Community- Ornamental Pond, mitigating storm spillage/overflow
Community- Ornamental Pond, mitigating storm spillage/overflow
(OP)
Hi guys...Firstly I am an EE so my knowledge of this kind of thing is limited.
I'll preface my question with this description of what we currently have in our community to manage storm overflow of a relatively large (approx 300'x150' by 8'?depth) ornamental fish pond.
When (severe) inclement weather occurs it appears, and I assume, that the pond's rising level is mitigated by a riser/overflow pipe connected to storm drain piping and subsequently to a smaller detention pond nearby.
The problem is that the smaller detention pond's also used for storm water (watershed) of the 'typical' surfaces, blacktop and green space and *I* believe that it is sized for the ordinary runoff rate. It always performs flawlessly until the ornamental pond overflows and then the detention pond is overwhelmed and floods private property at lower elevations by sourcing water(and fish) via the storm drain grates at street level, all of which are also connected to the aforementioned detention pond.
It appears to me, and again I'm an EE so I don't know much about this stuff, that this is 'flooding by design'. It appears to intentionally divert the larger pond overflow to lower elevations as a ‘circuit breaker’ without regard to flow rate.
My question(s) is this:
1) Is this the 'typical' hookup to mitigate overflow of an ornamental pond?
2) Am I correct in my assertion that all the methodologies used to size, volumetrically, the detention basin are 'thrown out the window' when making this extraneous riser/storm drain connection to the larger pond?
3) Any other ways that this might be implemented (I think pumps and controls) would be better to divert the overflow to a different detention pond a short distant away under controlled flow rate to share the burden.
I might of course follow up with a couple more questions later...
Oh, and thanks in advance!
I'll preface my question with this description of what we currently have in our community to manage storm overflow of a relatively large (approx 300'x150' by 8'?depth) ornamental fish pond.
When (severe) inclement weather occurs it appears, and I assume, that the pond's rising level is mitigated by a riser/overflow pipe connected to storm drain piping and subsequently to a smaller detention pond nearby.
The problem is that the smaller detention pond's also used for storm water (watershed) of the 'typical' surfaces, blacktop and green space and *I* believe that it is sized for the ordinary runoff rate. It always performs flawlessly until the ornamental pond overflows and then the detention pond is overwhelmed and floods private property at lower elevations by sourcing water(and fish) via the storm drain grates at street level, all of which are also connected to the aforementioned detention pond.
It appears to me, and again I'm an EE so I don't know much about this stuff, that this is 'flooding by design'. It appears to intentionally divert the larger pond overflow to lower elevations as a ‘circuit breaker’ without regard to flow rate.
My question(s) is this:
1) Is this the 'typical' hookup to mitigate overflow of an ornamental pond?
2) Am I correct in my assertion that all the methodologies used to size, volumetrically, the detention basin are 'thrown out the window' when making this extraneous riser/storm drain connection to the larger pond?
3) Any other ways that this might be implemented (I think pumps and controls) would be better to divert the overflow to a different detention pond a short distant away under controlled flow rate to share the burden.
I might of course follow up with a couple more questions later...
Oh, and thanks in advance!





RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Before going to mechanical solutions, it would probably be a good idea to have the existing conditions modeled and seeing if non-mechanical changes (different sized pipes or structures) could be made in the system related to both ponds(this is typically much cheaper to construct and especially to maintain).
It would probably be a good idea to get the local agency responsible for stormwater involved to be sure one doesn't cause regulatory problems.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
The pond is wholly Ornamental. I think you hit the nail on the proverbial head in that this may have been an afterthought. Something like this was mentioned anecdotally by someone else in the community.
Good information, I'll pursue the report if it exists. It is hard to believe that they could have accounted for the fish pond as the detention pond's capacity is, just by sight, about 1/2 to 1/3 capacity of others (about 200) elsewhere in the community that handle 'typical' runoff sans any extraneous connections from ornamental fixtures in the landscape.
Umm, hiring a CE? We’re individuals on the receiving end of this flooding. The HOA operates the fixture so we cannot afford to initiate any studies. Our only hope is to force a defiant HOA to improve on this system by obtaining an injunction to shut the pond down until such time they find a way to manage its overflow/spillage.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Whether he did that right or not, though, depends on the math. Could have done it right, but there's lots of potential things he could have done wrong. Hard to say. Do keep in mind that pond size is a function of watershed area and land cover. You can't say a pond is undersized without analyzing the watershed.
