However, after the derby, a man jumped into their de-registered car.
"He said that he wanted it as a project car and we were going to send it to the wreckers anyway, so we were more concerned with getting our stuff out of it than the guy that wanted it," Rachel said.
"In hindsight, we shouldn't have let some random guy take it and convince us that he was going to use it as a project car or enter it into another derby."
She said it was frustrating how things had turned out. The de-registered car featured paintings by her children. Those positive memories have now been tarnished.
"The last thing we wanted is for any negative light to be shone on the speedway or demolition derby."
The woman says she feel "responsible" for the mess and has already contacted police with all the information they have.
"My partner and three of his friends went down to the river and spent about four hours gathering up the cars, dragging them from down the river to the entrance, so that they can pick them up and remove them."
Local Adam Codlin was one of the men who helped clean up the mess. He said he regularly sees burned-out cars by the river.
"It is absolutely appalling."
He says it is important to help keep the riverbeds clean to ensure the council doesn't close the area to the public.
Hawke's Bay Regional Council spokeswoman Joanne Lawrence said they weren't aware of the particular incident.
"When these sorts of things occur, it is frustrating and it is poor behaviour when people just dump their rubbish."
She said when they were forced into a clean-up, it was unbudgeted work and had an impact on rates.
"Security can be an issue at the rivers, but we are looking at funding extra security through the annual plan process, but that is unconfirmed at this time."
