Ever wonder how to find the depth of flooding on a bayou, river or stream near you? Here’s a simple way. But this only works for those in and around Harris County, Texas, and those who live on streams with gages.
FWS stands for Flood Warning System. The main function of this website is to alert you when streams are in danger of coming out of their banks. But the site also shows historical information for dozens of gages that blanket Harris and surrounding counties. That information includes flood peaks and bank elevations. By subtracting the bank elevation from the peak, you can easily determine the height of a flood and compare the height in your area to other areas.
For this exercise, start by selecting ALL gages in the left column. Gages across the region will pop up. See below.
By default, the map shows how much rainfall all those gages received in the last 24 hours. But there’s much more information behind them. Next…
Click on Any Gage
Another box pops up that is the gateway to historical information about that location. In this example, I clicked on the gage at the San Jacinto West Fork and US59.
Click on the hyperlink that says, “More information and alert signup.” Then, in the next screen…
Click on the Stream Elevation Tab
Scroll Down
You should see a box that looks like the one below.
The red “Flooding Likely” line represents the top of bank in that area. They say “Likely” because bank heights may vary slightly around a gage. But for most locations in a flat area like ours, that’s the point at which water starts to come out of the banks. Near this gage, the river starts coming out at 49.33 feet above sea level.
Below that box, three more boxes show:
Gage readings during the current time period (or any historical time period if you specify one).
Flood frequency for that gage location. For instance, the height of a 10-, 50-, 100- or 500-year flood.
Historical records for major storms.
This last box contains the information you want (if you’re looking for the Harvey peak). For instance, you can see that at this location, the West Fork reached 69.6 feet.
Subtract Flooding-Likely Elevation from the Flood Height
Subtracting the flooding-likely elevation from the high-water mark tells you the depth of flooding, i.e., how high the water got above the banks. At this location, that was more than 20 feet! (69.6 minus 49.33)
Step and Repeat
To compare the depth of flooding at other locations, repeat the same process. To visualize the differences, it helps to develop a spreadsheet with four columns: Location, Flooding Likely, Peak, Difference. Then you can then easily create a graph that looks like the one below.
Chart showing feet above flood stage at 33 gages during Harvey.
In this case, you can see that the San Jacinto, Spring and Cypress Creeks had the deepest floodwaters in the northern part of the county during Harvey. Some gages at other locations show that water didn’t even come out of banks.
What About Minor Floods?
The Harris County Flood Warning System contains information about stream levels going back 20+ years. If you’re looking for information about a flood not shown in the Historical Record box, you can search for it by specifying a time period and date range above the stream elevation and rainfall tabs.
Caution
Usually, Harris County Flood Control District personnel manually verify the historical records. So, you can trust the information. But if you’re researching smaller floods by inputting your own dates and time periods in the search fields, you may run into a problem.
Before 2010, sometimes gages recorded faulty readings. Gages during that period used pressure transducers, which could clog with floating debris and report false information.
So, if you see a hundred-foot flood that lasted 15 minutes, you’re looking at error. Cross check such readings against rainfall at the same gage. Also, check the readings immediately up- and downstream to rule out spurious readings.
The graph above shows wide ranges in the depth of flooding on the same bayous. Don’t assume that because a flood was 20 feet deep at one location that it will be the same along the entire stream. The topography could narrow, widen, deepen or flatten. All could affect the depth of flooding. So could other factors, such as the amount of surrounding development or previous flood mitigation efforts in an area.
Identifying Causes of Flooding
Using information from the Flood Warning System, you can help narrow down the source of flooding. If a neighborhood flooded, but the channel didn’t come out of its banks, you’re looking at a street-flooding issue. Most storm sewers and roadside ditches in Harris County and Houston are sized to handle a two-year rain. But older ones may have only a one-year level of service. And many become clogged over time. See below.
For More Information
To learn how to find and verify other flood-related information, make sure you check out this post.
