TextChange in RunoffTextInvestigating changes in runoff flow caused by a new development

Aaron EinsteinDepartment of Geopgraphy Earth ScienceShippensburg UniversityCapstone GIS ProjectFall 2016

In order to answer this question, I knew Ineeded some of the following data: DigitalElevation Model (DEM) of Bucks County,Warrington Township Polygon, Soilsinformation for Warwick, georefrencingan image, and various backgroundinformation.Once I acquired the appropriate data Ihad to focus in on the township ofWarwick and then a smaller area of theconstruction site. This was accomplishedby creating a layer from the PA countieslayer, but only consisted of WarwickTownship. Once this was accomplished Iwas able to clip the soils layer and the

DEM by the Warwick Township Polygon.This made geoprocessing more manageableand focused on the area of interest (AOI).Next, included taking a picture of the siteplan made available by the builders of theWoodlands at Warwick development (TollBrothers) and georefrencing that image tothe most recent google earth image (foundbelow). I created two polygons, one polygonof the whole development and anotherpolygon of all of the houses and roadsrepresenting the new impervious surfaces.These two polygons were used to clippedthe Warwick soil polygon to create a layer ofall the soils in the development and all of thesoils that will now be covered by an

impervious surface (house or roads). Ithan created a model to create ahydrologic analyses the would look at thedevelopment site before and afterconstruction. This model included therequired 24 hr. two-year rain event thetownship requires in its planing andzoning ordinance. Lastly, was creatingfinding the percent of rain that would beabsorbed into the soil while the rest isallowed to flow. Soil information wasgathered from the United StatesDepartment of Agriculture (USDA), websoil survey site for the AOI (Image below).This resulted in 58% of the soil in the AOIis somewhat limited or vary limited. I

It is important to note that analyzing was done only to the homesthat area being built and did not include any future homes thatmight be developed later on. Also, it is important to note that notall of the polygon that represents impervious surfaces will actuallybe impervious after construction is complete. This was donebecause it made geoprocessing more manageable. Another factorthat was assumed was that all of the soil has an infiltration rate of42%. This was chosen based off of research and soil characteristics.

A new neighb orhood d evelopm ent is b eing b uilta pproxim a tely one m ile from where I grew up, inWa rwick Township Pennsylva nia , which is representedin Figure 1. It is loca ted a t 1300 Mem oria l Drive,Wa rwick, PA 18974. As I would d rive pa ss theconstruction site I would im m ed ia tely notice thecha nges to la nd cover, vegeta tion, and the a d d ition ofim pervious surfa ces a s construction ha s progressedthroughout the yea r. While I witnessed the d ra sticcha nge in la nd cover a long with the introd uction ofnew im pervious surfa ces I b ega n to question howArcMa p would spa tia lly a nd num erica lly illustra techa nges of runoff ca used b y the Wood la nds a tWa rwick d evelopm ent.

PurposePurpose

In ord er to properly a nswer the resea rch question, thefollowing ob jectives were com pleted:1. Crea te the spa tia l a rea of stud y.2. H a ve the a rea of stud y includ e a ppropria te soil d a ta .3. Sim ula te the ra infa ll event required b y the Wa rwickZ oning Ord ia nce.4. Ca lcula te flow b efore a nd a fter d evelopm ent.5. Com pa re the spa tia l a nd num erica l results fromArcMa p with the results ca lcula ted b y the soil com plexm ethod used in Wa rwick's Z oning Ord ia nce.

ObjectivesObjectives

H ow will flow spa tia lly a nd num erica llycha nge d ue to the introd uction of a newd evelopm ent in Wa rwick township? Will thenum eric a nswer d erived from ArcMa p b e thesa m e a nswer ca lcula ted from the m ethodrequired b y the Wa rwick zoning ord ia nce?

