diff --git a/examples/tsunami/bowl-radial/maketopo.py b/examples/tsunami/bowl-radial/maketopo.py
index d1d618a09..f1ccdcf74 100644
--- a/examples/tsunami/bowl-radial/maketopo.py
+++ b/examples/tsunami/bowl-radial/maketopo.py
@@ -3,7 +3,7 @@
 Module to create topo and qinit data files for this example.
 """
 
-from clawpack.geoclaw import topotools
+from clawpack.geoclaw.topotools import Topography
 from numpy import *
 
 def maketopo():
@@ -17,7 +17,11 @@ def maketopo():
     yupper = 100.e0
     ylower = -100.e0
     outfile= "bowl.topotype2"     
-    topotools.topo2writer(outfile,topo,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+
+    topography = Topography(topo_func=topo)
+    topography.x = linspace(xlower,xupper,nxpoints)
+    topography.y = linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=2, Z_format="%22.15e")
 
 def makeqinit():
     """
@@ -30,7 +34,11 @@ def makeqinit():
     yupper = 50.e0
     ylower = -50.e0
     outfile= "hump.xyz"     
-    topotools.topo1writer(outfile,qinit,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+
+    topography = Topography(topo_func=qinit)
+    topography.x = linspace(xlower,xupper,nxpoints)
+    topography.y = linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=1)
 
 def topo(x,y):
     """
diff --git a/examples/tsunami/bowl-slosh/maketopo.py b/examples/tsunami/bowl-slosh/maketopo.py
index 4bf655450..afe8deb9d 100644
--- a/examples/tsunami/bowl-slosh/maketopo.py
+++ b/examples/tsunami/bowl-slosh/maketopo.py
@@ -3,7 +3,7 @@
 Module to create topo and qinit data files for this example.
 """
 
-from clawpack.geoclaw.topotools import topo1writer, topo2writer
+from clawpack.geoclaw.topotools import Topography
 from numpy import *
 
 #from pyclaw.data import Data
@@ -26,7 +26,12 @@ def maketopo():
     xlower = -2.e0
     ylower = -2.e0
     outfile= "bowl.topotype2"
-    topo2writer(outfile,topo,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+
+    topography = Topography(topo_func=topo)
+    topography.x = linspace(xlower,xupper,nxpoints)
+    topography.y = linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=2, Z_format="%22.15e")
+
 
 def topo(x,y):
     """
diff --git a/src/python/geoclaw/etopotools.py b/src/python/geoclaw/etopotools.py
index 16d4e2817..a3111a170 100644
--- a/src/python/geoclaw/etopotools.py
+++ b/src/python/geoclaw/etopotools.py
@@ -59,7 +59,7 @@ def etopo1_download(xlimits, ylimits, dx=0.0166666666667, dy=None, \
     y1,y2 = ylimits
 
     if file_name is None:
-        file_name = 'etopo1_%i_%i_%i_%i_%imin.tt3' \
+        file_name = 'etopo1_%i_%i_%i_%i_%imin.asc' \
             % (int(round(x1)),int(round(x2)),int(round(y1)),int(round(y2)),\
               int(round(60*dx)))
 
diff --git a/src/python/geoclaw/topotools.py b/src/python/geoclaw/topotools.py
index c54baddc9..580a13207 100644
--- a/src/python/geoclaw/topotools.py
+++ b/src/python/geoclaw/topotools.py
@@ -788,8 +788,8 @@ def read_header(self):
             
         return num_cells
 
-    def write(self, path, no_data_value=None, topo_type=None, masked=True, 
-                header_style='geoclaw'):
+    def write(self, path, topo_type=None, no_data_value=None, masked=True, 
+                header_style='geoclaw', Z_format="%15.7e"):
         r"""Write out a topography file to path of type *topo_type*.
 
