Pennison, Garland

Dr. Garland Pennison is an HDR Professional Associate and senior project engineer with over 45-years experience in project planning, engineering, and management. He has diverse experience in large civil, water resources, environmental, coastal, and flood protection projects. Dr. Pennison is a civil and environmental engineer with a MSCE in Environmental and Water Resources studies from Louisiana Tech University. His PhD is from the University of South Alabama in systems engineering focused on coastal systems. He is a member of ASCE, COPRI, LES, WEF, ASBPA, IISE, SAME, LFMA, and ASFPM.

Titles from this speaker

Changing Stormwater System Dynamics in Coastal Transition Zones

Abstract

We will present an overview of how evolving watershed system dynamics and large-scale watershed improvements, combined with increasing climate and environmental risks, are substantially changing the dynamics of urban stormwater systems in the Acadiana Region of Louisiana. While practitioners typically focus stormwater design on localized drainage system requirements, large-scale watershed improvements have been made over the years that have created unintended consequences impacting local/regional stormwater and flood risk management systems. In 1925, George H. Maxwell, a California lawyer who helped pass the National Reclamation Act in 1902, proposed a system of spillways, floodways, and storage basins on the Mississippi River that he called 'The Atchafalaya National Safety Valve'. He challenged the illusion of safety the existing Lower Mississippi River (LMR) flood control levees provided and warned that additional protections were needed. His proposal along with many others were considered by the Mississippi River Commission (MRC) but no action was taken, and the status quo remained until the devastating 1927 flood. This catastrophic flood ended the MRC's reliance on levees for flood control. The need for the Atchafalaya Floodway diversion and LMR gated diversions was no longer debatable. In 2025, a century later, we find that these large-scale improvements are evolving and changing drainage characteristics within adjoining watersheds and consequentially impacting local stormwater management systems. The design challenges and debates are increasing with regards to providing stormwater management and flood resiliency for an increasingly at-risk population and rapidly changing environment, particularly in the Acadiana region located approximately 200 miles east of Houston. HDR developed the Louisiana Watershed Initiative (LWI) regional-scaled watershed models for Louisiana DOTD in Region 5 (Atchafalaya, Teche, Vermilion, Mermentau Headwaters, and Mermentau HUC8 watersheds). HDR engaged in this complex modeling effort with extensive coastal transition zones utilizing coupled coastal and riverine models for this critical drainage area of over 10,000 square miles. The Region 5 calibrated/validated models have been completed for south-central Louisiana at a highly refined scale, with AEP frequency design storms and consequence models scheduled for completion before June. We will present a brief overview of the Region 5 modeling effort and changing stormwater system requirements, along with highlights of the stakeholder engagement and modeling efforts that led to 2023's newly created 'Acadiana Watershed District', one of the first regional watershed management districts in Louisiana. This initiative intends to promote understanding and encourage collective action among public and private sector partners to improve resilience and collaboration for local/regional stormwater and flood risk management systems. The benefit of this presentation is to show how fully integrated regional-scaled models can positively impact and inform practitioners in the design of local stormwater systems, such that the impacts are assessed more holistically, and proposed improvements/benefits are better understood. This is especially needed to address climate resilience and adaptation in evolving high-risk coastal transition areas.

This paper was presented at the WEF/WEAT Collection Systems and Stormwater Conference, July 15-18, 2025.

Presentation time

14:00:00

14:30:00

Session time

13:30:00

16:45:00

SessionStormwater and Coastal Resilience Modeling

Session number05

Session locationGeorge R. Brown Convention Center, Houston, Texas, USA

TopicClimate Change Adaptation, Coastal Systems, Watershed Management

Author(s)

Pennison, Garland

Author(s)G. Pennison1

Author affiliation(s)HDR Engineering, Inc., 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jul 2025

DOI10.2175/193864718825159874

Volume / Issue

Content sourceCollection Systems and Stormwater Conference

Word count9

Description: Intermodal Rail Logistics Park Prioritizes Stormwater and Sustainability with...

