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

2. 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)

3. 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

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

5. 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

6. 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

7. 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

8. Small Sites – Digitized Drainage Map
Drainage Area

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

10. 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Most development occurs in areas that are changing, so GIS data is often out of date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

11. 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