This document discusses three key factors for effective flood mitigation: upstream storm-water detention, channel flow enhancement, and levee height. It provides examples of potential projects involving installing water gates and adjusting dams to allow for temporary storm water storage and better management of flood crests down a river basin. Converting dams to adjustable structures could help manage flood heights by functioning as valves along a river.

1. The Most Effective Flood Mitigation
Is A Blend of 3 Factors:
 Upstream Storm-water Detention
 Channel Flow Enhancement
 Levee Height
Created by
Clark Rieke
319 521-5212
crieke@mchsi.com

2. These 42 mini-watersheds in the 26 sq. miles
of Palo’s Dry Creek Watershed demonstrate
potential locations for 42 watergates,
many of which would only
have to be 4’-8’ high.

3. This is an
example
of an
experiment
in water
gate
design.

4. This is an
example of an
experiment in
water gate
design in a
10’x8’
concrete
culvert just
outside of
Palo, IA.

5. This channel between Shaver Rd. and the Cedar
River can become the site for experimenting with
different water gate designs.

6. This creek bed
has significant
temporary
storm-water
storage capacity
if water gates
are installed in
front of these
concrete
culverts under
I-35 west of
Swaledale, IA

7. Big Marsh in
Butler County
along the west
fork of the
Cedar River is
4400 acres. Its
concrete culverts
with partial
water gates
gives it potential
as a temporary
low-cost stormwater storage
site.

8. The McCloud’s
Run and its
watershed in NE
Cedar Rapids
runs along I-380
and could be
used for
Upstream stormwater detention.

9. Water gates in
front of these
three culverts
would make
McLoud’s Run
basin a
temporary
storm-water
detention site.

10. A water gate in
front of this
culvert makes
the ditch
alongside the
railroad tracks
parallel to
McLoud’s Run
a temporary
storm-water
detention site.

11. Waverly, IA is
replacing its concrete
dam with this 99%
adjustable dam
because this dam,
with a channel flow
restriction of only 1%
when it is down, will
reduce future flash
flood crests by 2 feet
and also has
potential use as a
valve in the river
after the crest
passes.

12. Dam in Nashua, IA,
with large
reservoir/lake
needs to be
adjustable so the
reservoir can be
emptied before a
flood crest comes
to this city as it
progresses down
the river basin.

13. This is an
example of
adjustable
gates in a
dam in
downtown
Cedar Falls.

14. If all the many dams throughout the Cedar River
watershed were converted to adjustable dams,
they could be used as valves to manage the
height of a flood crest.

15. This bridge in downtown Cedar Falls demonstrates a
design that does not restrict the river channel’s flow.

16. Both ends of the Cedar Rapids
5-in-1 Dam restrict the river’s channel.

17. This is a
photo of the
hydroelectric
plant that
currently
blocks the
Cedar River’s
flow at this
gate in the
5-in-1 Dam.

18. The
hydroelectric
plant at the
5-in-1 Dam
restricts
channel flow
in one of the
10 gates.