Intermodal Rail Logistics Park Prioritizes Stormwater and Sustainability with Ecological Conservation Corridor in Kansas City

Abstract

U.S. Army Corps of Engineers (USACE) accepted in 2019 post-construction monitoring as completed for the BNSF (Burlington Northern Santa Fe, LLC) Railway Company Intermodal Facility (IMF) mitigation conservation corridor located in the City of Edgerton in southwest Johnson County, Kansas. Presentation focuses on the successful design and implementation of nature-based (NB) stormwater management strategies associated with development of a complex industrial site as verified by annual monitoring. The purpose is to demonstrate that a carefully planned and designed ecological corridor can work in symbiosis with an adjoining industrial development to mitigate adverse impacts and enhance environmental benefits. Site is located approximately 35 miles southwest of downtown Kansas City, providing positive local context in support of the WEF SWI Stormwater Summit 2023 conference. The technologically advanced IMF enables efficient intermodal freight shipments within the BNSF rail network to the Kansas City region. Strategically siting the complex industrial development relative to key rail and highway transportation infrastructure required realigning approximately 2 miles of an unnamed Big Bull watershed tributary. Onsite mitigation was required to beneficially enhance, create, and restore the ecosystem functions and values of impacted wetlands and streams. The conservation corridor is excluded from future development or disturbance by perpetual easement, providing ecologically sustainable and long-term natural environmental benefits. Planning and design required considering watershed functions and values relative to stormwater management; water quality improvement; flood risk management; wetlands preservation; erosion control; and in-stream/riparian habitat conservation. The resulting ecological conservation corridor comprises approximately 59 acres; includes seven stormwater best management practice (BMP) areas; relocated stream with floodplain/floodway; and five restored wetland cells. Natural stream restoration techniques were used to realign the stream in a strategically sited and centrally located ecological corridor. Stream relocation included 31.23 acres of riparian buffer creation and 8.79 acres of riparian buffer enhancement. Development required realignment of 9,247 linear feet of a perennial stream to 7,747 linear feet of relocated channel with reference channel dimension, pattern, and profile. Riparian buffer areas included 16.75 acres of newly created shallow marsh and emergent/scrub-shrub zone wetlands for stormwater management. BMP treatment features manage site runoff from the IMF and surrounding areas prior to discharging into the relocated stream. At each stormwater outfall, a treatment train approach is used, including a forebay area (energy dissipation and sediment trap), constructed wetland area (water quality treatment), and vegetated outflow swale. A detailed water budget analysis evaluated the expected surface water runoff into the wetlands and modeled the hydrology of the wetlands to replicate natural conditions with the design. Onsite wetlands restoration included 7.18 acres not within riparian buffers, including a large emergent (herbaceous) wetland area in the center of the conservation corridor. Sustainable materials were primarily used to construct natural stormwater and erosion control features to provide water quality treatment for onsite drainage runoff before discharge to the relocated channel. Restored wetlands, riffles, pools, and ecologically designed drainage basins improve water quality, promote detention/infiltration, restore natural habitats, and mitigate indirect environmental impacts. Hard structures constructed with concrete and riprap were minimized. Where possible, onsite rock and vegetation were sourced for wetland and stream stabilization. Sustainable nature-based stormwater techniques and features utilized in design/construction will be presented. Relocation of the stream with detailed design of drainage features effectively reduced downstream peak flows and upstream base flood elevations (BFE). The realigned conservation corridor reduces the BFE at the upstream project limits by 3.63 feet. The first decade of operation has shown no evidence of channel instability (down-cutting, deposition, and bank erosion). Approximately 300-acre feet of annual runoff is routed through the wetlands. Monitored wetlands continue to demonstrate healthy and flourishing hydrophytic vegetation. The wetland detention ponds have successfully promoted nutrient reduction, sequestered carbon, recharged local water tables, and generally improved water quality. The naturally inspired conservation corridor and mapped floodway is a readily identifiable feature at Logistics Park Kansas City (LPKC). The corridor represents one of the largest local on-site mitigation efforts in Johnson County, providing habitat creation in conjunction with stormwater runoff treatment. Johnson County's Big Bull Creek Park is located immediately downstream of the conservation corridor, extending the corridor's environmental and water resource ecological conservation benefits into a 2,060-acre strategic prairie conservation and restoration area. The managed conservation corridor demonstrates the project team's commitment to minimize environmental impacts and contribute to long-term sustainability of communities served. The naturally landscaped floodway provides sustainable habitat for wildlife, waterfowl, and pollinators, while prioritizing stormwater and floodplain management. The presentation objective is to demonstrate how stormwater management functional requirements can be sustainably integrated with nature-based design features strategically sited within an ecological conservation corridor. The desired outcome is that the presentation will encourage participants to consider similar stormwater management strategies that are both environmentally beneficial and consistent with best management and design practices.

This paper was presented at the WEF Stormwater Summit, June 27-29, 2023.

SpeakerPennison, Garland

Presentation time

15:45:00

16:15:00

Session time

13:30:00

16:45:00

SessionSession 05: Strategies for Stormwater Sustainability and Resiliency

Session number05

Session locationKansas City Convention Center

TopicResiliency and Sustainability