Jen WinstonExercise 3Flow path mapping with Arc Hydro

Q1. How many subcatchments were formed in your watershed partitioning? What was the drainage area in hectares that you used to define the beginning of each channel?

As can be seen in the map below, 305 sub-catchments were formed in my watershed partitioning. The drainage area in hectares is 3500 pixels * 900 m2 = 3150000 m2, or 315 hectares.

Q2. Remember this is all a model. What key assumptions were made, and how would you want to improve the watershed delineation to better match field conditions?

The model assumes that water that falls on any given pixel in a sub-watershed takes a single unique path to the outlet. It also assumes that, as water moves through the sub-watershed, it moves in a D8 pathway, meaning that water can only move in one of 8 directions. In addition, by filling pits, the model forces water to move through the sub-watershed, when in may actually

be pooling in behind reservoirs. It assumes that water flows over land (and is not artificially re-routed in sewers or other drainage systems. It also assumes that the watershed threshold is 3500 pixels. While this decision was informed by the NHD flowlines, it is still an arbitrary decision and may not reflect field conditions.

If we had infinite computing capabilities, we might want to improve the watershed delineation by incorporating a D-infinity pathway, or by doing field research to determine the best watershed threshold

Q3. Make impervious cover and land cover zonal statistics maps with your catchment boundary shape file. According to the zonal maps and tables, what is the range of % impervious area for the catchments?

As can be seen in the maps and tables below, the percent impervious area for the catchments ranges from 0% to 60.7%.

Majority land use table

HYDROID

MAJORITY

1 412 413 414 415 416 417 218 219 2110 2111 4112 4113 4114 4115 41

16 2117 4118 4119 2120 4121 4122 4123 2124 4125 4126 4127 4228 2129 2130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 2241 4142 4143 4144 4145 4146 4147 4148 2149 4150 4151 4152 4153 4154 4155 4156 4157 4158 21

59 4160 4161 4162 4163 4164 4165 4166 2267 4268 4169 4170 4171 4172 4173 2274 2375 4176 4277 4178 4179 4280 4181 4182 2383 4184 4185 4186 4187 4288 4189 4190 4191 4192 2193 4194 2195 4196 2197 4198 4199 41

100 41101 81

102 41103 41104 41105 21106 21107 41108 21109 23110 21111 41112 41113 21114 41115 41116 42117 41118 81119 81120 41121 41122 21123 41124 23125 41126 41127 41128 41129 21130 41131 41132 41133 21134 21135 41136 41137 42138 21139 41140 21141 41142 81143 21144 41

145 21146 21147 21148 41149 21150 81151 41152 41153 21154 21155 81156 21157 81158 81159 41160 23161 21162 41163 21164 81165 41166 41167 21168 41169 90170 21171 41172 21173 41174 90175 41176 41177 21178 21179 21180 21181 21182 21183 41184 41185 41186 90187 41

188 81189 21190 90191 41192 41193 41194 22195 21196 21197 42198 41199 41200 41201 21202 41203 21204 41205 21206 90207 41209 21210 41211 90212 21213 21214 41215 21216 21217 21218 21219 41220 41221 41222 21223 21224 21225 41226 42227 21228 21229 21230 41231 21

232 22233 21234 42235 41236 21237 90238 21239 21240 21241 21242 90243 90244 22245 90246 21247 41248 41249 41250 41251 42252 41253 21254 41255 71256 21257 81258 21259 41260 41261 21262 21263 21264 41265 41266 41267 21268 21269 90270 21271 42272 21273 21274 21

275 21276 21277 41278 21279 21280 21281 21282 21283 21284 21285 21286 90287 21288 21289 21290 41291 90292 90293 21294 41295 42296 90297 21298 21299 42300 41301 41302 41303 21304 41305 90

Impervious surface tableHYDROID MEAN

1 0.144669000002 0.668003000003 0.876995000004 1.210000000005 2.245650000006 1.209830000007 11.800700000008 11.344400000009 13.68650000000

10 17.9153000000011 0.0584498000012 1.5538000000013 2.0852000000014 13.2279000000015 2.0987500000016 9.4625000000017 0.6356530000018 4.3818400000019 11.6687000000020 0.0476190000021 0.5178130000022 0.2121360000023 21.5196000000024 1.1682800000025 4.7330800000026 2.1101400000027 2.8674300000028 26.7219000000029 17.5853000000030 0.0245989000031 0.1958330000032 0.2937850000033 0.4589910000034 0.2108960000035 0.9288670000036 0.0554245000037 0.5421230000038 0.5816830000039 0.0843137000040 35.0357000000041 0.2309470000042 0.0000000000043 3.8444000000044 0.3107590000045 0.3435750000046 0.0000000000047 0.3843720000048 15.8999000000049 0.5285130000050 0.7412860000051 0.6798520000052 0.05092300000

