1.4 Hard Engineering & Soft Engineering - Toward an LID Approach


Hard engineering systems for stormwater management typically include conventional catch basins, conveyance pipes, and pond or vault designs that present a mechanical approach to conveying, detaining, and/or treating stormwater runoff. A soft engineering approach utilizes ecological principles and processes, such as filtration, infiltration, and phytoremediation, or degradation of contaminants in the region surrounding plant root systems, to reduce peak flow rates, volumes, and pollutant loadings in stormwater runoff. Integrating hard and soft engineering approaches in an LID site design can provide redundancy and resiliency of the stormwater management and landscape systems and improved ecological function of the site (see Figures 1.4 through 1.7).


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Figure 1.4

Diagram of hard engineering and soft engineering
Source: AHBL, Inc.



Fig1-5_Page04_Graphics_rev2
Figure 1.5
Diagram of hard engineering and soft engineering
Source: AHBL, Inc.




Figure 1.6
Diagram of hard engineering and soft engineering
Source: AHBL, Inc.




Figure 1.7
Concepts of redundancy, resiliency, and distribution
Source: Courtesy of the University of Arkansas Community Design Center