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How does wetted perimeter change downstream?

I need to describe and explain how the cross profile, wetted perimeter, hydrualic radius, roughness and efficiency change downstream.

I understand the basics. I don't completely understand the explanations, particularly wetted perimeter and the cross profile and how they link.

My teacher said something like the wetted perimeter is large compared to the amount of water in the cross sectional area but in relation to the channel it's small. I don't really understand this so if someone could it explain it better that'd be great.

Thanks.
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pjm600
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Original post by dippers
I need to describe and explain how the cross profile, wetted perimeter, hydrualic radius, roughness and efficiency change downstream.

I understand the basics. I don't completely understand the explanations, particularly wetted perimeter and the cross profile and how they link.

My teacher said something like the wetted perimeter is large compared to the amount of water in the cross sectional area but in relation to the channel it's small. I don't really understand this so if someone could it explain it better that'd be great.

Thanks.


The wetted perimeter is simply the perimeter of the river touching the land.

As rivers go downstream, the river widens so the wetted perimeter increases. The wetted perimeter/the cross sectional area gives the hydraulic radius. I'm not sure what channel refers to, width or depth?

Have a look at http://www.geography-fieldwork.org/riverfieldwork/downstream_changes/stage1.htm

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