- - - - www.BrazoriaCountyFloods.com
Analysis of the Floods of 2016 and 2017
in Central Brazoria County, Texas
Bruce A. Warren, P.E.
Revision 22 - June 8, 2019
Please send an email if you find errors, or have additional information.
The goal is to keep improving the data and facts on this website.
This website has many very large and detailed images that are best viewed on a big computer screen or even better on a big TV that can connect to the internet via a FireStick or Roku. But the images can be seen on a phone if you swipe sideways and down. The purpose of this website is to reveal why thousands of acres in central Brazoria County north of Lake Jackson were flooded with one to six feet of water two years in a row, 2016 and 2017, and also in June 1992 (which most people have forgotten about). Because this land has never before in the history of Texas been flooded. We know this fact because the land was part of the Stephen F. Austin land grants for his settlements and the plantations of cotton and sugar cane and many records exist from that era. And those original settlers were smart enough to pick the high ground and not build levees and tall roads.
The primary purpose of this website is to educate residents that "drainage" is totally different from "flooding". Drainage is 'little' and flooding is 'BIG'. Improving "drainage" so the road ditches and yards don't fill up during a rainstorm is good, but has no relationship at all to the flooding we saw in 2016 and 2017. You have probably heard of the Velasco Drainage District. Their primary mission is maintaining the levees and pump stations built in the 1960s to protect the Dow plants and facilities in and near Freeport. Notice that the name is "Drainage District", not "Flood District". No organization can stop floods like the 2016 and 2017 Brazos River overflows. Big floods like that can only be mitigated if we pay attention to the historical hydrology of Brazoria county... the big picture of where Mother Nature designed the big water to flow. Big subdivisions in southern Fort Bend and Harris counties have built miles of levees to try to divert Brazos river flood waters. Those counties and Brazoria county are now criss-crossed with elevated roads that act like levees and block the historical natural water flow. We have now learned the hard way that "it's not nice to fool Mother Nature".
[Click to read 2001 article that reveals how Sienna Plantation destroyed Oyster Creek.]
County Road 682 pavement at 20ft elevation is under a foot of water.
2307 White Tail Lane, Sugar Mill Subdivision
My cars parked on the 21ft high bank of McFadden Bayou.
2307 White Tail Lane, Sugar Mill Subdivision
A little history: I built my house on the highest lot I could buy near Lake Jackson in 1980 (21ft elevation). This was one year after Tropical Storm Claudette set the record for the highest rainfall in Texas and the 5 acres we bought was not flooded during Claudette. The settlers in the 1800s picked the highest ground for the plantation houses and sugar mills. Later, the prison farm buildings were placed on the highest ground. The living room floor in my house is surveyed at 23.28 feet elevation. My property got flooded in 2017 because of changes made to the land and roads around us over the past 40 years -- levees and roads were added and raised higher and they now block the natural water flows. 40 years ago we moved into the house we built (no contractors) in Sugar Mill and we raised our family in that house. We don't want to see brown flood water cover our land ever again. We will find a way to be sure our home has a very long future. Looking out the kitchen window we see the tree the kids used to climb. We see the track where we raced our motocross bikes. We see the back yard where our daughter got married. We see the different grass where the swimming pool used to sit. We’re never going to move. It's the flood waters that have to move... back to where they used to flow.
In 2016 and 2017 Oyster Creek and Bastrop Bayou watersheds filled up with Brazos River water from the north (plus local rainfall) and that water was trapped by roads and levees and flood gates from taking its ancient routes into the marshes and down to the Gulf of Mexico. The Brazos river rose higher than its banks in central Brazoria county and flooded the fields and started flowing south. The flood waters along both sides of Oyster Creek flowed parallel with Oyster Creek over the farmland and forests after flooding out of the Brazos River starting near Sienna Planation and on down to Harris Reservoir. In some places north of Holiday Lakes the Brazos River flood water rose high enough to flow into Oyster Creek via low spots in its banks. Oyster Creek rose rapidly and did escape its banks after it crosses Hwy35 near Angleton. But Oyster Creek did not go over its 22-24 foot banks near Lake Jackson at FM2004 because the red flood water rose high enough (21feet) to flow south into Sugar Mill and Buffalo Camp Farms and finally over Hwy332 and back into the Brazos River. Remember, all these citations of elevations are obtained from Google Earth that is accurate to within 6 inches.
