Potholes one symptom of changing climate

Bob Hughes

Opinion

In answer to the many criticisms of our potholed roads, I suggest people read the July 18, 2023 Spinoff article Everything you always wanted to know about potholes but were afraid to ask by Shanti Mathias.

Aotearoa’s wet 2022/23 summer, followed by a wet winter, created prime conditions for potholes.

“Roads are made of several layers: the asphalt or chip seal on top, with a base material below, and then the actual soil underneath that. Rain is one of the main causes of damage to road surfaces. Once there are cracks in the surface caused by wear, water gets into the base material and washes it out, until the hole crunches open when something heavy goes over it. Once open, the pothole fills with water, which can make it bigger.”

Potholes are one symptom of a bigger issue — climate change.

Shanti spoke to Marc Wilson, a professor of psychology at Victoria University, who said: “We pay more attention to immediate annoyances than future annoyances” and compared potholes to climate change, “a challenge that always seems to be in the future even when it’s in the present”.

Bigger societal factors contribute too. “When we’re feeling more pessimistic overall . . . we’re more likely to attend to minor annoyances, and find them more annoying.”

Mike Marden, who has been observing and meticulously documenting changes to the land on the East Coast for decades, and is one of the foremost experts on its fragile geology, led an Australian and New Zealand Geomorphology Group Waipoa catchment field trip last week.

I gained knowledge from my geologist brother Dr Philip and his wife Professor Marjorie who were here for the field trip. The rocks in our district are of sedimentary origin, the oldest being of Lower Cretaceous age. Also, the large number of fault zones which exist in this district make it easier for water to enter the soil and lodge at or above the sliding surface, making erosion and stability problems more serious than in other districts.

Much of our road network covers challenging geological terrain. Highly erodible soils on top of weak geology makes roads vulnerable, especially during high-rainfall weather events.

In 1942 when our family first arrived in Gisborne, more than half of the district’s roads were metalled (covered in crushed gravel) and would suffer badly after heavy rain.

The sealing of roads gained momentum in the 1950s and 1960s. By the end of the 1970s, most of our roads were either tarsealed or metalled and we had county roadmen living on the spot with their wheelbarrows, picks and shovels at the ready to clear small slips, unblock drains and temporarily fill any potholes.

Unfortunately the 1970s marked the final passing of that era.

Gisborne District Council now has four roading contractors to maintain the district’s 879km of sealed and 1020km of unsealed roads. (Waka Kotahi is responsible for the state highways.)

Our district’s roading network goes over unstable and highly erodible land that’s prone to slipping. Other ongoing issues include climate impacts, more frequent flooding and increased heavy traffic volumes.

Let’s go easy on our GDC; potholes cannot be repaired permanently when it’s wet or too cold, and so far this summer we have had limited periods of permanently dry weather.

I add, on a kilometres of roadway per person basis, we lose as well.

Mayor Rehette Stoltz recently said, “I am not trying to make excuses but our teams are stretched like never before.”

Climate change is hitting hard. Time to focus less on potholes and to plan for the future.