Wetlands Group
Appendix D: Retention Ponds

Section 1: The Current Situation

The current detention pond, which is designed to hold water and release it slowly into the Harris Gully culvert, should be able to detain 2.5 acre-feet of water (which covers approximately 280,000 square feet of footprint space).  This volume will have to be eventually expanded with the recent decision to build more to the Rice campus.  The detention pond is also intended to store 1.25 acre-feet of water.

Although Walter P. Moore believes that the detention pond is working as designed, no studies have been made to verify the operation of the pond.  Research on the existing storm drain system, however, has determined that Rice does not have the capacity to effectively handle a two-year flood.  Had the system been constructed today, it would have been built three times as large.  However, as the storm sewer system in and around Rice is old, deteriorated, and disordered, a larger volume of detention is the only solution for taking unwanted water away from areas around campus.

Rice's position in Houston is crucial in understanding stormwater issues.  Rice is at the bottom of the Braes Bayou watershed, and like much of Houston, all of Rice's stormwater eventually runs into this bayou.  This situation has two consequences.  First, in large rain events, Rice will pick up sheet flow from the north and west, as the water tries to take its natural course into flowing toward the Harris Gully (which runs near Autry Court).  The Harris Gully, which is now a box culvert, spills water into the bayou.  A second consequence is that a full bayou will cease drainage from the culvert--and from Rice--and may even backflow through the storm sewers.  Because heavy construction in this area has decreased the amount of water-absorbing ground, the Braes Bayou cannot handle even a 5-year flood.  This situation gives Rice very little grace in protecting its property and buildings.
 

Section 2: Dry Detention Pond and Parking Structure Solutions

The current dry detention area designed by Walter P. Moore can (and ought) to be expanded.  This is a picture of the current retention pond on Rice campus.  The firm has tentatively developed a plan to expand the pond with "fingers" that cross the intramural fields (WMPA 1997).

Additionally, Dr. Phil Bedient has proposed the idea of constructing a multi-story parking garage.  The lower levels could be used as a detention area after very large storm events, which would otherwise flood the campus. (Bedient, 1998).  The aesthetics of building an above ground parking structure must certainly be considered.  By building it along Main Street, (where the Herring Hall lot is currently located), it would be facing the Texas Medical Center parking lot, instead of in the middle of the campus, and preserve Rice's architectural style.  Additionally, parking privileges could be leased to the medical center employees. Though initially expensive to build, revenue from the garage would help the university defray the costs of building a detention facility, as well as allow the university to use some of its current parking lots for development of new buildings or additional greenspace.

Section 3: Wet/Recreational Retention Pond Solution

A wet retention pond can serve as a recreational area.  Retention ponds are often used as part of the landscape in golf courses or public parks.  It could also be made into an attractive and useful space if a lake walk or jogging trail was built around it.
 

In addition, the area could be wildscaped with native flora and fauna which would encourage wildlife, and also allow the area to be used as a teaching tool about Texas ecology, similar to the building of the Rice prairie.  Harris County Flood Control has recently begun studying methods of building and aquascaping retention ponds in the Houston area.

A Wildscaped Retention Pond

Additionally, a study conducted by the United States Navy describes how retention ponds can be used to treat stormwater, through solids settling and eutrophication.  Sediments, trace metals, nutrients, phosphorous, BOD and COD levels can be reduced over time.  In urban areas, they are especially good at removing heavy metals from parking lot runoff, and nitrogen from fertilizer runoff from nearby green areas.

Functional Wetlands at the University of Florida

A particularly good example of wildscaping of retention ponds can be seen at the University of Florida.  Students there formed a wetland club, and developed a three-acre wetland habitat/retention pond.  Native trees and plants were chosen to attract nesting birds and animals.  It serves both as storage for stormwater, as a functioning, beautiful conservation laboratory.  Similar projects have been undertaken throughout the nearby communities.
 

Retention Pond at George Mason University

George Mason University created a water retention pond on a smaller scale, more similar that which would be suitable for the Rice University campus.  They were able to significantly reduce their sewage load due to solid pollutants settling in the ponds.  The university also installed a solar aeration system to efficiently provide oxygen to the water. An attractive fountain was used to circulate and aerate the water, and prevent it from becoming a breeding ground for mosquitoes.  The oxygen rejuvenated the water and attracted wildlife, without polluting the pond.
 

Problem 4: Stormwater

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