A peer review of the hydro study with a site investigaton might not be too expensive. (Maybe a grand if you can get all the info together) In lieu of that, sharpen your pencil and learn a new profession. Hydrology isn't any less complicated than electrical engineering. You wouldn't (shouldn't) trust me to identify what's wrong with a circuit. Reverse applies as well. In my experience, it typically costs about half as much to engineer a solution than it does to hire a lawyer.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Yes, I thought of the storage of the fish pond itself and the fact that it rises considerably before finally spilling over.
The fact that it floods on average every 3 to four years, and it does cause property damage to private property, seems to suggest that he didn't get it right in my opinion.
Agreed, but you have to have parties that are mutually cooperative to do that. The HOA refuses to discuss at all.
Thanks again.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Regardless if the ornamental pond is part of the flood control system or not, the entire system should be designed to function adequately for a design storm which is much greater than 3- or 4-year rainfall.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Yes, that's what I've intuitively known for awhile....thanks
Well, some probably died but I didn't see any dead fish but all were actually alive, some swimming in pools, at or near my home foundation to the street level where they came from...They seemed to be able to find their way back (probably 1000+ feet) as the water recedes over time, into the larger pond.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
LOL, not quite....I meant that the fish are schooling, in groups, and swimming in about 18~24 inches of water in front of my home and nearly up to the top of the driveway....Hard to explain here but no flooded swimming pools....
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Hmmm, this has me wondering if the HOA made the illegal connection to the detention pond. Maybe an overzealous board member or two taking things into their own hands?
Now you don't want to be responsible for any illegal connections, as you mention you are considering connecting to another pond. You are not suppose to transfer drainage problems to another area and could get sued. There is a design in place somewhere more than likely, a storm drainage circuit network design if you will.
I would first go give an earful to your city or county engineer that you are being adversely impacted and see demand they look into it. If they say it's all private and they are out of it, then you will need to protect yourself with effective legal representation if you are truly being adversely impacted.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
The latest is that the HOA just repaired what they say was a shoreline erosion problem. I'll give them the benefit of the doubt but it seems to me that if it indeed eroded then all the material that comprised the shoreline before is still there within the confines of the pond.
Their contractor just added materials to the pond to produce a higher shoreline boundary, some sort of wrap and lots of stones. They removed no materials from the pond so the pond's effectively smaller in volumetric capacity.....the Community pond's designated, on the County Map (aerial photo), as a DRA in of itself.
But wait, it gets worse yet. I found in the minutes of the "grounds commitee" meeting a comment that states that a SWTMUDD ((Sothwest Water District) technician advised them to run the pond at a higher level to prevent future erosion.
The Community Pond is now in what I call a perpetual flood state as there's several inches of water in the DRA pond at all times now, regardless of rainfall.
So I'm not sure where to go with this from here. I'm going to visit the SWTMUDD to poke around and see if I can't recover the Hydrolgy study/model information but my neighbor and I don't have the wherewithal to hire a CE whereby the HOA has unfettered legal expenses and money (our HOA dues/money)....
Any advice? Perhaps I can post some photos (Aerial) and whatever else I can get my hands on so that I can (hopefully) not look too stupid when/if I need to take this in front of a judge to obtain an injunction.....
Thanks again.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Go down to the County Engineer if you're in the County, or the City Engineer if you're in the City, and ask for a copy. Also, ask for a copy of the final approved civil construction plans for your subdivision.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
But dont assume they are malicious in not cleaning out the bottom of the pond. Unless they have an O&M plan for the pond or an engineer on the board, they simply hired a landscaper to replace the riprap at minimum cost. They probably are not fully aware of the ramifications.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
I'm headed there this afternoon.....
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
They have already referred the matter to their attorney as a result of our insistence that if they don't act then we would seek an injunction. This argument stems from their insistence that we (my neighbor and I) simply need to suck it up and put up with recurrent flooding (every 3~5 years) from their operation of an ornamental fish pond. We asked them to allocate money to study ways to improve on the performance of the drainage system. That request was made long before this recent modification....(read through the entire thread)
Well, no they used an engineering firm, Coastal. Not clear to me if they actually did the shovel work or just consulted because the minutes don't specify.
