph paper. The tape was used in conjunction with punch cards to create computer code on a massive mainframe computer.
A large part of Andy’s time was spent moving the roughness elements, and making sure the water level followers were correctly located.
“It was all about calibrating and plotting tide curves and currents”, says Andy. “The main difference with today’s physical models is that fast computers allow us to process much more data, much more quickly. Now numerical and CFD (Computational Fluid Dynamics) modelling would play a major role if we were ever to re-create the Maplin Model.”
Hydraulics Research Station Director, Robert Russell (on the far right of the picture) standing next to Harry Dedow, Assistant Director. Alan Price,Coastal Department Head, is on the far left of the picture. Project manager, John Broster, is in profile view talking to one of the VIPs in this ministerial visit during 1973.