Streaky　structures　have　been　reported　in　open-channel　flows　by　various　investigations　in　the　inner　and　outer　layer.　Although　the　ubiquity　of　streaks　is　well　recognized,　it　remains　unclear　how　the　streaky　structures　in　the　inner　and　outer　layers　are　related　to　each　other.　This　paper　employs　a　unified　algorithm　to　identify　streaky　structures　which　can　be　applied　in　both　inner　and　outer　layers　with　exactly　the　same　subjective　threshold.　The　characteristic　scales　of　streaky　structures　are　quantified,　including　the　width　and　the　spanwise　spacing.　The　results　reveal　that　the　spatial　scales　increase　from　the　near-wall　region　to　the　outer　layer.　The　continuous　linear　growth　trend　indicates　a　close　relationship　between　the　streaky　structures　in　the　inner　and　outer　layers,　which　can　be　plausibly　explained　with　the　attached-eddy　hypothesis.