So two streams of floodwater were flowing south towards Lake Jackson - farmland floods and Oyster Creek. The Brazos River crested at 53 feet while the farm land and forests to the east and south near Rosharon are generally at an elevation of 45 feet. That creates a very wide shallow river flowing south. The land near Harris Reservoir 8 miles to the south is about 35 feet elevation. At 15 miles to the south Bailey's Prairie is about 25 feet. The flood water will spread in all directions finding the lowest elevations to speed its way south to the Gulf of Mexico. Oyster Creek filled up with flood water, but since its banks are higher than the surrounding land (just like every stream or river in Texas) Oyster Creek really did not 'cause' the flooding. The water that flooded Lake Jackson Farms, Buffalo Camp Farms, and Sugar Mill flowed over the 45 miles of fields and forests between Missouri City and FM2004. Oyster Creek starts near Sugarland and is just a mile from my brothers house in Lake Olympia. The lower roads in Lake Olympia are at 65 ft elevation and they were flooded in 2017 while my brothers house at 76 feet was high and dry.
When all this water arrived at the airport (parking lot elevation is 21 feet, same as my driveway) and Wayne Scott Prison Farm (parking lot elevation 25 feet and fields at 19 feet) it had to keep flowing south... in some places trying to flow back into the Brazos river which was at an elevation of 30 feet at West Columbia... a lot lower than the 45 foot elevation it started at near Rosharon. Some of that water found Buffablo Camp Bayou near the Brazoria Resevoir dam. A lot of flood water flowed via Buffalo Camp Bayou/Reservoir because the highest the Brazos River got near the FM 2204 bridge was 15 feet, the wonderful low elevation all that water was seeking. But only a fraction of the water could flow under the Hwy332 bridge over Buffalo Camp Bayou. The northern flood water rose up to form a 2.75 mile wide river at Sugar Mill at a peak elevation of 22.5 feet at my house before it was high enough to go over the Hwy 332 pavement between Lake Jackson and the Dow Reservoir Dam. If Hwy 332 had not be raised up many times since 1954, Sugar Mill would not have flooded. Also, the flood water that found some low routes towards the east used to enter the Bastrop Bayou watershed, but the new divided Hwy 288 that was finished in 1990 blocks much of that flow.
The 2017 Harvey rainfall showed that it is now possible for northern flood water flowing south to rise up over the 1950s era 22ft levee protecting Lake Jackson on its north side along FM2004. We watched Hwy 332 block the natural floodwater flow back into the Brazos River and the divided Hwy 288 block the flow via Bastrop Bayou into the marshes and Intracoastal Canal. Today, flood water now has no where to go but up and over the FM2004 Levee. The Solution?? - Both 332 and 288 need big drainage trestles and many culverts to let floodwater flow under them. If not, Lake Jackson might see a tidal wave from the north if a rainfall like Harvey happens again AND there are hurricane winds from north to south as the wast wall of the eye passes over southern Brazoria county.
The very large annotated 1984 topomap below summarizes my investigations...
I have been trying to identify and explain what turned my house into an island in September 2017. Of course, it was Hurricane Harvey water. But why and how did it reach our 5 acres? What caused the clear water, then brown water, then red water that my family watched flowing across our front yard and rising up from one inch on the driveway all the way to two feet deep over a very long scary week. We stayed in our house the entire time. The water flowed pretty fast the whole week directly in a due south direction. The front of our house is oriented almost exactly north-south. The water never sat still for a day, or an hour. It was always flowing and swirling from north to south. Many homeowners think the Brazos River near us rose up and did the flooding. Not true. Water flowing with a visible current from north to south across prison farm and my land could NOT be the Brazos river rising up and overflowing near the Lake Jackson golf course, over Hwy332 and up to my house. That flow would be from south to north. ALL the flood water came from the Oyster Creek and Bastrop Bayou watersheds to the north of Sugar Mill and Lake Jackson Farms. You can see some of this water in the video below which shows water being pumped from the oxbow lake named Lake Jackson into Oyster Creek.
