Long-Term Hydrologic Impact Assessment Model Inputs and Outputs Assessing Performance of an Adaptive Green Infrastructure Toolkit in Galena Park, Texas
Funded By:
National Academies of Sciences Gulf Research Program
Funding Cycle:
Healthy Ecosystems 4
Research Group:
Development of Gulf Coast Resiliency Management Plan Using Sentinel Species and Natural Infrastructure
Gioia Kennedy
Environmental Defense Fund
gkennedy@edf.org
Flooding, Nature-based features, Containment transport, Numerical model, Hurricane, Surge, Residence time, Water level, Waves, Winds, Tides
Abstract:
Galena Park is a space-constrained and overly developed community home to one of the world’s largest collections of petrochemical complexes. This makes it challenging to implement green infrastructure (GI) to reduce flooding and pollution. To respond to this challenge, researchers developed an adaptive and flexible toolkit, the Green Infrastructure Adaptive Stormbox, that employs a combination of flood-proofing tools and pollution-relief techniques and can be applied broadly, based on both on-ground spatial size and underground depth to existing infrastructure. This Toolbox was then used to develop, through a community-engaged process, a master plan for Galen Park. We assessed the performance of the proposed master plan in flood and nonpoint source pollutant reduction by using Delft3D-FM and with the Long-Term Hydrologic Impact Assessment Low Impact Development (L-THIA). While the use of landscape performance tools which seek to quantify the impacts of designs and plans on cities has rapidly increased in recent years, no research has coupled their plans with sophisticated modeling techniques to simultaneously evaluate the impact of design on rainfall-induced inland flooding and hurricane-induced storm surge in any of the current literature. Most studies on flooding for urban planning have focused only on assessing flooding impacts under specific scenarios that are relatively static and have not focused on flooding that may occur at smaller time scales. However, in low-lying coastal areas such as Harris County, TX, determination of the impact of compound flooding from both rainfall-induced inland flooding, hurricane-induced storm surge, as well as the level of mitigation provided by flood reduction master plans is needed. See the related publication for more information on the Galena Park master plan: Zhu, Rui et al. “An Adaptive Toolkit for Projecting the Impact of Green Infrastructure Provisions on Stormwater Runoff and Pollutant Load-A Case Study on the City of Galena Park, Texas, USA.” Landscape Architecture Frontiers vol. 11,2 (2023): 72-87. doi:10.15302/j-laf-1-040031
Suggested Citation:
Galen Newman, Jim Kaihatu. Long-Term Hydrologic Impact Assessment Model Inputs and Outputs Assessing Performance of an Adaptive Green Infrastructure Toolkit in Galena Park, Texas. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/bst83mmp
Purpose:
This model was used to assess flood and nonpoint source pollutant reduction in a green infrastructure plan with a focus on incorporating nature-based solutions and evaluating their impact.
Data Parameters and Units:
L-THIA: land use [unitless], soil type [unitless], land use area [acres] Delft3D: Boundaries: time [minutes], free surface elevation relative to mean water surface (south, east, west) [m], boundary type [dimensionless] Grid: grid coordinates in x (east-west) [decimal degrees], grid coordinates in y (south-north) [decimal degrees], water depth and topography (referenced to NGVD) [m], enclosures defining grid boundaries via grid indices [dimensionless] Wind: time [minutes], wind velocity component in east-west direction at each grid point for each time step, at 10 m elevation [m/s], wind velocity component in south-north direction at each grid point for each time step, at 10 m elevation [m/s], atmospheric pressure at each grid point for each time step [millibars] Drogue: time [minutes], latitude position of drogue for each time step [decimal degrees], longitude position of drogue for each time step [decimal degrees]
Methods:
To assess the performance of Galena Park’s master plan, the L-THIA/LID model was utilized to estimate the annual average stormwater runoff and pollutant loads of land-use configurations for each phase based on the city’s daily precipitation data, soil type, land-use data, and LID practice percentages. The Long-Term Hydrologic Impact Assessment (L-THIA) model was developed in 1999 to more easily calculate pollutant load with runoff during a simulated period. The L-THIA model is a user-friendly and accessible online resources that characterize the impacts of LID practices on runoff, recharge, and pollutant loading. The model calculates the average annual estimates on the basis of modified curve-number (CN) values for the type and size of land use change, soil type, and long-term climatic data. Function of the Curve Number (CN) is calculated as: S =25,400/CN - 254 Under the condition that precipitation, P(mm) > 0.2S, direct runoff depth, Qh (mm) isestimated as: Qh =(P - 0.2S)2/P + 0.8S Qh = 0 when Pless than or equal to 0.2S The volume of runoff from an area is determined by: Qv = Qh x A where Qv is the volume of water; and the A is the area of interest. In order to determine the impact of the master plan on flooding from rainfall and/or storm surge, as noted, the Delft3D-FM model was applied. This computational model solves the dynamical equations for shallow-water fluid flowing on a geographic grid, upon which environmental variables such as water depth, terrain elevation, wind velocity, tidal elevation, surge height, and waterway discharge rate can be input. The output consists of wave heights, water levels and velocities, (if activated) sediment transport, and changes to topography. The grid used by the model is not limited to rectangular-shaped cells and can thus be manipulated to fit into complicated shorelines and waterway geometries. For this application, the overall grid extends from the Florida and Yucatan Straits in the south-eastern Gulf of Mexico, to the westward extent of the Houston Ship Channel. Terrain data for the coastal area came from the Coastal Relief Model[33] which has a spatial resolution of 3 arc-seconds (approximately 100 m at the latitude of the area). To represent hurricane surge, we used wind field information (Hurricane Ike, which attacked Galveston Bay and Houston in September 2008) from the HURDAT2 database to drive the model. Since the actual landfall point was along the western edge of Galveston Bay, the strongest winds associated with the hurricane were located east of the bay. In order to determine the impact of the master plan on flooding under severe conditions (maximizing the surge and thus providing a strenuous test of the master plan), the landfall point of the simulated hurricane was manually shifted within the model a distance of 50 km to the southwest from its actual location to place the strongest hurricane winds over Galveston Bay. In addition to hurricane surge, both waves and tides present within the Gulf of Mexico area were also included. As a proxy for representing rainfall, discharge information for Panther Creek recorded over the duration of the storm was input into the model. This was done under the reasonable presumption that the surface runoff in the area contained the entirety of the hurricane-induced rainfall, and all of the runoff eventually discharged into Panther Creek. As a result, the inclusion of this discharge information into the model is considered a sufficient accommodation for rainfall input.
Provenance and Historical References:
Cai Z, Zhu R, Ruggier E, Newman G, Horney JA. Calculating the Environmental Impacts of Low-Impact Development Using Long-Term Hydrologic Impact Assessment: A Review of Model Applications. Land (Basel). 2023 Mar;12(3):612. doi: 10.3390/land12030612. Epub 2023 Mar 4. PMID: 37324780; PMCID: PMC10270665.