Presenter: Tushar Solanki GIS Workshop Subdivision Design in the City of Wilmer

Scope and objectives To design a subdivision in the City of Wilmer (Dallas County) that includes Grading, Paving and Storm Drainage Softwares used – Survey Analyst, 3D Analyst, Arcscene-Arcinfo, ArcToolbox, Infrastructure/GIS Solutions, Microsoft office Data used and its sources: Ground Survey data and DEM (Digital Elevation Model), City of Dallas Aerial Photos

Basic issues involved with laying out a new subdivision Each City has its own policies, standards and regulations on land use, property development and construction review are designed to help ensure the health, safety, and welfare of its citizens, while protecting rights and privileges of property owners. The development review process is the City’s administrative system to efficiently and consistently enforce these policies, standards and regulations. The Development Review process is made up of three types of processes that may be required in order to develop property or build and occupy a building: 1. Land Development 2. Construction Review and 3. Special Review Examples of these processes are the platting and the Zoning processes, the building permit and construction approval process: Platting process for the City is to subdivide, plat or replat land and to prepare infrastructure for development in a comprehensively planned manner. It establishes a legal building site and is required before a building permit or certificate of occupancy can be issued.

Zoning is the division land into districts based on the allowable use of the land. These districts have uniform zoning regulations that provide for permitted uses, height, setbacks, lot size, density, coverage, and floor-area ratio (F.A.R.) When a planned Development District (PD) is approved with a conceptual plan, a development and/or landscape plan must be approved by the City Plan Commission before the issuance of a building permit. The development and/or landscape plan must comply with the conceptual plan and the conditions of the PD ordinance. The development plan may on a single drawing and must clearly indicate: Any proposed public or private streets and alleys Building sites Areas proposed for dedication or reserved as parks, open space, parkways, easements, etc. Points of ingress and egress from existing public streets Accurate survey of the boundaries of the site Topography of the sites with contour intervals Location of proposed land uses Location of buildings and the minimum distance between buildings and property lines, street and alley rights-of-way, and private streets Special traffic regulation facilities proposed or required etc.

Board of Adjustment Variance or Special Exception The Board of Adjustment is a citizen board, and appointed by the City Council to hear and take appropriate action on variances and special exceptions to Development Code regulations. Staff will review these requests and make recommendations to the Board prior to the hearing. If any project needs a special exception or a variance to requirements such as setbacks, lot width or depth, floor area ratios, or height, you may choose to go to the Board of Adjustment. Site Plan Review And Building Permit Process The developer should submit site plan for review before a building permit review can be finalized. A building permit represents the City’s authorization to begin construction. Tree Mitigation If the developer is planning to remove trees that are greater than 8 inches of diameter for a new subdivision, the developer has to go through tree mitigation process.

I was given the ground survey data and DEM (Digital Elevation Model) for the subdivision in the City of Wilmer. I With the help of Arc-GIS Survey Analyst, I was able to bring in the data with xyz coordinates Survey Analyst is an application that allows to store work with survey measurements collected from field notes, survey equipment, and data collectors. Survey analyst helps to integrate survey measurements in the geodatabase, improve the accuracy of the mapped features and also helps to organize survey data in the project. Survey Analyst performs Data Management and Data Reduction I performed the plats calculations that helped me to place the individual 1 acre lot in the right place where the owner wants. I created all the plat lines, streets, Lot numbers, Lot dimensions with the help of Infrastructure/GIS solutions.

Wilmer_subdivision_plat Total area of subdivision is 3,754,431 square feet Acres

I created contours from the data points with XYZ coordinates by using 3D Analyst. At this point I was not sure about how the proposed design will take place. I needed some more information about the proposed grading for individual lot. So I can design the right size defined ditches on the both sides of the street for the drainage purpose. As you see on the screen It shows how the original ground is out there. I created TIN by using.lin file. This is a ASCII file. I opened.lin file in the WordPad and arranged them in the format of Id, X coord, Y coord, Elevation

To create TIN, Opened ArcToolbox and selected conversion Tools/Import to TIN Wizard Click next to second dialog box Select Line feature class, choose hardlines for surface. Since I have TIN I did not need the breaklines anymore. Now I wanted to drape an aerial photographs that I got from the City of Dallas-GIS Department. This was a challenge for me. When I tried to bring in the Aerial Photos in the last, it did not work. So, I recreated the project and I brought in the aerial photos in the beginning. Now, the other shape files were following the same coordinates and projection system that Aerial Photos had.

Wilmer_Original_breaklines

Wilmer_original_Tin

Wilmer_original_Aerial1

Wilmer_Original_Aerial2

I created proposed grading plan by calculating the horizontal/vertical slopes at the survey points around the lots. Also I calculated the volume of the each lot area to balance the ground. Also, I wanted to place all the streets lower than the lots elevations so, that the water can easily run from the lots to the ditches along the street. By doing that, It has changed the elevations on most of the points compare to the existing ground. Also, It balanced the volume of the sand within the Wilmer Subdivision

Wilmer_grading1_breaklines

Wilmer_Grading1_ Contours_Breaklines

Wilmer_grading_TIN_View1

Wilmer_grading_TIN_View2

Wilmer_Grading_Aerial_contours_View1

Wilmer_Grading_Aerial_View2

Aerial view really helped me to come up with the precise drainage area analysis. By, looking at the picture and analyzing where exactly the sag point is in the whole Wilmer Subdivision. I calculated the Drainage area by using the Rational Formula Q = CIA Where Q = Runoff rate in cfs (cubic feet per second) C = Runoff coefficient I = Rainfall Intensity in inches/hour A = Drainage area in acres All runoff calculations shall be based upon a fully developed watershed and existing zoning. Runoff Coefficients for various land uses are different.

Drainage Area Map for a Subdivision in the City of Wilmer

Cross-section for Friendship Drive (Wilmer Subdivision)

Plan_Profile for Friendship Drive (Wilmer Subdivision) Friendship Drive

ESRI products can not cut the cross sections or create plan & profile sheet for the street design. So, I used Infrastructure/GIS solutions to do that. Current Infrastructure/GIS solutions version can support shape files, coverages, Geodatabase etc.