         Writes out a topography file of topo type specified with *topo_type* or
@@ -799,13 +799,25 @@ def write(self, path, no_data_value=None, topo_type=None, masked=True,
 
         :Input:
          - *path* (str)  - file to write
-         - *no_data_value* - values used to indicate missing data
          - *topo_type* (int) - GeoClaw format topo_type 
+           **Note:** this is second positional argument, agreeing with
+           the read function in this class.  It was the third argument in
+           GeoClaw version 5.3.1 and earlier.  
+         - *no_data_value* - values used to indicate missing data
          - *masked* (bool) - unused??
          - *header_style* (str) - indicates format of header lines
              'geoclaw' or 'default'  ==> write value then label 
              'arcgis' or 'asc' ==> write label then value  
                         (needed for .asc files in ArcGIS)
+         - *Z_format* (str) - string format to use for Z values
+           The default format "%15.7e" gives at least millimeter precision
+           for topography with abs(Z) < 10000 and results in
+           smaller files than the previous default of "%22.15e" used in
+           GeoClaw version 5.3.1 and earlier.  A shorter format can be used
+           if the user knows there are fewer significant digits, e.g.
+           etopo1 data is integers and so has a resolution of 1 meter.
+           In this case a cropped or coarsened version might be written
+           with `Z_format = "%7i"`, for example.
 
         """
 
@@ -883,23 +895,25 @@ def write(self, path, no_data_value=None, topo_type=None, masked=True,
 
                 # Write out topography data
                 if topo_type == 2:
+                    Z_format = Z_format + "\n"
                     if masked_Z:
                         Z_filled = numpy.flipud(self.Z.filled())
                     else:
                         Z_filled = numpy.flipud(self.Z)
                     for i in xrange(self.Z.shape[0]):
                         for j in xrange(self.Z.shape[1]):
-                            outfile.write("%22.15e\n" % Z_filled[i,j])
+                            outfile.write(Z_format % Z_filled[i,j])
                     if masked_Z:
                         del Z_filled
                 elif topo_type == 3:
+                    Z_format = Z_format + " "
                     if masked_Z:
                         Z_flipped = numpy.flipud(self.Z.filled())
                     else:
                         Z_flipped = numpy.flipud(self.Z)
                     for i in xrange(self.Z.shape[0]):
                         for j in xrange(self.Z.shape[1]):
-                            outfile.write("%22.15e   " % (Z_flipped[i,j]))
+                            outfile.write(Z_format % (Z_flipped[i,j]))
                         outfile.write("\n")
                     if masked_Z:
                         del Z_flipped
@@ -1414,7 +1428,7 @@ def smooth_data(self, indices, r=1):
                 self.Z[index[0], index[1]] = summation / num_points
 
 
-    def crop(self, filter_region):
+    def crop(self, filter_region=None, coarsen=1):
         r"""Crop region to *filter_region*
 
         Create a new Topography object that is identical to this one but cropped
@@ -1429,6 +1443,10 @@ def crop(self, filter_region):
         if self.unstructured:
             raise NotImplemented("*** Cannot currently crop unstructured topo")
 
+        if filter_region is None:
+            # only want to coarsen, so this is entire region:
+            filter_region = [self.x[0],self.x[-1],self.y[0],self.y[-1]]
+
         # Find indices of region
         region_index = [None, None, None, None]
         region_index[0] = (self.x >= filter_region[0]).nonzero()[0][0]
@@ -1437,8 +1455,8 @@ def crop(self, filter_region):
         region_index[3] = (self.y <= filter_region[3]).nonzero()[0][-1] + 1
         newtopo = Topography()
 
-        newtopo._x = self._x[region_index[0]:region_index[1]]
-        newtopo._y = self._y[region_index[2]:region_index[3]]
+        newtopo._x = self._x[region_index[0]:region_index[1]:coarsen]
+        newtopo._y = self._y[region_index[2]:region_index[3]:coarsen]
 
         # Force regeneration of 2d coordinate arrays and extent if needed
         newtopo._X = None
@@ -1446,8 +1464,8 @@ def crop(self, filter_region):
         newtopo._extent = None
 
