City Council

Agenda Request

Agenda Of:

04-06-10

Agenda Request No:

viii-a

Initiated By:

Shashi K. Kumar, P.E., CFM

Senior Engineer

Responsible Department:

Engineering

Presented By:

 

Shashi K. Kumar, P.E., CFM

Senior Engineer

 

and

 

Department Head:

Christopher Steubing, P.E., CFM, City Engineer

 

 

Additional Department. Head (s):

n/a

Subject / Proceeding:

Integrated Storm Water Management Model (ISWMM)

Workshop to Update The City Council

Exhibits:

n/a

Clearances

Approval

Legal:

N/A

Executive Director:

 

Purchasing:

N/A

Asst. City Manager:

Karen Daly

Budget:

N/A

City Manager:

Allen Bogard

Budget

Expenditure Required:  $

n/a

Amount Budgeted/Reallocation:  $

n/a

Additional Appropriation:  $

N/A

Recommended Action

Review and receive presentation on the results of the first phase of the Integrated Storm Water Management Model.

 

Executive Summary

The City Council awarded an engineering services contract in November, 2008 to Halff Associates, Inc. for the development of an Integrated Storm Water Management Model (ISWMM).  This project is funded through the City’s Capital Improvement Program (CIP DR0804).  ISWMM is a planning tool that is used to evaluate the performance of the City’s stormwater (drainage) collection system, aid in identifying relief projects, and to serve as a tool in predicting potential for flooding during the occurrence of major rain events.

The development of ISWMM is planned in two Phases: Phase I and Phase II.  The Phase I part of the ISWMM project is substantially complete.  Engineering and the City’s consultant staff will highlight the salient features of the ISWMM - Phase I project, which are:

 

  • Integration of data from different studies

Since Tropical Storm Allison in 2001, drainage studies were initiated in a number of watershed’s Citywide. This led to the development of hydrologic and hydraulic models specific to these watersheds.  One of the tasks identified under ISWMM is to integrate all this data in a GIS (Geographical Information System)-based environment that would enable evaluation of the City’s drainage system at a macro level.

 

  • Delineation of floodplain limits outside “unmapped” areas

Traditionally, the 100-year floodplain limits are delineated in a community for major flooding sources such as the Oyster Creek and Brazos River by FEMA (commonly referred to as studied streams).  However, there are a number of streams in the City (such as Ditch A-22 and East Sugar Creek Ditch) which are not mapped due to the absence of detailed studies (unmapped streams).  As part of ISWMM Phase I, an effort was made to capture the floodplain limits for the major unmapped streams.  This will help in identifying flood hazards along these areas as well.

 

  • Developing a Citywide ponding map

Streets are designed to serve as an integral part of the drainage system, especially during major rain events.  It is common to see street ponding during extreme rain events, such as tropical storm Allison.  However, the extent of ponding varies citywide which is attributed to a number of factors.  One of the key aspects of ISWMM Phase I was to develop a citywide ponding map that would provide an estimate of ponding at a particular location during the occurrence of an extreme event.  Such a map would serve as a valuable tool for emergency preparedness and response.

 

The ISWMM Phase II project is identified in the City’s 2010 CIP.  However, this phase of the project is currently on “hold” pending re-authorization from the City Council due to budgetary constraints.  The proposed tasks for Phase II part of the ISWMM project will also be discussed in this workshop.

Exhibits

 

N/A