53 0.9564580000054 8.7142900000055 0.0000000000056 3.5025000000057 0.3775360000058 5.3491800000059 0.1086110000060 0.3167780000061 0.6475830000062 0.7271150000063 0.2035930000064 1.5497500000065 0.1423450000066 38.5107000000067 1.5560700000068 0.3399470000069 0.0384615000070 0.2769870000071 0.4931990000072 0.4214450000073 45.0701000000074 60.7195000000075 0.0183318000076 0.4760960000077 0.1448200000078 0.3236430000079 0.4405970000080 3.0392400000081 0.3698230000082 35.2647000000083 1.4935100000084 0.3436950000085 0.5929390000086 0.4076430000087 6.9497500000088 0.0698795000089 1.9747500000090 0.2946100000091 2.3394700000092 6.8099400000093 0.4880210000094 18.4963000000095 0.14298600000

96 30.1679000000097 0.3179900000098 0.1396930000099 0.77608000000

100 0.75925900000101 0.32968000000102 0.49261400000103 1.96215000000104 0.48250000000105 4.43662000000106 30.70160000000107 0.44507700000108 14.09120000000109 49.85840000000110 4.12697000000111 0.43363100000112 0.00000000000113 3.71104000000114 0.04947000000115 0.39050700000116 0.00330761000117 0.15963500000118 0.64310600000119 1.51656000000120 0.49316200000121 0.24845100000122 9.54839000000123 0.00000000000124 49.12060000000125 0.38080100000126 1.00220000000127 0.12874300000128 0.00734214000129 15.90970000000130 0.24577600000131 0.42714900000132 0.03711790000133 17.89260000000134 7.42219000000135 2.43441000000136 3.26579000000137 0.97306400000138 2.70327000000

139 5.76718000000140 2.67950000000141 4.48757000000142 3.46992000000143 1.44681000000144 0.18717100000145 17.68290000000146 13.86250000000147 5.38567000000148 7.43293000000149 17.13170000000150 0.55083700000151 0.91495000000152 0.77753400000153 22.29130000000154 15.10030000000155 0.14862000000156 11.16110000000157 1.33461000000158 0.49137900000159 0.34676400000160 46.21880000000161 7.48659000000162 3.65469000000163 6.38051000000164 0.00000000000165 0.00000000000166 0.27254100000167 21.83630000000168 3.30845000000169 0.69461100000170 18.89840000000171 0.26009400000172 10.62450000000173 0.36940700000174 4.84629000000175 0.17896300000176 0.56011100000177 13.97240000000178 12.35880000000179 28.15700000000180 19.98030000000181 26.27440000000

182 9.33285000000183 0.00000000000184 0.26650900000185 1.77558000000186 2.18987000000187 16.16250000000188 0.53224300000189 13.47240000000190 9.68113000000191 0.24977700000192 1.50998000000193 6.02899000000194 32.86760000000195 11.05050000000196 14.97780000000197 5.44176000000198 3.74163000000199 4.05460000000200 1.08621000000201 4.57969000000202 0.21065300000203 2.99288000000204 0.27096400000205 13.23280000000206 3.93243000000207 0.91200000000209 11.64240000000210 0.42871500000211 11.26600000000212 5.24615000000213 2.35685000000214 1.72296000000215 2.25000000000216 15.37810000000217 24.90870000000218 14.98900000000219 0.01884420000220 5.46814000000221 0.89693000000222 1.47120000000223 6.97600000000224 9.11880000000225 0.59670000000

226 6.43895000000227 2.61416000000228 18.37200000000229 11.60750000000230 19.57010000000231 9.74742000000232 18.74390000000233 3.30653000000234 14.36590000000235 2.50256000000236 21.83190000000237 0.00000000000238 17.23350000000239 10.27520000000240 5.47037000000241 3.70184000000242 0.00000000000243 8.02745000000244 25.83620000000245 1.36013000000246 6.08716000000247 0.78042700000248 0.08348680000249 0.09427210000250 1.60596000000251 1.35454000000252 4.05556000000253 10.72620000000254 1.61558000000255 2.52275000000256 10.08340000000257 0.27902900000258 10.10260000000259 0.02576110000260 0.93761300000261 3.23956000000262 15.72680000000263 7.36522000000264 0.00000000000265 0.00000000000266 1.55485000000267 13.66670000000268 17.49310000000

269 0.26778200000270 12.71840000000271 1.25458000000272 6.84731000000273 6.91130000000274 15.29700000000275 19.44530000000276 3.97382000000277 0.93455100000278 10.63390000000279 6.89063000000280 25.75100000000281 15.87970000000282 21.92580000000283 10.70370000000284 10.38510000000285 6.96700000000286 1.84030000000287 16.09620000000288 17.68620000000289 8.04868000000290 5.92823000000291 0.00000000000292 3.43069000000293 6.60726000000294 1.80094000000295 3.68822000000296 0.00000000000297 8.46041000000298 10.61390000000299 0.26744200000300 0.27545900000301 0.01551720000302 2.42030000000303 10.32110000000304 0.00000000000305 0.00000000000