IN the Dutch province of Limburg, the Grensmaas Consortium extracts about 100,000 tons of gravel every week, a quantity that requires an enormous logistical operation. Stopping the process is not an option. And certainly not unannounced.

This is where sensor technology comes in, helping Hans van der Meer, head of production and technical services at Grensmaas gravel extraction site to monitor the operation for any hint of flooding.

In 1993 and 1995, the province of Limburg was confronted with two floods on the river Meuse, which caused 200 million euros in damage. The public demanded better flood safety measures, but the cost of some 700 million euros was a stumbling block for years.

This was until an agreement was made with Consortium Grensmaas – a partnership of contractors, gravel producers – and ‘Natuurmonumenten’ – the Dutch organisation for the conservation and development of nature. Both high-water safety and nature development would be paid for with the proceeds from sand and gravel extraction along the Meuse.

In the meantime, the river has been given 350 hectares extra space to drain off water. That is the size of some 500 football fields. The stream bed was widened, banks lowered, and dikes raised.

The residents noticed it immediately: after long periods of rain the water level rises less quickly and stays lower. The land in the south of Limburg now stays dry at the same water level as in 1993 and 1995. And along the Maas, a thousand hectares of new nature are being created, which in time will attract a million cyclists and walkers, as studies have shown.

The consortium’s ability to recoup its investment depends on the smooth running of the gravel extraction process. “One ton equals eleven wheelbarrows. On an annual basis, we extract four and a half million tons of gravel at this site. And this gravel extraction is an important part of the Grensmaas project. It is the financial engine,” said Van der Meer.

“All the minerals are transported by barge, and the ships have to be able to come and go continuously. It is a constant puzzle to be able to transport everything at the right time.”

The production process, progress is largely dependent on the water level in the Meuse. This water level fluctuates greatly, which is also affected by the operation of the locks. Van der Meer wanted to be able to monitor and record the water level properly.

“In the harbour, I have mounted a level sensor on a mooring post that communicates the water levels with the cloud via a LoRa network. This system from KELLER gives me up-to-date information about the water level on a dashboard in my office. KELLER’s Martijn Smit helped us get the system up and running and thanks to the sensor’s communication with KELLER’s own Kolibri cloud, we now have all the information we can from that sensor.”

If the water level is too low or too high, the process may come to a halt. “We had a feeling the water level fluctuated much more than the Directorate-General for Public Works and Water Management indicated, and that turned out to be true. Since we now have the ability to monitor it ourselves, we can also sound the alarm in good time.”

The digital level sensor – series 26 X – not only measures the water level, but also the temperature of both the water and the air. “We cannot produce if there is ice formation, so we also want to be aware of that risk as early as possible. Under normal circumstances, production here goes on for six days a week, from 7am to 7pm. If we know that this is going to change, we need to be able to respond as quickly as possible.”

Van der Meer said recent flooding in the area did not affect the locations where the Grensmaas project was completed.