Water monitoring
“Much research has been undertaken in an attempt to be able to monitor scour, but this is obviously problematic because potential scour takes place at times when it is not possible to see the river bed and certainly not possible to deploy divers,” Brown adds. “For this reason, the continuous monitoring of water level is not the perfect solution, but may be the best and most practicable.” Water level is already used as a risk factor
by the inspection teams where the one in 200 flood level is shown on structures by a fixed marker. However, Transport Scotland have to monitor 700 structures which are over or adjacent to water, and site inspections are costly; both financially and in resources. The inspection system could therefore be more efficient if it could be informed by remotely available water level data, especially if the data enables faster, more efficient implementation of mitigation measures. If a structure is determined to be high risk,
a hydrological assessment is undertaken. This may prompt a requirement for strengthening of the structure itself, as well as measures to protect or fill potential scour zones, and/or to alter water flow and disrupt vortices. In extreme cases, when a potentially vulnerable structure is exposed to high water, it may be necessary to close highways or rail lines until the level of risk can be lowered.
VALES BURN TRIAL In light of the potential for live water level data to inform the bridge inspection process, OTT HydroMet was invited to propose a monitoring system that could be evaluated at a culvert on the Vales Burn. “Our solution was comprised of an OTT ecoLog 1000 water level logger in a stilling well, with cellular data connection to Hydromet Cloud; a web-enabled platform for processing, displaying and storing hydrometeorological data,” explains Wendy Strain. “Data were set to be transmitted routinely every six hours, but two alarm levels were set to prompt SMS alerts, when necessary.”
The monitoring system was installed in September 2021, and Jim Brown says: “The trial is a great success; we utilise the Scottish Environmental Protection Agency (SEPA) flood alert warnings to monitor flooding and
level data, we will be able to optimise the deployment of the inspection teams and mitigate risk...
‘‘ ’’ Instrumentation Monthly April 2022
it has been our experience that the highest water levels generally occur about one or two days after a storm, so one of the main objectives of the trial was to determine the best time to despatch inspection staff. “The monitors did issue alerts during the
trial, but these were when levels met the lower alarm level, and in these cases, further interventions were not required. With the
benefit of water level data, we will therefore be able to optimise the deployment of the inspection teams and mitigate risk.”
SUMMARY With the benefit of water
Bridge scour is a long-standing problem for transport infrastructure, so the deployment of remote water level monitors/alarms that can be accessed via PCs or a mobile App offers rail and highway authorities an opportunity to optimise their scour assessment activities, prioritise countermeasures, improve transport resilience and protect safety. Reflecting on the trial Brown says: “This
project has shown that a network of water level monitors could inform bridge engineers of potentially affected structures. I understand that the Hydromet Cloud platform is able to connect with an almost infinite number of water level monitors, so we may be able to roll this out on a larger scale in the future.”
OTT HydroMet
www.otthydromet.com 45
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