The flood affected areas in the North Island have farmland and orchards covered in layers of silt and other flood debris. The farmers have the muscle, but I suspect they lack the quantity of machines able to move rock and dirt quickly.
Here's an idea: instead of the government setting up a relief fund, how about they get off their backsides and organise thousands of earthmoving machines. Then, make those machine available at reasonable rates to the affected farmers.
There is an issue with this, however, as existing contractors and hire companies along the East Coast of the North Island will complain about being undercut by such an initiative. However, the national interest comes before those of individual private interests - we must get food.
One idea to address this problem would be for the government to coordinate these companies to bring in machines from around the country, and to make up the difference between what the farmers pay and what the hire companies are worth. This would be a justifiable subsidy to avoid food prices taking off and causing inflation.
The lack of action from NZ's awful government is quite concerning. They're completely out of their depth and prefer to talk about climate change all day.
The type of machines of immediate need (different brands displayed as this is about the type of machine, not the brand):