Thad Wester
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Using aerial LiDAR to defend an accusation of property damage

5/30/2014

4 Comments

 
A colleague of mine is being accused of damaging an adjacent residential property when a pipe busted in his storage shed on the rear of his property, during a winter storm earlier this year.  The busted pipe released approx. 1 quart/min. of water onto the ground.

The question is: does water flow towards the adjacent property?  We can answer this quickly with LiDAR.
Picture
The above image shows ground elevations - and in fact does show that water would flow towards the damaged building (siding with the accuser).  However, my colleague happens to be a smart engineer and was able to make this assumption from my LiDAR elevation map. 


"What that tells me that not only my property but several properties  are higher than his because he is lower in the watershed area, so every time it rains several properties contribute to runoff. I calculated that 1”/hr. rainfall gives 600% more runoff than a broken pipe that is flowing at 1 quart/min. We have had storms 2-3 times bigger than that (July 27, 2013). In my calculations, I assumed conservatively that the Jackson Avenue properties above him (there are 3) are the watershed area that causes runoff on his property. If I add the properties on Madison Avenue (there are 5-6) the runoff from 1”/hr. storm is much more than 600%. His problem is old and relates to poor grading for slab-on-grade shed."


Without Aerial LiDAR, you might have to hire a surveyor... Who then may need access to the accusers property... Which he may or may not get.  The information in Aerial LiDAR saved $1,000's and probably a 100 hours worth of worrying and work.
4 Comments
Doug
6/2/2014 01:37:16 am

Interesting. How did you get the aerial LiDAR? It would help to be able to ID the Accuser and the Accused properties.

Reply
Thad Wester
6/2/2014 01:56:57 am

Doug,
I obtained it from a source at the County GIS Office. For this example I am working from the raw .las data. Working with the raw data allows me some flexibility in how I identify ground returns, and display the data. There are some other options for getting the LiDAR data, but they usually don't give you access to the raw .las files.

I didn't identify the properties to protect the individuals involved. The image should give a sense of the value LiDAR brings to this example.

Reply
James
6/2/2014 03:55:04 am

How did you determine direction of flow? Just because an area is higher doesn't mean water will naturally flow in a particular direction. There could be other issues like a grade on the higher property directing water away from the lower property, retaining walls, or other man made drainage measures. What was the resolution of the Lidar data? If it was 1 foot, there could still be that much variance.

I guess I'm saying that determining the water damage is coming mostly from other adjoining properties can't be made with absolute certainty, only that they contributed to the issue.

Reply
Thad Wester
6/2/2014 04:48:03 am

Hi James,
Thanks for your comments.

I believe the LiDAR is 1 point per square meter. You right we can't see perfectly the direction of water flow from this data, but I think we can see well enough. This is definitely right up to the limits of the data.

We didn't conclude that the water damage was mostly coming from other adjoining properties. We did however, believe it would be safe to assume that if all the properties have similar grades into the damaged property, that the property with the broken pipe (which released a relatively small amount of water) is not responsible for the damage.

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    Thad Wester

    Founder @ Clarity Scanning.  Lead the WeWork Reality Capture team.  Likes tennis, ping pong and college football.

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