         # Modify Z array as well
-        newtopo._Z = self._Z[region_index[2]:region_index[3],
-                          region_index[0]:region_index[1]]
+        newtopo._Z = self._Z[region_index[2]:region_index[3]:coarsen,
+                          region_index[0]:region_index[1]:coarsen]
 
         newtopo.unstructured = self.unstructured
         newtopo.topo_type = self.topo_type
diff --git a/tests/bowl_slosh/maketopo.py b/tests/bowl_slosh/maketopo.py
index 4bf655450..855b6df03 100644
--- a/tests/bowl_slosh/maketopo.py
+++ b/tests/bowl_slosh/maketopo.py
@@ -3,7 +3,8 @@
 Module to create topo and qinit data files for this example.
 """
 
-from clawpack.geoclaw.topotools import topo1writer, topo2writer
+from clawpack.geoclaw.topotools import Topography
+
 from numpy import *
 
 #from pyclaw.data import Data
@@ -26,7 +27,10 @@ def maketopo():
     xlower = -2.e0
     ylower = -2.e0
     outfile= "bowl.topotype2"
-    topo2writer(outfile,topo,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+    topography = Topography(topo_func=topo)
+    topography.x = linspace(xlower,xupper,nxpoints)
+    topography.y = linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=2, Z_format="%22.15e")
 
 def topo(x,y):
     """
diff --git a/tests/bowl_slosh/regression_data/regression_data.txt b/tests/bowl_slosh/regression_data/regression_data.txt
deleted file mode 100644
index 6d3cad183..000000000
--- a/tests/bowl_slosh/regression_data/regression_data.txt
+++ /dev/null
@@ -1,55 +0,0 @@
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diff --git a/tests/bowl_slosh/regression_tests.py b/tests/bowl_slosh/regression_tests.py
index 940799625..a4ceb542c 100644
--- a/tests/bowl_slosh/regression_tests.py
+++ b/tests/bowl_slosh/regression_tests.py
@@ -33,7 +33,8 @@ def setUp(self):
         topo.topo_type = 2
         topo.x = numpy.linspace(-2.0, 2.0, 200)
         topo.y = numpy.linspace(-2.0, 2.0, 200)
-        topo.write(os.path.join(self.temp_path, "bowl.topotype2"))
+        topo.write(os.path.join(self.temp_path, "bowl.topotype2"), \
+                topo_type=2, Z_format="%22.15e")
 
         from make_fgmax_grid import make_fgmax_grid1
         make_fgmax_grid1(self.temp_path)
diff --git a/tests/dtopo1/maketopo.py b/tests/dtopo1/maketopo.py
index 7a5a29d6f..a5488d1fe 100644
--- a/tests/dtopo1/maketopo.py
+++ b/tests/dtopo1/maketopo.py
@@ -3,7 +3,8 @@
 Module to create topo and qinit data files for this example.
 """
 