Curiously, they are 28k over on legal expenses in their budget for this year already. They (HOA) have a propensity to make up for their own bad management by leaning heavily on the association's law firm. They are litigating a grass cutting complaint, a geo-thermal pool heater installation gone wrong and a couple other capital projects gone wrong, mostly due to their own misconceptions and ignorance.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
There are many other solutions here... but all require a Civil experienced in Hydrolology. Good luck.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Make sure you get the FINAL stamped and approved editions of both.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
They (the HOA) did not get the permits and compliance certification(s) needed for the latest modification. The last permit pulled was for the original pond construction in 1996. There's no record of any other permit since.
I asked if it could still be in process and the answer was no given the time involved. They were also supposed to contact 'Compliance' to touch base and notify them of pending work ( a little fuzzy on this though).
They did none of this......The best I can surmise is that they contracted Coastal Engineering for advice and possibly design of the restored shoreline but likely used a GC to intall materials in accordance with what Coastal said.
This is all speculation on my part as they will not even talk to me and refer me to their attorney....
I think I have adequate evidence that they at a minimum modified the DRA (pond) without approvals and at the most did so that places myself and my neighbor at increased risk.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
By operation do you mean instructions on levels to operate and instructions not to exceed, and so forth?
As an aside, I did verify that the frequency is supposed to be 100 year interval.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
http://dnrc.mt.gov/wrd/water_op/dam_safety/dam_own...
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Does this mean that the frequency of storms, worst case, that would produce a failure of the storm drainage system, by whatever means, is defective and below design expectations?
Would a flood frequesncy of 4~6 years constitute a failed system?
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
yes, 4-6 years would not be acceptable anywhere that I know of
100-year recurrence interval rainfall is used for 100-year design and a 100-year design should not fail in a 100-year storm.
http://en.wikipedia.org/wiki/Return_period
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Just a couple curious questions about these 3 to 6 yr events:
1. Are any structures being inundated with surface water on your property?
2. If not, what is the elevation difference between the flood water surface and the lowest floor of your home (i.e., depending on your home's construction: top of slab on grade, crawl space lowest floor, or basement floor?
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
We are generally concerned with sinkhole damage, foundation probelms, driveway/cars, and the never ending dead lawn (cost me $1200 to replace the last time) as sometimes it takes days for the water to recede...Oh, and the flood water blocks our entry/exit from the property.
I've been reading through all the documentation I copied (it's all on microfishe and I had to do all the work copying) and some of it is illegible but the best I can surmise is that the expected 100 year rainfall is approximately 13".
I've been searching trying to find any mention of the Fish pond's calculated self storage but no mention. I probably don't know what to look for.
I'm also curious as to how the level of the pond is set and if there was a specified depth during design...
I still need to visit the South West Florida Water Mangement District office (SWFWMD)and find out what the process is supposed to be for modifications to an existing Pond.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Background: In civil design there are two storm events to accommodate in subdivision design, the Minor and Major (100yr) storm events. There are certain restrictions on the Minor storm event design, such as you typically can not allow runoff to overtop the curbs, and that subsequently dictates the placement of the street inlets. The Major storm can run deeper down the road, 12"-18" deep depending on local criteria, but structures always have to be kept safe with adequate freeboard above the Major event flood levels.
Across the country the Minor storm event ranges from the 2 though 10 year events by jurisdiction. So the storms you mention are close to your Minor event.
Don't worry about researching the pond volumes and hydrology, you're not qualified, waste of your time, your layman opinion won't be considered in that area. What you can do is build your case that an unauthorized alteration was made to you subdivision's storm detention pond system and it is adversely impacting you. Maybe they changed the grading tributary to your lot also, increasing the tributary area and possibly increasing the runoff you receive.
You need to be able to honestly say, before reasonably going forward with this, "I never had these problems until after the unauthorized alterations occurred".
So build the preponderance of evidence like you have started (you mentioned no authorized permits since 1996, etc.) for arbitration with the HOA and your attorney, or if that fails, convincing the judge you have been adversely affected.
In your favor:
"the flood water blocks our entry/exit from the property"
The runoff depth within the right-of-way should not be deeper than 6" (no curb overtopping) for these order of magnitude Minor storm events.
