Ever wonder how high your slab is compared to the elevation of your street? Or where water is likely to collect in a neighborhood? The US Geological Survey (USGS) has given us a quick and easy way to lean more about elevation.

While the site says the elevations are not as good as a survey’s, I found the elevation for my house to be within inches. This is not something to take to the bank, but if you’re trying to:

• Screen several properties for purchase
• Figure out why some people in a neighborhood flooded and others didn’t
• Understand where floodwaters might collect

…this is a good place to start.

To Find Elevation

• Go to this U.S. Geological Survey website called the National Map Viewer.
• Enter an address or just zoom into the area of interest.
• Select a base map by clicking on the icon with the four squares that form another square. Different base maps allow different degrees of zooming and show various features such as streets, water features, topography, etc., so experiment.
• Above the map area, click on the icon that shows an XY.
• A box will pop up on the right side of the screen. Within it, click “Activate.”
• Click on the map location or locations that interest you.
• An info box will pop up that shows the location and elevation at the blue dot(s) where you clicked.
• To erase the points you selected, click “Deactivate.”

You can click as many different points as you want. A list of ALL the places you clicked with their elevations will show up in the right hand box.

In the example shown above, you can see that Riverwood Middle School at the intersection of High Valley and Kingwood Drive is at 65.03 feet. You can also see that the entry for East End Park is at 53.68 feet – more than 11 feet lower just a couple blocks away.

How High Is A Home Above Street Level?

This question is crucial if you want to avoid street flooding during high intensity rainfalls that overwhelm the capacity of storm drains and force water to back up in the streets.

• Switch to the base map called Streets (if you were in something else)
• Zoom in on the area of interest or enter an address.
• Again select the XY tool.
• Click on the home that interests you to see the elevation of the slab.
• Click on the street in front of it.

Three feet is a pretty good difference. But another home in the same neighborhood has a 4.5 foot difference!

Click around in different neighborhoods, especially those that flooded. On a block that flooded badly in Elm Grove, one home escaped. It was also 4.5 feet above street level. Others around it ranged from 1 to 3 feet above street level.

When buying a home, elevation above street level can be a valuable consideration.

Streets are usually considered part of the flood retention system. Developers size storm drains to hold a 1- or 2-year rain. Everything beyond that up to a 100-year rain backs up into the street until it can be safely released into drainage ditches. If you aren’t high enough…

Slope Within Neighborhoods

USGS offers another useful tool called elevation profiling. To the left of the XY tool, click the tool called Profile.

• A box will pop up on the right of the screen. To activate this tool, click on the ruler icon in the box.
• Define a path with two or more points.
• In the example below, I followed the curves of a street by clicking multiple times.
• When you get to the end of the area of interest, DOUBLE click.
• Double clicking changes the tab in the right hand box and starts compiling an elevation profile result.
• Give the site a few seconds to compile and display the profile.

When this profile popped up, I saw that this street had six feet of slope from the west end of the block to a low point in the middle and then rose back up three feet to the school on the right.

It’s common practice to slope streets; developers must to ensure that water drains to storm sewers. But when the rain comes down so fast that the storm drains can’t handle it, guess where the rain will collect. I’m not sure I would want to buy the house at the bottom of the bowl. (At least not without a discount to compensate for the risk.)

Powerful Tools at Your Fingertips

USGS has given us a fascinating tool kit. I have just begun to explore the power of this site.

Several people in Kingwood’s Woodstream Village approached me about some flooding on their street. Using the tools on this site, I quickly developed a theory that accounted for all the eyewitness stories.

Have fun exploring this fascinating tool.

Posted by Bob Rehak on 8/1/2020 with thanks to Laura Norton

1068 Days since Hurricane Harvey and 316 since Imelda