Current flooding in Missouri and Arkansas bring back memories of 2008 for Iowans. Let's take a look at the latest management planning advice.
(June 12, 2017) - Watching national news this week has been painful for many, but, if you live in Cedar Rapids, Iowa City or any of the riverfront towns in Eastern Iowa, it's been kind of a PTSD moment. Our poor neighbors to the south are experiencing the kind of flooding we went through in 2008; arguably on an even larger scale. We've seen shots of rivers lapping up near the bottom edge of freeway signs and rising many feet above the foundations of homes and businesses throughout Missouri and Arkansas. Our flooding cost us dearly, both in financial and emotional terms. Many businesses never recovered and more than a few of our neighbors were forced to permanently leave.
Iowa has done a lot since 2008 to improve our odds of surviving a similar event. Cedar Rapids, in fact, dodged a bullet earlier this year thanks to planning and quick action on the part of both citizens and city government. The process here is ongoing, which suggests it might be a good time to look at what has been learned in the years since.
The growing trend toward urbanization (yes, even in Iowa) is one of the biggest changes that affect planning. Increased urban developement adds impermeable surfaces like streets, parking lots, sidewalks and driveways, contributing to run-off. It's currently estimated that only 15% of rainwater sinks into the ground. With rain events trending toward increased amounts of precipitation with each storm, this amplifies an obvious problem.
Beyond flooding, heavy storms are problematic because they can frequently overwhelm water treatment facilities, causing a release of untreated sewage. Untreated stormwater is itself an issue, since runoff contains pollutants in the form of industrial chemicals, fuels, sump oil, heavy metals, fertilizers and more. Some estimates say that rainwater runoff may account for as much as 50% of pollutants that flow into rivers and onto beaches in urban settings. (http://www.emag.suez-environnement.com/en/stormwater-management-2413)
The world is employing many approaches to mitigate these effects. In China, for example, the concept of "Sponge Cities" has gained traction. In short, this approach works to both reduce the number of impermeable surfaces introduced and include things like urban farming, gardens, collection (for use in various 'gray water' strategies).
In Europe, there has been a marked increase in the use of rooftop gardens and 'green' roofs as a means to hold rainwater and reduce run-off. This has been shown to be effective in reducing the impact on treatment plans after a storm as well as reducing the acid content and removing excess nitrogen.
Many places are actively seeking to work with surrounding rural areas to re-establish flood plains. By allowing rivers to flood unpopulated areas, the immediate impact on cities is significantly reduced. For obvious reasons, this results in some tension between cities and agricultural areas, but can be beneficial to both with careful planning and good communication.
There are a lot of places that are either implementing or considering changes to infrastructure to separate rainwater from sewage in underground systems. While this alone doesn't address the problems with run-off content, it does prevent storm-related sewage releases.
One of the more aggressive (and effective) methods being used in discrete developments is the installation of water attenuation and infiltration systems. Tanks (that may include side filtration panels) are installed underground to both slow and filter run-off. Many units are modular and can be linked together to meet the needs of the area they are in.
Cities are also upping their efforts to keep current sewer systems clean and flowing freely. A system that's clean works better and makes all water management easier.
All of these developments are in addition to the construction of permanent physical barriers that protect property, improved forecasting and monitoring, and thoroughly thought-out action plans to address needs as they arise. Eastern Iowa has seen improvements in all of these areas.
MMS Consultants, Inc. provides professional civil engineering and land surveying services — from simple property surveys to complete design and construction management. Since 1975, the firm has successfully completed nearly 40,000 municipal improvement and private land development projects throughout Eastern Iowa.
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