The most difficult part of maintaining urban streams is to sustain a stable cross-section and profile with a flow regime that is haywire....i.e. incredibly flashy. Streams downcut and downcut with the additional water created by impervious surfaces. Its important to recognize that we use detention or retention ponds to "meter" these flows...but most are for flood control not stream quality. In other words, they meter huge storms. The 25-year is the standard in this Ohio county. The Ohio EPA requires all new development to detain a "water quality volume" that has been gauged to maintain channel quality. This is part of my job. Other more
stormwater diligent states such as Maryland require the detainment of multiple volumes such as the "channel protection volume" and usage of the "critical storm method". The Crit storm method is in a way based on Rosgen methodologies, essentially metering the "dominant discharge", generally a 1-2 year storm. These methodologies are aimed-in-limiting the amount of downcutting and widening of stream channels, in addition to settling some of those "first flush" pollutants that come off a site. That whole first flush method is hairy though because of storm sewer routing, you may not actually be capturing that first 1/2 inch of rain that comes off a site.
Research has shown though that regardless of how much we detain, channel quality still suffers with urbanization. The main point is that more water is still being directly transported to surface waters (just takes longer with our pond routing and metering). Essentially rainwater is not being metered through groundwater (either shallow or deep recharge). So I, as a stormwater professional, and following the new paradigm in stormwater management, have been trying to get as much water into the ground as possible through reviewing new development plans. Limiting impervious area, sand filters, bioretention, treatment swales, etc.
True- water quality is always an issue too, especially in urban areas. A common error with municipal folks, developers, etc is that they think ponds remove a lot of these pollutants. Well, they do remove some suspended solids. This is limited to very coarse material though. If you take Stokes Law, under laminar (non turbulent) flow conditions, I have figured it takes-in-least 7 hours to settle the largest piece of silt 14 centimeters. So, essentially your able to settle sands and not clay or silt. Unless the smaller sediments are still cohesive clods. Soluble stuff zips through however, especially in detention ponds that drain all the way.
A big water quality problem in Toledo is CSO, combined sewer overflows, where if we get 1/2 inch of rain or more, the "combined sewers" (sanitary and storm) overload the system and raw waste gets dumped directly to our urban streams. Yucky stuff.
Sorry for the long post, but I had to chime in.
Jeff
Dave Neely <rheopresbe-in-hotmail.com> wrote:
...so this morning I dragged some gear out to a small nature center here in
St. Louis to do a fish inventory as a favor for a friend. The center is
nice, and doing some really neat stuff with native plants, but happens to be
along a heavily degraded urban stream. The stream was clear, and flow was
extremely low (~ 0.5 cfs). Substrate included some nice cobble, chert
gravel, silt, and intricately shaped bedrock; sparse mud/clay in deeper
pools. There were some sparse patches of Justicia and a lot of funky greyish
algal mats (I don't even want to think about what the fecal coliform levels
were like). We rounded up a grand total of seven species, not including a
bullfrog and a large snapping turtle. The list was a who's-who of tolerant
taxa - central stoneroller, red shiner, fathead minnow, creek chub, white
sucker, green sunfish, and bluegill. No darters, no fun minners, not even a
silly bullhead!! The banks were blown out to-in-least 2 m higher than the
water level, and there was recent flood debris even higher. Outside curves
were scoured clean, with a lot of bare mud. Not the worst I've ever seen,
but certainly not good.
When you're constrained by only having access to a bit of downstream area
along a creek, how can you expect to make any meaningful restoration to a
stream channel? Yeah, you might be able to stabilize the banks a little, but
only if you can get stuff growing between storm events. Even if you do,
what's the point of having perfectly Rosgen-balanced channels when your
water chemistry is totally screwed up? How do you fix water chemistry when
50% of your upstream watershed is impervious surfaces - shopping malls,
highways, and asphalt parking lots? Seven species is a lot when you consider
this stream probably gets a 20 degree temp shock with every midsummer storm
event. We managed to do a fun little show for a couple of school groups who
happened to be touring the grounds, but I'm just depressed and a little
angry. The contrast between the really nice nature center and the crappy
stream was just too stark. Systems like this aren't going to get fixed on a
timescale that's reasonable to any of us, and certainly not on the
mythological EPA "swimmable waters" timescale.
Sorry to be so down. One thing's for sure - playing in that cesspool today
will certainly make me appreciate the crystal streams of the 'Zarks next
month that much more...
