An ice protection system includes an aircraft surface and a gutter defined in the aircraft surface between raised rails. The gutter includes a mouth that narrows into a trailing portion of the gutter. The mouth is configured to channel water runback rivulets into the trailing portion of the gutter. The gutter can be a first gutter of a plurality of side by side gutters, each including a respective mouth narrowing into a respective trailing portion, wherein the gutters are separated from one another by respective rails.