Authorize the execution of an Interlocal Agreement (ILA) with Fort Bend County LID #2 to perform a 2-D modeling to determine the cause of the flooding in two neighborhoods located inside FBC LID #2 during Hurricane Harvey, in the amount of $54,000.00.

The City of Sugar Land and Fort Bend County LID #2 (FBC LID #2) will enter in an Interlocal Agreement (ILA) to perform a drainage study using the updated 2-D hydraulic model to provide an analysis of the effects Hurricane Harvey had on the communities protected by FBC LID #2. Specifically, the study will look at the neighborhoods that experienced flooding during the storm event. The study will concentrate on the areas drained by the tributary to Ditch “A” and the City storm sewer system in the southeast corner of the District.

Using the InfoWorks model that was previously created for the Levee District, the following is the scope of work to be accomplished:

1. Add the City of Sugar Land underground storm sewers to the model (GIS data to be provided by CoSL).  This will be to aid in showing how the streets/storm sewers fill and empty to the ditches.

2. Apply rainfall-on-grid data (15-min interval NEXRAD rainfall) provided by FBC LID #2.

3. Compare the model results to field collected high water marks and slab elevations (provided by FBC LID 2 & CoSL) and homeowner provided time-stamped water surface data (generally security camera images), to aid in “calibrating” or adjusting the model results to closely match the actual storm event.

4. Present the results to the project principals in a format that clearly demonstrates how they relate to the actual flooding levels experienced.

The deliverables include the following:

1. An executive summary of the event suitable to explain the results to public officials and particularly residents.

2. Ponding area maps showing the “calibrated” ponding areas.

3. A graph showing the cumulative rainfall, internal elevations at the pump station, recorded elevations on Ditch “H” and internal elevations on Upper Ditch “A” (near outfalls from flooded sections).

Funding is available in the Engineering Professional Services budget, Account No. 010-1650-516-31.01.

The Engineering Department recommends that the City Council authorize the execution of an Interlocal Agreement (ILA) with Fort Bend County LID #2 in the amount of $54,000.