Harvey Flood Pumping Video
Scroll down for more maps and diagrams showing water flows and elevations that make it clear why the floods around Buffalo Camp Bayou happened in 2016 and 2017. There are no links to other documents, just one very tall web site. These images are large and best viewed on a big screen, but you can scroll around on your phone to see them.
Google Earth Pro is the primary data source. It provides elevations instantly anywhere you place the cursor. The accuracy of these elevation readings was verified by comparing to the USGS topo map below showing one elevation line of 20 feet where Lake Road crosses FM 2004 in the city of Lake Jackson. This matches exactly with the reading from Google Earth Pro. In the limited areas of the flood the accuracy is probably plus/minus 6 inches. Google Earth will show you that your road ditch is 2 feet lower than your front sidewalk. Or it will show you that the high spot in your backyard along the bank of the bayou is two feet higher than the county road. If you have a survey showing your driveway is 17.5 feet and Google Earth shows 18 feet then you can have high confidence in the elevations Google Earth shows in the areas a few miles around you.
Below is a very wide and tall Google Earth map of central Brazoria County from Darrington Prison Farm in the north to Quintana Beach at the south. Oyster Creek is right in the middle of the picture and is labeled. Oyster Creek was the watershed that delivered the flood water to the Lake Jackson area. The Brazos River did overflow into Oyster Creek at the top of the picture, but never rose high enough near Lake Jackson at FM2004 to cause any of the flooding we experienced.
The purpose of this website is to provide technical justification for actions that need to be taken if we are to prevent another flood like 2016 and 2017. Bottom Line: there are two solutions... 1) Add lots of culverts under the 4-lane Hwy 288 east of the airport and 2) Add lots of culverts and drainage under Hwy 332 between Lake Jackson and Brazoria. There is an active project to make Hwy 332 a four lane road and add a big drainage canal heading south beside the golf course down to the Brazos River. If this new Hwy 332 has lots and lots of culverts and drainage bridges under it so water can flow into that new canal and down into the Brazos River, then Lake Jackson Farms, Buffalo Camp Farms and Sugar Mill will not get flooded again. And/or, if the 4-lane new 288 has much more drainage added from west to east (as existed before 1990) this will also stop the flooding.
Since Lake Jackson was founded, its citizens have expressed concerns about the Brazos River rising up and flooding Lake Jackson... driven by hurricane winds and tides. This has never happened; not even during Hurricane Carla. And not in the long history of Texas. (Carla did put about 2 ft of water into some areas of Clute.) And it never will happen simply because the land to the west and south of the Brazos River is 5 feet lower than Lake Jackson land. Any hydraulic forces pushing saltwater inland will cause it to spread into the lowest elevations, not up and over a levee. What CAN happen is just what we saw in 2017 and 2016. The Brazos River becomes very high north of us from heavy rains in the Houston area. The flood crest of the Brazos River up north can be 50ft and that water overflows into Oyster Creek and Bastrop Bayou and all the surrounding watersheds. And that water flows south looking for the Gulf of Mexico. If you block that path with tall roads and levees to protect local interests, you flood many square miles of beautiful homes.
There is a proposal to add a flood gate on Buffalo Camp Bayou and also on the proposed future Hwy 332 drainage canal. The presumption is the Brazos River can rise up high enough to flood over the existing 22ft tall levee built in the 1950s along the north side of FM 2004. Google Earth shows that all the land to the south of the Brazos River is lower than 22 feet, with hundreds of square miles at less than 15 feet. Study the maps and diagrams below and you will see clearly that the Brazos River cannot rise up to flood any land north of the river near Lake Jackson. This has never happened. Look at where Abner Jackson put his plantation buildings (you can visit the ruins just north of FM 2004)... that land never flooded... not from rainfall or the Brazos River.
The map below shows the direction of flow of flood water after it got high enough to flow over the top of Hwy 332 pavement at the golf course and all the way west to County Road 532 (the Dow Reservoir). At the peak of the 2017 flooding, water averaged a foot deep on Hwy 332 with a very visible current flowing due south into the Brazos River. The Hwy 332 pavement elevation ranges from 19 to 21 feet. The Brazos River crest never even reached the 17foot pavement elevation of FM2004 (traffic was never blocked) so we know the river level was about 15 feet under the FM2004 Bridge.
