diff --git a/xrspatial/hydro/tests/test_flow_accumulation_d8.py b/xrspatial/hydro/tests/test_flow_accumulation_d8.py
index 18af2bcb..778e6e16 100644
--- a/xrspatial/hydro/tests/test_flow_accumulation_d8.py
+++ b/xrspatial/hydro/tests/test_flow_accumulation_d8.py
@@ -427,3 +427,22 @@ def test_error_message_mentions_dask(self):
         ):
             with pytest.raises(MemoryError, match="dask"):
                 flow_accumulation(agg)
+
+
+# ---------------------------------------------------------------------------
+# Degenerate-shape tests (issue #2713)
+# ---------------------------------------------------------------------------
+
+@pytest.mark.parametrize("shape", [(1, 1), (1, 4), (4, 1)])
+def test_degenerate_shape(shape):
+    """Single-pixel and single-row/column input.
+
+    Every cell is a pit (code 0) that drains only itself, so each cell
+    accumulates exactly 1 at the input shape.
+    """
+    flow_dir = np.zeros(shape, dtype=np.float64)
+    agg = create_test_raster(flow_dir)
+    result = flow_accumulation(agg)
+    assert result.shape == shape
+    assert not np.isnan(result.data).any()
+    np.testing.assert_array_equal(result.data, 1.0)
diff --git a/xrspatial/hydro/tests/test_flow_direction_d8.py b/xrspatial/hydro/tests/test_flow_direction_d8.py
index da9686bc..33258a18 100644
--- a/xrspatial/hydro/tests/test_flow_direction_d8.py
+++ b/xrspatial/hydro/tests/test_flow_direction_d8.py
@@ -391,3 +391,21 @@ def test_valid_output_codes():
         if np.isnan(v):
             continue
         assert v in VALID_CODES, f"Invalid code: {v}"
+
+
+# ---------------------------------------------------------------------------
+# Degenerate-shape tests (issue #2713)
+# ---------------------------------------------------------------------------
+
+@pytest.mark.parametrize("shape", [(1, 1), (1, 4), (4, 1)])
+def test_degenerate_shape(shape):
+    """Single-pixel and single-row/column input.
+
+    Every cell sits on the kernel boundary, so flow_direction returns
+    all NaN at the input shape.
+    """
+    data = np.arange(np.prod(shape), dtype=np.float64).reshape(shape)
+    agg = create_test_raster(data)
+    result = flow_direction(agg)
+    assert result.shape == shape
+    assert np.isnan(result.data).all()
diff --git a/xrspatial/hydro/tests/test_flow_length_d8.py b/xrspatial/hydro/tests/test_flow_length_d8.py
index 5d35fcb3..a6c0b229 100644
--- a/xrspatial/hydro/tests/test_flow_length_d8.py
+++ b/xrspatial/hydro/tests/test_flow_length_d8.py
@@ -368,3 +368,22 @@ def test_numpy_equals_dask_cupy(self, direction):
         np.testing.assert_allclose(
             result_np.data, result_dc.data.compute().get(),
             equal_nan=True, rtol=1e-10)
+
+
+# ---------------------------------------------------------------------------
+# Degenerate-shape tests (issue #2713)
+# ---------------------------------------------------------------------------
+
+@pytest.mark.parametrize("direction", ['downstream', 'upstream'])
+@pytest.mark.parametrize("shape", [(1, 1), (1, 4), (4, 1)])
+def test_degenerate_shape(shape, direction):
+    """Single-pixel and single-row/column input.
+
+    Every cell is a pit (code 0) with no downstream/upstream neighbour,
+    so flow length is zero at the input shape.
+    """
+    flow_dir = np.zeros(shape, dtype=np.float64)
+    raster = _make_flow_dir_raster(flow_dir)
+    result = flow_length(raster, direction=direction)
+    assert result.shape == shape
+    np.testing.assert_array_equal(result.data, 0.0)
diff --git a/xrspatial/hydro/tests/test_hand_d8.py b/xrspatial/hydro/tests/test_hand_d8.py
index 68138856..401fa1bc 100644
--- a/xrspatial/hydro/tests/test_hand_d8.py
+++ b/xrspatial/hydro/tests/test_hand_d8.py
@@ -344,3 +344,23 @@ def test_cupy_huge_raster_raises(self):
         ):
             with pytest.raises(MemoryError, match="GPU working memory"):
                 hand(fd_r, fa_r, el_r, threshold=1)
+
+
+# ---------------------------------------------------------------------------
+# Degenerate-shape tests (issue #2713)
+# ---------------------------------------------------------------------------
+
+@pytest.mark.parametrize("shape", [(1, 1), (1, 4), (4, 1)])
+def test_degenerate_shape(shape):
+    """Single-pixel and single-row/column input.
+
+    Every cell is a pit (code 0) and a stream (flow_accum >= threshold),
+    so each cell drains to itself and HAND is 0 at the input shape.
+    """
+    fd = np.zeros(shape, dtype=np.float64)
+    fa = np.full(shape, 200.0, dtype=np.float64)
+    el = np.ones(shape, dtype=np.float64)
+    fd_r, fa_r, el_r = _make_hand_rasters(fd, fa, el)
+    result = hand(fd_r, fa_r, el_r, threshold=100)
+    assert result.shape == shape
+    np.testing.assert_allclose(result.data, 0.0)