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Hurricane Harvey Recap
Posted on Sep 7th, 2017

From the Municipal Utility District Board President
We have made it through one of the worst storms in history.  I want to thank Levee Management Services (LMS) - our levee management company - who tirelessly monitored our levee and operated our pump station to keep our homes dry.  Our levee is the most expensive system thawt the MUD maintains and we spend a significant amount of our resources on it.  I want to also thank Fort Bend Count Judge Bob Hebert, the Fort Bend County Office of Emergency Management, and our MUD engineer, Wallace Trochessett with LJA; they provided critical and timely information to the MUD board.  I cannot also thank enough to Kelly Force, our Riverpark West Community Coordinator, who was able to distribute information to our residents while evacuating her family.  Due to everyone’s preparation and diligent efforts, no levees within Fort Bend County were breached.
MUD 121 experienced two separate events during Hurricane Harvey.  One was a “rain event” and one was a “river event”.  Since MUD 121 is surrounded by a levee, direct rainfall within our neighborhood must be drained out.  Water in the streets flows into the storm drains which empties into the drainage channels within the levee.  These channels flow into the retention pond where the soccer fields are located.  When the Brazos River level is low, the retention pond gravity-flows into the river.  However, if the river level is high, we have a pump station that will pump the water from the retention pond to the river.  For this rain event, we fared well with minimal water in the streets for a short amount of time; this was better than surrounding neighborhoods, including Veranda that had about one foot of water in some of their streets.  As the rainfall ended mid-week, our concentration moved to the rising Brazos River.
Our levee management company continuously monitored the levee to look for weak points and potential failures.  Luckily, the areas upstream did not receive as much rain as forecast and the river did not rise to the projected 59 feet.  However, the river level did reach a record 55.19 feet, based on the Richmond river level gauge; this exceeded last year’s record by about 6 inches.
Why did we have a mandatory evacuation?  The National Weather Service provides all forecasting for rainfall and projected river levels; this is the best information available and used by all agencies.  On the evening of Sunday, August 27th, the forecast of the Brazos River was changed to 59 feet.  At this height, we expected the river to overtop our levee.  Since we have a mostly-earthen levee, overtopping would erode the levee as the water flows.  A river level of this height would fill up Riverpark West and we would see 6 to 10 feet of water in our homes; this could happen suddenly with only minutes notice.  For the safety of all residents, the County Judge issued the mandatory evacuation order.
Why did it take so long to rescind the evacuation orders?  Once the rain in our area had ceased, the evacuation order stayed in place because the danger had changed from a “rain event”, with local street flooding, to a “river event”. Before the evacuation order can be lifted, the county evaluates projected dangers pertaining to the rising river, the condition of the levee, local street accessibility, as well as entrances/exits for the subdivision.
Why didn’t we sandbag our levee to increase the height?  We have a combined levee with 3 other Levee Improvement Districts - LIDs 6, 10, and 11 - which is approximately 10 miles in length stretching from the City of Richmond to south of Greatwood.  We do not have the resources to increase the height of this entire stretch of levee on a short notice.  With our partners, we co-own a system called Tiger Dam which can be deployed where localized problems may occur.  This system was deployed in LID 10 (RiverPark) for some issues they experienced during the event.
Will the levee be raised?  The MUD board will be discussing this with the county, our engineers, and our levee partners.  The design standard is the 100-year flood elevation, which is defined as having a 1% chance of flooding each year.  This elevation is set by the federal government and those buildings within the 100-year flood elevation require mandatory flood insurance.  After Tropical Storm Allison in 2001, the Greater Houston Area was studied and the 100-year flood elevation was increased.  MUD 121 partnered with neighboring levee districts to join levees and raise them above the revised 100-year flood elevation.  This project was completed in 2008 and our cost was an approximate $3.5 million.  Without this project, MUD 121 residents would have been required to purchase mandatory flood insurance.  Mandatory flood insurance costs approximately $5,000 to $8,000 per year, while voluntary flood insurance is approximately $300 to $700 per year.  Adding additional height to the levee would be expensive due to necessary construction methods, and would require our partners to elevate their portions of the levee.
Why are there varying top-of-levee elevations reported?  We strive to distribute clear and concise data to our residents.  The top-of-levee reported by the MUD is 58 feet, and this elevation is in relation to the Brazos River level gauge located in Richmond.  This number was conservatively calculated by the MUD’s engineer who designed our levee; this allows the average homeowner a way of monitoring flood risk with real-time information.  There are several items necessary to make the conversion.  The first is that the river level gauge is not relative to sea level but relative to the bottom of the river at the gauge.  The bottom of the river is 27.94 feet above sea level.  The second conversion is that the river falls from where the river level is measured in Richmond to where our levee is located, which is approximately 4-5 miles downstream.  This drop in river elevation between the gauge and our levee is not constant and varies based on river level, flow rate of the river, and the constant change in the river profile.  As our engineer obtains more historical data, this calculated reference to the Richmond gauge may change.
My slab elevation is higher than the river gauge, am I safe?  As stated above, the river gauge is referenced to the bottom of the river at the gauge point in Richmond and not in reference to sea level.  During this storm, the highest projected level of 59 feet at the river gauge is approximately 87 feet above sea level.  The slab elevations of the homes within Riverpark West vary; the survey provided to you when you purchased your home should state your slab elevation, which is sometimes abbreviated TOS (Top of Slab) or FF (Finished Floor).  These elevations are based on sea level (my home is listed at 76.6 feet).  During this event, the river level was higher than the slab elevations of our homes. Since the levee was operating as designed, it kept the river water out of our homes in Riverpark West.
Again, I want to thank everyone involved for their tireless work during Hurricane Harvey.  The MUD board will continue to monitor and evaluate our system and coordinate with our partners to protect our residents and their homes.