How about using your Vehicle(Hopefully-Large 4-WD) to Push/Drag Huge Boulders,Trees,Debris,etc. into the river.If The River is 15' deep x 50' across,Theoretically,It should be quite Shallow for the 1st 10' or so,I would concentrate my efforts to Fill it with Debris,To Lessen the depth/Allow Floating debris to Accumulate enough for a possible fording.Hopefully My Large 4-WD will have enough supplies for the Duration!The Bets Off,should I meet up with a Velociraptor or Close Cousin!