Use of ArcGIS 8.1 for Land Development Planning on Small Acreage Sites Tim Osting CE 394K.3 GISWR Fall 2001

Small Sites – Background I would like to explore the possibility of applying GIS technology to a typical Land Development project I would like to determine if existing GIS resources have adequate resolution for a typical small-acreage project (<100 acres)

Small Sites – Overview OBJECTIVE: Produce a PROJECT FEASIBILITY STUDY using readily-available GIS data without leaving my desk! Review General Development Planning Requirements Description of traditional methodology Description of GIS methodology Comparison of methods

Small Sites – A Typical Project Location Map Property Boundary Map Drainage Area Map Existing and Proposed Runoff Calculations Floodplain Map Area Geology Area Wells

Small Sites – Data Sources Traditional Methods Location Map from TxDOT CAD files Property Boundaries from plat (corners generated from ground and record information) Digitized Geologic Map from draft UT-BEG 7.5 quads Soils Map from UT-BEG Wells GIS-based Methods Location Map from TxDOT CAD files Property Boundaries from same GIS Geologic Map from USGS GIS Soils Map from SSURGO/TNRIS GIS Wells from TWDB

Small Sites – Drainage Calculations Traditional Methods Drainage Area digitized from 7.5 degree topo map Rainfall/Runoff: HEC-1 or HEC-HMS Tc (or Tlag) Drainage Area CN Channel: HEC-RAS Floodplain Map GIS-based Methods NED-generated Drainage Area Or…Rainfall/Runoff: HEC-GeoHMS Tc (or Tlag) Drainage Area CN Channel: HEC-RAS Floodplain Map not available

Small Sites – Sample Project 2.6-acre residential resubdivision Located in ETJ near Hutto, TX, portions in both Williamson and Travis Counties Large up-gradient drainage area Existing drainage channel at front of lot

Small Sites – Digitized Drainage Map Drainage Area

Small Sites – Drainage Map by GIS Drainage Area GIS Stream Network

Small Sites – Tentative Conclusions GIS speeds up data gathering process (Goal: Feasibility Study in 8 hours or less, <$600) HOWEVER, USE CAUTION! Most development occurs in areas that are changing, so GIS data is often out of date GIS data does not yet possess adequate resolution for a small-acreage site

Small Sites – Tentative Conclusions GIS is well-suited for producing a Preliminary Project Feasibility Study for a small-acreage site (Drainage Areas <250 acres) Current GIS is not well-suited to provide final design data Supplemental information is required for final project design