Posted by Bob Rehak on 10/29/22with thanks to the Harris County Flood Control District
1887 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/10/20221029-Screenshot-2022-10-29-at-8.22.46-PM.jpg?fit=1200%2C715&ssl=17151200adminadmin2022-10-29 21:19:072022-10-30 09:13:19Simple Way to Find Depth of Flooding Near You
This morning’s 7 a.m. report from Jeff Lindner, Harris County’s meteorologist, indicates that the severe weather threat predicted yesterday for Houston has shifted southwest toward Matagorda Bay and offshore. However, showers and thunderstorms will increase through the day. And few of the storms could be strong to severe.
Radar Image Shows Gap Between Storms at 11 AM
Radar images at 11 a.m. confirm that two major storms will not converge where predicted yesterday.
RadarScope image shows storms predicted yesterday to converge over Houston have diverged.
Activity along the coast should move eastward this morning while a second line of storms moves from central Texas toward Houston. The offshore warm front did not move as far inland as expected overnight.
Tornado Threat Limited, But Hail Possible
Lindner thinks the severe weather and tornado threat to the Houston area is fairly limited today, although the cooling of the air column may result in the threat for some hail with lingering storms into the evening hours.
Additional showers will develop ahead of this main line, but concerns yesterday for supercell structures appear lower today and confined to Matagorda, Jackson, Wharton, and Calhoun Counties.
Lindner now expects rainfall of 1-2 inches over the Houston area. Given current drought conditions, it is much needed.
Rainfall rates offshore have averaged 2-4 inches per hour, but that storm should remain offshore, he says.
The main line of approaching weather should clear the Houston region by 4:00 p.m., but areas north of I-10 could see additional showers and thunderstorms into the evening hours.
A few light rain showers or drizzle east of I-45 may linger into Saturday. This coupled with cold air advection and north winds of 10-15mph may lock temperatures in the upper 50’s/low 60’s on Saturday. However, where the clouds are able to clear, temperatures will warm into the mid 70’s. We could see significant differences in temperature over a short distance.
Skies should clear Saturday night into Sunday with cool conditions in place for a mild and dry Halloween.
Posted by Bob Rehak on 10/28/22 based on reports from the NWS and Harris County
1886 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/10/Screenshot-2022-10-28-at-10.54.42-AM.jpg?fit=1125%2C2200&ssl=122001125adminadmin2022-10-28 12:02:342022-10-28 12:02:41Highest Risk for Severe Weather Shifts SW and Offshore
Update: 10/28/22 11am: Today’s reports indicate the highest severe storm risk is shifting SW of Houston and offshore. Experts now predict 1-2 inches of rain for the Houston area today.Areas offshore are already getting 2-4 inches per hour.
Tomorrow will likely bring strong thunderstorms. Rainfall rates could exceed the capacity of street drains leading to localized street flooding. And the severe weather may also spin up some tornados, according to Harris County’s meteorologist and the National Weather Service (NWS).
Heavy Rainfall
NWS predicts two to three inches of rain could fall on Friday, as warm, moist air pushing in from the Gulf collides with a cold front pushing in from the northwest. Jeff Lindner, Harris County meteorologist, predicts the worst period for us will be Friday afternoon.
Tornados Possible
The NWS Storm Prediction Center in Norman, Oklahoma, issued this warning for Friday . It shows a marginal risk of severe weather for the entire Houston area and a slightly higher risk for areas south and west of us.
Reasons for Concern
For the weather wonks reading this, Lindner cites an unusual convergence of storm systems at different levels of the atmosphere.
A trough will begin to move eastward toward Texas later today. Surface pressures will begin to fall this afternoon as low pressure develops ahead of the approaching mid-level low. Southeast winds will increase today, letting Gulf moisture quickly return to coastal Texas.
As the mid-level low approaches us, it will meet the northward-moving, moisture-laden warm front moving in from the Gulf.
Severe threats will be highest along the boundary. Tropical moisture will march quickly northward tonight on a 30-knot low level jet. Precipitable waters – the amount of moisture in a column of air – will equal 1.8 inches by Friday morning over much of the region.
As large-scale lift increases over the developing warm sector, showers and thunderstorms will develop from southwest to northeast across the region.
The cold front associated with the mid-level low will sweep west to east across southeast Texas on Friday afternoon, touching off more thunderstorms. The front will slow Friday night, so showers will linger over the area.
