Agri-community on the Levee

PROJECT STATEMENT
The “Agri-community on the Levee” project, located in the upstream area of two reservoirs (Addicks Reservoir and Barker Reservoir) in Houston, provides a flood-proof system for the city and a sustainable life circle for residents in the future. From the perspective of flood-proof, the project takes advantage of farmland and prairies to mitigate storm-water runoff through building a super levee system, a more stable flood control technology. Instead of bringing negative influence on the environment and landowner, the super levee system will provide local animals and plants with a habitat away from flooding, as well as benefiting both farmers and residents. The Agri-community will integrate agriculture into a residential neighborhood to facilitate food production while at the same time providing recreation for residents of the community.

PROJECT NARRATIVE

CONTEXT AND CHALLENGES
Addicks and Barker Reservoir were constructed between 1942 and 1948 as part of a larger U.S. Army Corps of Engineers 1940 flood protection plan for the City of Houston. At the time, around $4 million were spent on construction of these two dams, including land acquisition for the dams and some of the land area behind the dams within the design flood pool of the reservoirs. The reservoirs were intended as part of a vaster system that was never implemented: a levee to prevent floodwater from Cypress Creek watershed from overflowing into the Addicks Reservoir, a reservoir on upper White Oak Bayou, and bypass channels to direct significant volumes of water being released from the dams out of Buffalo Bayou and around Houston. Initially, these two dams and reservoirs were far from developed areas of Houston. However, today, development has occurred in and around both, including thousands of single-family homes constructed within the reservoirs’ design flood pool for each dam, and within the pathway of floodwater releases from these dams along and outside the banks of Buffalo Bayou. The reservoirs are designed to hold more rainfall than a 1% event, so land upstream of the reservoir is considered “safe” because it is defended from flooding due to rainfall in a 100-yearevent. Therefore, during events greater than 1%, dam releases can occur, flooding areas downstream, along Buffalo Bayou, that is unmapped in the FEMA 100-year floodplain. This scenario occurred during Hurricane Harvey. During Harvey, unprecedented amounts of rainfall caused water levels to rise significantly. To minimize upstream flooding, risks of spillway overflow from the reservoirs and the risk of further rainfall exceeding the reservoir capacity, the Army Corps of Engineers released water at a controlled rate through the outlet gates during and after Harvey. The combined amount of water released through the gates of both dams well above the capacity of Buffalo Bayou, resulting in flooding in neighborhoods downstream of the dams. Furthermore, the upstream portion of the Cypress Creek watershed is quickly being developed, aided by the roadway improvements involving highways, with very little channel improvements or upstream storage added for necessary mitigation controls. Thus, during Harvey, the overflows in Cypress Creek Watershed contributed a significant amount of water entering into the Addicks reservoir. Fortunately, the upper part of Cypress includes the Katy Prairie Conservancy lands, a unique undeveloped area that provides natural detention storage over vast areas of the prairie and agricultural lands. This is a priority area for future upstream storage considerations to mitigate flooding.

OPPORTUNITIES AND PROPOSALS
Despite the challenges, lots of farmlands and prairies and Katy Prairie conservancy lands that can be used for flood protection. Multiple lines of defense system are proposed within the Addicks reservoir watershed, Barker Reservoir watershed and the upstream area of Cypress Creek watershed. The defense system includes three parts:

FIRST DEFENSE: KATY PRAIRIE AND SURROUNDING FARMLANDS
Phase 1 (by 2030) – For farmlands and pastures outside the Katy Prairie, some small detention ponds can be built along valleys. The captured water can be used by farmers to irrigate crops and pastures.
Phase 2 (by 2050) – Super levee system can be build up within the Katy Prairie. The Floodable area will not exceed the Katy Prairie area.
Phase 3 (by 2100) – To deal with more runoff, part of the super levee system will be constructed outside Katy Prairie. The floodable area will both include the Katy Prairie and private farmlands and pastures.

SECOND DEFENSE: FARMLANDS AND PRAIRIE WITHIN THE ADDICKS AND BARKER RESERVOIR WATERSHED
Phase 1 (by 2030) – Some detention ponds can be built on farmlands and pastures to collect storm water runoff, which is a low cost and low-risk strategy.
Phase 2 (by 2050) – Super levee system can be build up in the upstream area of the watershed.
Phase 3 (by 2100) – To store more runoff, super levee systems can be constructed along streams. Water can be collected between the area of two super levees. If the flooding problem becomes more severe, more super levees can be built between the previous levees to store more storm water.

