Stormwater Impervious Surface Area Application City of Indianapolis, INDIANA

Stormwater Impervious Surface Area Application City of Indianapolis, INDIANA

City of Indianapolis, INDIANA Stormwater Impervious Surface Area Application City of Indianapolis, INDIANA

City of Indianapolis, INDIANA Stormwater Impervious Surface Area Application City of Indianapolis, INDIANA

Indianapolis Storm Water Serves about 300,000 customers in Marion County Miles of storm sewer and ditches, inlets and other structures Two dams Miles of flood protection levees Estimated value of the system is approximately $1.1 billion I am going to start with a few words about the Indianapolis storm water system. The City of Indianapolis storm water is a complex system of miles of sewer, ditches, inlets and other structures. It’s also miles of flood protection levees. It includes 2 dams. It serves about 300,000 customers. The City of Indianapolis estimates its stormwater system about $1.1 billion. Storm water plays a major role in the cleanliness of waterways, the safety of neighborhoods and liveliness of business districts. The need to protect and conserve this valuable resource, while improving the infrastructure continues to grow as the city does.

Stormwater System Problems Poor Drainage and Flooding Water runs into the City’s storm water system off rooftops, parking lots, city streets, driveways (impervious surfaces) Lack of adequate storm sewer and drainage in many parts of the City Some home and business owners do not maintain inlets and gutters, ditches, swales and creeks on their private property Indianapolis, like a lot of other cities, experiences problems with poor drainage and streets flooding. During rain events in Indianapolis, storm water runs off rooftops, parking lots, city streets, driveways and other surfaces into the City's storm water drainage system. Other causes include the fact that many parts of the City lack adequate storm sewers and drainage, leading to standing water in yards and flooded streets and basements. Also, some home and business owners do not maintain inlets and gutters, ditches, swales and creeks on their private property, preventing these drainage systems from removing storm water from neighborhoods to local waterways.

Storm Water Utility Fee Stormwater fee used to be flat for all residential parcels regardless of the size, non-residential customers were billed depending on the impervious area size In December 2014, the Indianapolis City-County Council approved a proposal that may change stormwater utility fee Effective July 2015, stormwater fees for all types of parcels are calculated based on the City’s measurements of the impervious surface area on the parcel of any type, residential or non-residential In order to adequately address those issues, the department of public works had to revisit the way it charges its customers. Starting 2006, stormwater fee for Indianapolis residents was flat for all residential properties based on an established 2,800 square feet of impervious area for each property. For non-residential properties, the fee was established proportional to the measured amount of impervious area located on the property. So the city of Indianapolis storm water fee collection system did not reflect the amount of impervious area for residential property owners. In December 2014, the Indianapolis City-County Council approved proposal that may change stormwater utility fee. Effective July 2015, stormwater fees for all types of parcels (residential, commercial, churches, schools, etc.) would be calculated based on the City’s measurement of the impervious surface area on the parcel. That will allow the City to raise funds necessary for capital improvements to the storm water system.

Impervious Surface Area Area that has been paved and/or covered with buildings and materials such that the infiltration of stormwater into soil is prevented or impeded: Concrete Asphalt Rooftop or blacktop Gravel driveways Private roadways Parking lots and similar areas designed or used for vehicular traffic Others Impervious surface area is any area that has been paved and/or covered with buildings and materials that include, but are not limited to, concrete, asphalt, rooftop and blacktop, such that the infiltration of stormwater into the soil is prevented or impeded. Impervious area includes gravel driveways, private roadways, parking lots and similar areas designed or used for vehicular traffic.

Impervious Surface Area Here is the good illustration of impervious vs pervious surfaces. As you see, any building, paved area around the building, parking lot, road, etc. is an impervious surface. In some cases impervious surface could also be soil that cannot let the water through it. In one particular example, someone’s backyard in Indianapolis has more than 10 cars permanently parked there and this is considered impervious as well.

Fee Calculation From Indianapolis-Marion County Code, Title I, Chapter 131, Article IV, Division 2, Sections 131-425:  "The monthly stormwater user fee shall be calculated utilizing the measured impervious area (IA) for each parcel and assigning the parcel to a group assigned one (1) base billing unit (BBU) or a multiple of BBUs following the convention​: 1—1,000 square feet of measured IA is assigned one (1) BBU;  1,001—2,000 square feet of measured IA is assigned two (2) BBUs;  2,001—3,000 square feet of measured IA is assigned three (3) BBUs and progressing in a manner such that each additional 1,000 square foot unit of IA is assigned an additional BBU.  BBUs shall be assigned to each parcel proportional to each one thousand-square foot increment of IA contained on the parcel. " The City of Indianapolis calculates stormwater fees based on so called base billing unit which is calculated by the formula presented here. The total square footage of impervious surface area on a property (here is another good illustration of what would be considered impervious surface on a property), is measured and then every 1,000 sq feet is 1 base billing unit. BBUs are assigned to each parcel proportional to each one thousand-square foot increment of impervious area contained on the parcel.

Financial Impact Allows the City of Indianapolis to raise funds for capital improvements of the stormwater system (estimated $320 million) Raises approximately $30 million annually to address many issues Alleviate neighborhood and street flooding that plagues residents and impedes business development Improve water quality in our rivers and streams by improving neighborhood drainage Improve impervious infrastructure, such as streets and sidewalks, that is damaged by standing water Resolve many drainage complaints The City plans to raise about $30 million annually to address many issues including the a high priority list with $81 million in projects to be completed through 2018. The list includes Alleviate neighborhood and street flooding that plagues residents and impedes business development Improve water quality in our rivers and streams by improving neighborhood drainage Improve impervious infrastructure, such as streets and sidewalks, that is damaged by standing water Resolve many drainage complaints

Data Collection Light Detection and Ranging (LiDAR) Aerial imagery LiDAR technology and aerial image photography were used to most accurately determine the impervious surface for each and every property in the City of Indianapolis. Contractors (Woolpert is one of them) collect that data every year to make sure up-to-date data is used.

