In hydrology, a current in a stream or other water body is the flow of water influenced by gravity as the water moves downhill to reduce its potential energy. The current varies spatially as well as temporally within the stream, dependent upon the flow volume of water, stream gradient, and channel geometry. In tidal zones, the current and streams may reverse on the flood tide before resuming on the ebb tide.

The term upstream (or upriver) refers to the direction towards the source of the stream (or river), i.e. against the direction of flow. Likewise, the term downstream or downriver describes the direction towards the mouth of the stream or river, in which the current flows. The term "left bank" and "right bank" refers to banks as seen from the direction of flow.

• Discharge (hydrology) – Flow rate of water that is transported through a given cross-sectional area
• Ocean current – Directional mass flow of oceanic water
• Rheoscope – Instrument for measuring fluid viscosity
• Rheotaxis
• Rip current – Water current moving away from shore
• Volumetric flow rate – Volume of fluid which passes per unit time

v t e Coastal geography
Landforms	Anchialine pool Archipelago Atoll Avulsion Ayre Barrier island Bay Bight Bodden Brackish marsh Cape Channel Cliff Coast Coastal plain Coastal waterfall Continental margin Continental shelf Coral reef Cove Dune cliff-top Estuary Firth Fjard Fjord Freshwater marsh Fundus Gat Geo Gulf Gut Hapua Headland Inlet Intertidal wetland Island Islet Isthmus Lagoon Machair Mudflat Natural arch Peninsula Reef Ria Salt marsh Shoal Shore Skerry Sound Spit Stack Strait Strand plain Submarine canyon Tidal island Tidal marsh Tide pool Tied island Tombolo Waituna Windwatt
Beaches	Beach cusps Beach evolution Coastal morphodynamics Beach ridge Beachrock Beaches in estuaries and bays Pocket beach Raised beach Recession Shell beach Shingle beach Storm beach Wash margin Beach wrack
River mouths	Debouch River delta mega regressive Mouth bar baymouth
Processes	Blowhole Cliffed coast Coastal biogeomorphology Coastal erosion Concordant coastline Current Cuspate foreland Discordant coastline Emergent coastline Feeder bluff Fetch Flat coast Graded shoreline Ingression coast Large-scale coastal behaviour Longshore drift Marine regression Marine transgression Raised shoreline Rip current Rocky shore Sea cave Sea foam Shoal (Peresyp) Steep coast Submergent coastline Surf break Surf zone Surge channel Swash Undertow Volcanic arc Wave-cut platform Wave shoaling Wind wave
Management	Accretion Coastal management Integrated coastal zone management Submersion
Related	Bulkhead line Coastal engineering Grain size boulder clay cobble granule gravel pebble sand shingle silt Intertidal zone Littoral zone Physical oceanography River plume Region of freshwater influence
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