ENVIRONMENTAL MONITORING
Waterjet cutting pebbles aids flood safety scheme
I
n the Eastern Solent Coastal Partnership’s (ESCP) project to protect Hayling Island’s south coast, radio-frequency identification (RFID) tags are embedded in pebbles allowing sedimentary drift to be tracked. Using a
powerful 0.8mm diameter abrasive waterjet operating at a pressure of 90,000 psi, manufacturing services contractor ICEE Managed Services has cut small holes straight through more than 3,500 seashore pebbles for the ESCP, a government-funded scientific research group. Combining age-old pebbles with ultra-modern
RFID and digital mapping technology, the ESCP has devised and developed a ground-breaking method of tracking and logging the movement of off-shore sediment. Results from a current study will help form beach management decisions, which in the long term aim to improve coastal defence strategies. In many cases, flooding from the sea arises due to
gradual wearing away of the coastline, caused by the actions of waves and tides which are often accelerated by storms. Often, eroded sediment – mostly sand, shingle and pebbles – is transported to other parts of the coastline by these actions. If the effect is better understood then more effective protective steps may be taken. The innovative method, devised and developed by
the ESCP, involves embedding passive induced transponders (PIT) into the holes cut by ICEE which transform pebbles into ‘smart’ markers. The markers are placed on the seashore at low tide and over time are transported along the coastline by waves and tidal action. Using handheld scanners and quadbike-mounted
RFID antennae arrays, ESCP’s coastal engineers comb the seashore at low tide in the direction of the known sedimentary drift to monitor where the smart pebbles have moved to. Once found, the identity of a pebble and its
32 /// Environmental Engineering /// June 2018
❱❱ Coastal erosion can be tracked and predicted by observing the tidal drift of beach pebbles fitted with embedded RFID tags (top and inset); coastal engineers can track the movement of tagged pebbles using RFID antenna arrays mounted on quadricycles (right) or handheld scanners (above)
Andy Pye discovers how a Hayling Island project is creating ‘smart’ markers from pebbles to monitor coastal erosion
location is logged and uploaded to a geographic information system (GIS) so the path of that individual marker and others may be studied on a digital map. This data enables a far more accurate analysis of movements than has hitherto been possible and provides information to plan strategies and implement effective measures to reduce coastal erosion and strengthen sea defences. This high-tech approach has proved far better
than previous methods, such as painting pebbles and applying markings (which wore off), manufacturing aluminium pebbles (not the same weight as natural stone pebbles), and casting resin pebbles incorporating copper cores (costly and not durable). The latest development automates tracking, logging and mapping, is more accurate and cost-effective, and increases productivity. “Through the actions described, a pebble may move
westwards as much as 150m in a tidal cycle, but this is complicated by the fact movement may not always be in one direction,” says ESCP coastal engineer Sacha Neill. “The RFID system coupled to GIS transforms what we couldn’t fully prove before into demonstrable and measurable facts,” she explains. EE
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