Buffalo Bayou // Hurricane Imelda Sand Peel Sculpture

Context, Description, and Interpretation

 The Imelda sand peel sculpture was collected below the Jamail Skate Park  on a bend in Buffalo Bayou that was designed to collect sediments before they reached the Houston ship channel.  The design is very effective. The 2019 Hurricane Imelda deposits overlie 2017 Hurricane Harvey deposits (Sand Peel Sculpture X ) which overlie 2015 Memorial Day flood deposits.  The good news is that approximately 2000 cubic meters of sediment accumulated on the designed bench and was prevented from being carried down to the ship channel.  The bad news is that 2000 cubic meters of sediment was stranded in Buffalo Bayou, increasing local flooding potential and disrupting Buffalo Bayou Park.  This illustrates how storm mitigation designs do not make the problems (too much water, too much sediment) disappear, they primarily shift them to somewhere else.  There needs to be a continuous discussion of resilient, sustainable choices in how and where we shift the impacts of storms.  In this case the 2000 cubic meters of sediment accumulated on the Skate Park bench was trucked out and the bench recontoured.  The 1950’s design worked, but at the cost of increased flooding in the middle of Houston and disruption of a major recreational asset.  Would it have been cost effective and more efficient to redesign the bench so sediment is allowed to flow to the ship channel?  Or would increased sedimentation in the ship channel result in more frequent dredging?  These are the type of discussions that need to occur. We need to “change the paradigm from wait-and-pay to system-wide anticipate-and-accommodate” (HuRRI 2020 ).

 Summary: This sand peel records the erosion of Hurricane Harvey deposits during Hurricane Imelda and the 5 days of redeposition as Buffalo Bayou adjusted while returning to its channel.

The base of the sand peel sculpture is an organic rich poorly sorted sand and silt with some roots, which was deposited by Hurricane Harvey in 2017. An erosional surface (red line) has cut down into this layer.  Above the erosion surface is a 5 cm transition zone in which intraclasts of the lower material are incorporated into large scale low-angle cross stratification.  The next 30 cm is well sorted fine sand to silt with large low-angle bed forms (white dotted lines). This is truncated by another erosional surface (green line). The upper 10 cm package is fine sand to silt with abundant organic clasts and small scale ripple cross stratification. The three packages are interpreted as the Hurricane Imelda erosional surface overlain by a high energy deposit, followed by downcutting and deposition in a lower energy environment.

 Event Timing

• Sediment catchment bench built post 1953. Bench designed to catch sediments before they could reach the Houston Ship Channel.

• Pre Memorial Day flood, older floods and storms have deposited sediments on the bench.

• Memorial Day flood, May 27-30 2015, erodes and redeposits older flood deposits.

• Hurricane Harvey, August 28 – December 2017, erodes and redeposits sediments from the Memorial Day flood.

• Imelda flood phase

  • September 19, 2019: Highest water level reached at 4:00 pm marks erosional surface associated with Hurricane Imelda peak flood (red line). Too much flow to deposit sediment.

• Imelda early adjustment phase

  • September 19-21, 2019: Large scale trough cross beds, high energy, probably upper flow regime.

• Imelda late adjustment phase

  • September 22-24, 2019: erosion (green line) and deposition showing small-scale ripple marks during low energy flow as the bayou erratically dropped.

• Imelda recovery phase

  • November 2019: 2000 cubic meters of sediment were trucked out, removing the record of decades of storms.  The only surviving depositional records of the 2015 Memorial Day flood, 2017 Hurricane Harvey, and 2019 Hurricane Imelda are the sand peel sculptures.