How do we know this? Scroll down to the next drone photo showing the Brazosport Water Authority plant, FM 2004 and the Brazos River FM2004 bridge. The water has to rise about two feet higher up the 2004 ditch to reach the 2004 pavement that is at 17 feet elevation.
The 2016 drone photo below shows the Brazosport Water Authority water treatment plant, FM 2004 and the Brazos River bridge. This is as high as the water got in 2016. The 2017 flood water was about a foot higher... up onto the shoulder of 2004, but no FM2004 pavement east or west of the bridge got water over it. You can see on the low side of the Dam on Buffalo Camp Reservoir (which is about 10 feet tall) that the Brazos River level is much lower than the water flooding the BWA plant parking lots. The flood water at the BWA plant came from the north via Oyster Creek, not from the Brazos River near FM2004. The Brazos River never has and never will flood Lake Jackson from the south or west, only via overflow north of Lake Jackson that flows south along the Oyster Creek watershed.
The drone photo above shows clearly that at the peak of the flooding on Buffalo Camp Bayou, the Brazos rive is many feet lower. Therefore the brown water did not come from the Brazos river rising up at the 2004 bridge. It flowed south over and under Hwy 332 to flood the BWA plant.
The map below shows the city of Brazoria at the new FM 521 big bridge. The 2017 flood water on Old Main Street was about a foot deep; reported by a woman who lives there. That makes the Brazos river crest at downtown Brazoria equal to 23 feet. You can ask how the water can be 23 feet at Brazoria yet be only 15 feet at FM 2004. That is because the Brazos River has high banks north of FM 521 and low banks south of that to FM2004 and Hwy 36 and all the way to the Gulf.
The normal river bank at Brazoria is about 20 feet tall. This confines the floodwater to a narrow channel and it rises up. Once the water goes under the FM 521 bridge the bank drops down to about 12 feet at FM 2004. So the water flows out south across the Clemens prison farm land away from Lake Jackson and eventually into the marshland and then the Intracoastal canal.
This is the Brazos River at its zero flood normal level... basically the same elevation as the Intracoastal Canal, i.e. zero.
A perfect drone photo of Brazoria a few blocks east of Buckees showing the muddy Brazos water starting to flow into the streets and displace the initial clear rain water.
A perfect drone photo of the Brazoria riverfront at Old Main Street showing the muddy Brazos water starting to flow into the streets and displace the initial clear rain water. The Big Bridge at the top marks the end of the high banks, and 3 miles down river the banks are at 16 ft and River road is at 14 ft so this is when the flood water can escape by spreading out all over the low land to the west and south. This prevents the river from rising up near FM2004 and therefore Lake Jackson cannot get flooded from local high levels of the Brazos River.
Once the Brazos River water level rises up to about 14 feet in the zone south of Lake Jackson it overflows the banks near the Clemens prison farm and near the intersection of Hwy 36 and FM 2004. At the intersection of FM2004 and River Road 400, the elevation of those fields is about 13 feet. So the flood water flows south toward the Gulf. NOT north toward Lake Jackson. See how fast the elevation drops to the south... 15... 13... 11... 12... 10... 9... 7... BUT, we see blocking the way, FM 2004 built up to 17 feet because a primary mission of TxDOT is to ensure cars can evacuate during a hurricane flood event. No concerns and no studies are done to find out how many homes will get flooded by the water that is damned up by the taller roads. So every chance TxDOT gets, the pavement gets raised up another 6 inches. There are very few culverts under the road. Just enough to drain the typical rainstorm, not the Brazos River overflow. So the water level has to rise up over 17 feet to flow freely again. Until then, the flood water has to travel under the FM 2004 bridge and then it can find land at 12... 10.... 9... 8... feet down to the intracoastal waterway. The only impediments are River Road 400 at 9 feet and Hwy 36 at 10 feet.
Remember, the only way to prevent future flooding north of CR2004 in Buffalo Camp, Sugar Mill, Lake Jackson Farms and the Scott prison farm is to allow the flood water from Oyster Creek and Buffalo Camp Bayou to flow south unimpeded by roads and levees -- as it did when Texas was settled and thousands of year before.
