Water Erosion How do processes involving water change

Water Erosion: How do processes involving water change Earth’s surface? Part 1 1

What is the MAJOR agent of erosion that has shaped Earth’s land surface? moving water 2

Water moving over land’s surface is called runoff. Runoff may cause sheet erosion. 3

The amount of water runoff in an area depends on 5 main factors: 4

Factors that affect Runoff 1. The amount of rain an area receives. *More rain = more runoff 2. Vegetation - grasses, shrubs & trees reduce runoff. *More vegetation=less runoff 3. Type of soil - some soils absorb more water than others 4. Shape of the land – steep slopes have more run-off, which causes more erosion 5. How people use the land – parking lots & crop removal increase run-off. 5

Runoff overtime: How does runoff over time affect the land water? 6

Rills & Gullies As runoff travels across the soil, rills form. Rills are tiny grooves in the soil that grow larger forming gullies. A gully is a large groove or channel in the soil that carries runoff after a storm. It moves soil & rocks. Gullies only contain water after it rains. 7

Streams & Rivers Gullies join together to form a larger channel called a stream. Water continuously flows here and rarely dries up. Small streams may be called creeks or brooks. Small streams flow together to form a large stream called a river. 8

Rill, Rill erosion at a construction site. Image by M. Mamo, Labels added by UNL Gully, Stream Gully erosion in a pasture. Image by NRCS Stream 9

Tributaries Streams grow together by getting water from tributaries. A tributary is a stream or river that flows into a larger river. Tributaries collect their water from the drainage basin or watershed. An example: The Missouri & Ohio rivers are tributaries of the Mississippi river. 10

Rivers & Tributaries http: //images. google. com/imgres? imgurl=http: //knol. google. com/k/-/-/3 ajhc 7 zrwtav 1/c 1 ssz 4/figure-1%2520(2). bmp&imgrefurl=http: //knol. google. com/k/neworleans-the-geologic-difficulties-with-the-big-easy-part-1&usg=___SPqq. MAUDGF 2 VVg. D-x 0 Wwvs 5 xk=&h=394&w=432&sz=31&hl=en&start=5&um=1&tbnid=Sh. Jce. Jzlrt. Yl. WM: &tbnh=115&tbnw=126&prev=/images%3 Fq%3 DMississippi%2 Briver%2 Band%2 Bits%2 11 Btributaries%26 hl%3 Den%26 um%3 D 1

Rivers: * cause erosion and create valleys, waterfalls, flood plains, meanders and oxbow lakes. *form on steep mountain slopes. 12

How do they flow? Quickly and follow a narrow path How do they erode? Rapidly The result is that rivers form deep, V-shaped valleys. 13

Valleys http: //www. google. com/imgres? imgurl=http: //cgz. e 2 bn. net/e 2 bn/leas/c 99/schools/cgz/accounts/staff/r chambers/Geo. Bytes%2520 GCSE%2520 Blog%2520 Resources/Images/Rivers/Vshapedvalley. jpg&imgrefurl=http: //geobytesgcse. blogspot. com/2006/11/upper-course-of-river-v-shapedvalleys. html&usg=__Hp 8 C 8 YOunb. Wz. Jy 9 E 7 kb. Qc. Oi. URz. A=&h=308&w=411&sz=47&hl=en&start=0&zoom=1 &tbnid=giw. F 1 Fpp. YFy 8 z. M: &tbnh=116&tbnw=154&ei=kk 2 Tf. Kt. EMH 68 Ab. I__2 t. BA&prev=/images%3 Fq%3 Dvshaped%2 Bvalley%26 um%3 D 1%26 hl%3 Den%26 sa%3 DN%26 biw%3 D 1280%26 bih%3 D 531%26 tbs%3 Disch: 10%2 C 35&um=1&itbs=1&iact=hc&vpx=247&vpy=77&dur=701&hovh=194&hovw=259&tx=161&ty=116&o ei=g 0 k 2 Tb. G 1 L 4 T 58 Aa 8 n. OC 7 Aw&esq=12&page=1&ndsp=22&ved=1 t: 429, r: 1, s: 0&biw=1280&bih=531 http: //images. travelpod. com/users/theboy_picot/3. 1149265860. 580 x-nice-v-shapedvalley. jpg 14

Features of rivers: What features are formed by erosion along a river? 15

Waterfalls Occur where? Where a river meets an area of hard & slowly eroding rock Then flows over softer rock downstream. How does softer rock erode? The softer rock erodes away faster. What results from this erosion? A waterfall develops. 16

Waterfalls at the Plitvicka Jezera National Park in Croatia Minnehaha Falls, Minneapolis Minnesota http: //images. google. com/imgres? imgurl=http: //realestate-inminnesota. com/images/Minneapolis. jpg&imgrefurl=http: //realestate-inminnesota. com/&usg=__k. BYWa. Wcel. Jl. Cs. NAEDq 6 zr 8 e. LY=&h=599&w=800&sz=162&hl=en&start=5&um=1&tbnid=WO 5 G 4 j. C_r. IKDMM: &tbnh=107&tbnw=143&prev=/images%3 Fq%3 Dminnehaha%2 Bfalls, %2 B 17 mn%26 ndsp%3 D 18%26 hl%3 Den%26 sa%3 DG%26 um%3 D 1

Flood Plain What is a flood plain? A wide valley in which a river flows What happens to the land during a flood? The water in the river over flows its banks into this wide river valley area. 18

Flood Plain 19

Meanders What are meanders? Loop-like bends in the course of a river. Where & how do they occur? They occur as the outer bank of a river is eroded & deposits are dropped on the inner bank of the bend in a river. 20

Example: The southern stretch of the Mississippi River meanders on a wide, gently sloping flood plain area. 21

Mississippi River Meanders http: //images. google. com/imgres? imgurl=http: //www. ecology. info/img/Mississippi. River. jpg&imgrefurl=http: //www. ecology. info/article. aspx%3 Fcid%3 D 12%26 id%3 D 10&usg=__B 9 Cvp. JJ 70 Ydm 7 HE 2 Lj. Hs 3 GW 76 Ec=&h=450&w=600&sz=57& hl=en&start=8&tbnid=Q 3 zaqd. FNmc 7 QVM: &tbnh=101&tbnw=135&prev=/images%3 Fq%3 Dmeanders%26 gbv%3 D 2%26 hl%3 Den%26 sa%3 DG 22

Oxbow Lakes What is an oxbow lake? A meander that has been cut-off from the river. They may form when a river floods as high water finds a straighter path downstream. As flood waters fall, sediments dam up the ends of the meander and a lake forms. 23

Oxbow Lakes http: //muller. lbl. gov/travel_photos/Amazon. Web. Pages-Images/1. jpg 24