cheers,
Dave
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<DIV>The most difficult part of maintaining urban streams is to sustain a stable cross-section and profile with a flow regime that is haywire....i.e. incredibly flashy. Streams downcut and downcut with the additional water created by impervious surfaces. Its important to recognize that we use detention or retention ponds to "meter" these flows...but most are for flood control not stream quality. In other words, they meter huge storms. The 25-year is the standard in this Ohio county. The Ohio EPA requires all new development to detain a "water quality volume" that has been gauged to maintain channel quality. This is part of my job. Other more</DIV>
<DIV>stormwater diligent states such as Maryland require the detainment of multiple volumes such as the "channel protection volume" and usage of the "critical storm method". The Crit storm method is in a way based on Rosgen methodologies, essentially metering the "dominant discharge", generally a 1-2 year storm. These methodologies are aimed-in-limiting the amount of downcutting and widening of stream channels, in addition to settling some of those "first flush" pollutants that come off a site. That whole first flush method is hairy though because of storm sewer routing, you may not actually be capturing that first 1/2 inch of rain that comes off a site. </DIV>
<DIV> </DIV>
<DIV>Research has shown though that regardless of how much we detain, channel quality still suffers with urbanization. The main point is that more water is still being directly transported to surface waters (just takes longer with our pond routing and metering). Essentially rainwater is not being metered through groundwater (either shallow or deep recharge). So I, as a stormwater professional, and following the new paradigm in stormwater management, have been trying to get as much water into the ground as possible through reviewing new development plans. Limiting impervious area, sand filters, bioretention, treatment swales, etc.</DIV>
<DIV> </DIV>
<DIV>True- water quality is always an issue too, especially in urban areas. A common error with municipal folks, developers, etc is that they think ponds remove a lot of these pollutants. Well, they do remove some suspended solids. This is limited to very coarse material though. If you take Stokes Law, under laminar (non turbulent) flow conditions, I have figured it takes-in-least 7 hours to settle the largest piece of silt 14 centimeters. So, essentially your able to settle sands and not clay or silt. Unless the smaller sediments are still cohesive clods. Soluble stuff zips through however, especially in detention ponds that drain all the way. </DIV>
<DIV> </DIV>
<DIV>A big water quality problem in Toledo is CSO, combined sewer overflows, where if we get 1/2 inch of rain or more, the "combined sewers" (sanitary and storm) overload the system and raw waste gets dumped directly to our urban streams. Yucky stuff. </DIV>
<DIV> </DIV>
<DIV>Sorry for the long post, but I had to chime in.</DIV>
<DIV> </DIV>
<DIV>Jeff<BR><BR><B><I>Dave Neely <rheopresbe-in-hotmail.com></I></B> wrote:</DIV>
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">...so this morning I dragged some gear out to a small nature center here in <BR>St. Louis to do a fish inventory as a favor for a friend. The center is <BR>nice, and doing some really neat stuff with native plants, but happens to be <BR>along a heavily degraded urban stream. The stream was clear, and flow was <BR>extremely low (~ 0.5 cfs). Substrate included some nice cobble, chert <BR>gravel, silt, and intricately shaped bedrock; sparse mud/clay in deeper <BR>pools. There were some sparse patches of Justicia and a lot of funky greyish <BR>algal mats (I don't even want to think about what the fecal coliform levels <BR>were like). We rounded up a grand total of seven species, not including a <BR>bullfrog and a large snapping turtle. The list was a who's-who of tolerant <BR>taxa - central stoneroller, red shiner, fathead minnow, creek chub, white <BR>sucker, green sunfish, and bluegill.
No darters, no fun minners, not even a <BR>silly bullhead!! The banks were blown out to-in-least 2 m higher than the <BR>water level, and there was recent flood debris even higher. Outside curves <BR>were scoured clean, with a lot of bare mud. Not the worst I've ever seen, <BR>but certainly not good.<BR><BR>When you're constrained by only having access to a bit of downstream area <BR>along a creek, how can you expect to make any meaningful restoration to a <BR>stream channel? Yeah, you might be able to stabilize the banks a little, but <BR>only if you can get stuff growing between storm events. Even if you do, <BR>what's the point of having perfectly Rosgen-balanced channels when your <BR>water chemistry is totally screwed up? How do you fix water chemistry when <BR>50% of your upstream watershed is impervious surfaces - shopping malls, <BR>highways, and asphalt parking lots? Seven species is a lot when you consider <BR>this stream probably gets a 20 degree temp shock with every
midsummer storm <BR>event. We managed to do a fun little show for a couple of school groups who <BR>happened to be touring the grounds, but I'm just depressed and a little <BR>angry. The contrast between the really nice nature center and the crappy <BR>stream was just too stark. Systems like this aren't going to get fixed on a <BR>timescale that's reasonable to any of us, and certainly not on the <BR>mythological EPA "swimmable waters" timescale.<BR><BR>Sorry to be so down. One thing's for sure - playing in that cesspool today <BR>will certainly make me appreciate the crystal streams of the 'Zarks next <BR>month that much more...<BR><BR>cheers,<BR>Dave<BR><BR><BR>/-----------------------------------------------------------------------<BR>/ This is the discussion list of the North American Native Fishes<BR>/ Association (NANFA). Comments made on this list do not necessarily<BRhttp://www.nanfa.org
Please make sure all posts to nanfa-l are<BR>/ consistent with the guidelines as per<BR>/ http://www.nanfa.org/guidelines.shtml To subscribe, unsubscribe, or get<BR>/ help, visit the NANFA email list home page and archive at<BR>/ http://www.nanfa.org/email.shtml<BR><BR></BLOCKQUOTE><p>
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/-----------------------------------------------------------------------
/ This is the discussion list of the North American Native Fishes
/ Association (NANFA). Comments made on this list do not necessarily
/ reflect the beliefs or goals of NANFA. For more information about NANFA,
/ visit http://www.nanfa.org Please make sure all posts to nanfa-l are
/ consistent with the guidelines as per
/ http://www.nanfa.org/guidelines.shtml To subscribe, unsubscribe, or get
/ help, visit the NANFA email list home page and archive at
/ http://www.nanfa.org/email.shtml