-from clawpack.geoclaw.topotools import topo1writer, topo2writer
+from clawpack.geoclaw.topotools import Topography
+
 from clawpack.geoclaw import dtopotools
 import numpy
 import matplotlib.pyplot as plt
@@ -21,7 +22,10 @@ def maketopo():
     ylower = -10e0
     yupper= 10e0
     outfile= "topo1.topotype2"
-    topo2writer(outfile,topo,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+    topography = Topography(topo_func=topo)
+    topography.x = numpy.linspace(xlower,xupper,nxpoints)
+    topography.y = numpy.linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=2, Z_format="%22.15e")
     dx = (xupper-xlower)/(nxpoints-1)
     dy = (yupper-ylower)/(nypoints-1)
     print "==> topo1 has dx = %g, dy = %g" % (dx,dy)
@@ -37,7 +41,10 @@ def maketopo2():
     ylower = -0.1
     yupper= 0.4
     outfile= "topo2.topotype2"
-    topo2writer(outfile,topo2,xlower,xupper,ylower,yupper,nxpoints,nypoints)
+    topography = Topography(topo_func=topo2)
+    topography.x = numpy.linspace(xlower,xupper,nxpoints)
+    topography.y = numpy.linspace(ylower,yupper,nypoints)
+    topography.write(outfile, topo_type=2, Z_format="%22.15e")
     dx = (xupper-xlower)/(nxpoints-1)
     dy = (yupper-ylower)/(nypoints-1)
     print "==> topo2 has dx = %g, dy = %g" % (dx,dy)
diff --git a/tests/dtopo1/regression_data/gauge00001.txt b/tests/dtopo1/regression_data/gauge00001.txt
index dc19c1d4d..0e45cf0cb 100644
--- a/tests/dtopo1/regression_data/gauge00001.txt
+++ b/tests/dtopo1/regression_data/gauge00001.txt
@@ -1,53 +1,53 @@
 # gauge_id= 1 location=( -0.45 0.05 ) num_eqn= 4
 # Columns: level time q(1 ... num_eqn)
-4607182418800017408 0.0 1670.354 0.0 0.0 0.0
-4607182418800017408 0.0001 1670.354 -2.095048e-17 2.259404e-17 0.0
-4607182418800017408 0.0201 1670.354 -4.254983e-15 -8.172831e-15 0.0008
-4607182418800017408 0.0401 1670.354 5.819504e-15 -1.212058e-14 0.1608
-4607182418800017408 0.0601 1670.354 -4.012299e-14 -7.646864e-15 0.3208
-4607182418800017408 0.0801 1670.354 -1.406211e-13 -3.199637e-15 0.4808
-4607182418800017408 0.1001 1670.354 -3.559817e-13 3.460132e-14 0.6408
-4607182418800017408 0.1201 1670.354 -7.687797e-13 3.331292e-15 0.8008
-4607182418800017408 0.1401 1670.354 -1.661697e-12 4.434144e-15 0.9608
-4607182418800017408 0.1601 1670.354 -3.135409e-12 3.358414e-15 1.1208
-4607182418800017408 0.1801 1670.354 -5.476332e-12 1.614664e-14 1.2808
-4607182418800017408 0.2001 1670.354 -8.939487e-12 4.108562e-14 1.4408
-4607182418800017408 0.2201 1670.354 -1.38962e-11 4.354217e-14 1.6008
-4607182418800017408 0.2401 1670.354 -2.072384e-11 -1.22292e-14 1.7608
-4607182418800017408 0.2601 1670.354 -2.98276e-11 -4.305891e-14 1.9208
-4607182418800017408 0.2801 1670.354 -4.164306e-11 -8.479047e-14 1.9192
-4607182418800017408 0.3001 1670.354 -5.66928e-11 -1.387227e-13 1.7592
-4607182418800017408 0.3201 1670.354 -7.550907e-11 -2.233382e-13 1.5992
-4607182418800017408 0.3401 1670.354 -9.850911e-11 -2.740684e-13 1.4392
-4607182418800017408 0.3601 1670.354 -1.26101e-10 -4.230222e-13 1.2792
-4607182418800017408 0.3801 1670.354 -1.587222e-10 -5.199631e-13 1.1192
-4607182418800017408 0.4001 1670.354 -1.967043e-10 -6.957309e-13 0.9592
-4607182418800017408 0.4201 1670.354 -2.403526e-10 -8.937129e-13 0.7992
-4607182418800017408 0.4401 1670.354 -2.899325e-10 -1.063955e-12 0.6392
-4607182418800017408 0.4601 1670.354 -3.456806e-10 -1.308005e-12 0.4792
-4607182418800017408 0.4801 1670.354 -4.077496e-10 -1.590064e-12 0.3192
-4607182418800017408 0.5001 1670.354 -4.763515e-10 -1.903784e-12 0.1592
-4607182418800017408 0.5201 1670.354 0.07013447 0.01938294 1.759766
-4607182418800017408 0.5401 1670.354 0.1456844 0.04027292 1.896394
-4607182418800017408 0.5601 1670.354 0.2264722 0.06262068 2.028536
-4607182418800017408 0.5801 1670.354 0.3123216 0.0863774 2.15623
-4607182418800017408 0.6001 1670.354 0.4029363 0.1114608 2.276441
-4607182418800017408 0.6201 1670.354 0.4981114 0.137814 2.39148
-4607182418800017408 0.6401 1670.354 0.5976709 0.1653882 2.502072
-4607182418800017408 0.6601 1670.354 0.7013452 0.1941087 2.605865
-4607182418800017408 0.6801 1670.354 0.8089024 0.2239109 2.703802
-4611686018427387904 0.7001 1670.354 0.9201664 0.2547462 2.88466
-4611686018427387904 0.7201 1670.354 1.034283 0.2864247 2.884683
