Surface Water

Surface water notes: Where is all the water? 97.5% in Oceans 1.8 % in Ice .63% in groundwater .007% in salty lakes and streams .009% in fresh water lakes and streams .0001% in the atmosphere

Where is all the fresh water? 73.9% in ice 25.7% in groundwater .36% in freshwater lakes and streams .04% in the atmosphere

What happens to water when it rains? It either infiltrates (soaks) into the ground or It remains on the surface

Watersheds Its an area that drains to a stream Watershed boundaries or divides are high places First order streams have small watersheds 2.5 km Mississippi River basin is a tenth order stream. It drains 320 million sq. miles

Chesapeake Bay Watershed Surface Water James River York River Potomac River Susquehanna River Rappahannock River All of the rivers listed above drain into the: Chesapeake Bay Watershed

Label your River diagram in your notes Drainage Divide Meander Flood Plain

Streams are constantly changing? Young streams flow straight, smaller, have rapids, faster Mature streams meander or curve Old streams are widest, carry the most water, slower

Young River Characterized by: _________ Slope: (steep, moderate, or gentle?) Velocity: (slow, moderate, or fast?) Erosion rate: (slow, moderate, or fast?)

Mature River Characterized by: _________ Slope: (steep, moderate, or gentle?) Velocity: (slow, moderate, or fast?) Erosion rate: (slow, moderate, or fast?)

Old River Old River Characterized by: _________ Slope: (steep, moderate, or gentle?) Velocity: (slow, moderate, or fast?) Erosion rate: (slow, moderate, or fast?) Old River

Meanders: Curves in Rivers Cut Bank- where the bank is eroding away, faster moving water Meanders: Curves in Rivers Point Bar- the inside of the curve where sediment is being deposited. Slower water with less velocity. Cut Bank up close

How Rivers become straight again? A meander forms Over time, the meander gets curvier It gets so curvy that the two cut banks meet each other Eventually none of the water goes around the meander anymore The leftover lake is an Oxbow Lake

What is a flood plain?

Floodplains Flat or gently sloped region around the river, in which the river flows during flooding The larger the river, the bigger the flood plain Deltas: Flood plains at the mouths of rivers are known as deltas Alluvial fans form when rivers drop the soil at the base of the mountain.

Rivers carry sediment Three types of loads bed load at bottom include sand, gravel, & pebbles, suspended loads in the middle include clay and silt solution includes dissolved materials The faster the velocity of the water, the greater the load (MORE EROSION!!!)

Factors that influence flooding Rainfall amounts Topography Type of Soil how permeable how saturated Amount of Impermeable land area Vegetation A 10 year flood may occur once every ten years or has a 1/10 (10%) chance of occurring yearly

Glaciers carve U- shaped valleys riVers carve V-shaped Valleys

Flood Frequency Curves R= N+1/r Are we at risk for flooding?