The calculation of stream power / unit stream power have to challenge the following problems :
- Estimation of bankfull decharge
- Estimation of channel slope
How to estimate or approximate them from old maps in order to propose stream power change ?
I afraid your question is too general to answer it in the current form.
First thing you should do include in your question a comprehensive description of the map you want to use in your experiment. Try to answer three questions first: - What is the scale of the map? - Is this a topographic map (includes contours and spot elevations)? -Are you sure that a hydrographic model for the river does not exist somewhere already? It would be useful to have it as an reference to test your estimates.
Best Regards,
Kazimierz Becek
Your question is indeed a bit too general to answer.
It is a topographical map I guess.... in such a case I would advise you to digitize it and from ArcGIS or any other open-source software like QGIS, you could define the channel slope and then the cross-section calculation necessary + knowing what is at the bottom of your chenal (or should be) for the roughness parameters....
The real question comes as Kazimierz said from the map scale... as I guess you will want to do comparison with present-day discharge.... and you will need to make sure that you pick the coarsest scale as a reference scale for the different measurements.
J'espere que c'est ce que tu voulais!
If you have contours on your old map and channel is alluvial, it would be not difficult to calculate the channel slope. As far as, power of a river not only depends on the slope, volume of water that is discharged at a particular point of time at a particular point on the channel course, it is also a function of flow velocity which not only depends on slope and volume of water but also on the forcing of water entered into a channel from its tributaries. Therefore, the old idea that river in its last stage, moves slowly is redundant.
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