1	Streams & Flooding
2	Overview of Material Hydrologic Cycle Streams & Stream Processes Types of Streams Flooding
3	What is the Hydrosphere? Contains all of Earth’s water (1.5 billion km³) Oceans 97.2% Fresh Water 2.8% Ice/glaciers 2.15% Groundwater 0.63% Surface water 0.023% Fresh water lakes 0.0009% Saline lakes/seas 0.0008% Soil water 0.005% Atmosphere 0.001% Streams 0.0001%
4	What is the Hydrologic Cycle? Describes where water is found (reservoirs), and the flow between reservoirs at a local & global scale. 4 parts to cycle: Evaporation Transportation Precipitation Runoff
5	The Hydrologic Cycle
6	Surface Water Water found above ground surface Streams, lakes, ponds, oceans, seas, swamps Streams- ‘Overland Flow’ Occurs for short distances until joining a larger flowing mass (streams) and/or Collects in topographic lows are “Channelized Flow”
7	Channelized Flow River: largest stream Creeks: medium stream Brook, streamlet: smallest stream Discharge (Q) = Area x Velocity Measured as cfs Columbia River- ~275,000 cfs during peak run-off seasons
8	Important Variables of Stream Flow Velocity feet/second of flow Gradient Slope (rise/run) (ft/mi) Steeper gradient= faster velocity Discharge Channel area (width x depth)
9	Laminar vs. Turbulent Flow Laminar Flow: Straight Turbulent Flow: Multi-directional
10	What is a stream’s purpose in life? Answer: reach base level! Streams DOWNCUT until they reach base level Results in: deeper stream channel erosion of channel bottom/sides widening of stream valley (floodplain)
11	Types of Streams Braided Carry high sediment load Meandering Wind through flat valleys Straight Downcut through steep hilly or mountainous areas
12	Braided Stream Brahmaputra River, India
13	Straight Channel in Yellowstone Natl Park, WY
14	Meandering Stream Mississippi River, USA
15	Development of a Meandering River
16	Meandering Streams
17	Parts of a stream Drainage Divide Drainage Basin
18	Parts of a Stream Mouth Bar Delta
19	Fluvial Processes Fluvial Processes: Physical processes catalyzed by the flow of water Play large Role in the Sedimentary Process
20	The Sedimentary Process Weathering & Erosion Development of deeper, wider channel Transportation All streams have a capacity to carry a load Bed, suspended & dissolved Sorting & Rounding of sediments Deposition Creates bars, channel islands, deltas & alluvial fans
21	Flooding Discharge exceeds channel capacity Causes include: excess precipitation Described by: MAGNITUDE FREQUENCY Recurrence interval R = (N + 1)/M
22	Types of Floods Upstream Flood Upper part of drainage basin Short-lived Flash Floods- Runoff is rapid & intense Often in a constriction (wash, canyon) Downstream Flood Affects larger areas Usually more damaging
23	Urbanization & Floodplains Why Live There? Rich, fertile soils Easy access to transportation & water Cheap land ..well, sometimes.. Development INCREASES magnitude & frequency Increases runoff increases discharge Increases erosional capability Widens channel Enlarges floodplain More flooding, more quickly, more extensively!
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25	Flood Damage Lives Property Stream Channel Water Quality Turbidity Pollutants Slope failure
26	A Few Other Significant Floods Big Thompson Flood, CO, 1976 19 feet of water, 145 lives lost Mississippi River Basin, 1993 48 lives lost, $20 Billion in damage Heppner, OR, Flood of 1903 Willow Creek destroys town
27	Mitigation Create ‘greenway’ corridors along riverbanks Restoration of riparian zones & vegetation stabilization of slopes
28	Mitigation Engineered Controls Channelization Levees & floodwalls Dams Retention ponds & diversion channels Flood-hazard maps & zoning restrictions
29	End Streams & Flooding