BIOFLow International Research Experience for Students (IRES)

Great Lakes coastal and riparian forest root structures for coastal infrastructure

Background.

The manifestation of sea-level rise and stronger storms has given rise to global coastal ecosystem restoration efforts as a natural line of defense for coastal communities. Biomimetic coastal structures have developed as a response to both rehabilitate natural ecosystems and/or integrate ecological multi-functionality with existing hardened infrastructure (1,2). In a similar vein to how mangrove forests consolidate sediments and reduce water velocities (3), coastal and riparian forests also provide these functions both rooted along the banks of waterways and if effectively placed, as fallen trees with relatively intact root systems (known as rootwads) (4,5). Mangrove roots are studied extensively for their hydrodynamic effects using physical models in laboratory-scale flumes, but the models are often too simple in their abstraction as circular cylindrical patches (6,7). Previous mangrove flume studies will provide the blueprint to design the appropriately scaled experiments to include freshwater rootwads. This project will study root systems of Great Lakes coastal and riparian tree species through 1) developing simplified physical models from scanned and imaged 3D models of real root systems out in the field, 2) examining effects of porosity, branching angle, branching hierarchy and diameter class on water velocity reduction, wake profile and vortex generation in a flume, and 3) assessing scale effects from laboratory results to generate realistic prototype-scale designs for bio-inspired coastal infrastructure for the Great Lakes.

RootModel

Figure 1. Root model sample in the water tunnel (left) and PIV tests (right).

IRES student involvement

Drs. Gruber and Zhang will work with an IRES student on this project. The IRES students will be provided with root models and 3D printer access to simplify and abstract the models into select geometrical parameters in modeling programs for the printing of physical models. They may also consider the opportunity to develop their own root models through field work from additional tree species or rhizome models from freshwater coastal wetland pioneers and emergent plant species. Printed models will be subjected to various flow velocities and Reynolds numbers in the flume to understand their hydrodynamic effects (Fig. 1). The IRES student can also consider the additional parameter of flexibility and its hydrodynamic effects through material choice and evaluation.

 

References

(1) Goad, A. (2019) MARS: The World’s Largest 3D Printed Reef. Retrieved from https://www.alex-goad.com/mars/

(2) Van De Riet, K. (2019, March 6). Biomimicry of Mangroves Teaches How to Improve Coastal Barriers. Retrieved from https://www.ansys.com/blog/biomimicry-mangroves-improve-coastal-erosion-coastal-barriers

(3) Kathiresan, K., Rajendran, N. (2005). Coastal mangrove forests mitigated tsunami. Estuarine, Coastal and shelf science, 65(3), 601-606.

(4) Holsman, K.K., Willig, J. (2007) Large-scale patterns in large woody debris and upland vegetation among armored and unarmored shorelines of Puget Sound. People for Puget Sound.

(5) Larson, M. (2000) Effectiveness of Large Woody Debris in Stream Rehabilitation Projects in Urban Basins. Center for Urban Water Resources Management.

(6) Kazemi, A., Van de Riet, K., Curet, O.M. (2017). Hydrodynamics of mangrove-type root models: the effect of porosity, spacing ratio, and flexibility. Bioinspiration & Biomimetics 12: 056003.

(7) Chen, Z., Ortiz, A., Zong, L., Nepf, H. (2012). The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation Water Resources Research 48: W09517.