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STORM WATER EVALUATION ENHANCEMENT TOOL (SWEET)

FOR THE CITY OF HOUSTON

September 3, 2015 TFMA Fall Summit ‘15

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City of Houston:

Carol Ellinger Haddock, P.E. – Sr. Assistant Director

Paresh Lad – Sr. Project Manager

RPS-Klotz Associates:

Gary Struzick, P.E. – Sr. Technical Advisor

William Conlan, P.E. – Sr. Project Manager

Phil Bullock, P.E. – Project Engineer

Manuel Razo, GISP – Sr. GIS Technician

THE TEAM

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Identify Areas of ‘Need’

Ability to identify, prioritize & rank City-

wide

Move away from reactive process and

subjective inputs

Use new technology

HOUSTON’S CHALLENGES

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THE SOLUTION

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Identify Need

•Comprehensive Drainage Plan, Flooding Complaints, Structural Flooding Damage, Mobility

Assess/Evaluate Need AreasStudy needs through pre-engineering

Score and Rank Needs

•Use City-wide data

Prioritize Candidate Projects

•Use a cost-benefit score

•Refer candidates to CIP for programming

Implement Projects

•Design & Construction

Operate System

•Maintenance & Repair

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GIS Based Tool

Easily Updatable/Dynamic

Consistent/Replicable Results

Transparent

THE TOOLBAR

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Existing Conditions

DEA adequacy- Polygon

Flood Complaints – Point

Ponding over 2ft – Raster

Capacity

Structural Flooding - Point

FEMA Repetitive Losses - Point

NFIP Losses - Point

Regulatory

Impassable Streets Complaints - Point

SWEET TOOLBAR - STORM

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Expand on current CDP coverage and detail

Determine Level of Service (LOS) of areas served by roadside ditch

Update LOS determination of areas served by closed conduit storm sewer

Incorporate roadside ditch adequacy determination into city-wide Drainage Evaluation Analysis (DEA)

Utilize improved technology and data to refine process and accuracy of calculations

PURPOSE OF UPDATES

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Determine LOS in Roadside Ditch

Delineate drainage areas at control points (U/S node of culverts)

Determine % Impervious to define flow for design storms

Determine carrying capacity of each ditch segment through cross sectional area with calculated slope (Manning’s Eq’n)

Determine LOS in Storm Sewer Systems

Analyzed 18” and larger pipes that are longer than 30-ft

Delineate drainage area at control points (Manholes)

Define flows using % Impervious raster

Determine carrying capacity with variable velocity based on pipe diameter

DEA UPDATE PROCESS

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ROADSIDE DITCH NETWORK

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DATA GATHERING PROCESS

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TYPICAL CROSS SECTION

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PYTHON Programming Script

Free, cross-platform, open- source

Incorporated into ArcGIS (9.0 release)

Large processing time

Access in ArcMap and ArcCatalog

1. DEM Slice Script (67 DEMs into 16 Grids)

Systematic sorting of geodatabase

Contains processes rasters

2. Drainage Area Script

Over 62,500 points to delineate watersheds

Automated process• Ensures consistency, timeliness, and accuracy

Zonal statistics tool used to calculate imperviousness

PROGRAMMATIC AUTOMATION

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Parent folder

DEM quarter-quad

Processed rasters from ArcHydro routine

Buffered DEM, impervious raster

Transect points

Cropped ditch and road centerlines

Reduces redundancy

Comprehensive structure

Each Single DEM = ~1.5 GB

FILE STRUCTURE

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DOQQ DATA SLICING

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1 2 1 2

3 4

5

7

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8

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11

10

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15

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4 5 6

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TOPOGRAPHICALLY CORRECT

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1

2

3

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TOPOGRAPHICALLY CORRECT CROSS SECTION (N.T.S.)

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HYDROLOGICALLY CORRECT

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INCORRECT CULVERT DIRECTION

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REFINING CULVERT DIRECTION

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Roadside Ditch

Flowline

Downstream Elev:

45.1213

Culvert Line

Upstream Elev:

45.1214

Roadside Ditch

Flowline

Shortened

Drainage Area

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FLIPPING CULVERT DIRECTION

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Roadside Ditch Flowline

Correct Culvert Direction

Roadside Ditch

Flowline

Incorrect Culvert

Direction

ALL RED

ALL GREEN

MIXED RED

& GREENMIXED RED

& GREEN

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MINI-LAKES ROUTINE

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QUAD COVERAGE 29095G32

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• 4,359 individual

delineations

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OVERLAPPING DRAINAGE AREAS

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IMPERVIOUS RASTER

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1 Mile

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IMPERVIOUS RASTER

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CONTROL POINT DETERMINATION

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41.2841.24

40.52

38.75

39.98

40.85 40.82

40.37

38.53

39.34

40.04

Elev

atio

n (

Ft)

Station (Ft)

Acting Control Point

for Roadside Ditch

containing Points 1-5Acting Control Point

for Roadside Ditch

containing Points 7-11

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CONTROL POINT DETERMINATION

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ADEQUACY LAYER (SHAPEFILE)

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DATA CHECK

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STATISTICS

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Linework Statistics

LOS Statistics

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STORM WATER EVALUATION ENHANCEMENT TOOL (SWEET)

FOR THE CITY OF HOUSTON

September 3, 2015 TFMA Fall Summit ‘15

QUESTIONS