THIRD DEFENSE: THE ADDICKS AND BARKER RESERVOIR
To prevent future releases of these reservoirs, strategies including excavating and clearing vegetation in the reservoirs’ storage areas can be applied to increase their storage volumes.

CO-BENEFITS
For farmers
Within Cypress Creek watershed, the Keyline design can be applied to valleys. Keyline design, invented by Australian farmer and engineer P. A. Yeomans, is a system of principles and techniques of developing rural and urban landscapes to optimize the use of their water resources. The Keyline design will divert storm water from the valley to the ridge so that the water has a chance to soak into the landscape before running downhill. Additionally, this design pattern and system is a kind of sustainable agriculture system, which will confer generous benefits in many farming scenarios. The natural patterns of Keyline design will restore and increase the depth and fertility of the soil, while increasing its water-holding capabilities, and has deep benefits beyond the native dryland landscapes. Keyline Design integrates terraces, ponds, tree plantings on contour, and a special cultivation technique using the Keyline plow to infiltrate water into the soil efficiently and hold it on the land as long as possible.
For residents
Super levee is a stable and the most significant flood-proof technology that applied in this project. The slope of the super levee is gentler than traditional levee, so some buildings and farmlands can be developed on it. During an unexpected flood, overtopping water will flow slowly on levee rather than break it. Except for the function of holding back the flood, the super levee can additionally provide an Agri-community and sustainable life circle for residents. According to the difference in population density of the levee’s location, the living patterns on the super levee are divided into three categories. For the low-density pattern, located in Cypress Creek watershed, is mainly farmlands and pastures operated by local farmers. An orchard at the top of the levee can provide food products as well as have the ecological benefit of purifying the air. For the medium-density pattern, the Agri-community will integrate agriculture into a residential neighborhood to facilitate food production while at the same time providing recreation for residents of the community. For the high-density pattern, it is mainly residential and municipal services area, also the levee is topped with a linear urban park.

Problem
During Hurricane Harvey, catastrophic rainfall- triggered flooding caused many deaths and enormous costs. The inundation brings negative influence to adjacent houses upstream of the two reservoirs and downstream neighborhoods along with the Buffalo Bayou.

Reason
With the development of Houston, the ratio of impervious surface and population increase rapidly. Some unimplemented measures and proposals also cause the exceed of the storage capacity of two reservoirs.

Reason
The new development in Cypress Creek watershed, located in upstream of two reservoirs, also exacerbates flooding issues. Massive runoff of Cypress Creek floods the surrounding area and overflow into the downstream watershed.

New Challenge
After Hurricane Harvey, the NOAA updated the precipitation-frequency standard and took 1000- year precipitation into consideration. For the study area, the standard of 24-hr 100-Year precipitation increased about 3 to 4 inches.

Existing solution and Precedent
For the existing solution of resilient Houston, the third reservoir is proposed to build and some development regulation is put forward. For the precedent study, the super levee is the most important case I learned from. The slope of the super levee is gentler and not easily break down by flooding when compared to the traditional levee.

Defense System
This is the defense system within these three watersheds.
1.) The first defense is Katy Prairie and farmland within Cypress Creek Watershed.
2.) The second defense is farmland and pasture in Addicks and Barkers Reservoir Watershed.
3.) The third defense is the existing two reservoirs.

First Defense System
By 2030 – Creating small ponds in valleys of the upstream area of Katy Prairie.
By 2050 – Building up super levee within Katy Prairie.
By 2100 – Part of the super levee may build outside Katy Prairie.

Second Defense System
By 2030 – Building up some detention ponds on farmland and pasture.
By 2050 – Building up the super levee on upstream farmland or pasture.
By 2100 – Building up the super levee along streams. Water can be collected between the area of two levees.

Co-benefit – Cultivation
For the valley on the upstream of Katy Prairie, the Keyline Cultivation can be applied. The Keyline pond can collect storm water, which can be used by farmers. And the plow line will serve the function as swales to divert overflow from valley to ridge.

Other Benefit
To build the super levee, some parts of the prairie needs to be replanted. Plants that are existing species of Katy Prairie and can tolerant poorly drained soils are preferred. Besides the function of mitigating flood problems, the Katy Prairie can also provide some activities for people to enjoy.

Future Houston
For the low-density pattern, located in Cypress Creek watershed, is mainly farmlands and pastures operated by local farmers. An orchard at the top of the levee can provide food products as well as have the ecological benefit of purifying the air.

Future Houston
For the medium-density pattern, the Agri-community will integrate agriculture into a residential neighborhood to facilitate food production while at the same time providing recreation for residents of the community.