-4611686018427387904 0.7401 1670.354 1.15157 0.3189926 2.965533
-4613937818241073152 0.7601 1670.329 1.271853 0.3518861 3.112886
-4613937818241073152 0.7801 1670.329 1.370447 0.3760791 3.112885
-4613937818241073152 0.8001 1670.329 1.471689 0.4010228 3.176775
-4613937818241073152 0.8201 1670.329 1.575404 0.4266645 3.290882
-4613937818241073152 0.8401 1670.329 1.681405 0.4529531 3.290882
-4613937818241073152 0.8601 1670.329 1.789379 0.4798042 3.337627
-4613937818241073152 0.8801 1670.329 1.899149 0.507167 3.417743
-4613937818241073152 0.9001 1670.329 2.010542 0.5349928 3.417744
-4613937818241073152 0.9201 1670.329 2.123247 0.5631976 3.447727
-4613937818241073152 0.9401 1670.329 2.237075 0.5917271 3.493551
-4613937818241073152 0.9601 1670.329 2.351851 0.6205329 3.493553
-4613937818241073152 0.9801 1670.329 2.467293 0.6495374 3.507077
+01 +0.000000000000000e+00 +1.670354000000000e+03 +0.000000000000000e+00 +0.000000000000000e+00 +0.000000000000000e+00
+01 +1.000000000000000e-04 +1.670354000000000e+03 -2.095048000000000e-17 +2.259404000000000e-17 +0.000000000000000e+00
+01 +2.010000000000000e-02 +1.670354000000000e+03 -4.254983000000000e-15 -8.172831000000000e-15 +8.000000000000000e-04
+01 +4.010000000000000e-02 +1.670354000000000e+03 +5.819504000000000e-15 -1.212058000000000e-14 +1.608000000000000e-01
+01 +6.010000000000000e-02 +1.670354000000000e+03 -4.012299000000000e-14 -7.646864000000001e-15 +3.208000000000000e-01
+01 +8.010000000000000e-02 +1.670354000000000e+03 -1.406211000000000e-13 -3.199637000000000e-15 +4.808000000000000e-01
+01 +1.001000000000000e-01 +1.670354000000000e+03 -3.559817000000000e-13 +3.460132000000000e-14 +6.408000000000000e-01
+01 +1.201000000000000e-01 +1.670354000000000e+03 -7.687797000000000e-13 +3.331292000000000e-15 +8.008000000000000e-01
+01 +1.401000000000000e-01 +1.670354000000000e+03 -1.661697000000000e-12 +4.434144000000000e-15 +9.608000000000000e-01
+01 +1.601000000000000e-01 +1.670354000000000e+03 -3.135409000000000e-12 +3.358414000000000e-15 +1.120800000000000e+00
+01 +1.801000000000000e-01 +1.670354000000000e+03 -5.476332000000000e-12 +1.614664000000000e-14 +1.280800000000000e+00
+01 +2.001000000000000e-01 +1.670354000000000e+03 -8.939487000000000e-12 +4.108562000000000e-14 +1.440800000000000e+00
+01 +2.201000000000000e-01 +1.670354000000000e+03 -1.389620000000000e-11 +4.354217000000000e-14 +1.600800000000000e+00
+01 +2.401000000000000e-01 +1.670354000000000e+03 -2.072384000000000e-11 -1.222920000000000e-14 +1.760800000000000e+00
+01 +2.601000000000000e-01 +1.670354000000000e+03 -2.982760000000000e-11 -4.305891000000000e-14 +1.920800000000000e+00
+01 +2.801000000000000e-01 +1.670354000000000e+03 -4.164306000000000e-11 -8.479047000000000e-14 +1.919200000000000e+00
+01 +3.001000000000000e-01 +1.670354000000000e+03 -5.669280000000000e-11 -1.387227000000000e-13 +1.759200000000000e+00
+01 +3.201000000000000e-01 +1.670354000000000e+03 -7.550907000000000e-11 -2.233382000000000e-13 +1.599200000000000e+00
+01 +3.401000000000000e-01 +1.670354000000000e+03 -9.850910999999999e-11 -2.740684000000000e-13 +1.439200000000000e+00
+01 +3.601000000000000e-01 +1.670354000000000e+03 -1.261010000000000e-10 -4.230222000000000e-13 +1.279200000000000e+00
+01 +3.801000000000000e-01 +1.670354000000000e+03 -1.587222000000000e-10 -5.199631000000000e-13 +1.119200000000000e+00
+01 +4.001000000000000e-01 +1.670354000000000e+03 -1.967043000000000e-10 -6.957309000000000e-13 +9.592000000000001e-01
+01 +4.201000000000000e-01 +1.670354000000000e+03 -2.403526000000000e-10 -8.937129000000000e-13 +7.992000000000000e-01
+01 +4.401000000000000e-01 +1.670354000000000e+03 -2.899325000000000e-10 -1.063955000000000e-12 +6.392000000000000e-01
+01 +4.601000000000000e-01 +1.670354000000000e+03 -3.456806000000000e-10 -1.308005000000000e-12 +4.792000000000000e-01
+01 +4.801000000000000e-01 +1.670354000000000e+03 -4.077496000000000e-10 -1.590064000000000e-12 +3.192000000000000e-01
+01 +5.001000000000000e-01 +1.670354000000000e+03 -4.763515000000000e-10 -1.903784000000000e-12 +1.592000000000000e-01
+01 +5.201000000000000e-01 +1.670354000000000e+03 +7.013447000000000e-02 +1.938294000000000e-02 +1.759766000000000e+00
