AGENDA #5d

 

MEMORANDUM

 

TO                   Mayor and Council

 

FROM:            W. Calvin Horton, Town Manager

 

SUBJECT:       Response to Petition Regarding Flooding and Maintenance of Booker Creek Near Willow Drive

 

DATE:             June 9, 2003

 

 

The following information responds to a petition from a Willow Drive resident regarding concerns about flooding from Booker Creek.

 

BACKGROUND AND DISCUSSION

 

At its April 14 business meeting, the Council received and referred an oral petition from Mr. Michael Schwartz, 1110 Willow Drive, expressing concerns about periodic flooding of Booker Creek and the effects such flooding has on adjacent properties.  The petitioner noted that flooding occurs even after moderate rainfall events, and sometimes floods as much as 50% of his back yard with water as deep as one foot.  Please see the attached map of the area in question.

 

Mr. Schwartz believes that the Town has a responsibility to maintain the conveyance capability of Booker Creek and he requested that the Town:

 

1.                  Investigate means and methods to alleviate periodic flooding of Booker Creek and the resultant damage to adjacent properties.

2.                  Dredge and otherwise clear debris out of the creek channel to improve its capacity to convey stormwater runoff without flooding.

 

Means and  Methods to Alleviate Flooding

 

Mr. Schwartz’ property and those of his neighbors are partially or wholly within the 100 year floodplain of Booker Creek according to the existing Federal Emergency Management Agency (FEMA) maps for this segment of Booker Creek.  The existing maps are approximately 20 years old, and are currently being updated through a joint Federal/State revision project expected to be completed by the end of 2004.  As a result of development that has occurred in the Booker Creek watershed during the past 20 years, we expect the new mapping to show that the floodplain extends even farther onto adjacent properties and may even surround some dwellings in this area.  (The attached map shows the approximate floodplain boundary on and around Mr. Schwartz’ property, based on currently available FEMA mapping.)

 

Floodplain areas exist adjacent to all natural creeks and they function as temporary storage areas for water that over tops the normal channel of the creek during periods of high flow.  Most properties along the lower segments of Booker Creek, Bolin Creek and Little Creek in this area of Town have experienced increased levels and frequency of flooding over the past 20 years as land was developed and more impervious surface area was constructed in the respective watersheds.

 

The only way to significantly reduce flooding at the lower end of Booker Creek (the area where the petitioner’s property is located) is to reduce the amount of stormwater runoff entering the creek from its contributing watershed.  Because the majority of developable land area in this watershed is built-out, we do not expect to experience a significant increase in stormwater runoff entering Booker Creek in the future.   However, this built-out condition also leaves us with no practical means to significantly reduce runoff volumes entering Booker Creek from the watershed.

 

Dredge and Clean out the Booker Creek Channel

 

We inspected all primary stream channels in Town following the ice storms this past winter.  Major debris dams were cleared and channel repairs were made where necessary.  We are currently in the process of re-inspecting channels throughout Town to identify trees that are leaning and branches initially damaged during ice storms that may have subsequently fallen into the creeks in recent months causing stream flow obstructions.

 

We will include lower Booker Creek for re-inspection this summer and will clear debris to the extent possible based on accessibility for our equipment.

 

Based on past experience, we know that it is not practical to dredge and channelize the streams in this area of Town in order to increase conveyance capacity.  The creeks discharge into the headwaters of Jordan Lake, and the elevation difference is so small that even the engineered channel is nearly flat, and it rapidly fills with silt and sediment after the first significant storm event to re-create its natural flow line before it was dredged.

 

We have also found that dredging streams at the lower end of their respective watersheds has little effect on mitigating overbank flooding because the resultant increase in channel storage volume is small in comparison to the large volume of water being contributed from the upstream watershed area during significant rainfall events.

 

CONCLUSION

 

Although we cannot significantly reduce the overbank flooding from Booker Creek onto and around the petitioner’s property, we are available upon request to provide technical advice about measures that might mitigate the effects of such flooding when it occurs.  Depending on the outcome of the new floodplain mapping with respect to Mr. Schwartz’ property, we will discuss with him any opportunities that may be available through Federal or State government programs for existing residences that fall within mapped floodplain areas.

 

We will inspect lower Booker Creek this summer for debris that may be impeding stream flow, and will remove it to the extent practicable.

 

ATTACHMENTS

 

1.  Area Map (p. 4).