FLOODPLAIN STORAGE AND LAND USE ANALYSIS AT THE WOODLANDS, TEXAS 1

Landscape and Urban Planning

2011

Keywords:Ian McHarg GIS Ecological planning Flood mitigation Soil and water assessment tool Kinematic runoff and erosion model a b s t r a c tThe 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.Published by Elsevier B.V.

Section: Discussionsupporting

confidence: 74%

“…The Panther Creek watershed boundary was delineated using the outlet located at the confluence of Panther Creek and Spring Creek (Bedient et al, 1985). The drainage area of the watershed is 94.2 km 2 .…”

Section: Study Sitementioning

confidence: 99%

Assessing planning approaches by watershed streamflow modeling: Case study of The Woodlands; Texas

Landscape and Urban Planning

2011

“…Other quantitative and modelling assessments have been made regarding The Woodlands landscape performance. Bedient, Flores, Johnson, and Pappas (1985) compared more than a dozen development scenarios and concluded that The Woodlands development plan mitigates flooding, and Doubleday, Sebastian, Luttenschlager, and Bedient (2013) further showed that The Woodlands can attenuate peak discharges during 100-year storm events. Compared with adjacent Houston communities, The Woodlands showed substantially lower levels of forest fragmentation (Kim & Ellis, 2009), lower run-off volume and pollutant loadings , and on average, 2°C lower land surface temperature (Sung, 2013;.…”

Section: Introductionmentioning

confidence: 97%

Ian McHarg’s Ecological Planning in The Woodlands, Texas: Lessons Learned after Four Decades

Huang

2015

Landscape Research

The Woodlands, Texas, is well known as a new town development (29,000 acres) that followed Ian McHarg's ecological planning approach. Primarily by literature review, this paper indicated that early development that followed McHarg's approach has met the original planning goals to preserve the forest environment and to minimize the development impacts on watershed hydrology. McHarg's approach was largely abandoned after the ownership change in 1997. Barriers came from each side of the development: homeowner (demand), developer (provider), designer (professional service) and government (policy-maker). The Woodlands' environmental planning success in early development was also attributed to developer George Mitchell's personal commitment and financial support, the US Housing and Urban Development's $50 million loan, and the relatively flexible planning system in the 1970s. However, in the current planning and economic systems, it would be a hard undertaking to replicate McHarg's ecological planning approach at this scale.

“…Development started around the same period in these two watersheds in the 1970s, whereas stormwater management methods differ. The Woodlands has been well-managed as a planned community from its inception [45,47]. Ecological planner Ian McHarg laid out a suite of decentralized, infiltration-based drainage designs to reduce runoff volume and improve water quality [48][49][50][51].…”

Section: Study Sitementioning

confidence: 99%

“…One of the projects, The Woodlands, is a renowned large-scale community development. It is a precursor of the USEPA's GI design initiative: a series of integrated GI design strategies were used to meet flood control and stormwater quality goals [44][45][46][47]. Several recent studies have demonstrated the effectiveness of The Woodlands GI design on flood mitigation [31,32,46].…”

Section: Introductionmentioning

confidence: 99%

Green Infrastructure Design for Stormwater Runoff and Water Quality: Empirical Evidence from Large Watershed-Scale Community Developments

2013

Water

Green infrastructure (GI) design is advocated as a new paradigm for stormwater management, whereas current knowledge of GI design is mostly based on isolated design strategies used at small-scale sites. This study presents empirical findings from two watershed-scale community projects (89.4 km 2 and 55.7 km 2 ) in suburban Houston, Texas. The GI development integrates a suite of on-site, infiltration-based stormwater management designs, and an adjacent community development follows conventional drainage design. Parcel data were used to estimate the site impervious cover area. Observed streamflow and water quality data (i.e., NO 3 -N, NH 3 -N, and TP) were correlated with the site imperviousness. Results show that, as of 2009, the impervious cover percentage in the GI site (32.3%) is more than twice that of the conventional site (13.7%). However, the GI site's precipitation-streamflow ratio maintains a steady, low range, whereas this ratio fluctuates substantially in the conventional site, suggesting a "flashy" stream condition. Furthermore, in the conventional site, annual nutrient loadings are significantly correlated with its impervious cover percentage (p < 0.01), whereas in the GI site there is little correlation. The study concludes that integrated GI design can be effective in stormwater runoff reduction and water quality enhancement at watershed-scale community development.