How can I stop water from flowing back into my Honda WB30 Water Pump 1100 LPM 80mm Outlet when the heavy duty hose attached gets blocked?

I have a 1000l take of water attached to a Honda WB30 Water Pump 1100 LPM 80mm Outlet, alongside a heavy duty hose I use to water window boxes around London. When I park up the van and have to cross the road to water certain jobs, the pipe is occasionally temporarily blocked when a car runs over the hose pipe. This sends water back to the pump, and eventually breaks it. What can I do to stop the water/ pressure breaking the pump?

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