Allegheny Land Trust
Helping local people save local land

Flood Prevention - Preventing Rainwater from Becoming Storm Water in Our Streams and Floodwater in Our Streets

By Roy Kraynyk, Executive Director, Allegheny Land Trust

From a presentation to the University of Pittsburgh Institute of Politics, Water Resources Task Force during their September 6, 2007 Chartiers Watershed Bus Tour Stop at Wingfield Pines Conservation Area, Upper St. Clair, Allegheny County, PA

We need to spend more time and more money on how to prevent floods from happening by preventing rainwater from becoming storm water.  We need an approach that emphasizes flood prevention strategies, not just flood control strategies.  Flood control is necessary, but it's an "end-of pipe" solution that tries to mitigate a problem after it is created.

We need to think upstream figuratively and literally.  In fact, we just need to think up—straight up—into the clouds and start thinking about how to treat that pure raindrop of water falling to earth BEFORE it commingles with a zillion others into a rioting mob of polluted storm water in our streams.

I would like you to think about prevention and remember: an once of prevention is worth a pound of cure.

To illustrate that point please look over at that sign that indicates the high water mark left from Hurricane Ivan.  If you were in those seats almost three years ago to the day your heads would be barely above water.  We estimated there were 50 million gallons of water stored here during Ivan.  That's 50 million gallons that didn't make it to Bridgeville, Heidelberg, Carnegie and other downstream communities devastated by the flood.  These communities endured $60 million worth of damage.  If Wingfield Pines was developed with houses as permitted under local zoning, that number would have been higher because all would have been lost under 15 feet of floodwater.  Since Wingfield Pines was not developed there were no economic losses, no insurance claims were filed, no federal, state or county funds were necessary to "bail out" the property or property owners.

Based on what ALT paid for Wingfield Pines, that 50 million gallons were stored here for about $0.01 per gallon.  ALT paid, in round numbers $500,000, which we raised from foundations, the local community and a grant from DCNR.  I challenge any engineer to design, construct and maintain a detention facility to hold 50 million gallons of water for $0.01 per gallon.

This is what I mean by prevention.  Conservation of Wingfield Pines prevented additional damage downstream.  It is hard to calculate how much, but for those residents and business owners who watched the floodwater creep up their steps that night every inch mattered.

Woodlands and floodplains are the region's water management system

Floodplains like Wingfield Pines and their companion wetlands are acknowledged nationwide as providing valuable environmental functions, wildlife habitat and recreational opportunities.  Regulating and protecting them is almost universally accepted for these reasons.  However, let's not be lulled into a false sense of security just because floodplains and wetlands are regulated and protected.

We need to turn our attention to another landscape feature that is prevalent in our region and almost entirely overlooked for the contribution it makes to preventing raindrops from becoming storm water in our streams, and floodwaters in our streets—it is our woodlands.

Last spring, ALT invited Peg Kohring of the Conservation Fund to Pittsburgh as part of ALT's GREENPRINT project.  Peg and her team is working with Milwaukee, Chicago, Kansas City and other cities in the Midwest to find nonstructural solutions to similar water quality and flooding issues we face here in Pittsburgh.  In those cities, land with hydric and porous soils is being mapped and conserved for its water absorbing and purifying abilities.  It wasn't long before Peg, who has a farming and soils background saw our hardpan, clayey soils and steep slopes and said, "You don't have much hydric soils to work with here. . .your woodlands are your hydric soils."

Woodland masses do more to prevent floods than floodplains do because woodlands intercept rainfall before it reaches the streams.  Once water is in a stream and subsequently a floodplain, it's too late.  Floodplains provide the emergency overflow areas.  Woodlands are the water interception and retention areas.

If we can regulate floodplains for their contribution towards flood control, why can't we better regulate woodlands for their contribution to flood prevention?

I want to underscore a few stats on water management function of woodlands from "Not All Green Space is Created Equal", an article from The Journal for Surface Water Quality Professionals:

• Rainfall interception of a lone oak tree can be up to 27% of total precipitation.  This means that up to 27% of the rain that falls on an oak tree doesn't reach the ground.
• Rainfall interception of a forest canopy—this is the canopy catching raindrops and intercepting their route to the ground—ranges from 15% to 40% of annual precipitation in conifer stands, and 6% to 48% in hardwood stands.  We don't have any old-growth forests around here but old growth forests can intercept more than 58% of annual precipitation.
• Total forest interception (meaning tree canopy, under story and ground litter, i.e. fallen leaves branches and herbaceous material) can range from 13% - 76% of total annual precipitation.

