Landscape and Urban Planning
The Woodlands, Texas, is well known as a town created following Ian McHarg’s ecological planning approach that uses soil permeability to coordinate development densities and land use. Very few studies have quantitatively measured the effect of this planning approach on stormwater management. In this study, watershed stream flow modeling was conducted to assess five hypothetical land use scenarios. These scenarios were compared with The Woodlands’ 2005 condition using the Automated Geospatial Watershed Assessment (AGWA) tool that simulates watershed long-term stream flow and peak discharges during single storms. The objectives are to: (1) assess The Woodlands development conditions during 1974–2005 on whether land use locations are based on soil infiltration capacities and (2) compare stormwater runoff generated in different planning approaches (conventional low-density, clustered high-density, and The Woodlands approaches) using watershed streamflow modeling. Stream flow data from U.S. Geological Survey gauge stations were used for AGWA model calibration and validation. The result of percent development on different soil types indicates that McHarg’s approach was more closely followed before 1997. After The Woodlands’ ownership was sold in 1997, later developments did not follow McHarg’s approach. The departure from McHarg’s approach after 1997 is also reflected in the stream flow simulation results. The 2005 observed stream flow volume is around 50% higher than that of the simulated condition that would result if McHarg’s approach was kept. Overall, McHarg’s approach using soil permeability to coordinate development densities and land use is effective in mitigating flood, especially during intense storm events.
Yang, B., Li, M.-H. (2011). Assessing planning approaches by watershed streamflow modeling: Case study of The Woodlands, Texas. Landscape and Urban Planning, 99, 9-22