Prior to the construction of a causeway in 1968, the Petitcodiac River had one of the world's largest tidal bores, which ranged from 1 to 2 metres (3.3–6.6 ft) in height and moved at speeds of 5 to 13 kilometres per hour (3.1–8.1 mph).

During this period, Acadian resistance fighters based in Village-des-Blanchard (now Hillsborough) fought under the command of French leader Charles Deschamps de Boishébert in the Battle of Petitcodiac, attempting to repel British troops but ultimately suffering the destruction of most of their settlement.

According to Maliseet Elder and linguist Dr. Peter Paul of Woodstock Reserve, the name refers to a wall of water rushing in: "now they call that petakuyak.

[30] During their 2001 study, the Petitcodiac Watershed Alliance noted the effects of agriculture on the river's water quality, and recommended to work with local farmers to install cattle fencing around streams which run through their properties, and "eventually phase out" cosmetic pesticide usage.

[44] The Petitcodiac Riverkeeper holds a stronger position on the issue: the organisation notes that pesticides "find their way into the surface and ground water by leaching into the soil or as part of stormwater runoff."

[47] The province was the subject of a controversy in 2007 when it gave Vale Limited (formerly known as CVRD Inco) the right to mine for uranium at Turtle Creek, where the Greater Moncton water reservoir is maintained.

While the landfill was shut down in 1992, samples by the Environmental Bureau of Investigation and the Petitcodiac Riverkeeper showed that ammonium levels around the leachate exceeded Canadian quality guidelines by as much as 15 times, and contained heavy metals, petroleum hydrocarbons, and PCBs.

[56][57] The first European mention of the bore was by British Lieutenant Colonel George Scott on 17 November 1758, during a downstream voyage from Moncton to Fort Frederick, near Saint John.

[60][61][62] In 1825, Peter Fisher noted that the "noise of the Bore is heard a great distance, and animals immediately take to the highland, and manifest visible signs of terror if near it.

[68] Non-native species, such as the black-footed spider, the beech scale, the white-marked tussock moth, and the mountain ash sawfly have also made their home in the Petitcodiac River watershed.

Among others, the semipalmated plover (around 2 percent of the North American population), the short-billed dowitcher, the red knot, the sanderling, and the least sandpiper are also known for migrating through the Important Bird Area.

[5] The Petitcodiac River watershed covers an area north and east of the Caledonian Highlands; a low-elevation (on average 67 m; 220 ft) region with rolling hills, valleys, and ridges.

Examples of rare karst occurrences appear west of the village of Three Rivers, where large sinkholes alternate between small ridges to form honeycomb-shaped patterns.

A publication by the New Brunswick Department of Natural Resources notes that the soils in Salisbury, made from calcareous sandstone and mudstone, are fine-textured and, when properly drained, "are the most fertile glacial tills" in the watershed.

[87][90] In spite of resistance led by Jean-Louis Le Loutre, representatives eventually agreed to sign,[87] but their reluctance persuaded Governor Charles Lawrence to order the Acadian population expelled from British territory.

[92] Two hundred British troops led by Major Joseph Frye were sent to destroy the settlements of the Three Rivers, beginning with Shepody and Village-des-Blanchard (now Hillsborough).

[93] French resistance commander Charles Deschamps de Boishébert, hoping to evacuate as many Acadians as possible, was unable to march the distance between Nerepis and the Shepody settlement in time, but fought at the second threatened village on 28 August 1755.

[95] The commander and the evacuated Acadians, whom Edward Larracey estimated to total around 700,[93] suffered a massive famine from 1756 to 1758, largely caused by the scarce resources following the battle.

[97] On 28 June, Scott learned of reports that cattle were stolen outside of Fort Beausejour; the British issued an order for Captain Beloni Danks to send 75 men up the Petitcodiac River.

[100] Scott was told that the area was virtually defenceless, so he sent three parties to La Chapelle (now Bore Park in Moncton), Silvabro (now Lewisville), and Jagersome (now Dieppe).

[102] The crew sent an Acadian prisoner on the 17th to request the surrender of the remaining residents, but when he returned, he reported that they had all begun to flee to Cocagne, Shediac, and the settlements around the Miramichi River.

[133] In 1968, the provincial and federal governments completed the construction of a causeway between the communities of Moncton and Riverview, to provide a crossing over the river, and to keep water levels from impeding agricultural production.

[136] Although the causeway was equipped with a fishway, problems arose when fish were unable to cross it freely due to sedimentation build-up; some 82 percent of the salmon were prevented from travelling upstream by the structure.

In 1976 and 1977, reports pointed out several problems related to the gates' function due to erosion, winter ice jams, and "unsatisfactory fishway operation".

[135] More reports documented problems related to the passage of fish in the river until 1995, when the Department of Transportation agreed to open one gate from April to December, as suggested four years earlier.

[143][144] Phase 1 consisted of the prevention of erosion along the shorelines, improvements to the nearby drainage system, and the construction of dikes and aboiteaux; the work was carried out from 7 July 2008, to 14 April 2010.

[154] Residents near the headpond west of the causeway criticized the project, citing the decrease in property values of about 480 homes (by approximately 30 percent, according to the EIA report),[155] the $68 million price tag,[156] unstable ice conditions,[157] and a lower water quality.

[158] In spite of legal threats by the Lake Petitcodiac Preservation Association (LAPPA) and various residents, the causeway opened its gates on 14 April 2010, coinciding with the beginning of various studies.

An AMEC engineer participating in the firm's studies, Jacques Paynter, said that the banks of the river had begun widening "at a noticeable pace", with the tidal bore growing closer to its pre-1968 levels: "We were actually anticipating a fairly modest increase in height.

[164][full citation needed][166] However, a study by the PWMG showed that fecal coliform levels in the headpond from June, July, and September 2009 exceeded 2,419 parts per 100 millilitres; more than 12 times the 200/100 ml recommended by the Canadian Water Quality Guidelines for recreational purposes.