1. BASIN and RIVER SYSTEMS Divide Dam at Lake TravisDEM of Trinity River

2. Watershed Parameters  Size  Slope  Shape  Soil type  Storage capacity Reservoir Divide Natural stream Urban Concrete channel

3. 1. Rainfall intensity / duration 2. Size, Slope, Shape, Storage 3. Channel morphology 4. Location of Developments 5. Land use/land cover 6. Soil type 7. Percent impervious Divide Floodplain Reservoir Natural stream Urban Concrete channel Parameters that Affect Response in a Watershed Floodplain Q

4. Divide Floodplain Confluence Channeliized stream Urban Concrete channel Urbanization Effect in a Watershed Urban Effects Increase Peak Decrease timing Q T Natural

5. The Floodplain and Floodway Top Width

6. Watershed Hydraulics Reservoir Floodplain Divide Main Stream Confluence Tributary Cross Sections A B C D QA QA QD QD QC QC QB QB

7. Watershed Topography

8. Flood Control Methods - Structural Objectives  Increase channel flow rate  Decrease flood levels Means 1. Earthen or concrete 2. Swale clearing 3. Gobi mats 4. Gabions 5. Rip-raps

9. Non-Structural - Buyouts Objectives  Manage old and new structures  Minimize future damages Means Relocate old structures Condemn frequently flooded structures Replace storage as areas develop

10. Adding Useable Storage for Flood Control Objectives  Runoff storage controls  Decrease peak flows Means 1. Retention/detention ponds 2. Natural drainage system 3. Runoff catchment areas 4. Reservoirs 5. Dikes and levees

11.  The Woodlands is a 30-year-old totally planned community north of Houston.  Designed to minimize the floodplain and water quality impacts as development proceeds. The Woodlands

12. USE of Storage Reservoirs

13. Guidelines for Planning in an Urban Drainage Basin  Maximize the distance of storm water travel from the site to a collection area or stream.  Maximize the concentration time by slowing the rate of storm water runoff.  Minimize the volume of overland flow per unit area of developed land.  Utilize buffers such as forests and wetlands to protect collection areas and streams from urban impacts.  Divert storm water away from critical features such as steep slopes, unstable soils, or valued habitats.

14. Grogan’s Mill Indian Springs Lake Woodlands Town Center Research Forest Bear Branch Reservoir College Park Cochran’s Crossing Alden Bridge River Walk

15.  The Woodlands planners wanted to design the community to withstand a 100-year storm.  In doing this, they would attempt to minimize any changes to the existing, undeveloped floodplain. The Woodlands

16.  The community was designed as if it were fully developed.  Strict requirements were made about land use and drainage and storage volumes.

17.  More than 33% was designated as open space  There are 3.5 lots per acre in residential areas, or about 20% impervious  Extensive use of roadside ditches Land Use

18.  Designed detention ponds that are both effective and attractive.  Incorporated these ponds into the fabric of communities and golf courses.  Ponds were used to control the volume and quality of urban runoff into Panther Branch. The Woodlands

19.  Most streams and ditches have been left in their natural state, thus increasing their Manning roughness coefficients and their storage capacities.  This drainage system design minimizes the impact of urbanization on the peak runoff response. Channel Design

20.  Another method of controlling the flow rate is placing energy dissipaters in the streambeds.  These are commonly located directly near bridges due to steeper downward slopes. Flow and Erosion Control

21.  Only channelized under the bridges in order to reduce erosion of the banks and the deterioration of bridge structures.  Since this increases the flow rate, structures are built at each end to control velocities Bridge Designs

22.  Urban development designed to complement waterways.  This reflection pool also serves as storage for runoff from local parking facilities.  The concept is to allow for full urbanization but with a minimum environmental impact on the watershed. Urbanization

23. Detention Ponds - Amenities  Ponds constructed so that amenities such as the golf course and other community centers could be built up around them.  These ponds store and treat the runoff from such facilities and also add to the aesthetics of the overall development.

24. Detention Ponds  Community Center -  One of the first ponds built in Texas - 1972  Fountains added for aesthetic value and to increase circulation of air for water quality

25.  Culverts are used to move water under streets.  An attempt is made to blend these culverts in with their natural surroundings. Roadside Drainage

26.  The hydrologic system at The Woodlands was severely tested during October 17-18, 1994, when a greater than 100- year event dropped heavy rains over the area.  The design worked well, with only a few houses impacted.  The same storm flooded 1000s in other watersheds. The Woodlands - a Major Test

27. Amenities  Hike-and-bike trails  Wildlife and habitat  Water quality benefits

29.  Example of how to build an environmentally sound community  70,000 and will reach 150,000 population 2020  Example of a sustainable watershed concept that has worked  Concepts need to be studied and expanded to other areas Conclusions

30. Brays Bayou - Low Flow

31. Brays Bayou High Flow

32. Kissimee River - The Everglades

33. Bull Creek, Austin - CEVE 412

34. San Antonio River

35. California - Temecula

36. I-45 Bridge over Clear Creek - 1979

37. Rice Blvd at Entrance 16 looking west Jeep indicating high water mark - inlet to Harris Gully T.S. Allison - Houston, June 9, 2001

38. Southwest Freeway (US 59) Detention storage between Mandell and Hazard Looking East Looking West

39. Flood Warning Systems Downtown Houston Emergency Response  Flood Doors  Flood Gates  Facility Entrances  Communications  Operations  Training

40. Brays Bayou-Typical Urban System Concrete-lined urban channel ($200 million) Built in the 1960s Increase flow rates Capacity eroded with upstream development Current Federal Project will completely update the channel and add upstream storage areas - $450 million rebuild by 2012 288 Crossing