+01 +5.401000000000000e-01 +1.670354000000000e+03 +1.456844000000000e-01 +4.027292000000000e-02 +1.896394000000000e+00
+01 +5.601000000000000e-01 +1.670354000000000e+03 +2.264722000000000e-01 +6.262068000000000e-02 +2.028536000000000e+00
+01 +5.800999999999999e-01 +1.670354000000000e+03 +3.123216000000000e-01 +8.637739999999999e-02 +2.156230000000000e+00
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+02 +7.000999999999999e-01 +1.670354000000000e+03 +9.201664000000001e-01 +2.547462000000000e-01 +2.884660000000000e+00
+02 +7.201000000000000e-01 +1.670354000000000e+03 +1.034283000000000e+00 +2.864247000000000e-01 +2.884683000000000e+00
+02 +7.401000000000000e-01 +1.670354000000000e+03 +1.151570000000000e+00 +3.189926000000000e-01 +2.965533000000000e+00
+03 +7.601000000000000e-01 +1.670329000000000e+03 +1.271853000000000e+00 +3.518861000000000e-01 +3.112886000000000e+00
+03 +7.801000000000000e-01 +1.670329000000000e+03 +1.370447000000000e+00 +3.760791000000000e-01 +3.112885000000000e+00
+03 +8.001000000000000e-01 +1.670329000000000e+03 +1.471689000000000e+00 +4.010228000000000e-01 +3.176775000000000e+00
+03 +8.201000000000001e-01 +1.670329000000000e+03 +1.575404000000000e+00 +4.266645000000000e-01 +3.290882000000000e+00
+03 +8.401000000000000e-01 +1.670329000000000e+03 +1.681405000000000e+00 +4.529531000000000e-01 +3.290882000000000e+00
+03 +8.601000000000000e-01 +1.670329000000000e+03 +1.789379000000000e+00 +4.798042000000000e-01 +3.337627000000000e+00
+03 +8.801000000000000e-01 +1.670329000000000e+03 +1.899149000000000e+00 +5.071670000000000e-01 +3.417743000000000e+00
+03 +9.001000000000000e-01 +1.670329000000000e+03 +2.010542000000000e+00 +5.349928000000000e-01 +3.417744000000000e+00
+03 +9.201000000000000e-01 +1.670329000000000e+03 +2.123247000000000e+00 +5.631976000000000e-01 +3.447727000000000e+00
+03 +9.401000000000000e-01 +1.670329000000000e+03 +2.237075000000000e+00 +5.917271000000000e-01 +3.493551000000000e+00
+03 +9.601000000000000e-01 +1.670329000000000e+03 +2.351851000000000e+00 +6.205329000000001e-01 +3.493553000000000e+00
+03 +9.801000000000000e-01 +1.670329000000000e+03 +2.467293000000000e+00 +6.495374000000000e-01 +3.507077000000000e+00
diff --git a/tests/dtopo1/regression_data/regression_data.txt b/tests/dtopo1/regression_data/regression_data.txt
deleted file mode 100644
index e293eed3e..000000000
--- a/tests/dtopo1/regression_data/regression_data.txt
+++ /dev/null
@@ -1,51 +0,0 @@
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-1.000000000000000000e+00 3.000000000000000000e+00 9.001000000000000112e-01 1.670328999999999951e+03 2.010542000000000051e+00 5.349928000000000461e-01 3.417743999999999893e+00
-1.000000000000000000e+00 3.000000000000000000e+00 9.201000000000000290e-01 1.670328999999999951e+03 2.123247000000000106e+00 5.631975999999999649e-01 3.447726999999999986e+00
-1.000000000000000000e+00 3.000000000000000000e+00 9.401000000000000467e-01 1.670328999999999951e+03 2.237074999999999925e+00 5.917270999999999503e-01 3.493551000000000073e+00
-1.000000000000000000e+00 3.000000000000000000e+00 9.600999999999999535e-01 1.670328999999999951e+03 2.351850999999999914e+00 6.205329000000000539e-01 3.493552999999999908e+00
-1.000000000000000000e+00 3.000000000000000000e+00 9.800999999999999712e-01 1.670328999999999951e+03 2.467293000000000180e+00 6.495374000000000425e-01 3.507077000000000222e+00
diff --git a/tests/dtopo1/regression_data/regression_data_test2.txt b/tests/dtopo1/regression_data/regression_data_test2.txt
deleted file mode 100644
index f116e4c9b..000000000
--- a/tests/dtopo1/regression_data/regression_data_test2.txt
+++ /dev/null
@@ -1,2 +0,0 @@
-2.450499999999999901e+01
-8.518780199999996694e+04
diff --git a/tests/dtopo1/regression_tests.py b/tests/dtopo1/regression_tests.py
index ac4da46f2..eba923e37 100644
--- a/tests/dtopo1/regression_tests.py
+++ b/tests/dtopo1/regression_tests.py
@@ -31,7 +31,8 @@ def setUp(self):
         topo.topo_type = 2
         topo.x = numpy.linspace(-10.0, 10.0, 201)
         topo.y = numpy.linspace(-10.0, 10.0, 201)
-        topo.write(os.path.join(self.temp_path, "topo1.topotype2"))
+        topo.write(os.path.join(self.temp_path, "topo1.topotype2"), \
+                topo_type=2, Z_format="%22.15e")
 
