Florida Sinkholes Explained

By Eban Bean

Since Hurricane Irma, several sinkholes have developed around Alachua County and Florida, many in infiltration basins. An infiltration basin is sometimes also referred to as a dry retention pond or basin. You can find these in many residential and commercial areas where soils are sandy and the water table is not near the surface. Western Alachua County has hundreds of these.

Sinkholes are common in Florida, often forming after heavy rains. A popular video (see below) explains sinkhole formation, but there’s more to consider with development and stormwater management.

Karst Talk
Weak acids dissolve karst, CaCO3. Karst refers to topographic features where the subsurface is dissolved by surface or groundwater. This leaves large openings that allow water to move very quickly through the material. Karst is not unique to Florida and can be found in many parts of the US and around the world. Karst topography and sinkholes are naturally occurring.

Infiltrated rainfall leaches organic acids from surface that naturally dissolves Florida karst. Acid rain can accelerate this. Eventually, voids develop and overlying soil is not supported, collapsing at the surface. In well drained, undeveloped landscapes infiltration occurs across the entire area, uniformly except in low lying areas. When urbanized, runoff is conveyed from impervious areas commonly into dry infiltration basins. Several times more water is now infiltrating through the bottom of the basin, compared to before the area was developed. The acids in rainfall or from the landscape are focused in a much smaller area, accelerating dissolving CaCO3. Increased infiltration volumes also accelerate erosion of overlying soils as the karst void develops.

Sustainable Solutions

Sinkhole in Land O' Lakes, FL - Summer 2017 (image via NYT)

Sinkholes are often ‘fixed’ by filling them with concrete to stabilize the soil and geology below. Green infrastructure (GI) and low impact development (LID) distribute infiltration in developed landscape, using it more effectively. Examples of GI & LID: permeable pavement, bioretention, swales, cisterns, downspout disconnects, and infiltration trenches. Several local governments have incorporated LID practices into recent updates to stormwater programs. The water management districts are generally in support of it as well. The big hurdle is mainstreaming it into the engineering and design process. The first step in that direction is showing examples of these types of practices and projects where they not only perform well, but are cost effective, and easily maintained, compared to the conventional approach to land development.

Green infrastructure examples

We will be putting out a new series of EDIS documents and short videos that cover individual practices in the next few months. We are also working with developers to implement LID and green infrastructure into their projects, and evaluating the effectiveness of these practices. In the future we expect to offer continuing education for engineers and landscape architects on these subjects. UF/IFAS works with developers, government officials, and researchers on solutions for a more sustainable Florida future.

My Week with the Irrigation Industry: An E3 Report Back

By Justice Diamond

Experience, exposure and education are the three tenets of Irrigation Foundation’s E3 Learner Program. This is accomplished by inviting selected students to take part in a week of course work and networking during the annual Irrigation Show and Education Conference. 2017’s E3 Class included 28 students and 2 instructors from 17 states. IrriGator asked UF-ABE masters student Justice Diamond to report back on his E3 experience in Orlando, Florida.

E3 Learner Justice Diamond and industry reps 

My focus

The focus of my graduate work is to develop best management practices and deliver those to farms throughout the Suwannee and lower Suwannee basins in North Florida. What I’m working on specifically is to develop an app for irrigation scheduling for corn.

Suwanne River Basins (USGS)

My advisors Drs. Migliaccio and Dukes encouraged me to apply when they saw the opportunity arise and I went ahead and applied. The courses I selected for E3 were Landscape Water Management and Planning and Center Pivot Design. I’m really interested in Center Pivot technology and was especially looking forward to learning more about that.

The Big Week

My E3 experience was very positive. The highlight of the week for me was getting to know other people - having conversations about what they’re doing, the research they’re doing, and having conversations with people in the industry about how they perceive what the industry is going to look like in the future and what they want out of students. 

An informative day two with E3 Learners enrolled in Center Pivot Design course #IrrigationShow pic.twitter.com/EqKev11c82

— UF/IFAS IrriGator (@IrriGatorUF) November 7, 2017

The least enjoyable part was how long classes were. The teachers were very good, but with an eight hour class there actually isn’t a lot of time to go see the exhibits and I think that part could be condensed. Nevertheless, having an in depth discussion with someone who lives and breathes center pivots I learned a whole lot more. In that sense it was very educational.

Sponsors like The Toro Company ensure the success of the E3 Program

Takeaway

Thank you to the Irrigation Foundation for the opportunity to participate in E3. Meeting people who are all about irrigation, it can only benefit me because that’s what I work with, too. I can only learn and grow from their experiences. My advice to eligible students in 2018: definitely apply! There’s nothing you can lose from the experience and you’ll only learn and meet people who will help you out in the long run.