May 13, 2020

"Drought-fueled" flood?

Drought and flood are usually ...

Two opposite extremes.

The unusual flooding, as seen looking south
of the Tamiami Trail near Everglades City

Not this year:

Thanks in part to the depth of the drought ...


A strong south wind pushed a high tide high into what is normally freshwater marsh.

2 comments:

Gohydrology said...

Question by email: Hello, Is the saltwater intrusion dangerous to the natural makeup of the ecosystem in that particular area? Does is it pose threats to drinking water in that area? And lastly, does this drought-flood interaction seem like a scenario that may become more common due to climate change? Thank you.

Gohydrology said...

Answer:

Hello, and thank you for your questions.

To be sure, that is a transition zone, so it is an area that receives a mix of freshwater and tidal sources of water. In the area that got the slug of coastal water is also the portion of Tamiami Trail that is closest to the coast. Plus, it is an area where the freshwater lens is shallowest, event during the wet season. That being said, more and more the saltwater arm of the equation is making itself known in that area, and in doing so, playing a greater whole in the geomorphic, floral and faunal composition of the area. We see this in any number of ways, and ways that evade our grasp. Geomorphically, there has been an increase in pocking of the landscape, as caused by saltwater killing salt intolerant plants and their roots, leaving holes behind that are filled with water and expand into one another. The death of freshwater tolerant fish is seasonal, and talapia will move back in, but the seesaw seasonal flip flop and long term trend definitely is changing the ecological flavor of the area. A long-time fisherman in the area has recounted to me a story when he used to catch epic large mouth bass in the New River headwater pools decades ago that have all but vanished due to the seasonal pulse of saltwater. There are still bass there in the summer, just not as big as a result. As to the threat to regional freshwater, in my mind that is the solution. Once Picayune Restoration is complete and if we manage any semblence of success on resuscitating flows from OK Slough to Fakahatchatee and into East Hinson Marsh, we will both expand and attenuate the presence of freshwater on the landscape. This can only help balance the equation in favor of the regional freshwater regime. That goes hand in hand with filling in coastally connected canals whenever we can. And finally with respect to sea level rise, it was a very strong southerly wind and at high tide, which superimposed on the gradual decades-long creep of sea level also has an effect. The surge from Irma was much higher, but because it occurred in the summer when freshwater was present the full affects were muted.

Hope this answers at least some of your questions, which are each much more involved and complex than I could touch on above.

It would be interesting to have a round table of local and regional experts to discuss more.

Thanks again