Not in your favor:
"and the never ending dead lawn (cost me $1200 to replace the last time) as sometimes it takes days for the water to recede"
Unfortunately, this is not in your favor when considering Minor storm events. A properly grade lot should adequately drain the volume created by these storms. This reflects possible poor grading (ponding) on your lot due to original poor grading of the lot, or landscaping detrimental to the approved lot grading. i.e.,
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Thanks for that posting as it gives me some much needed perspective. The flooding, at the street level, is near 20~24" as best I could measure it from ground level near my mailbox and close to the storm drain grate.
The lawn area is covered from this same flood water but absolutely is not due to grading because the water is sourced at that point from a street storm grating and travels uphill onto to my property (against a very steep grade).
My property slopes from my garage door to the street level (where the grate is) about 2 feet over approximately 25ft. It is rather steep. The adjacent lawn areas are covered in flood water all sourced from the grate.
It's difficult to visualize this but I'll try to clarify further. The DRA is near the back of my home. The larger fish pond is even further back behind my home on the other side of a main road. The storm drain pipes are under the road to the DRA.
The street in front of my home is the lowest elevation and the street storm drain inlet (outlet in this case) is at the curb level to the left side of the end of my driveway.......
Since water seeks its own level, the DRA assumes the level of the far away pond and begins to fill the DRA. At this time the storm connection that attaches this DRA to the my street storm drain grate sources water to the street (lowest elevation)....Phew, wish we could post pictures......
P.S. I'll post a picture to my Flickr account and hopefully you can see what I mean.
I'll post the link here.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Hope it works this time because I don't know how to edit on this site, LOL.....
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
"The street in front of my home is the lowest elevation and the street storm drain inlet (outlet in this case) is at the curb level to the left side of the end of my driveway......."
Oh... I get it now. I should have read more closely up earlier in the thread..
You are at the low point, or one of the low points, of your subdivision, yes?..Lucky you having all the fun!
Yes, that is too deep for the Minor storm event range at the gutter flowline in front of your home...Too deep for the Major event!! Reference my post above on flow depth criteria.
So this is a problem sourcing out of the public right-of-way, adversely impacting your property. This is a driver safety issue also.
So take your pictures, and pictures of your depth measurements wearing your waders if you have them, down to your City/County engineer and file your complaint.
They may have sewer maintenance issues and/or other system problems. They will need to work backward from this problem location at the storm grate in front of your home.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
How many inches of rainfall was storm Debby in your area?
How many times have you experienced this type of flooding over what time period?
How old is your subdivision?
May be a developer/developer's engineer issue here from what I am seeing...
Warning: This could get interesting. For example, I just finished a 5 year $42 million subdivision structural, grading and drainage repair job. The subdivision was about 5 years old.
We worked for the developer's insurance who was sued by the homeowners and HOA. The attorneys like to bring everyone to the party during the litigation process part of the project >>> The City did not really want to deal with us too much. They were worried about being brought in because they approved the plans..
I am part of an experienced team of forensic engineers that specialize in this type of work. We are civils, geotechs, structurals, geoscientists, mechanicals (and attorney colleagues)ready if you need to go that route. We not only did the repair designs, but supported the attorneys with copious analysis and court exhibits.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Read more: http://www.foxnews.com/weather/2012/06/27/florida-..."
I just quickly searched and read a little about the accounts of Debby. Probably not a good reasonable example for your case. (Hey, that's Florida?
However, if the street flooding criteria is consistently being exceeded for Minor storm events, that would be the strength of your case.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
The subdivision is 10 years old and the frequency of flooding is about once every 3 years (three former flood events like this).
If you look at the aerial photo you can see that the Fish pond's connected to the same DRA that my street, Mistwood Ct. is connected to. What's not apparent is that this same DRA services part of the Wexford Ave (main road) as well.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
I alluded to this above.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Option B would be a stupid design, but I have seen things like this done in the past...
Get the storm drain as-builts from the city and take a look at the details.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
For now I want to sincerly thank all and have a Merry Christmas. See you in January!
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
The design of these ponds would have been governed by the SWFWMD Basis of Review:
https://www.swfwmd.state.fl.us/files/database/site...
Chapter four covers water quantity discharge criteria. The peak discharge mitigation requirements are NOT the 100 year storm, they're the 25 year storm, since you're presumed to be evacuated for anything larger than that anyway, and watching your home on TV from the comfort of a Days Inn in Valdosta. The 100 year storm only kicks in if you're in a closed basin, meaning it doesn't eventually discharge to the ocean. (lots of places like that around Lakeland FL, hence the name) And even then, that criteria is to match runoff volumes, not rates. You're still held to the 25 year rate, or sometimes a unit area rate established by the district, with either a 100 year volume match for closed basins, or no volume match for open basins.
