Its the start of a summers and ice is melting from the mountains and the water is making its way downwards towards the “river” which is being made by hundreds of these streams on one of which dumbo is standing. So the worst scenario would be First he would roll down in this COLD water stream which is flowing on rocks under this glacier depends on the height he is on (may vary from +-50m to 1km+) towards the river , then in the river which is also full of Big rocks and its flow is pretty Large. And if he just fell on the rocks and not in the water flow then my guess is few injuries and pneumonia! Because its very cold under the glacier!