GPHY 103 Lecture 22: GPHY 103 Lecture 22
22 Dec 2016
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Document Summary
Ecological function and natural value of rivers and wetlands. Rivers: all land is part of a watershed, or a river basin. Most land we see is shaped by rivers which flow over, through it. In many places landscape = riverscape: more than flowing water to the sea. Organic matter from decomposition of plants, aquatic biota. River flow and morphology: watershed starts in mountains, hilltops. Flow generated by seasonal rain, snow and/or ice melt. Steep gradients, high energy streams erode and carry sediment. Rivers slow (braid and/or meander) and deposit sediment (=alluvium) If it(cid:495)s deposited at the mouth of a river then it(cid:495)s a delta: alluvial valley floor formed by millennia of sediment laden floods. Due to climate, sea level changes or tectonic uplift: eventually rivers flow into a lake or ocean. Essence of a river; variation (in flow: seasonal and annual fluctuations in water, sediment, nutrients delivered by rivers.