Severe Threat:
The surface low approaching from the northwest will meet the warm front coming from the opposite direction along a NW to SE axis on Friday. This warm front will extend from near San Antonio to near Freeport during the day and produce strong to severe thunderstorms. Low-level winds near the warm front will circle back toward the ESE and enhance low-level storm rotation.
Such collisions are notorious for tornado production, according to Lindner. Discrete cells may develop ahead of the line of storms approaching from the west. The location of the greatest severe risk will depend on where the warm front sets up Friday morning. Areas along and south of the front will have the highest risk.
If the warm front moves just a few miles farther north, it will increase risk to the Houston metro area. Kingwood was struck by tornados in a similar setup earlier this year.
Damaging winds will be the main threat. The worst of the storms should be over by 3-5 pm Friday, but lighter rains may linger well into the evening hours.
Heavy Rainfall:
Moisture will deepen Thursday into Friday. By Friday morning, a saturated air mass will be in place over the region. “Strong divergent lift coupled with low-level inflow will increase the potential for heavy rainfall along with cell training from southwest to northeast.”
Lindner describes himself as “aways wary of such setups.” They can help anchor and train convection.
The overall pattern favors supercell formation with both a tornado and heavy rainfall risk.
Jeff Lindner, Harris County Meteorologist
These storms could become significant rainfall producers – if they become sustained along the warm frontal boundary. The good news is that the ground is dry and can handle several inches of rainfall. “However, rainfall rates may exceed localized drainage capacities and result in some street flooding regardless of the dry ground conditions,” says Lindner.
Weekend:
Cloudiness should linger much of Saturday keeping temperatures in the 50’s under northerly winds. South of the cloud line temperatures will warm into the 70’s. Where that line will be Saturday is hard to determine. Clouds should erode Saturday night with mostly clear skies. Sunday will be mild.
Tropics:
The hurricane season has another month to go. It isn’t over yet! The National Hurricane Center now gives an area of low pressure moving WNW across the Caribbean a 50% chance of turning into a tropical depression in the next five days. No one is yet predicting what will happen if it does.
Posted by Bob Rehak on 10/27/22based on information from Jeff Lindner, NWS, and NHC
1885 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/10/Rainfall-10.28.22.png?fit=793%2C561&ssl=1561793adminadmin2022-10-27 14:16:182022-10-28 10:52:03Strong Thunderstorms, Street Flooding, Tornados Possible Tomorrow
Simple Way to Find Depth of Flooding Near You
Ever wonder how to find the depth of flooding on a bayou, river or stream near you? Here’s a simple way. But this only works for those in and around Harris County, Texas, and those who live on streams with gages.
Step-By-Step Guide
Go to HarrisCountyFWS.org.
FWS stands for Flood Warning System. The main function of this website is to alert you when streams are in danger of coming out of their banks. But the site also shows historical information for dozens of gages that blanket Harris and surrounding counties. That information includes flood peaks and bank elevations. By subtracting the bank elevation from the peak, you can easily determine the height of a flood and compare the height in your area to other areas.
For this exercise, start by selecting ALL gages in the left column. Gages across the region will pop up. See below.
By default, the map shows how much rainfall all those gages received in the last 24 hours. But there’s much more information behind them. Next…
Click on Any Gage
Another box pops up that is the gateway to historical information about that location. In this example, I clicked on the gage at the San Jacinto West Fork and US59.
Click on the hyperlink that says, “More information and alert signup.” Then, in the next screen…
Click on the Stream Elevation Tab
Scroll Down
You should see a box that looks like the one below.
The red “Flooding Likely” line represents the top of bank in that area. They say “Likely” because bank heights may vary slightly around a gage. But for most locations in a flat area like ours, that’s the point at which water starts to come out of the banks. Near this gage, the river starts coming out at 49.33 feet above sea level.
Below that box, three more boxes show:
This last box contains the information you want (if you’re looking for the Harvey peak). For instance, you can see that at this location, the West Fork reached 69.6 feet.