FM2004 is essentially a 17 foot levee blocking the flow of a flood stage Brazos River down to the Gulf of Mexico. Remember, the elevation of Hwy 332 between Brazoria and Lake Jackson is 19 feet along the base of the Dow Resevoir Dam. The hydrology is pretty simple... north of Brazoria, if the Brazos River overflows its banks, most of the water will flow east into Oyster Creek. BUT, once Brazos River flood water reaches south past the FM 521 big bridge at Brazoria is can spread out rapidly and find a way down south through the Clemens prison farm fields flowing in a natural 2 mile wide low elevation channel to get down to the intracoastal waterway. The Brazos River can never rise up high enough to overflow the 22 foot Lake Jackson levee north of FM2004, or flood my 20 foot high five acres in Sugar Mill. In fact, the Brazos River can never rise high enough to flow over 2004 at 17 feet elevation, and that did not happen in the 2016 or 2017 flood.
We see from the picture above how the Brazos River flood water escapes fast and easy to the south. Now, below is a picture showing Oyster Creek near the airport. Look at the big yellow arrows. They show where flood water flowed in the days of the Austin settlements, the plantation era and up until 1990. Back then, some water flowed southwest across Buffalo Camp Farms and Sugar Mill via McFadden Bayou and Buffalo Creek (its name back then). But most of the flood water flowed east towards the closer/lower elevations on the east side of old Hyw 288. This is the Bastrop Bayou watershed. Look at the elevations: 15... 12.... 11... 10... 8.... 4... Notice that their are no houses on the land in the right side of this map. It is too low. It floods because it is the natural drainage from floods like we saw in 2016 and 2017
But the 2016-2017 flood waters did not follow the yellow arrows, instead it flowed due south across the prison farm, the airport and the thousands of houses in Lake Jackson Farms, Buffalo Camp Farms and Sugar Mill. None of this flood water got into the city of Lake Jackson on the other side of FM 2004. The water was blocked by the Dow Levee and FM 2004 and the high elevation of the original Alden Dow downtown area of Lake Jackson.
WHY? Take a look at the 4-lane divided Hwy 288 running north to Houston that opened in 1990 with an elevation of 23 feet. The original Hwy 288 elevation is 12 feet. The new Hwy 288 is a perfectly placed dam to block flood water from flowing east into Bastrop Bayou (which ends up flowing east into Christmas Bay). So the water rises up high enough to eventually flow south over Hwy 332, a dam which averages 20 feet high. So all the homes north of Hwy332 which are 20 feet or below are flodded and trashed. All the roads that are below 20 feet are impassable.
A little history here. Two years after the new 4-lane 23 feet high Hwy 288 was finished this happens:
A news story found on UPI.com -
Jan 7, 1992 -Brazos floodwaters surge south towards Gulf of Mexico
LAKE JACKSON, Texas -- Residents of southeast Texas braced themselves Tuesday as floodwaters along the swollen Oyster Creek and the Brazos River surged south toward the Gulf of Mexico. Brazoria County Judge Jim Phillips said Lake Jackson, Clute, Richwood and nearby areas expect high waters in the next two days as the flood surge moves slowly along Oyster Creek, which is flooded by runoff from the Brazos River.
Look at the drone picture below from the 2017 flood to see that flood water is damned in by the new Hwy 288. This was done on purpose to protect land on the east side of Hwy288 in the Bastrop Bayou floodplain so subdivisions could be developed in the future. The roads in Northwood Estates which borders 288 to the east are 17 foot elevation. The forests and marshes further to the east are at 15 feet into Bastrop Bayou. Now look to the west to see Timbercreek Court at 19ft. Brazos River floodwater naturally used to flow east into Bastrop Bayou. Now it is blocked by divided Hwy 288 and that water floods Timbercreek and all the land to the west and south.