Now what happens when these rain absorbing woodlands, that are acting like sponges, are replaced with impervious surfaces, closely clipped lawns and steep highly compacted cut and fill slopes?  Runoff volumes can increase by a range of 6 - 50 times depending on the slope of the ground.

When woodlands are displaced, it's a lose - lose situation.  The watershed loses its natural water interception/detention capacity and runoff is increased.

Woodlands are simply our region's greatest water management resource and need to be treated as such.  Conservation of strategic woodlands needs to be the centerpiece of a multifaceted, inter-governmental, watershed-based flood prevention plan.  Thru coordinated public and private actions steep wooded slopes can be maintained to provide invaluable flood prevention functions.

The riparian thread of responsibility is clear.  Water runs downhill and will forever.

The riparian thread of accountability is not so clear.  How can one municipality knowingly make decisions that will impact downstream neighbors without any accountability?

Summary of problems

Let me summarize a short list of problems as I see it from almost 20 years working in land planning, development and conservation:

1. Municipalities are not cost accounting for the incremental loss of highly functional natural infrastructure like woodlands as development occurs.
2. Downstream communities need to have a say, and perhaps even legal standing, in the land use decisions of upstream communities, especially in the area of storm water management.
3. We desperately need durable economic data that quantifies the economic services provided by highly functional natural infrastructure.  If we had locally based—and I underscore local—compelling and sound economic data to complement the science we are compiling, local governments, who control land use, would have the backing and confidence they need to better regulate highly functional natural infrastructure such as woodlands.

Summary of Possible Solutions

1. The land use and development decisions made by local government can work to reduce or, unfortunately exacerbate the flooding and combined sewer overflow (CSO) problem.  We need to enlist and in some cases educate local government on how to be a key part of the solution, not part of the problem.
2. Storm water detention facilities need to be audited to determine if they are functioning as designed.  The day after detention pits are constructed they begin to fill in with silt losing capacity to hold water.  In ten years how much storage capacity have they lost?  5%?  10%?  Multiply that times the hundreds of detention pits out there; we've lost a lot of storage.  I argue the money spent last month dredging Girty's Run should have been spent dredging detention pits upstream to restore their capacity.
3. The concept of temporary land-banking needs to be explored.  This is banking of developable land in flood prone and CSO watersheds until infrastructure is upgraded to accommodate the additional storm water and sanitary inputs that new development brings.  I personally find it absolutely irresponsible for new construction to be approved knowing that the additional sanitary is being added to a dysfunctional system that pollutes our waterways with raw sewage.  Bank the land until the infrastructure is fixed and then sell the land at appreciated values to help offset the cost of the infrastructure improvements.

Roles

Now I'd like to take a shot at prospective roles for the stakeholders:

For municipalities - simply be part of the solution not part of the problem by. . .

1. Strictly regulating woodland resources especially on slopes exceeding 25%.
2. Prohibit breeching of wooded ridges.  The ridgeline is a highly visible and vulnerable transition zone where the flatter plateau rolls off to the steep slope.  When this zone is denuded of vegetation, runoff is increased and the risk of landslides can increase.
3. Don't subsidize development in the form of tax incentives or even variances in flood prone watersheds and slide prone areas, and don't subsidize development that displaces wooded slopes, ridgelines or woodland masses.
4. Audit detention facilities to determine if they are functioning as originally designed.  Funding could be provided by establishing a centralized Fund that developers contribute to on a project-by-project basis.  Much like a land trust's Stewardship Fund, interest from the fund could support staff to do the audits and monitoring.

For the County

1. Don't subsidize development in flood prone or landslide prone areas.
2. Fund feasibility study of land-banking concept.
3. If feasible, commit seed funding and seek additional funding sources to initiate land banking program.

For land trusts

1. Help acquire key parcels that provide environmental services and are vulnerable to being displaced by development, that would in turn exacerbate existing problems.
2. Assist with land-banking feasibility study and implementation if feasible.
3. Work with local government to audit development for its impact on highly functional natural infrastructure.

Allegheny Land Trust stands ready to enroll strategic land conservation to address the regional threats of flooding, sewer overflows, landslides and the loss of biodiversity and scenic character.

We believe that land conservation of properties like Wingfield Pines and the other 1,350 acres that ALT has conserved is a cost effective and sustainable tool that can address these threats while providing communities with attractive open spaces that enhance property values, provide quality wildlife habitat and places for passive recreation.

Finally, I hope that as you travel throughout Southwestern Pennsylvania, you will look at the surrounding woodlands with a new appreciation for the role they play in our effort to manage our water resources.