Subtract Flooding-Likely Elevation from the Flood Height
Subtracting the flooding-likely elevation from the high-water mark tells you the depth of flooding, i.e., how high the water got above the banks. At this location, that was more than 20 feet! (69.6 minus 49.33)
Step and Repeat
To compare the depth of flooding at other locations, repeat the same process. To visualize the differences, it helps to develop a spreadsheet with four columns: Location, Flooding Likely, Peak, Difference. Then you can then easily create a graph that looks like the one below.
In this case, you can see that the San Jacinto, Spring and Cypress Creeks had the deepest floodwaters in the northern part of the county during Harvey. Some gages at other locations show that water didn’t even come out of banks.
What About Minor Floods?
The Harris County Flood Warning System contains information about stream levels going back 20+ years. If you’re looking for information about a flood not shown in the Historical Record box, you can search for it by specifying a time period and date range above the stream elevation and rainfall tabs.
Caution
Usually, Harris County Flood Control District personnel manually verify the historical records. So, you can trust the information. But if you’re researching smaller floods by inputting your own dates and time periods in the search fields, you may run into a problem.
Before 2010, sometimes gages recorded faulty readings. Gages during that period used pressure transducers, which could clog with floating debris and report false information.
So, if you see a hundred-foot flood that lasted 15 minutes, you’re looking at error. Cross check such readings against rainfall at the same gage. Also, check the readings immediately up- and downstream to rule out spurious readings.
The graph above shows wide ranges in the depth of flooding on the same bayous. Don’t assume that because a flood was 20 feet deep at one location that it will be the same along the entire stream. The topography could narrow, widen, deepen or flatten. All could affect the depth of flooding. So could other factors, such as the amount of surrounding development or previous flood mitigation efforts in an area.
Identifying Causes of Flooding
Using information from the Flood Warning System, you can help narrow down the source of flooding. If a neighborhood flooded, but the channel didn’t come out of its banks, you’re looking at a street-flooding issue. Most storm sewers and roadside ditches in Harris County and Houston are sized to handle a two-year rain. But older ones may have only a one-year level of service. And many become clogged over time. See below.
For More Information
To learn how to find and verify other flood-related information, make sure you check out this post.
Posted by Bob Rehak on 10/29/22 with thanks to the Harris County Flood Control District
1887 Days since Hurricane Harvey
Highest Risk for Severe Weather Shifts SW and Offshore
This morning’s 7 a.m. report from Jeff Lindner, Harris County’s meteorologist, indicates that the severe weather threat predicted yesterday for Houston has shifted southwest toward Matagorda Bay and offshore. However, showers and thunderstorms will increase through the day. And few of the storms could be strong to severe.
Radar Image Shows Gap Between Storms at 11 AM
Radar images at 11 a.m. confirm that two major storms will not converge where predicted yesterday.
Activity along the coast should move eastward this morning while a second line of storms moves from central Texas toward Houston. The offshore warm front did not move as far inland as expected overnight.
Tornado Threat Limited, But Hail Possible
Lindner thinks the severe weather and tornado threat to the Houston area is fairly limited today, although the cooling of the air column may result in the threat for some hail with lingering storms into the evening hours.
Additional showers will develop ahead of this main line, but concerns yesterday for supercell structures appear lower today and confined to Matagorda, Jackson, Wharton, and Calhoun Counties.
1-2 Inches of Much-Needed Rain Likely
Lindner now expects rainfall of 1-2 inches over the Houston area. Given current drought conditions, it is much needed.
Rainfall rates offshore have averaged 2-4 inches per hour, but that storm should remain offshore, he says.
The main line of approaching weather should clear the Houston region by 4:00 p.m., but areas north of I-10 could see additional showers and thunderstorms into the evening hours.
A few light rain showers or drizzle east of I-45 may linger into Saturday. This coupled with cold air advection and north winds of 10-15mph may lock temperatures in the upper 50’s/low 60’s on Saturday. However, where the clouds are able to clear, temperatures will warm into the mid 70’s. We could see significant differences in temperature over a short distance.
Skies should clear Saturday night into Sunday with cool conditions in place for a mild and dry Halloween.