Research QuestionResearch Question

•Da ta were collected from sources listed in Ta b le 1.•All m ea surem ents in ArcMa p were m ea sured in m eters (m ).•All d a ta spa tia lly a na lyzed were projected using theNAD_ 1983_ Sta tePla ne_ Pennsylva nia _ South_ FIPS _ 3701 d ue toloca tion of the a rea of interest (AOI) in PA and use ofLa m b ert_ Conform a l_ Conic projection.•Spa tia l a na lysis wa s com pleted in ArcMa p 10.4.1 (Figure 2 & 3).•The Wa rwick township la yer wa s used to clip the soils la yer toprod uce SoilsinWa rwick, seen in Figure 2.•The d igita l eleva tion m od el (DEM) wa s clipped b y Wa rwicktownship la yer to focus on the AOI.•A new polygon (stud y a rea ) wa s crea ted to includ e a ll of thenecessa ry hea d w a ters crea ted from flow a ccum ula tion. Thispolygon wa s used a s the m a sk for a ny future geoprocessing.•Georeferencing wa s done to figure 4 to result in figure 5. Bothpolygons crea ted were then used to clip SoilsinWa rwick.•The required two yea r 24hr ra in event of 3.26in (0.083m )required b y Wa rwick township wa s sim ula ted through a ra sterla yer.•0.083 * 0.42 wa s used a s ca lcula tion for a ra ster la yer to crea tea la yer ta king the ra in event (0.083m ) a nd ca lcula ted how m uchwould b e a va ila b le post infiltra tion of soil.•Soil properties were a quired from Web Soil Survey.•Terra in Ana lysis wa s com pleted twice using Figure 2 with soilproperties a ccounted for. The first one ra n b efore d evelopm entwhile the second one includ e d evelopm enta l fa ctors ofim pervious surfa ces. These fa ctors were includ ed in the ra sterca lcula tor seen in Figure 3.•To find ra in for runoff a fter d evelopm ent the following wa sused in ra ster ca lcula tor:Con(IsNull("H ousesSoils_ R a ster"),0.3486,0.083). WhereH ousesSoils_ R a ster is Polygon 2 represented in Figure 5.

Figure 3. Mod el representing flow cha nges b eforea nd a fter d evelopm ent.

Figure 2. Mod el representing the workflow tod evelop a la yer conta ining onlyWa rwick a nd it's soil.

Ta b le 1.Includ es a ll the d a ta tha t wa s downloa d ed for a na lysis.

Methods and DataMethods and Data

±Figure 1. Shows Wa rwick township (grey) in rela tion toPhila d elphia . The sm a ll a rea in ora nge is the a rea of stud y.

Figure 4. Displa ys the site pla ntha t wa s ta ken from the TollBrothers web site. This im a gewa s georeferenced to the b a sela yer im a ge seen in figure 5.Once this wa s georeferenced Iwa s a b le to crea te the twopolygons seen in Figure 5.

Figure 5. Displa ys the two polygons tha twere crea ted using the georeferencedim a ge from figure 4. A new field titledInfiltra tion wa s crea ted for b oth of thepolygons once they were clipped b ySoilsinWa rwick. Polygon two received a ninfiltra tion ra te of zero b eca use itrepresents im pervious surfa ces. Polygonone received a n infiltra tion ra te of 42d ue to the ra tings of the soils foundthrough Soil Da ta Access. These twopolygons were then joined b y a unionand ra sterized b y the infiltra tion field.Once ra sterized this a llowed forca lcula tion of flow post d evelopm ent.

Results and AnswersResults and Answers

Phila d elphia

Summary and ConclusionSummary and ConclusionFigures 6 and 7 b oth a ccura tely d ispla y howflowing wa ter from a two yea r 24hr ra in event willb e spa tia lly a ltered do to the introd uction of thenew d evelopm ent through ArcMa p. Looking a tFigure 6, flow clea rly follows the topogra phy ofthe la nd prior to d evelopm ent. Once thed evelopm ent is in pla ce the topogra phy ha s lessim porta nce d ue to flow a ccum ula tion occurring a tthe im pervious surfa ces instea d of the riversystem a lrea d y in pla ce (Figure 7). With flowa ccum ula ting a t the source of new im pervioussurfa ces it ca uses new flow networks to d evelop(Figure 7) tha t were not previously in pla ce. Withthe d evelopm ent of Wood la nds a t Wa rwick theNesha m iny wa tershed will see a n increa se ofrunoff of either 147,987 ga llons (soil com plexm ethod) or 551,327 ga llons(ArcMa p). Both ofthese a nswers provid e ind ica tion tha t with a nincrea se of runoff from Wood la nds a t Wa rwickthe increa se in downstrea m im pa cts for the loca lriver system , Nesha m iny wa tershed, a nd theDela w a re R iver wa tershed will b e seen. Bothm ea surem ents of runoff resulted in two veryd ifferent results, which is prob lem a tic a s we strive

for m ore susta ina b le la nd use pra ctices.This work should open the d iscussion for if b othof these m ethods should b e integra ted into onesingula r progra m . If this is done it would likelyprod uce the m ost a ccura te result a nd a llow form ore precise estim a tion of downstrea m im pa cts.Consid era tions should b e m a d e for lookingfurther a nd into m ore d eta il to d eterm ine whichca lcula tion is the m ost a ccura te. If this is done itwould a llow for m ore a ccura te pred ictions ofwha t cha nges in surfa ce flow a nd runoff will b epost d evelopm ent for the surround ingenvironem nt.