Where did the 2016 and 2017 (and 1992) flood water come from? For the first few days, the rising water was clear, which means it was rainwater that fell on the land in massive quantities. All the low spots filled up. All the road ditches filled up. The water found its way down to the Brazos river until the river level rose high enough to match the land water level. Then the flood water slowly turned red (that took a day) because it was now overflow water from the Brazos River up north. The Brazos River collected thousands of square miles of Hurricane Harvey rain from Fort Bend and Harris counties for about 7 days. The Houston rainfall for August was 39 inches, with 12 inches in one day - August 27. A lot of that water flowed into the Brazos River which overflowed its banks way north of Lake Jackson, near Brazos Bend State Park at Rosharon and the Darrington Prison Farm. At the Rosharon Gauge the Brazos River crested over 53 feet in 2016 and 2017. The elevation of the Oyster Creek banks is only 45 feet. So guess where that red water flowed... into Oyster Creek and then south. And remember in 2016 the flood was in June; there was no hurricane. Just lots of rainy days and nights.
In the picture below, the address of the house in the lower left of the picture is 206 Buffalo Trail in Buffalo Camp Farms. The Buffalo Trail road pavement elevation is 19-20 feet. The Wayne Scott prison farm fields are to the right. This is a Google Earth image taken March 31, 2018. The banks of Oyster Creek to the east are about 22 feet.
Below is a frame from a drone video taken September 3, 2017 and posted on Youtube. All the water you see came across the prison fields at the right and is flowing toward the left. The depth of the water on Buffalo Trail is about one foot, putting the flood water elevation at 21ft. The banks of Oyster Creek to the east are at 22ft, so water was not flowing out of Oyster Creek this close to Lake Jackson. All the flooded land you see was part of the 6400 acre Abner Jackson Plantation. It was planted with cotton and sugar cane. They choose this land because the elevation of 19-21 feet did not flood from the Brazos River to the south. The floodwater you see flowed from right to left across this picture.
Look at the drone picture below from the 2017 flood to see that the red flood waters are damned in by the new Hwy 288. The banks of Oyster Creek in this picture have an elevation of 22ft and are not overtopped by flood water in this photo. The banks are about 300 feet apart and some roads are on the west (left side) bank. The roads in Northwood Estates which borders 288 to the east are 17 foot elevation. The forests and marshes further to the east are at 15 feet into Bastrop Bayou. Now look to the west to see Timbercreek Court at 19ft. Floodwater naturally used to flow east into Bastrop Bayou. Now it is blocked by divided Hwy 288 and floods Timbercreek and all the land to the west and south.
Below is a diagram showing the flood water flows that flooded my house (the pin in the lower left corner - 2307 White Tail Lane).
Looking at the image above we see flood water flowing south. That water was moving at a speed that a leaf took about a minute to float the length of our house. About the speed of a lazy river. An important place to notice is the water that flows down on the north side of the Dow Reservoir between that dam and the railroad tracks (another tall dam). That water comes out near Hwy 332 at the big Brazoria bridge. Some homeowners in Sugar Mill saw water flowing from west to east along Hwy 332 and then flow north up Craig road (CR532) into the Dow gate and Sugar Mill West entrance. Immediately off Hwy 332, Craig Road has an elevation of only 15-16 feet so it did collect a lake quickly between 332 and the Dow Gate. This water came from two places... 1) initially via Brazos River overflow at the big bridge then through the rainditch on the north side of Hwy 332. And 2) the flood water shown in the above image.
The Brazos River reached 23 feet at Brazoria. This puts the water over Hwy 332 under the big bridge south of Brazoria and under the railroad bridge and at the base of the Dow Reservoir dam along 332. The pavement elevation of Hwy 332 averages about 18 feet. Also, water coming from the north over the prison farm was flowing down between the reservoir dam and railroad tracks and added to the flow volume. The railroad tracks are elevated from the river to Angleton. There are several big trestles to allow water to flow from north to south. During the 2017 flood, a boater saw huge amounts of water flowing under the railroad trestles towards Sugar Mill. The high water that reached Craig Road did not keep flowing east along 332 toward Lake Jackson. The elevation of Hwy332 just east past Craig Road is 19 ft and the land to the south of Hwy332 (towards the Brazos river) is at 16 feet. So the 23 foot flood water that rose up under the big bridge at Brazoria flowed east for about 3 miles at the base of the reservoir dam and then flowed back down into the Brazos River where the river was spreading out over its low banks at Cutoff Lake and the Sand Pits.