Posted by Bob Rehak on 10/28/22 based on reports from the NWS and Harris County
1886 Days since Hurricane Harvey
Strong Thunderstorms, Street Flooding, Tornados Possible Tomorrow
Update: 10/28/22 11am: Today’s reports indicate the highest severe storm risk is shifting SW of Houston and offshore. Experts now predict 1-2 inches of rain for the Houston area today. Areas offshore are already getting 2-4 inches per hour.
Tomorrow will likely bring strong thunderstorms. Rainfall rates could exceed the capacity of street drains leading to localized street flooding. And the severe weather may also spin up some tornados, according to Harris County’s meteorologist and the National Weather Service (NWS).
Heavy Rainfall
NWS predicts two to three inches of rain could fall on Friday, as warm, moist air pushing in from the Gulf collides with a cold front pushing in from the northwest. Jeff Lindner, Harris County meteorologist, predicts the worst period for us will be Friday afternoon.
Tornados Possible
The NWS Storm Prediction Center in Norman, Oklahoma, issued this warning for Friday . It shows a marginal risk of severe weather for the entire Houston area and a slightly higher risk for areas south and west of us.
Reasons for Concern
For the weather wonks reading this, Lindner cites an unusual convergence of storm systems at different levels of the atmosphere.
A trough will begin to move eastward toward Texas later today. Surface pressures will begin to fall this afternoon as low pressure develops ahead of the approaching mid-level low. Southeast winds will increase today, letting Gulf moisture quickly return to coastal Texas.
As the mid-level low approaches us, it will meet the northward-moving, moisture-laden warm front moving in from the Gulf.
Severe threats will be highest along the boundary. Tropical moisture will march quickly northward tonight on a 30-knot low level jet. Precipitable waters – the amount of moisture in a column of air – will equal 1.8 inches by Friday morning over much of the region.
As large-scale lift increases over the developing warm sector, showers and thunderstorms will develop from southwest to northeast across the region.
The cold front associated with the mid-level low will sweep west to east across southeast Texas on Friday afternoon, touching off more thunderstorms. The front will slow Friday night, so showers will linger over the area.
Severe Threat:
The surface low approaching from the northwest will meet the warm front coming from the opposite direction along a NW to SE axis on Friday. This warm front will extend from near San Antonio to near Freeport during the day and produce strong to severe thunderstorms. Low-level winds near the warm front will circle back toward the ESE and enhance low-level storm rotation.
Such collisions are notorious for tornado production, according to Lindner. Discrete cells may develop ahead of the line of storms approaching from the west. The location of the greatest severe risk will depend on where the warm front sets up Friday morning. Areas along and south of the front will have the highest risk.
If the warm front moves just a few miles farther north, it will increase risk to the Houston metro area. Kingwood was struck by tornados in a similar setup earlier this year.
Damaging winds will be the main threat. The worst of the storms should be over by 3-5 pm Friday, but lighter rains may linger well into the evening hours.
Heavy Rainfall:
Moisture will deepen Thursday into Friday. By Friday morning, a saturated air mass will be in place over the region. “Strong divergent lift coupled with low-level inflow will increase the potential for heavy rainfall along with cell training from southwest to northeast.”
Lindner describes himself as “aways wary of such setups.” They can help anchor and train convection.
These storms could become significant rainfall producers – if they become sustained along the warm frontal boundary. The good news is that the ground is dry and can handle several inches of rainfall. “However, rainfall rates may exceed localized drainage capacities and result in some street flooding regardless of the dry ground conditions,” says Lindner.
Weekend:
Cloudiness should linger much of Saturday keeping temperatures in the 50’s under northerly winds. South of the cloud line temperatures will warm into the 70’s. Where that line will be Saturday is hard to determine. Clouds should erode Saturday night with mostly clear skies. Sunday will be mild.
Tropics:
The hurricane season has another month to go. It isn’t over yet! The National Hurricane Center now gives an area of low pressure moving WNW across the Caribbean a 50% chance of turning into a tropical depression in the next five days. No one is yet predicting what will happen if it does.
Posted by Bob Rehak on 10/27/22 based on information from Jeff Lindner, NWS, and NHC
1885 Days since Hurricane Harvey