Ice observations

Ice breakup is either mechanical or thermal

Ice definitions (from NWS Alaska Pacific River Forecast Center) Ice chunks: smallest size of ice Ice pans: medium sized ice Ice sheet: large size ice Shorefast ice Bottomfast / anchor ice Frazil ice Pre-breakup unbroken ice: continuous ice surface that has few cracks Rotten ice: weak ice that appears brown or black Arched ice: Ice that is attached to the banks which rises in the center of the channel due to increased flow beneath the ice, causing melt water to collect in channels along banks Shifted ice: large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move Moving Ice / Breakup Ice run: continuous length of moving ice Breakup front: location along river in between moving and stationary ice The ice breakup front may stall out temporarily while moving downstream like an inchworm, this is not an ice jam. A significant amount of ice run accumulating upstream from the location where the breakup front stopped due to an obstruction (sharp bend, constriction, island, bridge, etc.) is an indication of an ice jam. If an ice jam is observed, estimate the height. Flooding: water that has gone over the banks and covered areas of lands that are normally dry. Post breakup Ice or debris run: a length of river channel containing moving ice or debris Stranded ice: ice pushed onto the banks or side channels that is left behind after the ice has cleared out of the main channel Field notes: Describe breakup daily Estimate the size of the ice (length, width, thickness, height above water level) Estimate the speed of the ice