You do have to do a 100 year flood analysis, but that's not to set discharge rates, it's to set minimum FFEs. There are rules about not flooding out your downstream neighbors, but those rules are presumed to be met if you can show a pre/post match for the 25 year storm. I do not recall whether SWFWMD requires a "Glass Box" analysis, but I've done those quite a bit in SFWMD, and for those you drop the 100 year storm on your site with zero discharge, presuming the entire site acts as a pond with a glass wall at the property line, and you see how high the site stages up, setting FFEs above that. (and ensuring that's no higher than the FIRM elevation) The intent is to design for a case very similar to your photos. If I saw those photos out of a site in Naples or Miami (SFWMD) after a hurricane I'd say it was performing as designed!
The most likely source of this flooding in SWFWMD style engineering designs is the prior engineer did not properly account for variable tailwater on the system. You need to hire an engineer to review his model, which was probably in ICPR, to check his tailwater rating cuves / etc. Doubtful the District is willing to do this for you, considering they already approved the permit. Where the District may help you is if the HOA has done things to the pond post-permit that are impeding its performance. Certainly go to them, but don't expect them to overturn an ERP they've already issued without an engineer giving them good reason.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Whoa! You slow down there big fella
You are getting all excited about Major design event volumes. We've already ruled (best you can in this forum without actually doing the work) he is not being flooded in the Major storm. Look at the pictures of Debby also.
He states his street, driveway and lot frontage are being flooded deeply frequently. That's why I advised him about how Minor storm criteria is the more restrictive criteria regarding street flooding performance for his perspective. I gave him Minor storm event street flooding design criteria for reference.
Also, remember to a layman, the Minor storm design events, such as the 5yr storm design event which has an exceedance probabiltiy of only 20% in any given year, is going to look like a small flood, with the street full and water surface out to the crown per that Miami-Dade criteria.
The flooding should not be at the depths as frequently as he is reporting. Something is up with design and/or maintenance that an engineer needs to review.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
It's hard to tell where the primary control is from his diagram, but it appears that his inlet and the fish pond both drain to "DRA," and that "DRA" drains out of the project. "DRA" is highly likely to be a combination detention and retention pond, with a retention volume at the invert that either bleeds down through a bleeder orifice (not true retention) or infiltrates into the ground. Should say in the BOR linked above, but I think the recovery time is 72 hours for dry retention systems in SWFWMD, which would explain why it's still wet "48 hours after the storm" in the photo above. That's probably by design.
I'd bet that the primary control at DRA is either a slot or an orifice set at this retention volume, with an overflow weir above that, perhaps in a weir box. I'd further bet that the design screwup came in one of two very easy forms:
1) Civil Engineer forgot to check the elevation of the culdesac inlet vs the 25 year stage when sizing the pond, or
2) Contractor ran out of fill dirt when building the thing, and set his culdesac lower than it was intended to be in the design.
I have seen both happen before.
A third option, which is much simpler, is that the primary control is clogged. 457 should walk out to DRA and stand on the outlet control box, and site to his house - to see whether the top of the box coincides with the flooding elevation he's experiencing in the street. He should also see if some pesky critters haven't clogged up the primary control with sticks or what-have-you. Weir boxes in FL typically have a wooden baffle out in front of them to catch floatables, but they might not stop everything.
For what it's worth, Screwup Possibility (1) should be a pretty easy thing for even a EE to check (grin) if he's got the hydro report in hand. Find the 25 year design stage of the pond, and compare that to the rim elevation of your inlet in the culdesac. Post both numbers in the thread.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
Just FYI: From the isopluvials that would be in the 50 to 100 year range for SW Florida.
Anyway, to address his frequent flooding due to his reports about surcharged flow reversals coming from the pond and up out of that gutter drain grate in front of his house, it may be as simple as installing a flap gate on the end of that storm sewer run on the end that discharges into the pond.
That hydrograph from the short storm sewer run would more than likely beat the hydrograph peak of the detention pond system, making this a viable solution.
RE: Community- Ornamental Pond, mitigating storm spillage/overflow
As I say, the name of the game in Florida is tailwater and interconnected pond routing.
SFWMD FIRMs are hilarious, if you've never seen one. It's one big grey blob with a flood elevation number in the middle of it.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com