         h0 = 1000.0
         topo_func = lambda x,y: -h0*(1. + numpy.exp(x+y))
@@ -39,7 +40,8 @@ def setUp(self):
         topo.topo_type = 2
         topo.x = numpy.linspace(-0.5, -0.3, 21)
         topo.y = numpy.linspace(-0.1, 0.4, 51)
-        topo.write(os.path.join(self.temp_path, "topo2.topotype2"))
+        topo.write(os.path.join(self.temp_path, "topo2.topotype2"), \
+                topo_type=2, Z_format="%22.15e")
 
         # Make dtopography
         subfault_path = os.path.join(self.test_path, "dtopo1.csv")
diff --git a/tests/dtopo1/setplot.py b/tests/dtopo1/setplot.py
index be5a16cd8..ef78dc95f 100644
--- a/tests/dtopo1/setplot.py
+++ b/tests/dtopo1/setplot.py
@@ -135,10 +135,10 @@ def add_dtopo_plot(current_data):
             if len(itlist) > 0:
                 it = max(find(dtopo.times <= t))
                 #print "+++ t, it, dtopo.times[it]: ",t, it, dtopo.times[it]
-                dz = dtopo.dz_list[it]
+                dz = dtopo.dZ[it,:,:]
                 dzj = dz[j,:]
                 if it < len(dtopo.times)-1:
-                    dz1 = dtopo.dz_list[it+1]
+                    dz1 = dtopo.dZ[it+1,:,:]
                     dz1j = dz1[j,:]
                     alpha = (t - dtopo.times[it])/(dtopo.times[it+1] - dtopo.times[it])
                     #print "+++ alpha = ",alpha
diff --git a/tests/storm_surge/regression_tests.py b/tests/storm_surge/regression_tests.py
index 0baae264f..b97d59a31 100644
--- a/tests/storm_surge/regression_tests.py
+++ b/tests/storm_surge/regression_tests.py
@@ -47,7 +47,8 @@ def setUp(self):
         topo.x = numpy.linspace(-100, -69, 125)
         topo.y = numpy.linspace(7.0, 33.0, 105)
         topo.Z = 25.0 * ((topo.X + 84.5)**2 + (topo.Y - 20.0)**2) - 4000.0
-        topo.write(os.path.join(self.temp_path, 'gulf_caribbean.tt3'))
+        topo.write(os.path.join(self.temp_path, 'gulf_caribbean.tt3'), \
+                topo_type=2, Z_format="%22.15e")
 
