Sunday, September 16, 2012

Does Urban Development effect runoff in Whiteoak Bayou watershed?


Olivera, Francisco, and Buren B. DeFee. "Urbanization and Its Effect On Runoff in the Whiteoak Bayou Watershed, Texas1." JAWRA Journal of the American Water Resources Association 43.1 (2007): 170-82. Print.


The study, “Urbanization and its effect on runoff in the Whiteoak Bayou Watershed, Texas”, by Francisco Olivera and Buren B. DeFee studies the ability of a watershed to urbanize without changing its “hydrologic response”. This question is extremely important to take into account as development projects sprout up around the world; development means the creation of more impervious areas (such as roads and parking lots) where water can not soak into the ground. If the hydrologic response of a watershed is altered too much, local ecosystems could face degradation, and flooding could become a more serious problem.
The study compared precipitation, water flow and land development data for the Whiteoak Bayou watershed in the 52 years from 1949 to 2000. Using GIS, the study analyzed the effect development had on runoff. Once data was found, 52 maps were created depicting the development on the watershed for each year, the maps were put in a GIS and converted to raster format, dark pixels representing developed land and white pixels representing undeveloped land. The data shows that until the early 70’s the Whiteoak watershed was able to continue drainage at normal amounts. In the early 70’s the watershed was covered in 10% impervious area; once it past that 10% coverage, changes occurred to the watershed. Since then annual runoff depths have increased by 146% and peak flows in the mouth of the Bayou have increased by 159%. As the runoff and peak flow have increased over the years, so too has precipitation, but, precipitation has increased at much lower rates than runoff and peak flow, accounting for 39% of the increase in runoff and 96% of the increased peak flow. This means that urbanization is accountable for 77% increase of runoff water and 32% increase of peak flow in the mouth of the Bayou.
The study concludes that urbanization can affect the hydrologic responses of watersheds when development passes the point in which the watershed can no longer handle urbanization. For this specific watershed that point was 10% impervious cover, but the study points out that different types of development can have different responses, so further study will be needed for other urban areas.


1 comment:

  1. This is interesting to me because in my Independent Study we discussed the impact of impervious cover on the habitat of the Georgetown Salamander. Urbanization is the salamander's greatest threat and impervious cover is a main component of that threat because it decreases recharge of groundwater which the species depends on. Also, increased runoff due to impervious cover can mean more sedimentation, contamination, decreased vegetative diversity and reduced visibility of the above surface portion of their habitat. This is a interesting study, and it would be cool to do something similar but also take into account layers of habitat and runoff quantity to get a better idea of the impact of impervious cover on particular species.

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