Figure 6.Displa ys flowb efore the d evelopm ent ofWood la nds a t Wa rwicka long with ca lcula ted soild a ta .

Figure 7.Displa ys flowa fter the d evelopm ent ofWood la nds a t Wa rwick,which is represented b ythe a d d ed polygon(polygon one).

"Township of Wa rwick, PA Cod e." Township ofWa rwick, PA Cod e. N.p., n.d."Soil Da ta Access." Soil Da ta Access. N.p., n.d.

Works CitedWorks Cited

Data Source Provider Pennsylva nia m unicipa lity b ound a ries

Pennsylva nia Spa tia l Da ta Access Pennsylva nia Depa rtm ent of T ra nsporta tion

Nesha m iny Creek wa tershed conserva tion pla n

Pennsylva nia Spa tia l Da ta Access H erita ge Conserva ncy

Bucks County soils

Pennsylva nia Spa tia l Da ta Access U.S. Depa rtm ent of Agriculture

Bucks DEM Geospa tia l Ga te Wa y United Sta tes Depa rtm ent of Agriculture

Soil Properties Geospa tia l Ga te Wa y United Sta tes Depa rtm ent of Agriculture

Developers m ust ca lcula te runoff using the sta nd a rd soilcover com plex m ethod. Using this m ethod theca lcula tions resulted in 23,618.5m 3runoff pred evelopm ent a nd 43,402.2m 3post d evelopm ent.Accord ing to this m ethod a tota l of 19,783.7m 3of runoffwill b e crea ted from this d evelopm ent. All of this runoffm ust b e a ccounted for b y the d evelopers either througheva potra nspira tion or infiltra tion. Geoprocessigcom pleted in ArcMa p ga ve a flow a ccum ula tion of7,455.4m 2b efore d evelopm ent a nd 9,542.9m 2a fterd evelopm ent for a tota l of 2,087.5m 2of new runoffcrea ted from this d evelopm ent.

Com pa ring the two answers the soil com plex m ethodprod uced 147,987 ga llons and ArcMa p prod uced 551,327ga llons of new runoff crea ted from the d evelopm ent.These m ethods d iffer from ea chother b y 403,340 ga llonsof runoff. The d ifferencing a nswers were expected d ue tohow ea ch m ethod ha nd les d ifferent fa ctors tha t a ffectrunoff. ArcMa p includ es the spa tia l elem ent tha t the soilcom plex m ethod does while the soil com plex m ethodinclud es la nd cover ca lcula tions d ifferently tha n ArcMa p.

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Im a ge ta ken from -@tollb rothersinc. "New Luxury H om es For S a le in Wa rwick, PA |Wood la nds a t Wa rwick." Toll Brothers® Luxury H om es. N.p., n.d. Web . 04 Dec. 2016.

Source: Esri, Digita lGlob e, GeoEye, Ea rthsta r Geogra phics,

CNES/Airb us DS, U SDA, U SGS, AeroGR ID, IGN, and the GIS User Com unity

Source: Esri, Digita lGlob e, GeoEye, Ea rthsta r Geogra phics,

CNES/Airb us DS, U SDA, U SGS, AeroGR ID, IGN, and the GIS User Com unity

Source: Esri, Digita lGlob e, GeoEye, Ea rthsta r Geogra phics,

CNES/Airb us DS, U SDA, U SGS, AeroGR ID, IGN, and the GIS User Com unity.

Data Da ta Source Provid erPennsylva nia m unicipa lityb ound a ries

Pennsylva nia Spa tia lDa ta Access

Nesha m iny Creekwa tershed conserva tionpla n

Pennsylva nia Spa tia lDa ta Access

Pennsylva nia Spa tia lDa ta Access

H erita ge Conserva ncy

Bucks County soils

Bucks County DEMand Soil Properties

Geospa tia l Ga te Wa y United Sta tesDepa rtm ent ofAgriculture

United Sta tesDepa rtm ent ofAgriculture

Geospa tia l Ga te Wa y