[GRASSLIST:5151] Re: finding sinkholes

[phrostie]

in high school i was a member of a "cavers" group.  we used to locate 
caves/sink holes by looking for un-naturally straight tributaries on what 
ever maps were availible.  the "straight lines" were very good indecations of 
fracture zones and shallow faults that would also help form the sink holes in 
the limestone.

i'm not sure how to write a program to do this, but it might be a good 
starting point.

a "straight line" would have a given probability
a 90 degree bend in a "straight line" would have a higher one
the intersection of multipule straight lines would have a still higher.

if a straight line intersected,but stopped short of, a depression with no 
surface drainage then you are approaching 100%

just my .019999

On Wednesday 04 December 2002 20:50, you wrote:
> Hi John
>
> > It seems to me that the size of the sinkhole and the resolution of your
> > dem would have a serious effect on what you could identify.
>
> right, but for my purpose the quality of the data is good enough. perhaps
> sinkhole is not the most felicitous word. I mean "Depressed areas".
>
> > Valleys with
> > internal drainages such as bolsons
>
> by the way what are bolsons (my english dictionary does not include this
> word)
>
> > should show up, but a true sinkhole
> > such as you see in karst topography might be too small to register,
> > depending on dem resolution.  For bolsons, an hydrological analysis of
> > drainage patterns for centripetal systems might work to isolate discrete
> > closed basins.
>
> i just need a simple operation/command like "find all depressed areas"
> Nothing complicated.
>
> Johannes

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