Data Extraction Fuse LiDAR and aerial imagery data Perform segmentation Conduct analysis Extract features Refine data To extract impervious area features out of LiDAR and aerial imagery, the two need to be fused and then custom feature extraction software is used to create polygon feature layers. Woolpert, as one of the companies that did collection and data extraction for the City of Indianapolis, has developed a feature extraction technique that relies on automated data analysis for identifying various ground phenomena including impervious surfaces. The backbone of this automated technique is the effective fusion of electro-optical data and elevation data from LiDAR sources to recreate the landscape, thus enabling intelligent identification of land cover types. The process of feature identification semantically eliminates land cover types that do not represent imperviousness.

Data Validation Oblique Imagery Extracted Features Aerial Imagery The number of base billing units (BBU) is calculated based on the GIS data. That number is then used to calculate the fee amount charged to every property owner using rate defined set by the Department of Public Works. All that data were then sent to the billing system. So the whole billing calculation is done through the GIS. To assure data accuracy, City of Indianapolis staff performed comprehensive data validation using both aerial and oblique imagery. The total number of impervious area features extracted is over 305,000 (roughly 275,000 residential and 35,000 non-residential properties), so that was a huge amount of work.

Customer Service Interface An application that allows everyone to see the amount of impervious surface area on their parcel as well as stormwater utility fee amount Helps customers to understand their billing Helps City of Indianapolis staff to resolve any disputes with customers regarding the billing The application must be ready by the cycle of billing in fall of 2015 As a part of the City’s effort to be transparent about the billing, Woolpert, as the City’s GIS contractor, was tasked to build an application that allows everyone to see the amount of impervious area on their parcel as well as stormwater utility fee amount. The application would serve 2 major purposes. One is to help customers understand their billing, and the second one is to help the Department of Public Works staff to resolve any disputes with the customers regarding their bills. So the customers could be referred to the application to answer their questions. That would also allow the citizens of Indianapolis to be able to dispute the billing in case if they think it is wrong based on the data they see in the application. And the application needed to be completed and launched in fall of 2015 when the bills come out as the storm water bills were combined with property tax bills.

Customer Service Interface Requirements Must be Web application Has to be part of the MapIndy suite of applications (http://maps.indy.gov/MapIndy/) Provide detailed information on each property and its impervious surface Should allow map printing and reports generation Allows direct access to property information upon opening (can generate direct URL to selected property) Provide availability of oblique image photography Tools to find properties by address and/or parcel number The following requirements for the customer service interface were provided to us: Must be Web application Part of the MapIndy suite of applications (http://maps.indy.gov/MapIndy/, an one-stop shop for a lot of the City’s GIS applications) Provide detailed information on each property and its impervious surface Should allow printing and reports generation Allows direct access to property information upon opening (can generate direct URL to the feature) Availability of oblique image photography Provide various tools to find properties by address and/or parcel number

Customer Service Interface Data Sources Impervious Area Feature Class (SDE) Copy of the Property Management Data on SDE Indy Property Management System Parcel Number Impervious Area Map Feature Service The impervious area data for the customer surface interface comes from the map service that contains impervious surfaces feature class that is joined with the property system used by the City of Indianapolis. This is done with the purpose of being able to show users of the application not only the impervious surface feature information but also some general information about the parcel the impervious surface is located on. So the copy of the property management system data provided and maintained by a third-party vendor is copied to the SDE and stored there as a tabular data. That data is then joined with the impervious area feature class using parcel number field, and then published as a map service.

Storm Water Impervious Surface Area Application Technology Built using Flex Flex SDK 4.6 and ArcGIS Flex API 3.1 On top of ESRI ArcGIS Viewer For Flex (http://www.esri.com/software/arcgis/viewer-for-flex) Used out of the box and custom built tools and widgets The application uses tiled (cached) map services as a base map and feature map services as operational layers Operational layers data is joined with property management system data http://maps.indy.gov/MapIndy/Index.html?theme=imperviousareas The resulting application was built using Flex, runs on a Flash Player plugin. The main reason for us not to go with HTML5/JavaScript technology is that it had to be a part of the MapIndy which is written in Flex. The application is built on top of ESRI ArcGIS Viewer for Flex which was used to create MapIndy and was greatly expanded with the use of out-of-the box and custom built tools and widgets. Those widgets are shared between different themes of MapIndy therefore making development process faster and cheaper for the client. We used tiled map services as a base map and feature map services as operational layers that were joined with property management system.

Road Ahead Convert to HTML5/JavaScript Make the application mobile friendly Redesign of the application Improve the process of annual data update Other enhancements Since the application is built in Flex, this application cannot be run on a mobile device and we are automatically at risk of getting the application blocked by browsers on desktop as well. So we need to convert it HTML5/JavaScript and redesign it to make it mobile friendly. We might also improve the app to abstract billing logic outside of the application. As an example, the City recently changed the billing of residential properties to cap them at 20,000 square feet. The City of Indianapolis has a process in place for updating the datasets on annual basis. The process is in the stage of final development. And there might be other enhancements requested to the application based on customer experience and/or business needs.

Questions???