 
     def runTest(self, save=False, indices=(2, 3)):
diff --git a/tests/test_topotools.py b/tests/test_topotools.py
index 0f2824b55..e1d30074b 100644
--- a/tests/test_topotools.py
+++ b/tests/test_topotools.py
@@ -63,7 +63,7 @@ def test_read_write_topo_bowl():
     try:
         for topo_type in xrange(1, 4):
             path = os.path.join(temp_path, 'bowl.tt%s' % topo_type)
-            topo.write(path, topo_type=topo_type)
+            topo.write(path, topo_type=topo_type,Z_format="%22.15e")
 
             topo_in = topotools.Topography(path)
             assert numpy.allclose(topo.Z, topo_in.Z), \
@@ -172,7 +172,7 @@ def test_read_write_topo_bowl_hill():
 
         for topo_type in xrange(1,4):
             file_path = os.path.join(temp_path, 'bowl_hill.tt%s' % topo_type)
-            topo.write(file_path, topo_type=topo_type)
+            topo.write(file_path, topo_type=topo_type,Z_format="%22.15e")
             topo_in = topotools.Topography(path=file_path, topo_type=topo_type)
             assert numpy.allclose(topo.Z, topo_in.Z), \
                    "Written file of topo_type=%s does not equal read in" + \
@@ -207,7 +207,7 @@ def test_netcdf():
         # Write out NetCDF version of file
         ascii_topo = topotools.Topography(path=local_path)
         ascii_topo.read()
-        ascii_topo.write(nc_path, topo_type=4)
+        ascii_topo.write(nc_path, topo_type=4,Z_format="%22.15e")
 
         # Read back in NetCDF file
         nc_topo = topotools.Topography(path=nc_path)
@@ -313,7 +313,7 @@ def func(x, y):
     # Load (and save) test data and make the comparison
     test_data_path = os.path.join(testdir, "data", "unstructured_test_data.tt3")
     if save:
-        topo.write(test_data_path)
+        topo.write(test_data_path,Z_format="%22.15e")
 
     compare_data = topotools.Topography(path=test_data_path)