Levees in South Central Brazoria County
Since much of Lake Jackson has an elevation of 14-15 feet, the residents and FEMA want assurance that flood water from rivers and creeks will not get in and also salt water from surge tides during a hurricane will also not reach homes and businesses. Many people worry that surge tides from the Gulf of Mexico will flow up the Brazos River and rise up high enough to flow over the 22 ft levee along FM2004. That is impossible because there are millions of acres along that coast that are 10 feet elevation or less. There are no topographical 'funnels' to force surge tides up anywhere near the 22 foot high levees along FM2004
The map below shows the places along the Texas Gulf Coast that can be hit with surge tides from hurricane winds, low barometric pressure in the eye, and high moon tides. They are all 'funnels' that force the water into smaller and smaller volumes, thus making it rise up higher. Notice that the Freeport area bulges out into the Gulf... because of millenia of silt from the Brazos River which is the biggest river (most flow) in Texas. All the land near Lake Jackson is higher than land to the east and to the west. There is no bay to trap water and cause surge flooding near Lake Jackson. This means saltwater forced inland by a hurricane will spread out to the east and west and never rise high enough to flood Lake Jackson. The VDD levees protect the chemical plants from saltwater floods. The elevation of Dow Plant B Building B101 parking lots is 5 feet. The Levee bordering that parking lot is 13-14 feet. The elevation of the emergency room driveway at the Hospital in Lake Jackson is 14 feet. The elevation of the Buckees parking lot at Plantation and Hwy332 is 13 feet. (These elevations make differ from data posted on VDD documents, but the differences are consistant. Hurricane surge tides will never flood Lake Jackson. Why did the very smart people who designed and built the VDD levess put the top at 13 feet? They understood that once saltwater got higher than that, it would start flowing east and west to the lower elevations in those areas.
Lake Jackson and Clute are not in the protection zone of the VDD levees. The VDD Freeport Levees protect Freeport and Dow plants. The levee stops at the north end of Dow Plant B when the natural elevation reaches about 14 feet. Lake Jackson is protected by the levee that parallels FM2204 from the Dow Pump Station on FM 2004 near the Credit Union and crossing Hwy 332 and then south along 2004, then turning east bordering McLean Park and then south to the Dow Plant B fenceline.
The VDD levee to the east is positioned to protect property near Stratton Ridge. This levee blocks the natural flow of water from Bastrop Bayou floods. There are pump stations to lift rainwater and northern flood water and pump it out into the marshes. But these pump stations are no match for the floodwater flows seen after Harvey. We must remember that the levees built to block saltwater floods from the south can trap rainwater from the north.
If the Freeport Levee system did not exist, a record breaking hurricane surge tide might reach Clute and some low lying areas at the south side of Lake Jackson, but 90% of Lake Jackson would not be affected. The storm surge caused by the low pressure in a hurricane eye affects a coastal length of only a few miles-- where the eye and east side winds strike. If the surge happens to hit at a bay (like Galveston Bay), then the surge height is increased because the water is trapped by higher elevation land on all sides of the water. The Galveston Seawall, constructed in 1902, is 10 miles long, approximately 17 feet high. (Google Earth Pro shows the top of the Galveston Seawall to be 17ft and Wikipedia says it is 17ft, so we can trust Google Earth elevation readings.) It was built after the Galveston Hurricane of 1900. That Seawall has never been overtopped by a storm surge from hurricanes.
In 2016 and 2017 Oyster Creek and Bastrop Bayou watersheds filled up with Brazos River water from the north (plus local rainfall) and that water was trapped by roads and levees and flood gates from taking its ancient routes into the marshes and down to the Gulf of Mexico. This happened because Hwy 332 was raised up and the new divided Hwy 288 was finished in 1990. It is now possible for northern flood water flowing south to rise up over the 22ft levee protecting Lake Jackson on its north side along FM2004. We watched Hwy 332 block the natural flow back into the Brazos River and Hwy 288 blocked the flow via Bastrop Bayou into the marshes and Intracoastal Canal. The only route left was over FM 2004. Both highways need big drainage trestles and many culverts to let floodwater flow under them. If not, Lake Jackson might see a tidal wave from the north if a storm like Harvey happens again.